The Impact of Infection and Disease on Animal Populations: Implications for Conservation Biology

Abstract: The distinction between infection and disease may be subtle, and detection of disease in wild animal populations depends on the sophistication of sampling design and diagnostic techniques used in examining animal populations. The impact of infection on the host is dependent not only on the pathogenicity of the infection but also on the interactions between infection and other factors such as nutritional status and stress. In this paper I review mechanisms by which parasitic infections can influence the survival, reproduction, and movement patterns of infected individuals. I then discuss the implications for host populations, in particular with reference to the potential of parasites to regulate the abundance of host populations. The implications of infection and disease on host populations are then extended to demonstrate consequences on community structure. Difficulties associated with assessing the level of infection or disease in wild animal populations are discussed and used to account for the frequently held belief that disease rarely occurs in wild animal populations. Finally, the consequences of infection and disease for conservation biology are outlined. Disease is considered with regard to introductions and maintenance of genetic diversity. Emphasis is placed on the dangers associated with forcing animals into high‐density situations. High host densities lead directly to increased disease because of increased transmission rates, and also indirectly increase disease because of synergistic interactions between infection, reduced nutritional status of the host population, and increased stress all associated with high‐density situations. I recommend a surveillance program for monitoring prevalence or intensity in selected indicator age classes as a first step for preventing major disease problems in animal populations. I conclude that infection and disease will be an important determinant of the health and well‐being of animal populations, and as such must be considered in the design of conservation policy.