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Mange Mites

MANGE MITES Of the animal parasites which cause skin affections in the domestic animals none are of such practical importance as the mange mites. They belong to the same order (Acarina) as the ticks, and they are grouped under two families Sareoptidse and Demodecidre. They are all of small size and are best identified under a low power of the microscope.

I. Sareoptidae The mange mites belonging to the Sarcoptidm have a certain amount of resemblance to the cheese and hay mites, with which they are some times confused. They have all rounded, greyish bodies, convex above and flat below. There is no division of the body into thorax and abdomen.

The mouth parts (comprising maxillae, mandibles, palps) are arranged in the form of a conical rostrum placed at the anterior portion of the body. The body is covered with a tough, chitinous envelope, marked by wavy, parallel lines and carrying at places small spinules or hairs. There are four pairs of jointed limbs in the adult, the two anterior pairs being attached to the body close to the rostrum, and the two posterior pairs towards the posterior third. Each of the limbs is composed of five segments, and the last article is prolonged by an ambu lacral sucker or fine hair. The parasites are not provided with tracheae and the sexes are separate. The males are always smaller and fewer in number than the ovigerous or egg bearing females.

The following are the genera into which this group of mange parasites is divided: Sarcoptes, Notcedres, Cnemidocoptes, Psoroptes, Chorioptes (or Symbiotes), Otodectes.

The distinguishing features Of each of these genera may be stated as follows: Sarcoptes. This mite is hardly visible to the naked eye. It is oval in shape. The rostrum is stout, short, and horse-shoe shaped, and pro vided with two membranous cheeks. There is a Y-shaped thickening of the envelope imme diately behind the rostrum.

The dorsal surface of the body presents a rough aspect from the presence of a considerable number of thorn-like spinules directed back wards. Towards the central portion of the dorsal surface the spinules are small and numer ous over a considerable area. The limbs are stout, short, and thick. The anterior two pairs are placed at the side of the body close to the head, while the posterior two pairs are attached to the under as pect of the posterior third, and when the mite is examined from the dorsal aspectonly the hairs which are at tached to the extremities of these limbs can be seen projecting from the margin of the body. In the adult female the first and second pairs of limbs, and in the male the first, second, and fourth pairs, carry ambulacral suckers. Each sucker is small and bell-shaped, and attached by a fairly long, thin, unsegmented stalk to the extremity of the limb. The male has no copulatory suckers or abdominal appendages. The anus is terminal. The parasite is oviparous.

Notcedres. This genus has only recently been separated from the sarcoptes and used to be called Sarcoptes minor. It is much smaller than the sarcoptes, more nearly spherical in shape, the lines on the dorsal surface of the body are arranged in concentric circles, and the anus is dorsal.

Cnemidocoptes are the sarcoptes of birds. The adult female is more spherical than the sarcoptcs proper, shows no spines on the body, and the limbs are extremely short and are not provided with ambulacral suckers. The male carries suckers on all the limbs. The cnemidocoptes are ovoviviparous.

Psoroptes (or Dermatodectes). The adult psoroptes are the largest of the mange mites, and can readily be seen as grey specks with the naked eye. They are oval in outline, the rostrum is long and conical, and not provided with membranous cheeks. The limbs are long and attached near the margin of the body. The first, second, and fourth pairs of limbs in the ovigerous female, and the first, second, and third in the male, terminate in ambulacral suckers. Each sucker is tulip-shaped, fluted at its free border, and attached by a long stalk divided into three segments. The third pair of limbs in the female is prolonged each by two long hairs. The anus is terminal. In the male there are two round copulatory suckers near the posterior extremity, and a round projection, the abdominal prolongation, carrying a bundle of hairs at each side of the anus. These two sets of organs facilitate coupling of the sexes.

Chorioptes or Symbiotes are distinguished from the psoroptes in that they are smaller, the rostrum is shorter and triangular in shape, and the ambulacral suckers are large and bell-shaped and attached by very short unsegmented stalks. The male carries suckers on all the limbs, and possesses two rectangular abdominal prolonga tions each carrying four bristles. The female carries ambulacral suckers on the first, second, and fourth pairs of limbs.

Otodectes. This genus is commonly called Symbiotes auricularum, and used to be classified with chorioptes. Otodectes differ from the chorioptes chiefly in two details of structure— the adult female is without suckers on the last two pairs of limbs, and the abdominal prolonga tions are not distinct in the male.

On account of the varying importance of these genera it is often necessary to identify the particular genus under observation. Differ entiation is especially important between sar coptes, psoroptes, and chorioptes. For this pur pose special attention should be paid to the appearance and disposition of the ambulacral suckers.

Varieties of these Genera. All the domestic animals are subject to attack by a variety of one or more genera of these mange mites. The varieties of each genus are not easily distin guished from one another, but are proper to the species of host on which they are found. Each variety lives and thrives only on the species which acts as its common host. ' Life-history of the Mange Mites belonging to Sarcoptidm. These mites are essentially perma nent parasites, and their development can only be maintained on the bodies of their hosts. The stages in the life-history of all the genera are (a) the egg; (b) the hexapod larva; (c) octopod nymph; (d) male and pubescent female, and (e) ovigerous female.

Sarcoptes. The sarcoptes differ from the psoroptes, chorioptes, and otodectes in the burrowing propensities of the ovigerous female.

The ovigerous female sarcoptes burrows into the epidermis and there forms a small straight or curved channel, the gallery, in a few hours. It then begins to lay eggs. The female will be found at the end of the gallery with the eggs arranged in a row behind it. The rate at which the eggs are laid is difficult to make out. I have identified one case in which the eggs must have been laid at the rate of two per day. As a rule only one egg can be seen in the body of the female. In one exceptional case I noted five eggs in the body of a sarcoptes. The gallery of the parasite cannot usually be identified in the skin of the domestic animals because of the pigmentation of the skin and the presence of a thick coat. Occasionally in the dog and pig, where the skin is thin, the entrance to the gallery may be seen as a little dark spot on a slight elevation.

The egg is ovoid in shape, white and glistening. Its contents are granular, and it is covered with a thin, homogeneous, tough envelope. The number of eggs laid varied from 10 to 30, 15 being probably an average number. In the egg sometimes the larva may be seen in various stages of development. When fully formed it appears with its limbs under the body and is quite characteristic. After about 3 to 7 days the larva hatches out. In doing so, it splits the envelope at one end and the empty egg presents some resemblance to an oyster shell. The larva afterwards leaves the gallery, and the further stages in the development of the parasite are passed through under the scales and debris of the skin.

The larva is very small, with a rostrum and chitinous envelope like the adult. It is provided with three pairs of limbs (hence the term hexapod larva), the first two pairs carrying suckers, the last pair being prolonged by hairs. It gradually increases in size, and after 3 or 4 days moults. It undergoes certain changes, casts off its old envelope, and develops into the nymph.

The nymph is slightly larger than the larva; it is provided with four pairs of limbs similar to those of the adult female, but its sexual organs are not developed. After a few days it moults and becomes changed into the male or pubescent female. After coupling with the male, the pubescent female again moults and becomes the ovigerous female. The ovigerous female presents a transverse slit, the ovulating vulva, on the ventral aspect of the body behind the last pair of limbs, and eggs begin to form within its body.

The development of one generation of sarcoptes is thus completed in 2 or 3 weeks. The parasite cannot be kept under observation throughout its development, and therefore the period it takes is only approximately given. Gerlach, in studying the Sarcoptes scabiei var. hominis, regarded 15 days as the average time for development and the average number of progeny as 15 individuals-5 males and 10 females. He therefore estimated that from one ovigerous female 11 millions may be produced in 90 days. This is a moderate computation, and probably makes full allowance for numbers of eggs and young parasites which fall by the way and perish.

Notcedres. In this genus the ovigerous female forms little nests in the epidermis, straight channels vertical to the surface, in which the eggs are packed together like sardines in a box.

Psoroptes and Chorioptes live under the scales and debris of the epidermis.. They do not form galleries. In other respects their life history is similar to that of sarcoptes.

The usual periods commonly given for the different stages in the development of psoroptes are: The larva hatches out from the egg in 3 to 7 days, moults, and becomes changed into the nymph in 3 or 4 days. The nymph moults in 3 or 4 days and the male or pubescent female is formed. The latter after coupling with the male moults in 3 or 4 days and becomes the ovigerous female. The latter begins to lay eggs in about 4 days. The nymphal stage of these genera resembles in the appearance of its limbs the ovigerous female. The pubescent female has no suckers on the last pair of limbs, which are prolonged by two fine hairs, and is provided with a little round knob on either side of the anus for attachment to the copulatory suckers of the male during coupling. Coupling has not been noted definitely in the sarcoptes, but the male and pubescent female psoroptes and chorioptes may remain attached for several hours or 1 to 2 days. The ovigerous female presents a transverse slit-like opening, the ovulating vulva, on the under aspect of the body, behind the first two pairs of limbs.

The life-history of the Psoroptes communis var. ovis has been worked out carefully by Shilston and Bedford in South Africa, and they have followed the development of the parasites throughout all its stages on the body of the sheep. The life-history as observed by them is shorter than that previously given. According to their observations, the larva hatches out from the egg in 2 or 3 days on the skin, 4 or 5 days on thick crusts, and 6 to 9 days in wool in warm weather. It moults in 2 or 3 days, the moulting process in this stage occupying 12 hours, while it lasts for 36 hours in each of the succeeding stages. The nymph which forms moults in 3 to 4 days and becomes a male or pubescent female. The latter appears before the male. Male psoroptes are in the proportion of 1 to 2, 3, or 4 females. One male may fertilize 2, '4, or 6 females. Coupling takes 1 to 2 days. The pubescent female moults in 2 to 3 days, and the ovigerous female into which it is changed begins to lay one day afterwards, or 9 days from the time of hatching of the larva.

The female may lay as many as 90 or 100 eggs, and sometimes in one day as many as 5 to 12 eggs. The egg-laying period of the ovigerous female lasts about 20 to 29 days.

Habit of Life and Intertransmissibility of Species.As already noted, each variety of mange mite lives throughout its development and its life on the body of its host. It does not thrive as a rule on the skin of another species of animal. The psoroptes of the sheep does not live beyond the first generation on the ox, nor the psoroptes of the rabbit or goat on the sheep.

The only mange acari of the lower animals which will set up a serious skin affection in man are varieties of the Sarcoptes scabiei and Notcedres. The skin affection so set up is often temporary, but may be very extensive and require treatment before recovery is brought about. The parts usually affected are the hands, arms, and breast, but sometimes the affection extends over the body. It is quite common for the Sarcoptes scabiei var. canis and Sarcoptes scabiei var. equi to be trans ferred to their owners or attendants. The latter parasite has often produced serious trouble in cavalrymen and other soldiers in war time who come into intimate contact with mangy horses, their clothing, or harness.

Sarcoptes scabiei var. equi is said also to affect cattle, Sarcoptes scabiei var. ovis to affect horses, cattle, and dogs, Sarcoptes scabiei var.

canis horses and sheep; the Notcedres cati is sometimes transferred to dogs, and is said also to produce mange in horses and cattle.

On its proper host the mange mite lives on the juices, excretions, and debris of the skin.

It penetrates the epidermis with its strong rostrum and sucks up the juices which exude.

The length of life of the parasites on the host is not definitely known save for a few varie ties. Female sar coptes are said to die in 3 to 5 weeks after laying eggs; the males live for about 6 weeks. The life of the ovigerous female psoroptes of the sheep is 30 to 40 days including the developmental stages. The male lives for 22 to 34 days after moulting from the nymph. The mortality of the parasites is affected by various circumstances connected with the condition of the animal and the excretions of the skin.

