Lesions.—The lesions observed on post-mortem are remarkably slight and are out of all proportion to the severity of the symptoms manifested. The disease appears to start in the small intestines, especially in the lower portion, where the lesions are usually the most marked, but it also involves the large intestines, including the rectum. The mucous membrane may alone be affected, although usually in the long-standing cases the submucosa is also invaded and the entire intestinal wall is then much thicker than normal and the tissue infiltrated with an inflammatory exudate. The mucous membrane or inside lining membrane is markedly wrinkled or corrugated, showing large, coarse folds with more or less reddening or hemorrhagic patches or spots on the summits of the ridges, especially noticeable in the large intestines. The mesenteric lymph glands are usually somewhat enlarged and appear watery on section. The other organs do not appear to be affected except from the anemia present in the later stages of the disease.

Differential diagnosis.—The principal disease with which bacterial dysentery may be confused is tuberculosis, but the application of the tuberculin test will readily diagnose the latter disease, while no reaction will be noted in case the injected animal is suffering with the former affection. The disease may also be mistaken for the parasitic affections resulting from stomach worms (verminous gastritis) and intestinal parasites, especially uncinariasis, but a microscopic examination of the feces is necessary in order to establish definitely the diagnosis.

Treatment.—As with all other forms of infectious disease, it is advisable to separate immediately the diseased and suspected cattle from the healthy animals. The feces passed by the former animals should be placed on cultivated soil where healthy cattle will not be exposed to them, as the bacilli producing the disease are readily found in such manure. The stalls, stables, and barnyards should also be thoroughly disinfected, as has been described under "Tuberculosis," in this chapter, special attention being given to those places which have been soiled by feces. The administration of medicines has thus far been quite unsatisfactory, although treatment should be directed toward disinfecting the intestines with intestinal antiseptics, such as tannopin in 1 dram doses twice daily, and strengthening the animal by the use of stimulants such as strychnin in half-grain doses given twice daily hypodermically. Salol, turpentine, or subnitrate of bismuth in a starch or wheat-flour gruel may also give temporary relief, but the diarrhea is likely to reappear and cause the death of the animal. In all cases the feed must be carefully selected to assure good quality, and should consist preferably of nutritious dry feed.

NAGANA.

Nagana, also called tsetse-fly disease, is an infectious fever occurring chiefly in horses and cattle, characterized by alternating paroxysms and intermissions and produced by a specific flagellate protozoan (Trypanosoma brucei) in the blood. It is probably transmitted from animal to animal solely by the bites of the tsetse fly. This insect is something like a large house fly, and when it settles on a diseased animal, sucks the blood and infects its proboscis, it is enabled on biting a second animal to infect the latter by direct inoculation. This disease is found throughout a large portion of central and southern Africa, along the low-lying and swampy valleys. It has never occurred in the United States, nor is it known to be present in the Philippines, but its relation to surra and the possibility of its appearance in one of our island dependencies are the reasons for including a few remarks at this time.

Symptoms.—The chief symptoms in addition to the fever, which is usually about 104° to 105° F., are the muscular wasting, progressive anemia, and loss of power, together with the edema most marked about the head, legs, abdomen, and genital organs. The urine is yellow and turbid, and occasionally contains albumin and blood. There is paralysis of one or both of the hind legs, difficult urination and defecation, labored breathing, discharge from the eyes and nose, extreme thirst, and gradual extension of paralysis to other parts of the body. The disease runs a chronic course, lasting from three to six weeks in horses, and from one to six months in cattle. Besides these animals, the mule, ass, buffalo, antelope, hyena, camel, and dog contract the disease naturally, and sheep, goats, cats, and small laboratory animals succumb to artificial inoculation.

Lesions.—The spleen and lymphatic glands are enlarged. There are sero-fibrinous exudates in the body cavities, the liver is enlarged and engorged, heart flabby, and a catarrhal condition is present in the respiratory passages. Pathological changes occur in the spinal cord. The finding of the trypanosoma by microscopic examination of the blood will be conclusive evidence for diagnosis.

Treatment.—Treatment has not proved satisfactory. Quinin, arsenic, methylene blue, and other drugs have been used, but without success. Endeavors thus far made to produce immunity from this disease have likewise been unavailing.

CATTLE FARCY.

This is a chronic disease of cattle occurring in France and the island of Guadeloupe, West Indies. It is characterized by caseating nodular swellings, first of the skin and afterwards of the superficial lymphatic vessels and glands, finally proving fatal within a year by extension to the viscera. The swellings rupture and discharge a purulent yellowish fluid, which contains the causative organism. This affection, called farcin du bœuf by the French, resembles cutaneous glanders or farcy of horses, but is caused by an entirely different organism, the streptothrix of Nocard. Moreover, cattle are immune from glanders, and for this reason the name, unfortunately applied to this disease, should not lead to any confusion with the cutaneous glanders or farcy of horses. Although the disease has been described as occurring only in Guadeloupe and France, the possibility of its occurrence in American possessions warrants its mention in this chapter.