Cattle Scabies

292 Cattle Scabies IRWIN H.ROBERTS AND N. G. COBBETT SCABIES is a contagious skin disease laying eggs. The entire cycle takes no caused by minute parasitic organisms more than 12 days. known as mites. It affects cattle of all Psoroptic mites attack the hairy parts ages and breeds. Sometimes it is of the body. They generally begin an referred to as scab, mange, or barn infestation over the withers, but some- itch. Similar infections attack other times also over the back or around the classes of livestock, wild animals, and tailhead. The mites prick the skin to birds, as well as people. obtain food. Tissue fluids ooze from Scabies, the medical term for which the wounds. After many mites have is acariasis, is common throughout the fed, the fluids dry, become mixed with world. It generally causes a severe in- tissue debris, and form scabs. flammation of the skin and itching. The lesions made by the mites spread Mites are related to ticks, spiders, as the parasites increase in number and scorpions, and are not true in- and involve large areas of the back and sects. Unlike insects, adult mites have sides. The condidon may advance over 4 pairs of legs instead of 3. They are practically the entire body if it is not wingless and usually are so small that checked. As the disease worsens, hair they can barely be seen with the naked falls out, and the body is covered with eye. thick, rough crusts. The skin becomes Of the thousands of known kinds of hard and thickened and it takes on mites, four are commonly parasitic to a corrugated look. cattle. Each of the four produces a different type of skin reaction. Two, CHORIOPTIC SCABIES occurs chiefly in known as psoroptic and chorioptic farm herds. It is widely distributed mites, live on the surface of the skin from the Atlantic coast to the States and cause a condition generally spoken east of the Rocky Mountains. A per- of as scabies. Two others, the sarcoptic sistent disease, it spreads slowly over and the demodectic mites, burrow the infected animal, but may travel under the surface of the skin and pro- from one animal to most of the animals duce mange. in a small herd in a year. The mite responsible for it is Chori- PSOROPTIC SCABIES, also known as optes bovis var. bovis. Like the psoroptic common scab, was prevalent in range mites, it lives on the surface of the skin. cattle in the Western States until about Its life history is similar to that of the 1938. It is caused by Psoroptes equi var. psoroptic mites, and it obtains nourish- hovis, a whitish mite, which can be ment in the same way. seen as a minute speck if it is placed Chorioptic scabies mites do not usu- against a dark background. It spends ally produce such extensive and prom- its entire life cycle on the animal. inent lesions as psoroptic mites, and Female mites deposit about 20 eggs on the injury they cause is less severe. the surface of the skin. The eggs hatch This form of scabies usually begins on in about 4 days, and minute larvae, the inside surface of the hind legs in each with three pairs of legs, emerge. the fetlock region, high on the rear These molt, or shed their skins, become surface of the udder or scrotum, or nymphs, molt again, become adults, on the inside of the flanks and thighs. reach maturity, and mate, and the The infection is known commonly as females of the new generation begin leg or foot mange. Cattle Scabies 293 Chorioptic mites produce an infec- eggs, which are almost as large as she tion by piercing the skin. The serum, is. The mature female usually stays in or tissue fluid, that exudes from this the burrow her entire life. The mite wound forms a minute blister. The begins laying eggs within a few hours mites multiply, the blisters unite and after starting her burrow. She deposits break, and their dried contents slowly the eggs every second or third day for build up into little scabs or crusts, as long as 2 months, stringing the eggs beneath which the skin is raw and out behind her as she lengthens her bleeds easily. burrow. She usually lays about 30 eggs The mites live in colonies under the in her lifetime. scabs. If a scab is removed with the The eggs hatch in about 5 days, fingers and placed on a dark surface after which the larvae leave the chan- in some warm place, the flesh-colored nels. They move about on the skin, mites will be seen, just about visible where they molt, become nymphs, to the naked eye, crawling rapidly and molt again to become adult males away in every direction. A reading or immature females. glass will help one find the parasites. Larvae and nymphs can be found in The mites from one small lesion the skin follicles. The adult males and spread after a few months to various young females make short burrows, in places about the hindquarters, estab- which they remain briefly. Mating lishing new colonies. The disease takes place on the skin. After mating, eventually may involve large portions the fertilized female burrows into the of the underparts, side, and back. skin to lay her eggs and start a new Sometimes the disease progresses so generation. The full cycle takes about slowly that scabs the size of a half 14 days. dollar, in various places about the A female theoretically could have hindquarters, may go unnoticed for a more than a million descendants in year or two. six generations, or go days. In highly susceptible animals, the When huge numbers of mites are condition may eventually spread to present on an animal, they are rather the underparts of the body, forward easily found under scabs, which can along the midline, around the outer be removed from the skin with the surface of the legs, and over the sides fingers or a dull knife edge. Their and back. burrowing habits in the early stages make it rather hard to find the mites. SARCOPTIG MANGE used to be con- However, skin scrapings made with a sidered of no economic importance in knife edge, deep enough to draw the cattle in the United States. By 1950, blood, will usually disclose the active however, 30 percent of the scabies- parasites. They are barely visible, but infested cattle in one Northeastern a reading glass will show them as State were infested with the sarcoptic moving specks if they are placed variety ot the disease, either alone or against a dark background. in combination with chorioptic scabies. Sarcoptic mange mites may produce As in chorioptic scabies, sarcoptic lesions anywhere on the body of cattle. mange often is found in purebred They appear to adapt themselves best herds and may be spread about the in locations where the skin is thin and country with the sale of breeding tender and the haircoat is thin. They stock. are commonly found high on the rear The mite that causes it is Sarcoptes surface of the udder or scrotum, and scahiei var. bovis. It spends its entire life on the rear and inner surfaces of the cycle on the body of the animal. The thighs, where the lesions they produce mature female makes long channels may exist side by side with those within the horny surface of the skin. caused by chorioptic mites. In the burrows the female deposits her Sarcoptic mites may also start infes- 294 Yearbook of Agriculture 1956 tations at the root of the tail or the ance during the fall, winter, and lower parts of the neck and brisket. spring. Owners have observed that the Before many months a large portion of lesions appear to clear up and disap- the body surfaces may be involved. pear spontaneously when an infested Itching is more intense than in other herd is turned out to pasture. Some forms of scabies or mange. mites, however, survive the summer, Shortly after the onset of the disease, and infestations almost invariably be- hairless spots appear, dandruff is come serious again when the weather abundant, and the skin may become gets cool. thickened, hard, and covered with Often there is much less change in crusts or scabs. The skin may crack the status of infestations on animals and ooze blood and pus. It may bleed that remain housed or in close contact where the scabs become detached. with each other during the summer. The disease may spread rapidly—from The presence of oils in the skin, the in- one cow to practically every animal creased activity of skin glands, and the in a dairy barn in a winter. improved nutritional state of the animals when they are on pasture may be DEMODEGTIG, or follicular, mange of responsible for the diminished activity cattle is widespread in the United of the mites in summer. States, but few cattlemen are aware of Demodectic mange shows no re- its existence. sponse to the change of seasons. The It is caused by the mite DemodexJolli- nodules almost invariably discharge culorum bovis, a microscopic, cigar- their contents or are reabsorbed on shaped, sluggish organism that lives the body, regardless of time of year. within the skin. The lesions in the skin take the form THE SPREAD OF SCABIES and mange of nodules, usually in the region of the mites from one animal to another neck, shoulders, and brisket, and some- nearly always takes place through times on other parts of the body.

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