Off the host the parasites live only for a short time, in most cases less than one month. The sarcoptes die most rapidly; it is seldom they can be kept alive for more than a few days. In a dry atmosphere they perish in 5 or 6 days. When kept moist they do not live more than 14 days. Gerlach noted feeble signs of life in a sarcopt of the horse kept moist on a fragment of skin on the 24th day, but death had occurred by the 28th day. Psoroptes live apart from their host as a rule not more than 20 days. I have seen them live for 24 days, and the ultimate period observed by Stockman was 30 days. In dry air they are dead by about the 10th day. Chorioptes may live a little longer than the previous genera. Delafond and Bourguignon kept them alive from 60 to 65 days in boxes placed in a stable, but their observations have not been confirmed.

It will be noted in observations made with the object of ascertaining the length of life of these acarfi apart from the host, that the young parasites die first and the adult ovigerous females survive longest. After a few days, 10 days in the case of the psoropt, the chief evidence of life shown consists in slight move ments of the limbs. It is probable, therefore, that when the parasite becomes enfeebled, it will not thrive or propagate when placed on its proper host. The eggs retain their vitality at most for about 10 days, and then may be hatched out either in an incubator or on the body of the animal which it usually attacks. Gerlach, however, claims to have seen the eggs of the sarcopt of the horse hatch out after four weeks.

The Effects of the Mange Mite. The mange parasite produces its effect by puncturing the epidermis with its rostrum and injecting certain irritating secretions. Gerlach showed that this was the chief means by which the parasite sets up skin disease. He punctured the epidermis with the point of a needle, withdrew the latter and charged it with the juice of a crushed parasite. He then introduced the needle into the tract he had made in the epidermis. When the point of the needle reached the dermis an itching, painful sensation was produced, followed by the production of a papule and vesicle. The effect was more marked in the case of the psoroptes than with the sarcoptes, and was least severe with the chorioptes. The move ments of the acarus on the skin cause little trouble. The ovigerous female sarcoptes also does some damage by burrowing into the epidermis.

The disease of the skin which is set up is referred to as scabies, mange, itch, scab, or acariasis.

The skin affection produced is of the nature of a dermatitis, and is accompanied by itching or pruritus. The pruritus is more marked when the animal is heated as the result of exercise, or when kept in a warm house, and is not so evident when it is exposed to cold weather. It varies in degree with individuals, is perhaps greatest in the finer breeds and in adults, and is in no way related to the number of parasites present. Some of the most itchy patients may present only a few parasites on examination of scrapings, whereas in others where pruritus is not very apparent the acari may be in abun dance on the skin. It is often greater with the psoroptes than sarcoptes, and least evident with chorioptes. On account of the pruritus the animal rubs, scratches, and tries to bite the affected areas, so that at the points which it can reach, the hair is rubbed off in patches and abrasions and sores are produced. These obscure the lesions proper to the disease.

The dermatitis follows on the puncture of the epidermis by the rostrum of the parasite. A small papule appears, no larger than a pin point or pin-head, and is at first reddened. A little serous fluid may exude, which coagulates on the surface and may agglutinate a small tuft of hairs. This tuft is afterwards cast off. The epidermis proliferates, the skin becomes thick ened, scaly and dry, and covered with crusts. From repeated and simultaneous punctures of several parasites the areas extend. The gallery of the sarcoptes appears as a red point on a small elevation, but it is seldom seen, and there fore the lesion formed by this mite is difficult to distinguish from that produced by the other mange acari save by reference to the site of the lesion or the identification of the parasites. The nodular condition of the skin in the first stage is sometimes the only thing noted, the reddening seldom on account of the pigmentation of the skin, and so the lesion often presents no very characteristic feature.

At some places in the later stages the skin becomes wrinkled, especially over areas where the subcutaneous tissue is loose. The loss of hair is very extensive. Vesicles are seldom, if ever, seen, and pustules only occur from the inoculation of pyogenic organisms.

As the result of the restlessness and the absorp tion of toxic agents injected by the parasite, the affected animal may lose condition and even become emaciated. This is more notice able in attacks of sarcoptes and psoroptes, and is most likely to occur when the skin receives no attention, when the animals are left in a dirty condition, are poorly fed and over worked.

Transmission of the Parasite. In all cases the affected animal is the chief source of infec tion. The danger of transmission is in direct proportion to the number of parasites and the extent of the disease. When the parasites are few in number and the coat of the animal is unbroken, the acari are not readily transferred to the neighbouring animals.

Transmission rapidly takes place where animals are closely associated. The rapid spread of the disease is often associated with dirt and neglect, when the animals are neither groomed nor washed at frequent intervals; when they are in poor condition from overwork, exposure, or under-feeding. The parasites grow and thrive best when they are not disturbed.

The parasites may be transferred by direct contact or through intermediate carriers, such as common rubbing-posts, grooming utensils, clothing, harness, by the hands or clothes of attendants, or by the litter. Susceptible animals may become infected by introduction to houses, trucks or other vehicles, yards or fairs recently occupied by animals affected with mange.

It is curious that outbreaks of mange as a rule are most numerous in the domestic animals in the winter time. The explanation of this occurrence is not very clear. It may be related sometimes to the length of the coat at that time and the consequent lack of evidence of the disease until it is far advanced, perhaps also to atmospheric conditions. It cannot be connected with the temperature at which the acari are kept on the skin. Certainly when off the body of their host the parasites are quite dormant in the cold, whereas at body tempera ture they are very active and move about very rapidly. I have noted the sarcoptes moving at the rate of 11 inches per minute on the surface of the skin. It is also interesting to note that as a rule chorioptes are not so rapidly transferred to in-contact animals as the other genera of mange mites belonging to the Sarcoptidm.

The interval which elapses after infection, until appreciable symptoms appear is rather indefinite, and varies to some extent with the number of parasites which pass on to the host. In an average case the symptoms will be noted within a month. If, however, only a very few para sites are transferred, or if the animal is well fed, well kept, and frequently groomed and washed, the disease may not be apparent for two, three, or four months. This may account for the cases which appear without any distinct history of contagium. In some of such cases it has been thought that certain places have remained infected for years, and that these places are the source of the infection, but from our knowledge of the life-history of the parasites that would appear to be an erroneous opinion. The appli cation of acaricide dressings will also delay the progress of the disease, and certain conditions of the skin may militate against the rapid pro pagation and increase in numbers of the acari. That has been noted in sheep which have an excessive amount of yolk in the wool.

Diagnosis. The diagnosis of each form of mange is made from the appearance and position of the skin lesion, the itchy condition, and the identification of the parasite causing the lesions.

A clinical test commonly applied is to scratch the part of the skin showing evidence of disease. If the animal stretches out or turns round its head and makes nibbling movements of the lips, the condition is often diagnosed as mange. In the case of the dog or cat the animal makes scratching movements with the hind limb when the affected part is rubbed. The evidence ob tained in this way of the presence or absence of mange is not absolutely conclusive; it is only of relative importance, since in affections apart from mange itchiness or pruritus is often noted. The diagnosis is made absolutely certain only when the parasite is discovered, and a search should, as far as possible, always be made to ascertain the cause of a suspicious skin disease.

This may be done in one of several ways.

(1) The surface of the affected area of skin may be examined with a hand lens. Where psoroptes or chorioptes are the cause of the skin affections, sometimes they may be seen as little grey moving specks on the skin or the hairs. These specks can be picked off with a mounting needle or on the point of a knife, deposited on a glass slide, mounted in a little glycerin or Farrant's medium, and the particular genus to which the parasite belongs identified under the low power of the microscope. A magnification of 20 to 50 only is required, and in the inspection of the acarus a dull light is best for the discovery of its characteristic features.

(2) In most cases scrapings of the skin have to be taken and examined before the parasite can be found. This is especially the case with sarcoptes. In order to avoid difficulties in finding the parasite great care must be taken in selecting the area from which the scrapings are to be removed. Dark scabs covering sores and the outer portions of hair or wool fibres are useless. The scrapings should be taken from recent lesions where the skin is lumpy or nodular or covered with crusts easily broken down. In sheep scab the best material to examine is the yellow waxy matter at the base of the wool fibres in the more recent lesions.

In parts of the skin which have been dressed with a parasiticide preparation it is often difficult or impossible to discover the acari. In taking the scraping from the area, the hair, if long, should be clipped off. If there is a wind blowing at the time, the part should be moistened in order to prevent the scrapings being blown away. The skin over an area of 1 or 2 inches is scraped with a moderately sharp knife until serous fluid or blood exudes from the surface. This is done in all cases in order to ensure that sarcoptes which burrow into the epidermis, if present, will be included. The scrapings are then placed in a small box or petri dish, and put in a moderately warm place, as an incubator, for half an hour or more. The acari will often creep out from among the scales, and may be identified as in the first method. Obviously this method will not be successful when eggs only are present, but it is often useful.

(3) A portion of the scrapings is mixed in a watch-glass or a slide with a 10 to 40 per cent solution of caustic potash or soda. This is done to clarify the scales and decolorize the melanin present. This is effected after a few minutes in some cases, but often takes half an hour or more. The.solution has no effect upon the parasites to interfere with their identification. The mixture is then spread out in a thin layer on a clean glass slide, and a second slide squeezed down over it to ensure that the preparation is uniformly thin and transparent and easily inspected. The preparation is then examined under a low power of the microscope with a moderate light. Any or all of the stages in the development of the acari may be detected— eggs, larva, or adults. Their discovery may be made after a few seconds or minutes, but in some cases only after several preparations have been made and examined. This method is quite satisfactory, and can be relied upon to give good results in most cases.

(4) In order to hasten the action of the caustic alkali solution upon the scrapings, a fourth method has been introduced. The scrapings are put into a test-tube and shaken upon with a 10 per cent solution of caustic potash or soda. The contents of the tube are then boiled for about five minutes over a Bunsen burner or a spirit lamp. The skin debris which remains, portions of the hairs, and the parasites are quite transparent. The mixture is then centrifugalized for a few seconds and the solid particles are deposited at the bottom of the tube. The supernatant fluid is canted off, a little glycerin is added and mixed up with the deposit. A smear of this material is made on a slide and examined under a low power of the microscope. The parasites are found very readily if they are present, even in moderate numbers, in the skin scrapings. This method is particularly useful when the parasites are few and a large number of specimens have to be examined.

It has to be remembered that in the examina tion of scrapings hay mites and other acari may be found which have nothing to do with mange. These hay mites have as a rule a smooth envelope, and their limbs end in hooklets.

Treatment. The general lines of treatment are the same for all cases of mange. To be successful the treatment must be thorough, and that is the chief secret of success. Steps are taken to facilitate the action of some parasiticide dressing to be applied to the skin. The hair is clipped off the whole of the body in order to make sure that no spot escapes treatment when the body is affected. The hair is then burnt. The skin is afterwards washed or scraped to get rid of the scales and debris of the skin and permit of the penetration of the dressing and its action upon all the parasites present. When the skin is washed with soap, the whole of the soap is thoroughly rinsed off with water and the skin dried.

The dressing to be applied has for its object the destruction of the mange parasites. Many drugs are efficient in this respect, but those used must not only be efficient parasiticides, but in the proportion used must have no irritating effect upon the skin. Some dressings are discarded on that account. They may produce a more serious dermatitis than mange itself. The active agents in the dressings commonly used are sulphur and its compounds, coal-tar derivatives, and mercurial compounds. Arsenical preparations are used commonly in sheep, and sometimes in the ox. Tobacco decoctions are also employed, but great care must be taken on account of the danger of absorption of the nicotine and consequent poisoning. On that account also mercurial dressings must not be employed in the ox, or carbolic applications in the dog. The excipients used include water, oils and fats, such as rape oil, sperm oil, lard, train oil, fish oil. Linseed oil cannot be used, because it dries quickly and prevents the normal excretions of the skin. Some oily or fatty excipients sometimes, as in the case of rape oil, have an irritating action on the skin, probably on account of some adulterant. In mange affecting the body the applications must be thoroughly rubbed in over the whole of the skin. Where the dressing contains oil or fat, only one-hall or one-third of the body should be dressed on successive days, in order to avoid chills. It is necessary to repeat the dressings once or twice a week until a cure is effected, because some parasites may escape the action of the parasiticidal agent for a time. In sarcoptic mange especially the skin should be washed every week. The animal must be fed well during the treatment. That is most important. Occasional cases recover as the result of a generous diet.

