CHAPTER III.. Ringworm.

RINGWORM.

The old term “ringworm” is still used to indicate a well-marked skin disease due to parasitic fungi which grow at the expense of the epidermis. Other names, such as dermatophytis and epidermophytis, have been suggested, to indicate the mode in which the parasite grows. The term dermatomycosis suggests a cutaneous vegetable parasite.

The dermatomycoses of the domestic animals are caused by fungi belonging to six distinct genera:—

Trichophyton (horse, ass, ox, dog, pig); Eidamella (dog); Microsporum (horse, dog); Achorion (dog); Lophophyton (fowl); Oospora (dog).

Ringworm is common in animals of the bovine species, but very rare in other domesticated animals, except, perhaps, the horse. It is caused by the growth of a parasite, Trichophyton mentagrophytes (Robin), of the genus Trichophyton, family Gymnoascea, order Ascomycetes.

The ascosporaceous form of reproduction is still unknown, but the mode of reproduction by conidia is characteristic. In cultures the mycelium is represented by growing filaments branching off at right angles, and by separate superficial aerial reproductive filaments of the conidian form. There is some reason for believing that these fungi may lead a saprophytic as well as a parasitic existence, i.e., that they can exist and multiply apart from the animal body.

Their vitality is marked. Various experimenters have transmitted the disease with crusts kept for eighteen months. Thin declares that in two and a half years the spores had lost all power of germination. They resisted immersion in water for two days, but were dead after eight days. Soft soap and 1 per cent. acetic acid kill them in an hour.

=Symptoms.= The disease most frequently attacks young animals and milch cows—very rarely adults or old animals. This peculiarity is very difficult to explain.

In calves, ringworm seems specially to attack the head, the neighbourhood of the lips, the nostrils and submaxillary region, as well as the throat and neck. It assumes the form of circular patches, over which the hair stands erect.

Gruby in 1842 discovered the parasite of tinea tonsurans, or herpes, and thus proved that the cutaneous lesions were not due to any constitutional condition, as was long thought, although dirt, bad hygienic conditions, and crowded stables favoured the spread of ringworm.

Direct contact between healthy and diseased animals and the transport of spores, by combs, brushes, etc., favour contagion. The disease may not only be conveyed from one animal to another of the same species, but from the ox to man, and, with somewhat greater difficulty, from the ox to the horse. Cases of transmission from the ox to the sheep, pig, and dog have also been recorded.

Mégnin in 1890 attempted to prove that all the trichophytons producing ringworm in animals do not belong to the same species, and gave the name of Trichophyton epilans to that usually found in the ox, because it causes absolute loss of the hair by growing in the follicle, whilst he named the parasite found in the horse Trichophyton tonsurans, because it only grows on the surface of the skin and in the thickness of the hair, without causing inflammation of the hair follicle and without invading it.

The epidermis soon undergoes proliferation, and becomes covered with crusts, which adhere to the hairs, gluing them together, and finally causing them to be shed, leaving bare patches the size of a shilling or a florin. The lesion extends in an ever-widening circle, until it attains, perhaps, the dimensions of a five-shilling piece or more.

The affected hairs break off level with the free surface of the skin, rendering the patches more apparent. White hairs are less affected, and some always remain projecting above the crusts, causing the patches, when on a white skin, to retain a certain amount of covering.

At first the crust is closely adherent to the skin, and, if forcibly detached, exposes the dermis, which is swollen and bleeding. Gradually the centre becomes detached, whilst the periphery, representing a more recent lesion, continues to adhere. The crusts then rest on a thin layer of pus, and the dermis, whilst still inflamed, is punctuated with numerous minute apertures, representing the roots of the detached hairs. The pus lifts the crust; gradually it dries up and forms superposed layers, which may or may not prove adherent to the parasitic products, and which form a new crust. The latter is purely inflammatory in character, and is left after the fall of the first. It no longer contains any parasites, at least within its deeper layers.

