Exploring ecological immunology of the Rocky Mountain wood tick (Dermacentor andersoni)

Beginning with work of William Trager in 1939, researchers have documented that diverse vertebrate species can acquire immunological resistance to ticks. However, most of the research on tick “immunobiology” has focused on tick salivary chemistry and the molecular details of host-tick interaction at the feeding site. Very little is known about the effects of natural anti-tick resistance on tick population dynamics. This laboratory study followed the development and reproduction of Dermacentor andersoni ticks on two cohorts of hosts – tick-exposed and tick-naïve. The host species represented those naturally used by D. andersoni, including the deer mouse (Peromyscus maniculatus), cottontail rabbit (Sylvilagus floridanus) and Holstein cattle (Bos taurus). The effects of host exposure on tick recovery, post-feeding weight, molting success and reproduction (fecundity) were determined. The data were used to develop a predictive model for the effects of host immunity on tick population dynamics. Overall, feeding on a series of tick-exposed hosts negatively impacted ticks. Fewer ticks were recovered, post-molting size was reduced, and adult females produced fewer eggs. Relative to ticks feeding on tick-naïve hosts, the reproductive output of ticks on exposed hosts was reduced by 40%. These data suggest the anti-tick immunological status of the natural host community could play a role in shaping tick population dynamics.