The bedding should be completely changed weekly, and the house disinfected as well as the clothing and utensils or other agents coming in contact with the patient.

A cure is probable when the skin becomes normal, the itching has ceased, and the hair is beginning to grow. As a rule sarcoptic mange takes a longer time to cure than other forms of mange. Animals affected with mange should not be allowed in contact with their fellows for a period of two or three months after treatment. Cases of relapse may occur because some of the eggs or adult parasites have survived the effects of treatment.

Prevention. All cases of mange must be isolated, and the houses in which they have been living, the clothing, grooming utensils, harness, and any other object with which they have been in contact must be so treated as to destroy any stray acari. The latter are destroyed by heat, such as by hot water or flame of a painter's or brazier's lamp (this is useful for the floors, walls, and ironwork in a building), or by any of the ordinary disinfectant fluids. In-contact animals should also be dressed, and newly purchased animals should not be allowed to mix with the others until they are carefully ex amined or have been quarantined for a few weeks.

II. Demodecidm is the second family of acariens which contains mange acari. It includes only one genus, Demodex folliculorum.

This acarus is very small, worm-like, and transparent. The rostrum is prominent in front, a little narrower than the thorax, and is formed of similar parts to those noted among the Sarcoptidm. The cephalo-thorax is separate from the abdomen, convex above, flat on the lower surface, and in the adult carries four pairs of legs which appear like little knobs at the margins of the lower surface.

Each limb has three segments.

The abdomen is long and some what conical, finely striated transversely. The anus is placed near the anterior portion of the abdomen. The demodex is oviparous.

Of the Demodex folliculorum there are several varieties, each having a separate host. They are found in man, dog, ox, pig, goat, rarely the horse and other mammals. Each variety is named after the host which it infests. Thus the variety in the dog is named the Demodex folliculorum var. canis.

The stages in the life-history of the parasite are similar to those of the other mange acari. The egg is elliptical, the larva small with three pairs of legs, and in the nymph there are four pairs of limbs with the cephalo-thorax not well separated off from the abdomen.

Habit of Life. The demodex is found in the hair follicles and sebaceous glands of the skin, sometimes in great numbers from twenty to several hundreds.

In man it is regarded as a more or less harmless parasite, and is most frequently noted in the Meibomian glands and comedos, but sometimes it has been associated with acne.

In the dog, and occasionally in other domestic animals, it sets up one of the most serious and obstinate skin diseases. The disease is referred to as follicular or demodectic mange or acariasis. In the dog, and probably in other animals, the demodex is associated in its action with a pyogenic organism such as Staphylococcus pyogenes albus. This organism is probably carried by the demodex into the hair follicles and sebaceous glands. It is thus allowed to enter the tissues and set up a dermatitis, sometimes with pustule or abscess formation.

Transmission. In the dog it appears to be only very slightly contagious. It is observed often in one or two among a litter of puppies, although they have all been in contact for a considerable time. In occasional instances among other animals a number of cases have been discovered in a herd of cattle. Possibly there is some predisposition towards the disease required for its development.

Symptoms. There is very little pruritus in follicular mange. In some cases the skin in parts is roughened, scaly, becomes denuded of hair, reddened or pigmented, and may give off a peculiar odour. In other cases little nodules or pustules form in connection with the hair follicles. These pustules contain a thick semi-solid pus, or, when they become large, a blood-stained purulent fluid.

Diagnosis is made in the first cases, the squamous form, by examination of scrapings from the skin as in other forms of mange. In the second, the pustular form, the demodex is found in abundance in the pus from the small pustules. J. F. C.

conditions under which the animals are kept when the disease is introduced into an army, it spreads rapidly and is extremely difficult to eradicate. The close contact of equines, hard work, dirty surroundings, want of grooming, poor feeding, and other adverse conditions, hasten the course and development of the disease. It was rampant in army horses during older campaigns, e.g. in the Crimea and in the South African war, and has been a source of serious trouble during the recent world war. The disease is no doubt met with in the army in peace time, but it is also brought in by remounts, and it is contracted by intro duction to infected stables, railway trucks, yards and other places, and by direct or indirect contact with the horses of other armies and affected civilian horses. It is spread by direct contact, also by grooming utensils, clothing, harness, by the hands and clothes of attendants, and through infected stables or lines. The disease is not so common among thoroughbreds, because of the care and attention which they receive, and their more or less complete isolation from other breeds of equines. Carefully tended, well-fed animals are not so liable to contract the disease, and in them the disease does not develop so rapidly or extensively. Outbreaks are more frequently met with in winter.

Symptoms. The first symptoms that may be noticed are those of pruritus. When the animal is heated, after exercise, or in a warm stable, or when well clothed, it rubs itself against posts or walls and attempts to bite the affected areas. When the affected part is (a) Sareoptie mange in equines, the most serious form of scabies in these animals, is due to Sarcoptes scabiei var. equi (Linn, 1758). This parasite was discovered and described first by Delafond and Gerlach in 1856, and has been studied in more recent years by various investigators.

The ovigerous female is about long by 300, u broad. The male is 250µ long by 170 1.6 broad.

The disease is common in countries where there is much trafficking in horses, and its rapid spread is frequently associated with dirt and neglect, and with indiscriminate mixing of equines. It is one of the most common and serious contagious diseases which affect military horses in times of war. On account of the scratched or groomed, the horse leans over towards the hand or brush and stretches out or turns round the head and makes nibbling movements with the lips. Well-bred animals often become frantic with the itching. The degree of pruritus varies very considerably. In horses which are kept in the open the the condition from being noticed until the disease is very far advanced or the long coat is clipped off. The lesions may appear on any part of the body, but most frequently develop first on the withers, back, shoulders, neck, and sides. Thence they extend to all portions of the body, including the head, submaxillary space, under-aspect of the neck and inner sides of the thighs and forearms. The extremities of the limbs are affected only in advanced cases.

The lesions appear first as little nodules on the skin, with agglutination of a few hairs over the nodules. There may be a slight oozing of yellow serous fluid which coagulates on the surface. The hairs are cast off and a dry, scaly, hairless spot is left. A number of these hairless spots coalesce and form dry, irregular, rough, scaly patches. The coat becomes dry and dirty-looking.

In neglected cases the disease frequently extends very rapidly, and large areas become involved. Only a few hairs may remain scattered over these areas. The skin becomes thickened and wrinkled in the old-standing cases, and the wrinkling is especially marked when the subcutaneous tissue is loose, such as over the withers and neck and in front of the fold of the thighs. Sometimes small pustules appear.

On account of the rubbing and biting induced by the pruritus, the skin is denuded of hair at various points, and abrasions, sores, and ulcers covered with black scabs result. This com plicates and obscures the ordinary lesions.

The constant restlessness caused by the pruritus and the absorption of the excretions of the parasite bring about loss of condition and even extreme emaciation and debility. Indeed in advanced cases severe losses may be caused by this disease.

(b) Psoroptic mange is caused by Psoroptes communis equi (Hering, 1838). The parasite of this disease was first observed by Souting, and illustrated later in 1878 by Gothier.

The ovigerous female is about 710 pt long by 450 u broad. The male is about 500, u long by 330 pt broad. The disease is very highly con tagious, and is transmitted in the same way and occurs under the same conditions as sarcoptic mange. It is not, however, so diffi cult to cure, but sometimes the two diseases are associated in the one animal.

Henry noted psoroptes on the inner side of the ears of 71 per cent of the carcases of horses from one veterinary hospital in France, where only 7 or 8 per cent were affected with psoroptic mange. 42 per cent in another hospital were also affected, although mange of any kind was rare among the equines treated at that place. He concluded that the inner side of the ear was the normal habitat of the psoroptes, and that only on occasion did these parasites leave the ear for the body and set up the symptoms of body mange.

Symptoms. The symptoms of psoroptic mange are very similar to those of sarcoptic mange, but the degree of itching may be even more marked. The lesions appear first usually at the base of the mane, on the poll and the root of the tail, and thence extend over the body. Frequently a yellow serous coagulated material may be noted among the scales and scabs. The lesions often appear more circum scribed and moister than in sarcoptic mange, the scales thicker and more agglutinated together, and the disease does not spread over the body so rapidly.

These differences are so slight that they cannot be relied upon to differentiate the two conditions. The chief method of distinction consists in the identification of the parasite. In psoroptic mange the acarus may be seen some times as a grey speck moving over the surface of the lesions.

When the psoroptes are confined to the ears, slight signs of itchiness in these regions may be noted. The animal frequently shakes the head or rubs the base of the concha; occasionally it rubs the ear with the hind foot. Dust or mud may then be left on the ear with the hoof. The bottom of the auditory meatus is filled with a plug of a greyish colour sometimes an inch long.

(c) Chorioptic or Symbiotic mange or leg mange is due to Chorioptes (symbiotes) equi (Hering, 1845).

The ovigerous female is 420µ long by 260 p. broad; the male is 305 p. long by 225 pc broad. This disease is most commonly noted among heavy horses with long coarse hairs on the limbs. It is not so contagious or so serious as the other common forms, and may affect only one or two animals in a stud. Sometimes it involves a large proportion of the horses in the place. The chorioptes has been credited with producing grease; it certainly has been found in cases of grease in the horse.

Symptoms. The disease is chiefly confined to the limbs, and the hind limbs are most commonly involved. When the horse is heated, more especially when in the warm stable, it often stamps and rubs or even bites the limb. This is the cause of night kicking in horses. Such horses may be difficult to shoe, and are more difficult to treat in foot troubles. The lesion begins first about the pastern, the skin becomes scaly and thickened, and the hair is cast off cr rubbed off in patches. The disease extends upwards to the hocks or knees, and even as far as the stifles. Rarely it extends to the abdomen. In advanced cases the skin is very much thickened and scaly, and arranged in thick transverse folds covered only sparsely with hairs. The condition of the horse is not, however, much interfered with. The position of the lesions is characteristic, and the chorioptes are easily found in the hairs and scrapings. The lesions are most marked in the winter time; the animal appears to recover to some extent in the summer.

Diagnosis. These three forms of mange are distinguished by the itchiness of the skin, the position and appearance of the lesions, and also by the discovery of the parasites in the lesions or in scrapings. The method of discovering the mange mites has already been described (p. 455).

Differential Diagnosis. Itchy conditions of the skin are sometimes set up by other animal agencies—hay mites, lice, Dermanyssus avium, harvest bug; but one has to judge whether They may affect a large portion of the body, and are not accompanied by much itching, In mane and tail mange where elf-locks and rat tail appear, the disease is confined more or less to the base of the mane and the tail, and tends to become chronic. In chronic eczema also the lesions tend to be localized and itching is not a marked symptom, but in doubtful cases it is necessary to resort to a microscopic examina tion of scrapings from the lesions.

