D3229: Biological control agent changes the gut bacterial diversity of Rhipicephalus microplus ticks

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 studied as an alternative strategy for tick control that can be used combined with synthetic acaricides. Here, we investigated how the gut bacterial community of Rhipicephalus microplus is shaped after Metarhizium anisopliae treatment. Partially engorged females were artificially fed with pure bovine blood, or blood plus tetracycline. Two other groups received the same diet and were topically treated with M. anisopliae. The guts were dissected, the genomic DNA was extracted three days after the treatment and the V3-V4 variable region of the bacterial 16S rRNA gene was amplified. The gut of ticks that did not receive the antibiotic and were treated with M. anisopliae exhibited lower bacterial diversity and a higher occurrence of Coxiella spp. Simpson diversity index and Pileou equability coefficient were higher in the bacterial community of the guts when R. microplus were fed with tetracycline and fungus treated. Feeding ticks previously with the antibiotic did not change their susceptibility to the fungus, suggesting that the mycoacaricide action will not be impacted if the calf is under antibiotic therapy. The hypothesis that entomopathogenic fungi can affect the bacterial community in the gut of R. microplus engorged females is endorsed by the fact that ticks exposed to M. anisopliae exhibited a dramatic reduction in bacterial diversity. This is the first report of an entomopathogenic fungus affecting the tick-gut microbiota.