While a well-marked case of glanders or of farcy is not difficult of diagnosis, there are many obscure cases which escape detection for some time. If a horse has a well-marked discharge from one or both nostrils, with characteristic chancres visible upon the mucous membrane of the septum nasi, and hard enlarged submaxillary glands in the intermaxillary space, it is not a difficult matter to diagnose such a case, and any horseman ought to recognize it. The same is true of a well-marked case of farcy. When the lymphatic vessels on the inside of a leg, especially a hind leg, are swelled and corded, with a chain of farcy buds along their course, some of which have gathered and broken, leaving a discharging open ulcer in the skin, it is quite evident that the animal is suffering from farcy.
A peculiarity of glanders seems to be a tendency for the symptoms to appear on the left side; in many cases of glanders the discharge and ulceration is in the left nostril, and the left submaxillary gland is enlarged; and in a large number of the cases of farcy met with it is the left hind leg that shows the lesions of the disease. In obscure cases of glanders or farcy the diagnosis is not always so easy, even for experts, and then other methods for determining the trouble have to be resorted to. These are the guinea pig test and the mallein test. The guinea pig test consists of inoculating one or two of these little animals with the discharge from a suspected horse’s nose, or from a farcy sore. If they should develop glanders it would be proof positive that the suspected horse had this disease; if they do not develop glanders it is not always positive proof that the suspected horse is free from the disease. Sometimes more than one test is necessary, or another method of diagnosis may have to be resorted to. This is the mallein test.
Mallein is a product made from cultures of the glanders bacillus analogous to tuberculin as made from cultures of the tubercle bacillus, and is used for testing horses for glanders much as tuberculin is used for testing cattle for tuberculosis. A horse infected with glanders will react to a mallein test in much the same way as a cow infected with tuberculosis will react to the tuberculin test. It is not customary in some states to kill a horse that reacts to mallein unless it shows some clinical evidence of disease. All horses that show clinical evidence of glanders or farcy in some states are killed by the state authority, and the law requires persons knowing or suspecting cases of this kind to report in writing to the chief of the cattle bureau of the state board of agriculture or to the inspector of animals in the city or town where the disease is believed to exist, except in some cities where the city board of health has full charge of glanders and farcy. Anyone selling, removing, transporting, or concealing a horse knowing or having reasonable cause to believe it has glanders or farcy is in most states liable to a heavy penalty.