Bacterial communities in defecated contents and the gut of post-defecated females of the vector of bluetongue virus, Culicoides oxystoma Kieffer (Diptera: Ceratopogonidae)

Defecation by haematophagous insects allows for the rapid elimination of the water content ingested along with the blood meal from their hosts. Efficient vectors defecate during or shortly after the blood feeding, and the chances of pathogenic transmission via defecation during blood feeding to their hosts increase. The duration of blood feeding and defecation varies depending on species and sexes of haematophagous insects. Culicoides females take blood meal from their hosts. C. oxystoma Kieffer (Diptera: Ceratopogonidae) are the proven vector of many arboviruses, most importantly bluetongue viruses, and protozoa—the nematode of livestock. This study investigates the bacterial communities in defecated contents and the gut of post-defecated females of C. oxystoma. To observe any pathogenic bacteria in their defecated contents, field-collected engorged females were allowed to excrete under laboratory settings. The engorged females defecated within 48 hours of transferring onto moistened cotton beds. The defecated contents discharged by C. oxystoma consisted of the following bacteria: Bacillus cereus, Enterococcus faecium, and Alcaligenes faecalis. The following bacteria, Bacillus cereus, Lysinibacillus sp., and Paenibacillus sp., were identified from the gut of post-defecated females. Within the defecated content, the following pathogenic bacteria, B. cereus and A. faecalis, were detected, which raises serious concern and the chances of zoonotic posterior station transmission towards their hosts.