The following are the chief Zygophytous parasitic diseases:—Thrush is associated with the growth of a minute filamentous fungus, the oidium albicans. It is common in babies, who are improperly fed, and in old people, or in persons exhausted by any chronic disease. Small white patches collect on the tongue and neighbouring parts, and these are often followed by the formation of minute ulcers. When it occurs in children, the food must be carefully attended to, and feeding bottles frequently scalded, etc.
Ringworm is due to the growth of a large spored or a small spored fungus (known under the names of Microsporon Audouini; Trichophyton megalosporon endothrix, Trichophyton megalosporon ectothrix) which attacks the skin. It is most difficult to eradicate when it occurs in hairy parts, as the growth penetrates to the roots of the hairs, and continues to live here long after it has been destroyed on the general surface of the skin. The fungus spreads on the skin in gradually enlarging circles, forming rings with a slightly raised margin. It is extremely contagious, being especially apt to spread in schools. The spores may be carried about by means of hats or bonnets, by gloves, towels, razors, and other means. The disease often remains undetected for some time; and many cases, especially where the scalp is affected, remain contagious after they have been apparently cured.
The removal of ringworm, as of all other skin parasites, is effected by some local parasiticide. Prolonged treatment, including the pulling out of diseased hairs, is required for ringworm of the scalp. A special cap should be worn, when the patient mixes with others.
Favus, or “scald-head,” is due to the growth in the skin of a minute fungus called the Achorion Schönleinii, which invades the same parts as those affected by ringworm, but differs in its mode of formation of spores; yellow cupped discs from ¼; to 1 ∕ 3 inch in diameter being produced. It is very rare in England, and almost confined to persons (especially children) who are kept in a filthy condition. It is a common and fatal disease in mice. The treatment is similar to that of ringworm.
Tinea versicolor is caused by the growth in the epithelial cells of the skin, of a fungus called the microsporon furfur, which, unlike the two last, does not invade the hair or nails. It forms light brown patches covered with a horny scurf, which gradually spread, until nearly the whole trunk may be covered. It does not attack children, and never affects uncovered parts of the body. It chiefly occurs in those who do not take frequent baths, and who perspire freely. It can be removed by daily washing with soap and water and rubbing with a rough towel, followed by the application of a weak carbolic lotion.
Animal Parasites.—Animal parasites are found on the skin or in internal organs or in the blood or lymphatic vessels. The following are the most common:—
The Acarus Scabiei is a minute animal not unlike a cheese mite, which causes the disease known as scabies or the itch. It is probably never more than 1 ∕ 77 of an inch in length. The female has eight legs, with terminal suckers on the four front legs and hairs on the hind legs. The male is smaller than the female, and in the adult condition the two hindmost legs have suckers, as well as the four anterior. It remains on the surface of the skin, while the female burrows deeply in the substance of the epidermis. At the bottom of the oblique burrow it deposits ten to fifteen or more eggs, which hatch in a fortnight and then commence similar operations on their own account. Scabies generally starts between the fingers, whence it rapidly spreads. The disease is acquired from some patient suffering from the disease, or by contact with his apparel. It may become very severe when suspicion as to its parasitic character has not been entertained. Formerly it was called “the seven years’ itch,” from the great difficulty in curing it before its true cause was discovered.
The irritation caused by the insect produces eczema, and this may be thought to be the only disease present, unless careful examination is made for the burrows of the insect.
To remove this parasite, first the skin is softened, the superficial epidermis is removed, and the burrows are laid bare, by the daily use of hot baths with soft soap, and subsequent rubbing with flesh towels. Then some parasiticide, such as the well known sulphur ointment, is rubbed into all the affected parts of the skin. A few days’ perseverance in this treatment usually suffices for a cure. The patient’s clothes and bed clothes ought also to be thoroughly purified by boiling or by steam disinfection or by baking in an oven; otherwise he may become re-infected.
The Larvæ of several insects have been found embedded in the skin. In the ox, the larva or bot of the gadfly produces a troublesome disease, a large boil being formed under the skin as the larva grows. This larva has, on rare occasions, attacked human beings. Rare cases are recorded where other larvæ have become developed in men, in all upwards of twenty separate kinds of insects having been recognized. The treatment consists in removing the parasite.