Diseases of Animals Communicable to Man *

IN this paper I propose to deal with some of the diseases of animals which are communicable to man, to discuss some of the analogies and differences shown in these diseases, and the way in which they affect the different species. A study of the different ways in which a disease affects man with his highly developed thinking powers, and the various species of animals which have no thought for the morrow, but live only short, sometimes very short lives, whose highest ambition may be a meal, an automatic sleep and the excitement of an occasional fight or love affair, is well worth while, and produces points of value and interest. That is well recognised since comparative medicine is now a definite study. Through it our sphere of knowledge of disease as a whole has been definitely enlarged. By comparing the symptomatology, the sites especially affected in diseased conditions, immunity or susceptibility, in comparative medicine and pathology undoubted progress in the fight against disease has been made. I do not, however, propose to go into what might be termed the truly pathological or medical aspect of the disease problem. I propose more to deal with the better known diseases of animals communicable to man, first in so far as they manifest themselves in domesticated animals, how we try to control these diseases for the sake of the animals themselves, and the means we adopt to protect man against possible infection. The following diseases, indisputably communicable to man, will be dealt with: tuberculosis, anthrax, glanders, rabies, foot and mouth disease, brucellosis, salmonella infections, and certain parasitic conditions in man in which parasites require an animal host in order to complete their life cycle. TUBERCULOSIS. To none of us here is it necessary to emphasise the importance to man and to animals of that old and terribly powerful enemy, tuberculosis. Gladly, however, has it to be recorded that its ravages in man are lessening and that the mortality from the disease has been declining for many years. Is the assumption that we are at present at the end of a protracted epidemic of tuberculosis correct? There seems to be considerable evidence for that assumption. Tuberculosis as a disease stands in a category by itself, as it not only spreads from man to man, from animal to animal, and from animal to man, but in the last-mentioned case it does its deadly work …