This second crust dries up in its turn, falls away or breaks up, leaving a smooth spot, over which the hairs again appear, either at once, or at least after a short period of desquamation.

The disease is accompanied by well-marked pruritus, more marked at the commencement and towards the end than during the intermediate period, but, nevertheless, much less acute than in scabies.

Ringworm may undergo spontaneous cure in from six weeks to three months. It is more obstinate in calves than in adults, and the want of grooming tends to increase its duration. If it extends over a large part of the body the disease may seriously affect the animal’s health, and the cases described by Macorps prove that where pruritus is violent it seriously affects the animal’s general condition.

The patches may finally become confluent and the disease extend over the whole of the neck, shoulder and back, or it may attack the entire body, leaving it practically hairless.

When the hair has been shed, the crusts and discharge seen at the outset disappear, and the bare spots are covered with a scaly coating, due to excessive production of epidermic cells.

According to Gerlach, such crusts are thicker where the skin is black, and often exhibit a greyish-white, fibrous, starchy appearance. On unpigmented portions of the skin, which are usually thinner, the crust is less dense, and is slightly yellowish. Gerlach failed to reinoculate the bare patches of skin left after a primary eruption of ringworm. Where the hair had again grown an eruption could again be produced, though it was usually of a feeble character.

In a second form of the disease, the spots may be of very small dimensions. The hair falls away, but there is no exudative inflammation, and no formation of crusts. In this second form the animals simply show characteristic circular bare spots about the head, neck, or shoulders.

=Causation.= The disease is due to the growth of germs on the skin of animals which are in a receptive condition. The parasite thereafter develops in the hairs, the hair follicles and the epidermis, causing lesions which vary according to the species.

At the present time three groups of ringworm are recognised as occurring on animals, Trichophytic, Microsporous, and Favus.

Clinically the trichophytons are divided into the T. ectothrix, which lives outside the hair, and both outside and inside the hair follicles; T. endothrix, which penetrates the thickness of the hair itself, rendering it brittle and easily destroyed; and T. endo-ectothrix, which both surrounds and invades the hair.

The study of artificial growths of these fungi will probably afford valuable information on the above points. In the ox the particular parasite is invariably the Trichophyton mentagrophytes, whatever may be the characteristics of the clinical lesion.

In France ringworm is particularly common in Auvergne and Normandy, where hygienic precautions are neglected, but cases may also be found throughout the country.

After affecting cows throughout the winter, the disease often disappears in the spring. Throughout the winter cows are kept in dark and often filthy sheds, where the parasite propagates rapidly, whilst in spring they are sent to grass, where the conditions are inimical to contagion.

=Diagnosis.= The diagnosis of ringworm seldom presents any difficulty. The appearance of the lesions (Fig. 266), their particular tendency to spread and contagious character, facilitate the diagnosis. They entirely differ from those of eczema or mange, and should any doubt exist, the slightest microscopic examination is sufficient to dissipate it. In ringworm in the ox the base of the hairs is covered with enormous numbers of spore chains, which do not extend into the depths.

To detect the parasites it is best to shave off a thin fragment of skin from the periphery of the patch, place it on a slide with a drop or two of 30 per cent. caustic potash solution, and heat it for a few seconds almost to boiling point. By applying a cover glass with firm pressure the epidermal cells are spread out and the parasites can be seen, especially around the roots of the hairs. Sometimes they form little dirty-yellow masses, consisting almost exclusively of spores.

When ringworm has attacked the entire surface of the body, it is much more difficult to distinguish from sebaceous eczema, and a microscopic examination or experimental inoculation may become necessary. Inoculation with ringworm material always succeeds with calves.

=Prognosis.= Ringworm is not dangerous in itself. In time it may disappear spontaneously, but when it extends over the whole body it may be dangerous. Owing to their bare condition the animals easily catch cold, while the epidermic proliferation is very great, and makes great demands on the animal’s bodily powers. Under such circumstances it is better to slaughter early.