Treatment of Sarcoptic and Psoroptic Mange in Eguines. In the British Isles sarcoptic and psoroptic mange of equines are scheduled diseases dealt with under the Diseases of Animals Acts. Outbreaks of these diseases must be notified by the owner or attendant and the veterinary surgeon called in for professional advice or treatment.

these when found on the skin are sufficient to account for the lesions present; they may complicate mange. Hay mites (various species of Tyroglyphus, Tarsonemus) sometimes cause a temporary itchiness without any very manifest lesions. With lice the itchiness may be marked, and the scurfiness and other abnormalities of the skin present are usually in direct proportion to the number of parasites. The eggs and adults (trichodectes and hcematopinus) may easily be identified on inspection of the skin. Dermanyssus avium is derived from fowls or other birds which live in the lofts of the stable above the horses, and may perch on their back. The irritation they produce is very severe. Equines are attacked by the harvest bug in the autumn on certain pastures. The limbs and under-aspect of the body are affected. The parasites can easily be found and distinguished. Tick larvm sometimes attack horses at grass. The lesions appear suddenly and consist of thick yellow scabs which agglutinate the hairs.

The animals must be isolated, placed in a separate box or stable, provided with separate utensils and, if practicable, separate attendants. The stalls from which they are removed and structures with which they have been in contact must be properly disinfected as hereafter de scribed, and the bedding burnt.

The whole of the coat, including the hair of the mane and tail, must be clipped off. This is done in the first instance to find out the extent of the lesions, and in the second place to facili tate the penetration of the parasiticide dressing. Then the animal is washed all over with soap and water to remove the dirt, the scales and crusts, and the soap is afterwards rinsed off. There is no special kind of soap necessary. After washing, the skin is thoroughly dried and a dressing applied. Many kinds of parasiticide dressings are used, all more or less satisfactory in their way, but the chief thing necessary is to ensure that whatever one is used it is thoroughly applied. No irritant dressing should be used.

Sulphur or sulphur compounds form the base of a large proportion of mange dressings. A common and efficient application is composed of: Sulphur, 2 parts.

Oil of tar, 1 part.

Pot. bicarb., 1 part.

Rape oil, train oil, fish oil, or lard, 8 parts.

The chief trouble here is the excipient. Rape oil sometimes blisters the skin, probably because it is rancid or contains some irritating adulterant. Clarified horse fat is now used extensively among military horses as an excipient for mange dressings and has proved eminently satisfactory. This dressing must be thoroughly rubbed into the skin all over the body from the tip of the nose to the tip of the tail, not forgetting the under-aspect of the abdomen, the inner side of the thighs, the head and the limbs. Where the lesions are strictly limited, a dressing over that part of the body and over a large area around the lesions may be efficacious, but where the disease is at all extensive the whole of the body must be treated. In cold weather, where the whole body is to be treated, a third or one-half is dressed on successive days in order to avoid chills. Exercise is useful where it is permitted. As to rugs for the animals after dressings, they are not used for military horses, but their use may be permitted in cold weather provided they are frequently disinfected. The dressing should be applied twice a week. At the end of each week the skin should be washed and a day's interval allowed before dressing again. The skin remains scaly for a time, but the itching soon ceases. The treatment must be continued until the hair begins to grow. The new hair often grows rapidly, and is darker in colour than that of the old coat.

A cure is much more rapidly effected in psoroptic than sarcoptic mange. In the former recovery may take place in eighteen to twenty days, while in the latter at least a month will elapse, and frequently a longer time, even several months in extensive cases, before recovery is complete. This difference is due to the burrow ing propensities of the sarcoptes and the con sequent greater difficulty of bringing the dressing into contact with these parasites.

On account of the discovery of the psoroptes on the inner side of the ears by Henry, it is advisable in psoroptic mange to apply the dressing to the inner side of the ear. M. Henry advises, as the best acaricide, cresyl in 2 to 3 per cent warm watery emulsion; 50 c.c. of this emulsion is poured into the ear two or three times at intervals of eight days.

During the period of treatment the animal must be fed well. This is an essential part of the treatment and favours recovery. Internal treatment is not necessary. Arsenic in the form of liquor arsenicalis may be given internally in advanced cases. Bedding if used should be removed every week and burnt, and the floor and walls of the box flamed with a brazier's lamp or sprinkled with a reliable disinfectant, such as 1 or 2 per cent creolin. Halters and head stall or collar should also be frequently disinfected. After recovery of the animal, the box, clothing, harness, including collar or head stall, the grooming and other utensils must be disinfected.

From the box or stall the litter is cleaned out and burnt. The walls and floors are then flamed with a brazier's lamp or sprinkled with a strong disinfectant fluid, such as 2 per cent creolin or 5 per cent carbolic acid, or douched with boiling water. Afterwards the walls and posts are whitewashed or tarred. The utensils should also be disinfected by dipping in boiling water or immersing in a solution. Paraffin or paraffin emulsion such as that recom mended by Maj. Gen. Blenkinsop may be used for the brushes, curry-combs, clipping machine, collar, or head stall. The padding is removed from the harness and burnt, and the saddlery smeared with a disinfectant solution. The clothing, such as rugs, should be disinfected by dry heat or by immersing in 1 per cent creolin or other reliable disinfectant.

The horses after apparent recovery should not be allowed to come in contact with healthy animals for a period of three months. Relapses sometimes occur. A few parasites may survive the treatment; they do not multiply in sufficient numbers for a long time, it may be two or three months, to produce appreciable lesions.

Other dressings used for mange include: 1 Picis, Sulphur, as 1 part; Sapo moll., Spts.

vini meth. as 2 parts.

1j6 01. Picis, Sapo moll 5, 5, . 1 part, Spts. vini meth. 8 parts. Cresol, Sapo moll. as 1 part, Spts. vini meth. 5 to 10 parts.

Champetier's dressing consists of: Sod bicarb. 30 parts.

Petrol 300 „ Oil of cade 20 „ Pea-nut oil 100 „ Hydrarg. perchlor. 1 part.

Water 1000 parts.

After applying the dressing, the horse is powdered with sulphur. This dressing is applied two or three times only. Good results are claimed by Champetier for this method.

Major-General Blenkinsop recommends the following method of treatment: After clipping, washing, and drying the horse, apply dressing of sulphur 1 part, lard, train oil, or fish oil 4 parts. Lunge the horse daily and rub the dressing in well with the hand after exercise. On the sixth day apply the following emulsion: paraffin or kerosene oil 2 to 1 pint, soap solution (soft soap 1 lb., water 1 gallon) 1 gallon. On the seventh day wash the animal. Flame the box with a brazier's lamp. On the eighth day sulphur dressing again. On the thirteenth kerosene emulsion. On the fourteenth day the animal is washed. Treatment is carried on for three weeks. Three courses of dressings are used. No bedding is permitted. The animal is kept under suspicion for three months after wards. In-contact animals are dressed with the kerosene emulsion.

In the great European War, on account of the large numbers of animals affected with mange, individual attention could not be given to each case, and other methods of treatment have been tried, due regard being paid to economy of labour and the cheapness as well as the efficiency of the dressing. Where outbreaks have been large, special hospitals have been set aside for dealing with the cases, and special dipping tanks erected on the same lines as those used for dipping cattle and sheep. The common dip used is prepared from lime and sulphur. Unslaked lime is made into a paste with water and sulphur mixed in, in the proportion of lime 15 lbs., sulphur 20 lbs., water being added to 25 gallons. The mixture is boiled for two or three hours until the liquid becomes greenish yellow. The sediment is allowed to settle and the supernatant fluid is drawn off and water added to make 100 gallons of solution. The sediment is irritant and must not be used in the dip. The dipping tank holds about 3600 gallons of dip. This fluid is kept moderately warm when being used. After clipping and washing, the horses or other equines are passed through the dipping tank. This is repeated twice a week, and the dip rubbed in well after each immersion. A cure is rapidly effected with psoroptic mange, and good results have also been claimed with sarcoptic mange.

Last of all, Vigel and Chollet have introduced Lepinay's treatment of mange of the horse by sulphurous anhydride. A specially constructed air-tight box is used for the purpose. To it is attached an apparatus for the generation of sulphur dioxide. The horse is first clipped, washed, and dried. It is then backed into the box with the head protruding. Over the head is passed a cloth collar which is fixed, on the one hand, to the margins of the opening in the body through which the head protrudes, and, on the other, closely tied round the neck of the horse close to the head. This is done to prevent the escape of the fumes of sulphur dioxide and the gassing of the horse. The openings of the chamber are tightly closed and the gas turned on. As great a concentration as 6 per cent of sulphur dioxide is reached in the box. The animal is exposed to the action of the gas for two hours. Afterwards the ventilators of the box are opened and the gas escapes. The animal does not inhale gas at any time. The horse is then allowed to leave the box, and the head is treated with one of the ordinary dressings for mange, such as cresylated oil 1-10, and in psoroptic mange 3 per cent cresyl emulsion poured into the ears as recommended by Henry. This dressing is applied on several occasions. After exposure to the gas, the horse is put into a thoroughly disinfected stable, groomed daily, and washed on several occasions at intervals of a few days. A cure is rapidly effected (see p. 475).

Treatment of chorioptic or symbiotic mange is simpler than that of the two other forms in the horse. The hair should be clipped off from the limbs, and the limbs washed with soap and water and dried. Any of the dressings recommended in psoroptic or sarcoptic mange should then be applied on two or three occasions at intervals of a few days. Lime and sulphur dip, or 1 or 2 per cent creolin emulsion answer well. This is sufficient to ensure recovery.

Transmission of Mange of Equines to other Animals. The Psoroptes or Chorioptes of the horse does not cause anything but a temporary irritation in other animals or man. The parasites rapidly disappear from the skin. The Sarcoptes of the horse may occasionally be transmitted to the dog or ox or man. It has been observed to affect soldiers or grooms who are often in close contact with affected horses, especially where no great attention is paid to washing the hands or arms after contact. The hands and arms are most frequently affected, but sometimes the disease extends to the chest and other portions of the body. Recovery may be spontaneous, but at times the disease is rather severe, and treatment is required before recovery takes place.

Follicular mange in the horse has occasionally been observed. It is due to Demodex folli culorum equi. There is no evidence that it is identical with that of the dog or man.

It has been found by Wilson (1844) and Majouli (1897) in the eyelids, by Gros (1845) around the muzzle, and more recently by Walther, Schenzee, Berger, Meissner, Bidault, and Urbain.

In some cases the demodex appears to be responsible for skin lesions.

Symptoms. The disease is met with in isolated cases. There is very little itching. The lesions appear on the eyelids, nose, or face. Occasionally extensive lesions have been observed not only over the head, but over the lateral aspect of the neck and trunk. The hairs over the affected area are raised up and cast off and scales or crusts cover the hairless skin. There are no nodules or pustules. Microscopic examination of scrapings of the affected areas reveals varying numbers of demodex. This parasite has also been found associated with sarcoptic mange.

Treatment. A cure may be effected by any of the methods of treatment adopted against sarcoptic mange. In some instances treatment has to be applied over a period of several months. J. F. C.

Mange in the Ox 1. Sarcoptic mange is not so common as psoroptic mange. It is due to the Sarcoptes scabiei v. bovis. It is alleged to be transmitted also from the goat and pig.

Symptoms are rather similar to those of the horse. The animal frequently licks or rubs the parts affected. The disease may affect any por tion of the body; the back, sides, croup, escut cheon, and udder are frequently first involved. The skin becomes nodular, scaly, denuded of hair in patches, thickened and wrinkled. The disease slowly extends and may affect a large proportion of the body. It causes loss of condi tion, and in the cow reduction of the milk supply.

2. Psoroptic mange

is the most common form of scabies in cattle. It is due to Psoroptes communis v. bovis. It was studied first by Dorfeuille in 1813 and afterwards by Gohier, Delafond, and Gerlach. The ovigerous female measures 700µ long by 450µ broad, the male 550µ long by 310µ broad. The disease is rapidly transmitted from one animal to another, especially where they are closely housed.

