Ecologists often seek to understand how organisms are distributed in space and time in response to the environment, climate, and other species. However, parasite transmission between hosts is rarely observed and particularly challenging to study in the field. Moreover, sampling live hosts is often both invasive and logistically infeasible. We sought to assess the relative risk of environmental transmission of the juvenile life stage of the winter tick, Dermacentor albipictus, to four species of ungulate hosts in Yukon and to determine the likely contribution of new host species to regional winter tick dynamics. Data from 70 wildlife trail cameras were analyzed using spatial recurrent event models to estimate intensity of habitat use by a resident cultural keystone species, moose (Alces americanus), introduced elk (Cervus canadensis), feral horse (Equus ferus caballus), and mule deer (Odocoileus hemionus), that are naturally expanding their range in this region. Cameras were sited at locations with known larval winter tick activity and the resulting data analyzed across key periods of winter tick transmission to, and detachment from, hosts.
The frequency of use of both winter tick-infested and tick-free habitats varied in space and time among all potential host species. During the tick transmission period (Oct-Dec), tick-present areas did not appear to have a negative effect on the expected number of use events per week by elk, horses, and deer, indicating that these potential hosts are at higher risk of collecting larval ticks due to inherent habitat preferences. Moose were not detected during the tick transmission period and only infrequently during the tick detachment period (Mar-May) across the study region. Our results suggest that the winter tick-host system in this area of Yukon is most likely maintained by just one or two introduced host species (elk, horse), whose relative risk of infection is greatest given their use of tick-infested habitat over time. Our study illustrates how non-invasive, camera-trapping methods may be used to infer host-parasite interactions in space and time and when prioritizing wildlife species for parasite surveillance in future.