Spontaneous recovery from small lesions may occur in two or three months.

=Treatment.= The patients should be isolated, and any brushes, combs, etc., with which they have been in contact must be disinfected.

The diseased areas should then be dressed with some fatty substance, to soften the crusts and enable them to be removed without injury.

Dressings are useless unless these crusts have been removed, for the spores are always in the deepest recesses and in the follicles, so that the drugs employed never come in contact with them.

Once the skin is cleansed, numerous chemical substances may be utilised, the solutions being applied for several days in succession. Amongst them may be mentioned tincture of iodine, oil of cade, 10 per cent. solution of sulphate of iron, and solution of perchloride of iron. Such drugs, however, must not be used for a long time, as they all attack the skin to some extent.

When the patches are small and well defined the following mixture proves very efficacious:—

Crystallised carbolic acid } Equal parts. Tincture of iodine } „ Chloral hydrate } „

Two or three applications generally prove successful.

Despite the natural activity of the spores, which are capable of germination after three months’ desiccation, some medicines are useful, although it is necessary, in order to judge of their effects, to wait for the renewal of the skin, hair follicles, and hair.

Where the disease is generalised this form of treatment is scarcely practicable, or at least it becomes more difficult.

Nevertheless, by dressing with soft soap the disease may be cured in a few months. The soap should remain on the skin for some hours and then be washed off, after which dressings of creolin, lysol, or chloral solution, etc., should be employed.

RINGWORM IN THE SHEEP, GOAT, AND PIG.

Little information regarding the dermatomycoses of the sheep, goat, and pig is available. Allowing for modifications due to the nature of the coat, the =symptoms= of recorded cases seem to indicate a close relationship with ringworm in the horse and ox.

In sheep suffering from ringworm, the wool is at first matted into small irregular tufts, which grow larger and more numerous. The coat appears felted together at various points. The neck, chest, shoulders and back exhibit crustaceous patches covered with branlike epidermal scales, and the animals suffer from marked pruritus, which causes them to rub and injure the coat.

Ringworm is very obstinate in the goat.

Two pigs described by Siedamgrotsky showed irregular, rounded patches, due to trichophyton, from 1 inch to 2 inches in diameter, reddish in tint, without exudation, but covered with abundant scales.

In the pig ringworm attacks the croup, sides of the chest, flanks and sides of the abdomen, but is commonest on the back and outside of the quarters. It forms red isolated patches, from 1 to 2 inches in diameter, covered with miliary vesicles, which in turn are replaced by brown crusts. The bristles remain unchanged, and are not shed or broken. There is no pruritus. Contagion from pig to pig occurs readily. The disease may be conveyed from oxen to pigs through the medium of litter removed from the cowsheds to the piggery.

Gerlach was unable to inoculate sheep or pigs with ringworm from the ox. Perroncito mentions a case of contagion from the ox to a lamb. Schindelka has seen sheep contract ringworm as a result of confinement to sheds previously occupied by oxen suffering from the disease.

Siedamgrotsky successfully inoculated two pigs and two sheep with ringworm from the horse and a goat with the bovine form of the disease. The two pigs inoculated two others by contact. Contagion from the goat to the ox was noted in the canton of Zürich in 1852.

Fuller particulars on these heads will be found in a series of articles by Neumann in the Revue Vétérinaire, January to June, 1905.

In 1876 Laillier communicated to a French medical society a letter written by Lespiau describing an endemic of trichophyton disease in the cantons of Céret and Arles-sur-Tech. Thirty-four persons, including twenty-eight children, were affected. A dog was first attacked and seems to have inoculated a pig, which in these districts often lives with the human family. The pig inoculated the human beings. A moist season appears to have favoured the development of the disease. The parts principally attacked were the head, eyebrows, cheeks, and neighbourhood of the genital organs. The subjects showed considerable pruritus.