Genealogical Relationships Influence the Probability of Infection with Bovine Tuberculosis and Microgeographic Genetic Structure in Free-Ranging White-Tailed Deer

GENEALOGICAL RELATIONSHIPS INFLUENCE THE PR ILITU OF INFECTION WITH BOVINE MICROGEO HIC GENETIC STRUC IN FREE-RANGING WHITE-TAILED DEER BY Julie Anne Blanchong Zoonoses are of increasing importance to wildlife conservation and human health. It has become increasingly recognized that wildlife ecology plays a key role in disease transmission in wildlife populations. In domestic populations, contacts among individuals are controlled by humans and disease transmission is often density dependent. Unlike domestic animals, wildlife populations often have complex social systems in whch contacts among individuals are not solely density dependent, and can play an important role in the transmission and maintenance of disease. White-tailed deer (Odocoileus virginianus) in the northeast lower peninsula of Michigan (MI) are infected with bovine tuberculosis (Mycobacterium bovis) (TB). The practice of artificial feeding that brings large numbers of deer into contact likely facilitated the transmission of TB. Artificial feeding was banned in order to reduce contacts among individuals at artificial feeding sites and thereby reduce the risk of TB infection. White-tailed deer ecology may also play an important role in the probability of infection with TB. Deer have a complex social system in which females live in related groups (matrilines). The rate of contact among individuals within matrilines (relatives) is high relative to contact rates among individuals from different matrilines. Estimates of genealogical relationships were used to infer the role that white-tailed deer's social structure played in the risk of TB infection. TB-infected deer were significantly more closely related than were non-infected deer. Relatedness between pairs of TB-positive deer was higher than relatedness between non-infected deer independent of the occurrence of artificial feeding. The probability of TB infection was not random, but rather a function of genetic relatedness to TB-infected individuals. It can be inferred from these data that matrilines of deer likely serve as reservoirs of TB within the deer population. mte-tailed deer's matrilineal social structure would be expected to result in heterogeneity in allele frequencies among matrilines across space. Artificial feeding of the deer population in MI, however, results in the congregation of large numbers of individuals at artificial feeding sites. Molecular markers were used to characterize the impact of artificial feeding on deer spatial genetic structure in the northeast lower peninsula of MI. Spatial autocorrelation analyses indicated that when artificial feeding was occurring there was no significant relationship between the degree to which quadrats of deer were genetically differentiated and their geographic distance from one another. The aggregation of multiple matrilines at feeding sites likely homogenized spatial genetic structure. Following the ban on artificial feeding, there was significant heterogeneity in allele frequencies among groups of deer as a function of geographic distance. The significant microgeographic genetic structure that exists within the deer population following the ban on artificial feeding indicates that transmission of TB across genetically differentiated groups is likely to be limited.