Symptoms. There is considerable itching, which induces frequent licking and rubbing. The lesions begin along the upper aspect of the body from the root of the tail to the poll, and extend thence over the sides of the neck and body. The legs are last involved. The lesions begin as little nodules which soon become hairless, and the skin becomes covered with thick scabs, thickened, scaly, and wrinkled, parchment-like and dry. The disease extends gradually, and causes loss of condition and even emaciation.

3. Chorioptic mange or symbiotic mange is not uncommon in cattle. It is due to the Chorioptee bovis.

The ovigerous female measures 385µ long by 240µ broad, the male 285 f4 long by 210 /.4 broad.

The condition is only slightly contagious, and may affect only one or two animals in a herd. It is transmitted by contact, and by the litter. The disease is more marked in the winter.

Symptoms. There is only slight pruritus. The lesions appear at the extremities of the limbs and the base of the tail. The hind limbs are more often involved and the affection appears on the fetlocks, pasterns, and even extends upwards as far as the hock. The lesions

appear as thick crusts or wart-like growths. At the base of the tail bran - like scales are noted on the thin skin there. The parasites are often very numerous in the lesions. In very rare cases the disease may extend all over the body. The parasites are easily found in the crusts. As a rule, the condition is a very mild one, is more marked in the winter, and the condition of the animal is not markedly affected by this form of mange.

Treatment is on the same lines as the horse. Sometimes dips are used as for the sheep. Mercurial ointment must not be employed on account of the danger of poisoning from licking off the dressing. 2 to 5 per cent creolin or Lysol emulsions are also used.

Differential Diagnosis. The condition is recognized by the itching and general appear ance and by the identification of the acarus. The acari are often numerous in the skin lesion. It can easily be distinguished from lice by the discovery of these parasites, and from eczema by the results of a microscopic examination of scrapings.

Follicular mange in cattle

is not common. It is due to Demodex folliculorum v. bovis. This parasite is about long by 55 broad. It has occasionally been observed in a large number of animals in a herd. It was noted first by Gros in 1845, later by Faxon in America, by Grim and Gehl, by Bugge in Germany, and by Griffiths in Nyasaland.

Symptoms. As a rule there is not much itching.

The lesions appear first usually on the neck or shoulder and gradually spread to the ears, face, trunk, and upper part of the limbs. Gros saw the disease on the muzzle. The lesions have the form of round nodules varying in size to a hazel-nut. They contain a cheesy pus rich in demodex. Occasionally in the later stages after months they become reddened, denuded of hair, and rupture, giving exit to the cheesy pus. When the infection is a severe one in advanced cases the animals become emaciated, and some may even die of the disease, probably as the result of a toxaemia. The diagnosis is easy. The examination of the pus from the nodules reveals large numbers of the parasites. In many cases the disease is very mild, remains stationary, the hides only are affected, and the lesions are referred to as pimples.

Treatment. Very often no treatment is adopted. It consists in segregation of infected animals, disinfection of the places with which they have been in contact, squeezing out of the contents of the nodules, and the application of one or other of the dressings recommended in mange in equines. Cooper's improved cattle dip 1-200 is also used as a local application, but it seems to be chiefly useful in preventing the further development of the disease and the spread to other animals. In extensive cases destruction is recommended. In any case animals affected should be sent to the butcher as soon as they are sufficiently fat for slaughter.

J. F. C.

Mange in Sheep 1. Sheep Scab. The most important and common form of mange in sheep is Psoroptic mange, and is commonly referred to as sheep scab, although the latter term has been used to include the other forms of mange. One may say generally that when sheep scab is spoken of psoroptic mange in sheep is meant.

as the Psoroptes communis v. ovis. The parasite lives and propagates on the skin and does not move out on the wool fibres more than one inch from the skin. It, however, reaches the surface when tufts of the wool fibres are cast off or rubbed off in the older lesions.

The acari may live off the host for twenty or thirty days, but only the ovigerous females live after about the tenth day. Eggs may retain their vitality off the host for about eight or ten days, but in ordinary conditions often fail to hatch out. It has been maintained by Cause. It is due to Psoroptes communis ovis.

The female is 700µ long by 455µ broad, the male 550µ long by 360µ broad. The parasite lives on the skin of the sheep and does not thrive on the bodies of other species of animals. The psoroptes of the goat or rabbit will not live on the skin of the sheep beyond the second generation. Therefore, where a psoroptes is found on sheep, it may be taken sheep - owners that fields and manure remain infective for a long time. That, however, is not borne out by experiment. Infective material removed from a scabby sheep and stored for twelve to fourteen days reproduced sheep scab (Stockman), but in no case has the infective material been shown to remain active for a longer period. Healthy sheep, put into infected pens at varying periods after removal of affected sheep, became infected with sheep scab only when the intervals were not longer than eight or nine days.

Manure collected from a kraal in which infected sheep had been running for sixteen days was transferred to a clean kraal, and 4 clean sheep were admitted to the latter for five days. They became affected with sheep scab. When they were removed and clean sheep put into this kraal, no further infection resulted. This experi ment only proved that the manure may attract the acari; it does not indicate that the acari will live long in the manure. These experiments go to show that the main source of infection is the infected sheep. An interesting point is raised by Henry. He found psoroptes in the ears of sheep which were emaciated but free from sheep scab in 15 out of 32 cases examined. He chew the conclusion that the normal habitat of psoroptes is the inner side of the ears, and that the parasites only occasionally leave the ears and set up body mange. I have been unable to corroborate Henry's findings, but I found psoroptes in the inside of the ears of three sheep badly affected with sheep scab out of a flock of ninety-five sheep in which the disease had broken out. The results of investigation, however, point to the importance of the treat ment of the ears in sheep scab.

Transmission. Sheep scab is the most serious and most contagious form of mange in sheep. It sometimes causes serious losses and brings about considerable depreciation in the value of the fleece. It is easily transferred by contact, and through common rubbing-posts, hedges, or bushes, through public conveyances, railway wagons, markets, or fairs. Other parasites in sheep may facilitate the transmission, because of the use of common rubbing - posts. The transmission is easiest in proportion to the degree of close association of the sheep.

It is a remarkable fact that in the British Isles, at all events, outbreaks of sheep scab, like some other forms of mange, are much more numerous in the winter months. This may be due to several factors. There is a considerable amount of traffic in sheep in the autumn, and thus sheep scab may be more widely dissemin ated at this period. Summer dipping also is a factor in the decrease of outbreaks in summer. The sheep scab parasite probably thrives better under certain conditions on the skin of the host. Shilston has shown that dry weather causes a marked decrease in the reproductive activity of the psoroptes, and on skin covered with a thick layer of yolk they may eventually die off. No doubt also the long fleece of the sheep in winter favours the development of the parasite. The period which elapses after infection until noticeable symptoms appear conforms with what has been already written in connection with mange generally. It is generally accepted that in the average cases symptoms may be observed within twenty-five days after infection. But in some cases the period is increased to two, three, and four months, especially if the parasites which have passed on to the sheep are few in number or if the animal has been previously dipped. The reappearance of scab in sheep several months after apparent recovery as the result of dipping has frequently been noted. Thus in some experiments of Stockman, sheep infected with three female psoroptes showed symptoms only after seventy-seven days; and sheep after being dipped and then infected with twenty copulating pairs and twenty female psoroptes presented distinct symptoms only after two hunched days. Again it has been observed that lambs running with affected ewes usually get acari on their skin, but although the parasites seem to flourish and breed the symptoms of sheep scab do not appear on the lambs for months.

Distribution. Sheep scab is found in all countries wherever sheep are reared. The disease, however, has been completely eradi cated from Australia and New Zealand. It has been recognized from ancient times, and although it has caused serious losses and very extensive outbreaks it has not received, save in the countries mentioned, the attention it deserves so as to bring about its complete eradication. This is probably due to slip-shod methods or perfunctory actions which are adopted.

Symptoms. One of the marked symptoms of the disease is pruritus. This is particularly marked when the sheep is heated from exercise or kept in a warm place, or when the sheep are crowded together. It is not very evident when the animals are exposed to cold wet weather or have been douched with cold water. The sheep frequently rubs itself against posts or trees or fences, sometimes scratches the part with the limbs, or nibbles or bites it. Some times it may even pull out locks of wool. If the affected area is rubbed the sheep stretches out its head, turns round and nibbles with its lips.

The parts of the skin affected generally are those covered with fleece. Those first involved are often the back and withers, the tail and scrotum in lambs, occasionally the under aspect of the breast, but any part of the body may be attacked. It is only in extreme and exceptional cases that the disease extends to the limbs.

The early lesions often escape detection because of the necessity of a very careful examination of the body and the difficulties of inspection resulting from the presence of a long fleece. The early stage consists of little red papules, where the parasite has bitten, no larger than a pin-head. Soon a little serous fluid exudes and coagulates at the base of the wool fibres. This process is accompanied by proliferation Fm. 124.Sheep affeoted with sheep scab.

of the epithelium, and the surface of the nodule becomes covered with silver grey scales under and between which the serous fluid forms a wax-like material. The lesions may be multiple and fuse, and may extend in a centrifugal or peripheral, rarely linear, fashion. It is usually roughly circular, and soon attains the size of a sixpenny or a shilling piece. When the parasite has caused the lesion it passes to a fresh normal area of skin. In the older lesions the central portions become dry, and the wool falls out in tufts or is rubbed or torn out. The tufts con tain at their base the yellow wax-like material which agglutinates the fibres and is rich in psoroptes. The bare patches of skin become dry, thickened, and parchment-like, and covered with large greyish scales or crusts. These con tain very few parasites. As the result of this process the fleece becomes broken and ragged, and the wool fibres dry and brittle and depreciate in quality. Redness and abrasions of the skin sometimes result from rubbing, and occasionally small pustules or abscesses form.

On account of the restlessness caused by the action of the irritating material injected by the parasite the sheep loses condition and may become emaciated. In neglected cases emacia tion and debility become extreme after a varying time, and death may result from sheep scab.

If the animal survives, recovery from scab takes place usually after the disease has spread all over the body, head, and limbs. Should the disease recur it begins again at the tail or head. It has also been noted that shearing scabby sheep retards the progress of the disease.

Diagnosis. When a flock of sheep is being inspected for sheep scab a ragged fleece and evidence of pruritus are suspicious symptoms.

In the early stages the fleece may appear normal. To bring out symptoms of itching, the sheep may be huddled together for a time in a warm shed or given some exercise and then put into a pen, when affected sheep will begin to rub against posts or fences. The suspicious sheep are then caught and examined for lesions. In the early stages a close inspec tion must be made of various parts of the body, including tail, scrotum, and under aspect of the chest, before a lesion is found and a reaction obtained by scratching the part. Diagnosis is made certain by the discovery of the parasite. Scrapings are best taken from the early lesions, and the best material for examination is the yellow wax-like material which is found at the base of the wool fibres in the lesions. This material may be so rich in parasites that they may be recognized with the aid of a small hand lens, or it may be subjected to any of the methods already described for the discovery of mange parasite in scrapings.

Differential Diagnasie. Other animal parasites causing pruritus of the skin include sheep ked (Melophagus ovinus), sheep lice (Trichodectee sphcerocephalue), maggots, harvest bugs, and ticks.

The sheep ked causes only slight annoyance, and is easily detected in the fleece. Sheep lice cause as severe trouble as sheep scab, and are differentiated by the recognition of their pre sence. Ticks may also cause itching, but are easily discovered. Maggots most commonly affect the croup or the base of the tail in young sheep, and when nests of them are touched the animal smacks the lips vigorously. The scurfy condition of the skin which is left by maggots often causes some trouble in differentiating from sheep scab. Harvest bugs (the larvae of the Trombidium holosericum) appear in the autumn on certain pastures and attack the under aspect of the body. They may be so numerous as to give a rusty appearance to the wool fibres. They are easily detected, and the orange - red hexapod larvae are easily distin guished from the sheep scab parasite.

