Endosymbionts Alter Larva-to-Nymph Transstadial Transmission of in Ticks.

Maternally inherited endosymbionts inhabit a variety of arthropods. Some of them can protect the arthropod host against a wide range of pathogens. However, very little is known about the association between endosymbionts and pathogen susceptibility in ticks. The present study investigated the effect of endosymbionts on larva-to-nymph transstadial transmission of by ticks. Engorged female ticks were injected with PBS, ciprofloxacin or kanamycin. The offspring larvae were used to infest positive mice. Prevalence of among the nymphs in different treatment groups and its association with endosymbiont density in the larvae were analyzed. The results showed that the prevalence of in the kanamycin-treated group (63.9%, 95% confidence interval (CI): 52.8-75.0%) was higher than that in the PBS (23.6%, 95% CI: 13.8-33.4%) or ciprofloxacin-treated (25.0%, 95% CI: 15.0-35.0%) groups. This increased prevalence was associated with reduced density of -like endosymbiont but was not related to the density of -like endosymbiont. No direct evidence has previously been reported about the impact of -like endosymbiont on pathogen susceptibility in ticks. This study reveals that endosymbionts are potentially important defensive symbionts of which may influence the colonization or susceptibility of in the tick host.