A widespread family of pathogenic protozoa (Tripanosonsa) have eel-like, mobile bodies, with a delicate undulating membrane at one side running into a fine antenna at the tail. They are found mainly in the blood and animal fluids, but also in the tissues, and can live out side the body. They are found mostly in warm climates, but have no difficulty in surviving our North American winters when domiciled in a warm-blooded host, as in the case of the breed ing paralysis of horses, which has assumed a place in our studs. This demands castration of both males and females when affected and re manding them to work service by themselves. A progressive anamnia is common to all forms of tripanosomasis. They are largely carried from victim to victim by predatory flies. Hence 'they can be checked to a large extent by destruction of insects.
Larger Parasites.— These are usually large enough for recognition without the microscope. Like the microbes they are amenable to control or extinction in a district or country, thereby extirpating the diseases which they respectively cause. Each parasite must, however, be dealt with on the basis of its own genus and life habits.
Vegetable Parasites.— The cryptogams (non flowering) are allied to bacteria but larger, often quite visible to the naked eye. Fungi attacking the skin, hair, hair-bulbs and follicles are common in cattle, especially about the head and neck, showing as circular masses of scurf with loosening and dropping hair, leaving bare patches (ringworm). Microscopic examination shows fine filaments and spores, and the bare patches enlarge by extension around the edges. These are unsightly, but not deadly, and carp usually be checked by pulling out or shaving the hair and applying tincture of iodine or as alcoholic solution of bluestone, repeating this daily. Another filamentous fungus of a snowy whiteness (Fusariuni) attacking the skin of domestic animals (including cattle) is overcome by sulphur or coal tar ointment. Thrush of calves' mouths with formation of a filamentous, curd-like accretion, as in children, is to be treated by boric acid or chlorate of potash (powder or solution). The aspergillus of the air passages in mammals (including cattle) causing wheezy cough and breathing, fever and general disorder and an eruption on the bron chia, lungs, pleura, etc., at first as if sprinkled with water, but later with nodules and caseated masses filled with filaments and spores, and death as in acute tuberculosis, is to be met with antiseptics such as fumes of sulphur and alcohol burning in a close room till it causes cough, and repeated two or three times a day. A solu tion of bisulphite of soda may be injected into the windpipe. The walls of the building should be cleaned and thickly coated with a watery solution of bleaching powder.
Animal Parasites.---Two-winged flies (Dip tera), larva in wounds: The most prevalent and persistent enemies are the common house flies and near allies, which are not blood suckers. Without perforating stylet they suck off the scurf-skin so as to leave raw surfaces and make spreading sores. The horn fly is a familiar example of this. The maggot-like larva, like' those of the blood suckers, live in almost any decaying organic matter (animal or vegetable) that attracts by its fetid odor.
Suppurating wounds and sores attract them and the ravenous larva add to the sores in depth and width. These are particularly de structive in sheep infested with intestinal worms and scouring, so that the liquid discharges mat ting the wool make a special protection and feeding ground for the maggot. The blood suckers' are, however, the most irritating by drawing the blood through the stylet; they often transfer the most dangerous diseases, an evil that is not unknown in the case of the flies that suck only. Botflies pass their larval stage mostly subcutaneously in cattle in spring (in fall and winter they are usually, the gullet, being apparently licked in from the skin by the barbed tongue and swallowed). When numer ous they do much damage to health and hide, the loss rising to $15 a head. These grubs should be squeezed out and crushed in early spring to head off the next year's crop.
Mosquitoes and Small Black Flies deserve mention. Their bite is venomous and they may besides implant in the wound the germ of another disease from the blood of the last victim. It is common to cover drinking water by a film of kerosene to destroy their larva (wrigglers).
Fleas are common enemies and carry disease. Some carry larva of tapeworms to their next victims; others infections. The tropical bur rowing flea gets under the skin, forming a hatching nest and suppurating sore. The eggs, larva and pupa hide in furniture, clothing and even on filthy skin where they can find decaying organic matter for sustenance. Keep buildings scrupulously clean, boil clothing and use freely insect powder, creolin, laurel oil, tar water and even sticky paper to catch the offender in his leaps. Lice are among the most widespread and health-destroying pests. Cattle harbor two kinds, blood suckers and biters. Blood suckers prefer parts covered with long hair and best out of the way of the tongue (head, neck, back, tail). Itching leads to persistent rub bing, and hairless patches indicate the inva sion-areas. The safest remedies are weak tar or tobacco water, decoction of hellebore or stavesacre and naphthalin, though the latter will taint the milk. A second dressing is due in eight days to destroy the new crop hatched from the nits in the interval. Ticks and Mites are eight-legged insects (larva has but six legs), and form large classes, always injurious when attacking in numbers, which they do on the skin or in internal cavities. They develop through four successive stages: eggs, larva (hexapod), nymph (octopod) and mature. The larva attacks the mammal and lives on it until mature. Some ticks (Argus) generate a deadly venom and instil it into the victim. All produce some irritation and swelling where they bite. But they do most harm by trans ferring deadly infections and infestments from animal to animal, as in Texas fever, which long prevented the success of cattle industries in the South and created one of the most deadly epizootics when taken North. This last tick is now being exterminated in State after State in the South, though with imperfect pre cautions to prevent diffusion of other diseases, like anthrax, black leg, flukes., etc.