At the present time effective suppression of infectious animal diseases is obtained by a combination of control measures, which consist largely of sanitary procedures, eradication of carriers, and of attempts to fight the infection by aiding the animal's natural resistance by augmenting or exciting the body defenses. These aids consist of biologics which are of immense value in preventing and arresting the progress of disease, the use of drugs and antibiotics which are highly useful in halting some disease processes, and selective breeding which could prevent or reduce the severity of incipient infections. Genetics is the last of the 3 means of combating infectious animal diseases to be used consciously toward that end.