Risky business: Relating probability of direct contact with disease risk

Background/Question/Methods

Chronic wasting disease (CWD) is a fatal, prion disease of cervids that was first detected in Alberta in 2005. Transmission of CWD occurs by direct contact with infected individuals and via contaminated environments. We investigate the seasonal effects of grouping patterns and landscape heterogeneity on direct, pair-wise contacts within and between sex-specific (same or mixed sex) groups of mule deer (Odocoileus hemionus) in central eastern Alberta. First, we establish criteria based on spatial-temporal movements of collared deer to define sex-specific group membership. Second, we classify whether sex-specific dyads of collared deer are in different groups and model the relative risk of a sex-specific contact occurring in a locale based on landscape characteristics. Third, we relate seasonal predictions of the spatial probability of contacts to the risk of deer being CWD-infected in an area based on hunter-harvest, CWD surveillance data.

Results/Conclusions

Our findings suggest that contact locations reflect seasonal patterns of habitat use by mule deer, where winter contacts occurred in open habitats while summer contact between male and mixed sex dyads occurred in cropland. We determined that contact probabilities of within and between-group male dyads in winter and between-group female dyads in summer were the best predictors of CWD risk in central eastern Alberta. Our results relate habitat specific, social behaviours between conspecific mule deer to potential routes of CWD transmission and contribute to CWD research that guides management strategies.