On zoonoses and their relevance 

 to paleopathology 



Don R. Brothwell 



During the process of preparing this paper, at least one 

 national newspaper called attention to the concern of the 

 British health authorities about a sheep disease which is at 

 present affecting pregnant women. In farming areas in partic- 

 ular, infection of sheep with a Chlamydia species not only 

 causes abortion in sheep, but has posed a health problem for 

 many women living near farms. It is interesting that this same 

 genus of microorganism causes specific human conditions of 

 the eye and lymphogranuloma venereum, although closely 

 related parasites in rodents suggest that these are again zoo- 

 noses, but with a longer history. 



What is zoonosis? One might have expected international 

 agreement on such a commonly used term, but in fact this is 

 not so. Zoonoses can simply be taken to be "diseases and 

 infections transmitted naturally between vertebrate animals 

 and man" (White and Jordan 1963). Alternatively, it can have 

 the broader definition of a "disease of animals — as opposed 

 to disease of man" (Fiennes 1967). Halpin (1975) believes 

 the true meaning to be "a disease or infection shared by both 

 animals and man." The implication here is that parasites can 

 be shunted in both directions, and indeed it is known, for 

 instance, that humans can act as a reservoir for Myco- 

 bacterium bovis and reintroduce this parasite back into 

 tuberculosis-free livestock. 



Perhaps the right emphasis is achieved by regarding hu- 

 man groups as participants in "infection chains" (Schwabe 

 1964), sharing certain infectious diseases with other genera 

 for varying periods of time. As Aristotle and his world was 

 aware of rabies as a zoonosis and even some Third World 

 tribal groups understand certain disease links between spe- 

 cies (the Masai realize that anthrax can be caught from con- 

 taminated meat), the concept is likely to have had a long 

 history. Without doubt the implications of zoonoses are rele- 

 vant even to our study of the prehistory of disease. For we all 

 too often consider human diseases in relative isolation (other 

 than for the intrusive parasites themselves). So the zoonoses 

 provide a focus for considering a continuum and evolution of 

 diseases beyond the species level. 



Although more than one classification of the various zoo- 

 noses has been elaborated, I do not wish to expand on the 

 alternative classifications here. These are fully discussed in 

 Schwabe (1964). My concern is to emphasize, in general 

 overall terms, the importance of viewing human groups and 

 their patterns of disease against an environmental back- 

 ground in which there is "movement" of parasites over time 

 through to the hominids. This mosaic of disease has a prehis- 

 tory as long as that of the vertebrates. From our point of view, 

 diseases are linked to the hominids in the following ways:(a) 

 by adaptively following along the course of primate-hominid 

 evolution;(b) by direct links between hominids and other 

 vertebrates; during the Pleistocene, there must have been 

 profound changes associated with greater reliance on hunt- 

 ing;(c) the closer association of human groups with other 

 species, especially domestic livestock, as a result of agricul- 

 ture;(d) the development of high-density urban populations, 

 with enhanced or continued association with other verte- 

 brates;(e) the elaboration of cultural factors, from the keep- 

 ing of pets and the long-distance transportation of exotic 

 animals, to the improvement of hygiene. 



Has this kind of overall speculation about zoonoses any 

 great relevance to paleopathology? I think it has, and there 

 seems little doubt that anyone concerned with general issues 

 of past disease ecology, or paleoepidemiology, should not 

 ignore this subject. While zoonoses have received attention 

 at meetings for over a century, and the first London meeting 

 of the international Congress of Hygiene and Demography 

 devoted a special section to it (Shelley 1892), anthropology 

 and archeology have been remarkably slow to appreciate the 

 importance of disease in biological and environmental stud- 

 ies. Indeed, all aspects of the environment may be relevant to 

 a reconstruction of suitable habitats for disease vectors. For 

 example, the survival of the disease-carrying tick Ixodes 

 ricinus in Europe depends on moisture and vegetational 

 cover, and it is interesting to speculate on changes in its 

 distribution with the spread of farming and expansion of 

 permanent and well-managed pastures (detrimental to these 



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Zagreb Palenpalholojty Symp. 1 988 