Excoriation of the skin may result from dipping with too strong a dip, e.g. an arsenical dip. Parts of the skin become hard and necrotic, and patches become detached with a tuft of wool fibres attached. The fleece may thus appear somewhat ragged, but there is no itching.

A condition called has been observed in sheep in the wet season. The skin becomes very scaly and the wool dirty-looking, especially over the back. The sheep have rather a shaggy appearance, but there is no pruritus.

In some of the fine-wooled sheep, where the wool is thick and close, there is often a thick layer of yellow soft yolk at the base of the wool fibres. Sometimes such sheep react to scratching, but the skin is quite clean, and there are no parasites.

Last of all, an occasional sheep may show signs of pruritus without any signs of skin lesions. Such sheep have been spoken of as nibblers; they are not affected with sheep scab.

Treatment. Sheep scab in the British Isles is a scheduled disease dealt with under the Diseases of Animals Acts. An outbreak of the disease must be notified by the owner or shep herd and by the veterinary practitioner who is called in to see the animals.

Restrictions are placed upon the whole flock, although some of the animals may appear healthy. These latter are treated in the same way as the affected sheep, becaGse no one can be sure that they are free from sheep scab. The sheep must be confined to certain folds or enclosures, and must not be allowed to pass along or across highways.

They are then dressed with some parasiticide dressing. Previous to dressing they should first be clipped and the affected areas scraped to permit of intimate contact of the dressing. This is done not only in summer but also in winter. In -lamb ewes must also be dressed; any damage which may be done to the ewes is not due to the dip, but to the handling of the animals.

The dressings are applied usually in the form of dips. Various dips are employed, and are mostly proprietary preparations. They con sist of a variety of agents, including lime and sulphur, carbolic acid, creolin, arsenic, and tobacco decoctions.

Examples of some of the preparations used are: 1. Lime and sulphur dip, prepared in the same way as that described for mange in equines.

2. Arsenical dip: Arsenic. Pot. Carb.

Sulph. Sub. as lbs. ii.

Sapo Moll. lbs. iv.

to be dissolved in 10 gallons of boiling water and made up to 100 gallons. An arsenite of soda dip is also used, consisting of Arsenite of Soda 2i lbs.

Sulphur 5 lbs.

Water 100 gallons.

3. Creolin or cresyl in 2 to 21 per cent emulsion in water.

4. Carbolic Acid Dip: Acid. Carbolic. 3 quarts.

Sapo Moil. 5 lbs.

Water to 100 gallons.

5. Tobacco Decoctions. Standardized in America so that they contain not more per cent nicotine. This is necessary to avoid losses from nicotine poisoning.

A home-made preparation consists of 30 lbs. shag tobacco steeped overnight in 30 gallons of water, brought to boiling-point in the morning, allowed to simmer for a few minutes, strained through a sack, and left overnight. It is then made up to 100 gallons. The preparations must not be made too strong, and must be carefully mixed.

The dip used should be lukewarm when run into the dipping-tank. Many forms of dipping tank are used, and in all cases should be suffi ciently deep to allow of complete immersion of the sheep. In the dipping process the sheep should be kept in the tank for two minutes and completely immersed at least twice. Special attention must be paid to the head, neck, and tail to ensure that they are properly dressed. Afterwards the sheep are passed on to a strainer, and the excess of dip squeezed out, the excess draining off into the tank. Then the sheep is put into an enclosure free from fodder until it is dry. This is done to prevent poisoning from contamination of pasture or fodder with the dip which drips off the fleece or bodies of the sheep. Afterwards the animals are allowed into a grazing paddock. In a large flock dipped sheep may be allowed in contact with undipped provided (a) all sheep are dipped within a few days of each other, and (b) a second dipping of all sheep is carried out within eight days of the first. One dipping is not sufficient to bring about a com plete cure. Very few dips destroy the eggs (Shilston points out that the lime of sulphur may prove effective in this way), and a few adult parasites may survive. A second dipping must therefore be carried out within eight days of the first in order to prevent a second generation of the parasites being produced. A third dip ping within a month is also necessary for some cases, especially when they are advanced. The inner side of the ears should also be wiped out with the dip, or, as Henry recommends, a small quantity of 2 to 3 per cent warm watery emulsion of cresyl poured into each ear.

Where dipping-tanks are not available the sheep may be dipped in an ordinary tub filled with the dip, or hand-dressed.

Special precautions are taken to avoid losses from poisoning by arsenical dips. The sheep should not be dipped on a very hot day. They should be rested for some hours after being driven to the dipping tank before they are dipped, and they should not be driven long distances for twenty - four hours after they have been dipped. Affected sheep with large wounds should be carefully hand - dressed to avoid any danger of poisoning.

During the course of the treatment the sheep should be well fed.

Re-infection from the land on which the scabby sheep have been grazing is a minor point which should receive attention. Loose wool on the ground, on bushes or fences—manure in the folds should be gathered together and burnt. Rubbing-posts, fences, trees should be smeared with tar, lime-wash, or dip to destroy the acari. Experimental evidence has, however, shown that these places remain sources of infection for only a short time.

The sheep must be kept under restrictions until they are free from infection, the itching has ceased, the scabs have disappeared, the skin is normal, and the fleece growing well. A very careful inspection must be made before the sheep are regarded as cured. It would be well if restrictions are maintained for at least two or three months, because evidence of recurrence may only be shown in that time. The sheep may be only partially cured, and if restrictions are taken off the sheep farmer may sell his sheep in the market, and sheep scab may be distributed among other flocks.

Prevention. Sufficient powers have been ob tained in the British Isles under the sheep dipping orders to bring about a considerable decrease in the number of outbreaks, provided the orders are uniformly and rigorously carried out with the co-operation of flock-owners.

Sheep must be dipped on two occasions yearly, in the early summer after shearing and in the autumn. On the second occasion it is required that the sheep must be dipped twice at an interval of eight days. Movements of sheep are not permitted till this is done. Sheep scab is kept going through defects in the carrying out of the regulations. In the rounding up of sheep, some of them may be missed on large hill farms, and hence flocks in mountain districts are a frequent source of sheep scab. Dipping to be effective must be thoroughly carried out, and fines of sufficient severity imposed to ensure this being done. Owners of sheep should safe guard themselves against the admission of the disease to their flocks by first dipping all new sheep, and even their own sheep returned from the market, before mixing with the others on the farm. Trucks, sale-yards, enclosures at public fairs must be frequently disinfected.

2. Sarcoptic mange in sheep is very rare. In the British Isles it has occasionally been noted in Scotch black-faced mountain sheep.

It is due to the Sarcoptes scabiei var. ovis. In this variety the female is about 400µ long by 300µ broad, the male about 210 jk long by 160µ broad. This acarus according to Railliet may develop also on the goat, and it is only rarely transmitted to man.

This form of mange in sheep is not nearly so serious or so contagious as psoroptic mange.

Symptoms. The disease is accompanied by a severe pruritus which causes the animal to rub and scratch the affected parts. The affection is chiefly confined to the head (hence the term head mange applied to the disease). It does not affect the parts of the body covered with wool. It begins often about the lips and wings of the nostrils, sometimes the ears and eyelids, and thence extends to other parts of the head. Little papules first form on the skin, then the hair is cast off from over these papules. The skin becomes scaly and covered with light coloured or grey crusts of epidermis. The lesions, at first separate and irregular, become confluent. If the crusts are removed, a raw red surface is exposed. The disease is slowly progressive and causes loss of condition. It may be complicated with conjunctivitis. Ulcers and scabs are produced from the rubbing.

Treatment. The animals are treated on the same lines as sarcoptic mange in the horse, or with sheep dip at intervals of three or four days, until a cure is effected. The disease responds readily to treatment. Measures of isolation and disinfection are applied as in psoroptic mange.

3. Symbiotic or Chorioptic Mange in the Sheep.This is a comparatively mild affection and only sometimes requires attention.

Cause. It is caused by Chorioptes ovis.

The female is about 385 p. long by 240 p. broad, while the male is 310 p. long by 250 p. broad.

The disease is not very common, and only slightly contagious. Only about 1 per cent of the flock may be affected.

Symptoms. The disease affects the limbs almost solely, most commonly the hind limbs. There is some pruritus, the sheep sometimes rubbing or gnawing or stamping the limbs. The lesions begin in the hollow of the pastern and extend upwards. In neglected cases they may reach the scrotum or mammary gland. Sometimes it affects only the interdigital space and causes lameness. The skin on which the parasite develops is at first red and afterwards denuded of hair. Then greyish crusts form which vary in thickness and may present a wart-like appearance.

The parasite can easily be found in scrapings of the lesions.

Symbiotic mange is most marked during winter and tends to disappear in the summer months.

Treatment. The only treatment necessary is to pass the animal through a leg bath of sheep dip on one or two occasions, the second bath being given after a week's interval.

Mange in Goats 1. Sarcoptic Mange is the most common and serious form of scabies in goats.

It is due to the Sarcoptes scabiei var. caprce.

The female measures long by 342, a broad and the male 243 long by 188µ broad. This variety may be transferred to the sheep, ox, horse, pig, and even man. This disease has been observed in France, in Africa and Asia, but no case of it has been recorded in the British Isles. It is highly contagious and rapidly transmitted directly or indirectly through a herd.

Symptoms. The disease is accompanied by great itching. Lesions begin usually on the head and ears, thence pass to the neck, to the chest and abdomen, even the udder, and last of all extend to the limbs. They appear first as small nodules from which a serous fluid exudes and coagulates on the surface. The epidermis over the nodules forms a dry, scaly crust which is cast off with the overlying hair. The skin in the hairless patches becomes thickened, and scaly, rugged, cracked, and grey in colour. The patches afterwards coalesce. Numerous sarcoptes may be found in the crusts.

The disease if neglected becomes generalized, causes rapid emaciation, and even death.

Treatment is similar to that for sarcoptic mange in the horse. Measures of isolation must be adopted. Sheep-dip may be used as in sheep scab, but goats do not stand dipping well.

It may be more economic to destroy animals extensively affected with the disease than to treat.

2. Psoroptic Mange in Goats. Psoroptic Otacariasis in Goats. This disease is due to the Psoroptes communis var. caprce, a parasite similar to psoroptes of sheep. The disease set up by the parasite is highly contagious, and appears to be common only in certain districts or countries.

Symptoms. Otacariasis is confined to the inner side of the external ear. The skin there becomes covered with brown crusts, which may also fill up the opening. The parasites are present in abundance on and in these crusts. There is some itching and the animal sometimes rubs the ear or scratches it with its hind limbs. In some cases the affection induces some decrease in appetite; it seldom causes death.

Treatment consists in the isolation of affected animals, removal of the crusts from the ear, and the application by pouring or smearing of some parasiticide dressing into the ear, such as 2 to 2i per cent creolin or cresyl, or a watery warm emulsion of petroleum 1 part, cocoa nut oil 2 parts. One dressing may be sufficient to effect a cure.

3. Symbiotic or chorioptic mange in goats is not a common affection. It has been seen in Angora goats. It is due to Chorioptes caprce. The female measures 340, (2. long by 220 p, broad, the male 295 p. long by 295 p. broad.

Symptoms. The disease affects the side of the neck, behind the ears, on shoulders, back, and loins, and is accompanied by slight itching. There is an incomplete loss of coat, the skin becomes scaly, thickened, and wrinkled, and covered with yellow coarse crusts.

The disease progresses very slowly and is benign. The parasites are easily discovered under the crusts formed on the skin.

Treatment is as for sarcoptic mange.

