Exploration of stable isotope analysis for tick host identification

Due to the problem of tick-borne diseases, there is a need to better understand the importance of different host species in maintaining enzootic disease cycles. We explored the utility of stable isotope analysis to identify the larval hosts of questing ixodid ticks. In laboratory experiments, we used Ixodes scapularis and two host species that are important in the Lyme disease system in eastern North America. First, we tested how effectively a short-term dietary tracer (¹³C in corn) was reflected in molted ticks. Second, we attempted to identify the host species (either white-footed mouse (Peromyscus leucopus) or eastern chipmunk (Tamias striatus)), based on the isotopic signature of the ticks that had fed on them. The corn isotopic signal was easily detectable in the ticks that fed on corn-diet hosts despite the brief feeding period (96h). However, we were not able to differentiate between flat Ixodes scapularis nymphs that had fed as larvae on mice vs. those fed on chipmunks. Isotopic signatures of fur from mice and chipmunks were also indistinguishable, probably due to the similar diets of these two species in the wild. We conclude that, while stable isotope analysis of ticks may not be able to distinguish between ecologically similar host species, it may be useful in sorting ticks to the level of feeding guild of the host.