Influence of endosymbionts on the reproductive fitness of the tick Ornithodoros moubata tested through elimination of the microbiota using antibiotic treatments

Over the past ten years, many studies demonstrated the crucial role of the tick microbiome in tick biology. The soft tick Ornithodoros moubata is a hematophagous ectoparasite of Suidae particularly known to transmit the African swine fever virus. Its bacterial microbiota is characterized by a high prevalence of Francisella-like and Rickettsia endosymbionts. The present study aims to better understand the potential influence of the microbiota on the reproductive fitness of O. moubata. A total of 132 adult female ticks were treated using gentamycin or rifampicin added to the blood meal. Half of the ticks also received a supplementation with B vitamins to address the nutritional role of endosymbionts. Over two periods of 50 days, several traits related to reproductive fitness were monitored to investigate the importance of Francisella and Rickettsia for those traits. It appeared that most of the considered reproductive parameters were not affected. However, antibiotic treatments induced an increase in the tick survival indicating a potential fitness cost of harboring endosymbionts for ticks during the reproduction period. Similarly, 366 first-stage nymphs of Ornithodoros moubata were exposed to the same treatments for molecular quantification of both endosymbionts. Results from qPCR suggested that treatments produced a bacteriostatic effect on endosymbionts without fully eliminating Francisella or Rickettsia.