Entomopathogenic fungus treatment reduces gut bacterial diversity in Rhipicephalus microplus tick

Ticks are obligate blood-sucking parasites responsible for significant economic losses and concerns with human and animal health, mainly due to the transmission of pathogens. Entomopathogenic fungi have been intensively studied as an alternative and possible ally to synthetic acaricides in the integrated control of ticks. Here, we investigated how the gut bacterial community of Rhipicephalus microplus is shaped after Metarhizium anisopliae treatment and the tick susceptibility to the fungus after disruption of gut bacterial microbiota. Partially engorged tick females were artificially fed with pure cattle blood (negative control), or blood plus tetracycline (positive control). Two other groups received the same diet and were topically treated with M. anisopliae. The gut of ticks that did not receive the antibiotic and were treated with M. anisopliae exhibited lower bacterial diversity and a higher frequency of Coxiella. Shannon, Simpson, and Pileous diversity indexes indicated a higher diversity in the tick gut's bacterial community when R. microplus were fed with tetracycline and treated with the fungus. The antibiotic did not change the survival of ticks treated with the fungus in comparison to fungus-treated ticks with an unaltered gut bacterial community, suggesting that the micoacaricide action will not be impacted if the calf is under antibiotic therapy. Ehrlichia spp. were not detected in the gut of fungus-treated ticks, supporting the hypothesis that entomopathogenic fungi can affect the life cycle of tick-borne pathogens. This is the first report of the effect of an entomopathogenic fungus on the tick-gut microbiota.