Climate differentially impacts ticks infected and uninfected with Borrelia burgdorferi.

Climate change continues to alter the behavior and distribution of species worldwide, with major ramifications for the transmission and risk of infectious diseases, including those caused by zoonotic vector-borne pathogens. This study explores the potential implications of climate change for one such pathogen, Borrelia burgdorferi (the causative agent of human Lyme disease), in Ixodes pacificus ticks of the far-western United States. Nymphal tick infection prevalence and density are compared against several metrics for climate, while also accounting for habitat fragmentation, mammalian species richness, and rodent tick burden to eliminate confounding variables. Findings show that climate extremes, such as those forecast with climate change, correlate with a reduction in B. burgdorferi prevalence in nymphal ticks despite nominal impacts on uninfected tick density, contrasting traditional hypotheses that these changes will increase vector-borne pathogens.