MANGE IN YELLOWSTONE NATIONAL PARK WOLVES: THE ROLE OF MICROSATELLITE VARIATION IN A NOVEL HOST-PARASITE RELATIONSHIP

Abstract

The grey wolf (canis lupis) was reintroduced to Yellowstone National Park (YNP) in 1995. Reintroduced wolves were selected for good health and low parasite burden. Upon introduction to the park, wolves were vaccinated for local diseases and they benefitted from low infection rates. The disappearance of this induced immunity initiated novel host-parasite relationships. This study examines one such relationship between the wolf and the sarcoptic mite (sarcoptes scabiei). Infection by s. scabiei leads to sarcoptic mange, which is characterized by inflammation and hair loss. Inflammation is the result the host’s immunological response to mite infestation. Scratching and biting of the inflamed epidermal regions leads to hair loss. Wolf immune systems must balance resistant and tolerant mechanisms to maintain fitness during mite exposure without producing detrimental immune responses. Prior studies have associated genetic variation with optimization of the host immune response. Variable canine genes associated with resistance to mange are therefore subject to new selection pressures from s. scabiei. This study uses 26 microsatellite loci from intergenic and intronic regions of the canine genome to test for an association between disease progression and genetic variation. This study uses simple regression and multiple regression models to analyze the effect of microsatellite allele length and heterozygosity on the wolf’s response to mange. Certain microsatellite loci show a statistically significant relationship to the severity and duration of mange infection. Allele length of microsatellite loci was associated with disease outcomes, but not heterozygosity. This indicates that attenuation of the wolf immune response to s. scabiei happens in part through the contraction and expansion of non-genic microsatellite regions.