Introduction Concepts in Bacterial, Rickettsial, Chlamydial, and Mycotic Zoonoses
International transmission of disease, changes in human societies, and emergence or re-emergence of infectious diseases, many of them zoonoses, are again altering the course of human history. Since human beings developed separately from other animals some 4 to 6 million years ago, the adaptation of the infectious agents to humans leads us to recognize that historically the diseases of humans are/were zoonoses. The prevention of human exposure to zoonoses has largely been the task of veterinary medicine. Massive programs, national and international, to eradicate bovine tuberculosis, brucellosis in food animals, and canine rabies have been successfully conducted or are in various stages of progress. Progress toward control of zoonotic diseases in the immediate future will continue to be products of human manipulation. The recognition of the bacterial etiology of cat scratch fever has been an advance in studies on the obscure zoonotic disease. Among the spirochetal zoonoses, leptospirosis continues to be a widely disseminated infection in both people and animals.