4. Follicular mange in the goat

is rare. It is due to the Demodex folliculorum var. caprce. The disease appears in the form of small nodules about the size of a pea or slightly larger, which develop on the back and side. From the nodules may be squeezed out a cheesy pus which is composed largely of the parasites.

Mange in Camels Sarcoptic mange is the only form of scabies affecting the camel, dromedary, and other animals belonging to the CamelidT.

It is due to the Sarcoptes scabiei var. cameli.

The disease is very contagious, and easily transmitted by direct contact and by inter mediate carriers. Its spread is favoured by close associations of large numbers of animals, as when they are used for transport. It is more common and progresses most rapidly in the young and very old animals, and is often associated with debility and dirt. It may be transmitted to man.

Symptoms. A most marked symptom is pruritus, the animal frequently rubbing and biting the parts. The disease begins where the skin is thin, the under aspect of the abdomen and the inner side of the thighs, and it rapidly extends over the body to the withers, tail, and the limbs. First there appear small nodules from over which the hair falls out. The hair less spots extend and fuse and the skin becomes thickened, cracked, wrinkled, and scaly or covered with crusts. As the results of rubbing, ulceration of the skin occurs in places.

The disease progresses rapidly, causes wasting, debility, and even death.

Treatment is on the same lines as for sarcoptic mange in the horse. A parasiticide dressing commonly used consists of sulphur, salt, a, . lb., train oil 2 lbs. Abundant food forms an essential part of the treatment, and light exercise should be given. The natives sometimes treat the animals with daily sea baths. After immer sion in the sea, the skin of the camel is energetic ally scrubbed with a smooth stone. A popular dressing also used consists of tar 2 parts, water 1 part.

Mange in the Pig 1. Sarcoptic mange in the pig is due to Sarcoptes scabiei var. suis. This is the largest of the varieties of Sarcoptes. The ovigerous female is about 450 p long by 360 p broad, the male is about 300 p long by 250 p broad. This sarcoptes may be transmitted to man.

This disease is not common. It is slowly contagious and may pass through a litter of pigs. It affects young pigs most severely. Its progress is most rapid when it is associated with insufficient nourishment and debilitating diseases. It is often difficult to discover the source of infection among a herd of swine.

Symptoms. The first symptom noted is a most intense pruritus. The animals are con stantly rubbing themselves against posts, walls, their troughs, or along the ground or floor. They frequently scratch the abdomen and in side of the thighs. The parts of the body rubbed or scratched become red, denuded of bristles, and are marked by scratches or ab rasion.

The lesions begin frequently on the ears, along the abdomen, and inside of the thighs. They have the form of little firm nodules, which may be very numerous, but separate and present a little central point, and the skin around them is red. They soon become covered with small grey scabs or crusts and the bristles fall out. Later, the lesions fuse, become very large, the skin becomes thickened, dense, and leather-like, covered with thick fissured scabs, and form thick folds or cracks. The larger portions of the head, body, and limbs become involved, and the skin in addition to being thickened and wrinkled appears to be covered with a light grey powder. When the disease becomes extensive, the animal becomes very much emaciated and weak. The removal of the crusts exposes a raw red surface.

When the pigs are fed well and kept clean, the disease may spontaneously disappear in the summer after one, two, or three months. The progress of the disease is generally very slow. Sometimes it remains localized and does not interfere materially with the fattening process.

The diagnosis is easily made. The parasites can easily be detected in the crusts formed in the lesions. The condition is readily dis tinguished from eczema of sucklings and from the affection caused by lice (Hcematopinus suis).

Treatment is similar to that for sarcoptic mange in the horse. The thick crusts must first be removed by scraping and washing. Sulphur dressings are very efficacious. With lime and sulphur dip the deposit, as well as the liquid, may be used without ill effect. The disinfection of the styes must be carefully carried out.

Follicular mange in the pig is not common; it has been described on the Continent, Africa, and in America. It is due to the development in the hair follicles and sebaceous glands of Demodex folliculorust var. suis (Demodex phylloides). It is thicker than, the demodex of the dog. The female is 250 p long by 63 p broad and the male 220 p long by 55 p broad. The disease is only slightly contagious and does not affect the general health of the animal.

Symptoms. There is little pruritus. The lesions have the form of nodules or pustules which develop in the skin where it is fine, chiefly on the snout, neck, under aspect of the chest and abdomen, and inner side of thighs. The nodules are about the size of peas, some times pigmented and deep-seated, and often sur rounded with a red zone. The pustules may contain very large numbers of parasites, from 50 to 1000. Sometimes they rupture and leave large ulcers.

No treatment is adopted, as the disease does not interfere with fattening but affects the condition of the hide. It does not affect the suitability of the flesh for the food of man.

Mange in the Dog Sarcoptee mange is the most common of all the skin diseases in the dog.

The cause was first demonstrated by Gohier in 1814 and has since been described by Guth and Hertwig, Gerlach, Delafond, Megnin, and others. It is the Sarcoptes scabiei var. cans. The adult female is about 350 p long by 260 p broad while the male is about 210 p long by 150 p broad. Occasionally this parasite is transmitted to man, and according to Zurn, to the pig and horse. I have also observed a few cases of mange in the dog due to the Notcedres cati, probably due to infection from the cat.

Occurrence. Sarcoptic mange affects dogs of all breeds and various ages. I have seen the disease in puppies three or four weeks old.

Transmission. The disease is highly con tagious, is transmitted chiefly by direct contact with affected animals, but also to a lesser extent from infected litter, by introduction to infected kennels, by attendants, by clothing and brushes. The disease is commonly kept going in breeding and dealer's kennels, where the condition is fre quently referred to as eczema, and by dog shows. Animals frequently groomed and washed are not so liable to become infected.

Symptoms. There is marked pruritus. The dog frequently scratches itself with the hind or fore limbs, rubs its body against neighbour ing objects and bites itself. When the affected area is scraped, the dog makes vigorous scratch ing movements with the hind limbs. The intensity of the pruritus varies with individuals, is greater in older animals, and is most marked when the dog is warm.

The first part usually invaded is the head. The lesions there appear around the eyes, on the face, and the outer side of the ears. Then they develop along the under aspect of the neck, the under aspect of the abdomen and chest, on the hind and fore limbs, especially on the outside of the elbows and above the hocks. In severe and old-standing cases the disease involves the back and ultimately the whole of the body.

In the early stages the epidermis over small areas becomes roughened, lumpy, thickened, and scaly, and little tufts of hair are cast off. The patches are irregular and increase in size at the edges and by fusion. Little nodules about the size of a pin's head may sometimes be seen and felt. When the skin is unpigmented, it becomes slightly reddened, and a little dark spot may be seen on the centre of each nodule. This is most commonly noted on the abdomen and side of the chest. Occasionally small pustules about the size of millet seeds develop, especially on the abdomen. Later, the skin becomes scaly and large thin epithelial flakes are cast off or remain adherent to the overlying hairs which are not as yet detached. Where the skin around the eyes is involved and denuded of hair, the animal appears lemur - like. The eyelids may become thickened and slightly in turned, and symptoms of conjunctivitis result. In advanced cases the large proportion of the coat is cast off. On account of the scratching and biting, some areas of skin, especially over elbows, under abdomen and chest, and at side of head and base of ears, become reddened, moist, and ulcerated, and ultimately covered with dried blood and black scabs. As the disease advances, the dog loses condition, becomes emaciated and weak. The skin is greatly thickened and wrinkled. Even death may result from exhaustion. The progress of the disease is retarded by good grooming, frequent washing, and generous diet, but is hastened by debility, debilitating disease, such as distemper, and by bad hygienic conditions.

Diagnosis is made from the appearance and position of the lesions of the skin, the pruritus and the discovery of the parasite. The latter is carried out by the method described for mange generally. Scrapings are best taken as a rule from the outer side, and towards the tip of the ear and the front of the forehead.

Differential Diagnosis. The disease is thus differentiated from lice, the eggs and adults of which can easily be discovered (it must be remembered, however, that lice sometimes complicate sarcoptic mange), from attacks of the harvest bug, from the squamous form of follicular mange (in the latter cases there is a peculiar odour from the skin, pruritus is not marked, and the parasite is differentiated in scrapings), otacariasis (the disease here affects only the inner side of the ear. It may com plicate sarcoptic mange), dry eczema (many of the cases of which as diagnosed are really cases of sarcoptic mange), pruritus of the back and loins commonly seen in adult and old dogs.

Treatment is identical with that recommended for the horse. It is usually necessary to clip the dog all over. Sulphur, oil of tar, potassium bicarbonate and lard dressing as noted for the horse are extremely useful for the dog, and applied in exactly the same way. Attention is paid to isolation, changing and burning bedding weekly, and periodic application of disinfectants to the floor and walls of the kennels. In cold weather the animal must be kept warm, and in all cases must be fed well. Liquor arsenicalis given internally may be useful where the disease is advanced. In average cases a cure may be effected in a month if the treatment is thoroughly carried out.

Another useful dressing is Oil of tar.

Soft soap as 1 part.

Meth. spirit 8 parts.

This is applied every three or four days and three or four dressings are often sufficient. The skin, as the result of the application, be comes at first very red as well as scaly.

Petrol applications are good. Lime and sulphur dressings as recommended for the horse are used in the dog. Balsam of Peru 1 part, meth. spirit 5 parts, is also employed, is rather expensive, but is not so objectionable as the other dressings when applied at home to house dogs. Mercurial-and carbolic dressings must be avoided on account of the danger of poisoning from licking off the dressing.

After recovery the kennels are disinfected with boiling water or 2 per cent creolin or other reliable disinfectant, and the utensils, brushes, clothing, and collar boiled or immersed in some reliable disinfectant fluid.

Sarcoptic mange is also noted in foxes and other wild carnivora, and is similar in its appear ance to that disease in the dog. Destruction of the affected animal is often the most advis able method of eradication.

2. Otodectic or Symbiotic Mange in the Dog. (Otacariasis, Parasitic Canker of the Ear.)— This disease is due to Otodectis cynotis var. canis (Symbiotes auricularum) first noted by Hering in 1834, afterwards studied among others by Megnin and Nocard.

The ovigerous female is long by 310 pt. broad, the male 365µ long by 265µ broad.

The disease is noted in various breeds of dogs, including sporting dogs, setters, pointers. hounds, terriers. I have observed it most commonly in Pomeranians.

It is highly contagious and spreads rapidly from dog to dog by close association. Some times it is associated with sarcoptic mange.

Symptoms. The disease is confined to the ears. The affected animal frequently scratches and shakes the head. On account of the rubbing and scratching the hair is partly removed from the outer side of the ear and the side of the forehead, and some abrasions may result. The dog presses on the hand that rubs the ear. When the interior of the ear is examined, it will be seen that the skin to wards the depth is covered with a brownish semi-solid discharge across which little grey specks are moving. These are the parasites. The skin there is not reddened, painful, or ulcerated.

In some cases fits and rolling movements have been observed in affected dogs. In hounds, when exercising, fits were noted by Nocard as the first symptoms of the affection. Complica tions produced by the disease from the shaking of the head and scratching are ulceration of the edge of the external ear and othwmatoma. Deafness has also been noted. The itching may cause serious loss of condition.

Diagnosis. The parasite can, as a rule, be easily found in the wax-like material removed from the ear and identified under a low power of the microscope. The otodectes pass down wards as far as the tympanic membrane, hence are difficult to reach with a parasiticide dressing. Some of the parasites may leave the inside of the ear and appear on the surface of the skin in the neighbourhood, thus permitting of their easy transference to another animal.

