Further Exploration of Stable Isotope Analysis to Identify Prior Host in Ixodes scapularis

One of the most enigmatic concepts in tick-borne disease ecology is how to identify the prior host of a questing tick. The ability to do so would provide predictions to directly aid in controlling the spread of the many tick-borne pathogens, including the bacterial spirochete Borrelia burgdorferi, which causes Lyme disease in humans. We explored the application of a novel technique, stable isotope analysis (SIA), to identify the most recent host in molted Ixodes scapularis (black-legged tick). The common reservoir and feeding host, Peromyscus leucopus (white-footed mice; n=46), were trapped, infested with nymphal ticks, and fed restricted diets, simulating feeding guilds, to confirm previous findings regarding the temporal enrichment of δ13C and δ15N in molted adults. Over a feeding period of up to seven days, δ13C was found to be significantly higher in molted ticks that fed on animals on a corn diet than wild (p=0.014), standard (p=0.013), and meat diets (p=0.002), but was not significantly different in δ15N (Tukey HSD). To directly test the feasibility of SIA to identify prior hosts, we used isotopic data from multiple years of research to generate a k-means cluster analysis model using isotopic signatures from ticks fed on standard-fed and wild-fed hosts, organized by both feeding guild and species. We then tested the model using field-collected ticks. Seventy-two percent of field-collected ticks fell into the model's five 95% confidence ellipses. We propose the potential application of SIA to the identification of a prior host in questing ticks as an alternative or enhancement to DNA-based methods in the trophic ecology of tick-borne diseases.