Authors

Discussion

Desert bighorn sheep (Ovis canadensis nelsoni) are a bighorn sub-species distributed in fragmented populations across the southwestern US. Parasites in bighorns may be influenced by the distribution of hosts, variation in susceptibility, or the distribution of vectors. We studied the effects of demographic and ecological factors on the seroprevalence of tickborne, bacterial parasite, Anaplasma sp. in DBHS. We performed competitive enzyme-linked immunosorbent assays on >1000 serum samples collected from Mojave Desert bighorns from 1983-2022. Then, we used generalised additive models to describe potential linear and non-linear relationships between infection risk and environmental, heath, and demographic covariates. Models representing yearly fluctuations with increasing recent prevalence and ecological conditions favourable to tick populations were strongly supported. Specifically, ecological conditions involving the low/high rainfall and low temperatures were associated with greater Anaplasma seroprevalence. These results suggest that environmental conditions relevant for tick ecology are structuring tickborne parasite prevalence with other studieswhere increased global spread and susceptibility to Anaplasma is seen/predicted. Given the link demonstrated between tickborne disease, year, and environmental conditions favourable to ticks, it is assumed that with climate change the distribution of Anaplasma in bighorns could shift. Continued monitoring is highly recommended.