Treatment. The affected animal must be isolated. The discharge in the ear is first softened with some solution such as methylated spirit (1 to 4 of water), peroxide of hydrogen, or soap solution, and then carefully removed with plugs of cotton-wool applied at the end of a penholder or a pair of forceps. This should be done every week. Then a parasiticide dressing is inserted into the depth of the ear, such as sulphur ointment, salicylic ointment (1-8), or mercury nitrate ointment 1 part, olive oil 8 parts; this should be applied every second or third day until the disease disappears. The outer side of the ear should also be dressed. Two per cent warm watery emulsion of cresyl may be employed. Nocard used a dressing of Naphthol B 1 part.

Ether meth. 3 parts.

Olive oil 10 parts.

The material is poured into the ear, and the latter is kept plugged with cotton wool for about ten minutes to prevent evaporation of the ether. Then the animal is set free. This treatment is carried out daily. The ether is a solvent for the cerumen and allows of the penetration of the naphthol B, which acts on the otodectes.

Follicular

Mange. Demodectic mange is one of the most serious and obstinate skin diseases of the dog. It is due to the Demodex follicu lorum var. canis.

This parasite was first found by Topping and described by Tulk in 1843. The female measures 390µ long by 45µ broad, while the male is about 230 f.‘ long.

It invades the hair follicles and sebaceous glands of the skin, where it may be found in all its stages. The anterior end of the parasite is usually directed downwards. From 20 to 200 may be found in one hair follicle. In invading these structures the demodex carries with it the Staphylococcus pyogenes albus, which is inocu lated into the tissues of the skin and sets up a dermatitis. In the pustular forms these cocci form small abscesses or pustules. The disease is fairly common, is met with in all breeds of dogs and is particularly frequent in bulldogs. It is quite common in Irish terriers. It may appear in a litter of puppies, but only one or two of them become affected. The disease appears in dogs during their youth, but is also seen in adults.

Follicular mange is only slightly contagious. It is only very occasionally that indubitable evidence can be brought forward of the trans mission of the disease from one dog to another. Attempts at experimental transmission have not been successful. Sometimes the disease appears in certain strains of dogs. Probably there is some special idiosyncrasy or suscepti bility inherited or acquired necessary for the development of follicular mange.

Symptoms. There is very little pruritus in this disease, but the dog frequently shakes itself. The skin usually gives off a characteristic sulphur-like odour. In some cases it is dark pigmented, while in others it is reddened.

The lesions often appear in the same positions as sarcoptic mange, but may develop on any portion of the body.

Two varieties are distinguished, pustular and squamous. In the squamous form the skin is usually pigmented; it becomes thickened and scaly in patches, and the hair falls out. When these patches are washed, little nodules over the hair follicles may stand out prominently. In a few cases the bare spots take on a circular form (circinate variety) which present some resemblance to the lesions of ringworm. The patches sometimes become very large, and a large proportion of the body is involved.

The dog may remain in fair condition, but the disease is chronic; it is less difficult to deal with than the purulent form. The diagnosis in this case is made by taking scrapings from the skin as in sarcoptic mange, soaking them in caustic potash or soda solution, and examining them in a thin film on a slide under a low power of the microscope.

In the pustular form the skin becomes reddened, even copper red, hot, and scaly in patches, and the hair falls out in tufts. A circular arrangement of the lesions is sometimes noted also in this form. Small nodules and pustules form over the hair follicles. These are at first about the size of pin-heads or a little larger, and the tops of the pustules are white or greyish in colour. From them a little thick, white or cheese-like pus may be squeezed out, which when examined in a thin layer on a slide under the low power of microscope will be seen to contain quite a number of specimens of the Demodex folliculorum. Sometimes the pustules increase in size and are transformed into large abscesses, which are bluish or purple on the sur face, are easily ruptured, sometimes rupture spontaneously, and give exit to a blood-stained pus. This pus contains few specimens of demodex, but in films from it staphylococci may be easily identified after appropriate staining. On account of the burrowing of this pus, the skin involved is transformed into a sponge-work.

The disease in these latter cases often extends rapidly over the body and limbs. The skin becomes red, moist, and thickened, and forms thick wrinkles or folds.

As the result of a general coccus infection a toxaemia is rapidly produced, the temperature rises to 103°-105° F., the dog becomes very dull and weak, feeds badly, and rapidly looses condi tion. It may become emaciated within a week, and death in some cases rapidly follows.

The diagnosis is made from the absence of pruritus, the smell and characters of the skin lesions, and by the discovery of the demodex on microscopic examination of the scrapings of the skin in the squamous form or the pus in the pustular form. The pustular form is thus dis tinguished from acne and the squamous form from sarcoptic mange, dry eczema, alopecia, and erythema.

The prognosis of follicular mange should always be guarded. The cases may be under treatment for three, six, twelve months or more, sometimes they appear to recover, but the disease often recurs when treatment is stopped.

Treatment is not hopeful. There is no specific treatment. Large numbers of methods and applications have been adopted from time to time; a few cases may recover, and the method then enjoys a brief popularity. It is difficult to reach the parasites on account of their deep position. If treatment is adopted, the animal must be fed well. Autogenous vaccines as recommended by Professor Mettam have yielded some successful results. Nuclein has been adopted in its stead and appears useful in some cases. It is given hypodermically in the pro portion of 1 minim per lb. body weight once a week.

The body or area affected is clipped, better shaved and washed, the pustules squeezed out in the pustular form, and the skin dried well. Iodine preparations in the form of ointments or liniments such as Tr. Iodi are often useful applied twice a week. The same preparations which are used for sa, rcoptic mange have been tried in follicular mange with varying results. Hunting recommends a dressing of— Creosote 1 part.

Liquor Potassas 2 parts.

01. OlivEe 14 parts.

applied every third or fourth day.

Almond used successfully a 2i to 5 per cent zinc chloride solution in water. After shaving, washing, and drying the affected area, the solution was applied daily with a rag or brush, and the pustules squeezed out as they appeared.

In very limited cases after shaving, a dressing of collodion and iodoform to the parts has been used with the object of asphyxiating the para sites, and success has been claimed in occasional cases. Injections into the dermis of 1 per cent carbolic acid around the lesions have been tried. Gmeinin recommends after clipping, washing, and drying the daily application of 01. Carui Alcohol 15, 1 part. 01. Ricini 15 parts.

and a weekly bath in a 1 per cent solution of potassium sulphide. A change of dressing is often beneficial.

Mange in the Cat 1. Notoedric mange, commonly called sar coptic mange. This disease is due to the Notodre, s cati var. cati (Sarcoptes minor) which was noted first by Gohier in 1813 and later described by Hering. The female is 210 p long by 150 p broad, while the male is 140 p long by 100 p broad.

The disease affects cats of various ages. It is rapidly transmitted from one animal to another. Sometimes it affects the dog, occa sionally the horse and man.

Symptoms. This disease is found most commonly on the head, sometimes the neck, rarely the paws. There is much itching. The cat often scratches; shakes and rubs the head. Frequently it injures the ears with its claws, causing abrasions, scratches, and ulcers. The disease often begins about the ears and forehead. Little nodules appear. Epidermic scales are heaped up, become agglutinated together, and form thick crusts. The fur is cast off in patches. The whole of the head and portions of the neck ultimately become involved, denuded of fur, and covered with thick crusts up to s inch thick, very firm and adherent, wrinkled and cracked. The eyelids become swollen, inturned, and conjunctivitis is set up. The animal has a most repulsive appearance, loses condition, becomes feeble and emaciated. If the case is neglected, the cat may die of the disease in four to six months.

The diagnosis is easy. The parasites, as a rule, are very numerous in scrapings of the crusts. The disease may thus be easily dis tinguished from lice or dry eczema.

Treatment is on the same lines as for sarcoptic mange in the dog. The animal must be isolated. The fur is clipped off from head and neck. The crusts scraped and washed off, and then ointment or liniment used as in the dog.

In advanced cases a cure is not easily effected, and it may be advisable to destroy the animal.

2. Otodectic Mange or Symbiotic Mange in the Cat. (Otacariasis, Parasitic Canker of the Ear).This disease is due to Otodectes cynotis var. cati. The parasite is slightly smaller than the variety found in the ear of the dog. It was observed first by Huber in 1860, and later studied by Megnin. It has occasionally been transferred to the dog. The disease is highly contagious, and is very common. It may pass rapidly through a cattery, and is most frequent in Persian cats.

The symptoms and treatment are as for otodectic mange in the dog. Nervous symp toms are not common.

In the Rabbit notcedric mange similar to that in the cat has been noted, and otacariasis due to Psoroptes communis var. cuniculi is quite common, and is similar to that seen in the goat.

J. F. C.

Mange or Scabies in Poultry 1. Leg Mange or Scaly of the Legs. This disease is due to Cnem, idocoptes mutans (Robin and Lanquetin, 1859).

The ovigerous female measures about 420 J.

long by 350 IL broad, while the male is much smaller, being 195 jA long by 125 IL broad.

The disease has been recognized for a long time, but the cause was only demonstrated in 1859 by Robin and Lanquetin. It is observed not only in fowls, but also occasionally in pheasants, turkeys, and partridges.

It is transmitted by contact, especially when poultry are crowded together. It is only slowly contagious, but if the affection is neglected it may spread through the whole of the members of a flock.

Symptoms. The disease is confined to the limbs. It is accompanied by a certain amount of itching; the fowl frequently scratches or pecks the limbs. The tarsi and the upper parts of the toes are particularly involved. The scales have lost their smooth, regular arrange ment. They appear rough and lumpy, and joined together by white powdery crusts. If these are carefully examined, little openings may be found which may be followed by means of a needle to the ovigerous female cnemidocoptes which have burrowed under the scales. These crusts are very adherent. When they are raised up, a red, bleeding surface is exposed. If the inner surface of a crust be examined with 'a lens, numbers of the female parasite will be detected under a thin, clear pellicle at the end of the little tracts which they have made. These parasites are quite immobile. The crusts are often crumbly, and appear quite spongy. Under the superficial crusts may be found the male and other stages of the cnemidocoptes, which are very active. The disease is very slow in its course, and may continue for six or twelve months.

Sometimes the bird becomes lame, unable to perch. Rarely arthritis of one of the joints may be caused, and even necrosis of one of the toes result. The fowl loses condition, ceases to lay, and in advanced cases to feed. Death occa sionally results.

The diagnosis is easily made from the appear ance of the limbs and the identification of the parasite after raising up one of the crusts.

Treatment. The affected animals should be segregated, and the floor and perches which they have used should be disinfected. The limbs should be thoroughly washed with soap and water to remove the crusts, then dried, and a parasiticide dressing applied. Any of the following are useful: sulphur ointment, lime and sulphur dip, kerosene emulsion as used in sarcoptic mange in the horse, or petrol 1 part, rape oil 5 to 10 parts. Two or three dressings at intervals of a few days if thoroughly applied will be sufficient to get rid of the disease.

2. Depluming Scabies (Feather Rot). This disease is met with in chickens and pigeons. It is due to a variety of Cnemidocoptes lcevis, recognized first by Railliet in 1885 in pigeons and in 1886 in poultry. The parasite is similar to the Cnemidocoptes mutans, and the variety found in the pigeons is slightly smaller than that observed in the fowl.

The disease appears to be highly contagious in certain outbreaks described.

Symptoms. This form of scabies affects the bodies of the birds and commences about the base of the tail or the thighs. Then it extends over the breast, back, and wings in patches. Scales accumulate round the base of the feathers, and the latter become easily detached. The bird often pecks the feathers out. Under the scales and even inside the quills the parasite may be detected. As a result of the loss of feathers bare patches are left and the flying powers of the pigeons are much depreciated. Rarely is there much loss of condition.

The loss of feathers is most common in the spring and summer.

Treatment is on the same lines as in the previous disease in birds. Acaricide applications are rubbed into the parts affected. Sulphur powders or lotions are sometimes used, and their use continued at short intervals for some time.

J. F. C.

skin, sheep, disease, body and parasites