Hog Mange

N. G. COBBETT.

MANGE in hogs is a contagious skin disease caused by mites tiny, insect-like parasites that live in the skin.

Two kinds of mange affect swine. Each is caused by a different mite. The more common kind is known as sarcoptic mange. Demodectic, or follicular mange, is less common.

The mites spend their entire lives on infested swine. They produce wounds or lesions in the skin as they take food from the tissues and blood of the host.

Each kind of mite has distinctive habits in its feeding and other activities and causes peculiar skin lesions.

THE SARCOPTIC MANGE is caused by Sarcoptes scabiei var. suis. They are tiny, round, whitish mites, just visible to the naked eye. The mature female is about one-fiftieth and the male about one-sixtieth inch long. The bluntly rounded head is as broad as it is long and is equipped with strong mouth parts designed for piercing the skin tissues. Mature mites have four pairs of short, thick legs.

They penetrate the outer layers of the skin and excavate shallow burrows, or galleries, in which the females lay their eggs. Each female may deposit 10 to 25 eggs during the egg-laying period, which probably lasts 12 to 15 days. After that she dies in her burrow.

The eggs hatch in 3 to to days. The young mites escape from the burrow and excavate new burrows of their own, in which they begin laying eggs when they are about 10 or 12 days old.

As the average period of incubation is 4 days and the average period after hatching until egg laying begins is 11 days, a new generation of mites may be produced every 15 days or so.

Lesions of sarcoptic mange may start on any part of the body, but usually they appear first on the head, around the eyes, nose, or ears. They are often present inside the ears and may be overlooked when the hogs are examined or treated for mange. Since infested swine scratch the first lesions with their hind feet, the disease usually appears next on the hind legs.

The lesions grow gradually and may spread over the whole body.

The feeding and burrowing of the mites then cause irritation, itching, inflammation, and swelling of the affected tissues. Nodules and vesicles appear over and around the burrow.

The vesicles break and discharge serum, which dries into hard granules, or scales. The hair over the lesions stands erect, and much of it drops out.

As these mites multiply and the disease advances, increasingly large areas become involved. The intense itching causes the animals to scratch and rub the affected parts vigorously.

This mechanical injury to the skin causes it to become thicker, wrinkled, hairless, and crusted over with hard, granular-appearing scabs, which remain firmly adhered to the underlying skin and are difficult to remove.

The frequent rubbing of the hard scabs has a sort of polishing effect on them and gives them a slightly glistening, silver-gray appearance.

Occasionally the heavily scabbed-over areas are broken by movements of the animal, and blood and serum ooze out of the cracks. Then the lesions are moist and may be reddish or yellow.

SARCOPTIC MANGE SPREADS by direct contact with infested swine.

The disease can be transmitted to people and to some other animals, but the mites usually live only a limited time on such new hosts. It is advisable, however, to bathe and change clothes as soon as possible after handling mangy swine.

Because the sarcoptic mites live in their burrows, they do not spread to other animals so rapidly as the varieties that live solely on the surface of the skin.

Because of the hog's habit of resting and sleeping in close contact with one another, however, the disease frequently makes great headway in herds of swine. The infestation spreads most rapidly among swine kept in crowded or unclean quarters, especially when the animals are undernourished and exposed to cold or under other circumstances that tend to lessen their vitality.

The spread of the disease is not limited to any one season, although healthy hogs become infested less often during the summer and the mange lesions are usually less severe in summer, especially if the swine have access to good pasture.

Hogs of all classes, ages, and conditions are susceptible to sarcoptic mange but usually the disease is less severe and spreads less rapidly in well-fed, well-kept, vigorous animals than in weak, unthrifty swine.

Visible lesions of mange may develop in 14 to 45 days after exposure to the disease, or a much longer time may elapse before the exposed hogs show typical lesions. Cases of mange may become generalized in 6 weeks, but sometimes the lesions take much longer to spread to any great extent.

One or more attacks of the disease do not confer immunity. After the disease has been cured, the animals may become reinfested by contact with mangy hogs or possibly by confinement in quarters where infested swine have recently been kept.

While practically all cases of hog mange seem to originate from contact with infested animals, the possibility that swine may contract the disease from infested premises should not be overlooked.

Although the mites do not reproduce except when on the bodies of animals,they can live for 2 or 3 weeks when removed from hogs. They may live much longer if conditions are favorable. Therefore swine of questionable origin or swine that have been held in commercial yards or transported in commercial carriers should be regarded as potential carriers of sarcoptic mange. They should be held apart and treated before they are added to clean herds.