Diversity and significance of the microbial community in the larval development and vector competence of Culicoides sonorensis for EHDV

BACKGROUND AND PURPOSE: The biting midge, Culicoides sonorensis is a vector of epizootic hemorrhagic disease virus (EHDV) that causes fatal infections in wild and domestic white-tailed deer and also affects mule deer, pronghorns, and cattle resulting in great economic losses in animal agriculture worldwide. We investigated the diversity and significance of the bacterial community in the larval development and the vector competence of C. sonorensis for EHDV-2. METHODS: Adult midges were trapped from dairy and deer farms, identified by sequencing of cytochrome oxidase (CO1), and the bacterial diversity in their gut and the larval habitat was assessed by a culturing approach followed by sequencing of 16S rDNA. Larval development studies were conducted with  sterilized 1^st instar larvae placed on a substrate made from autoclaved pond shore mud (3/4^th) and unautoclaved manure (1/4^th) of different animals.  Aeromonas veronii isolated from the gut of wild midges was fed to teneral females in the lab. and its concentration was monitored after blood feeding and sugar feeding. RESULTS: Culicoides sonorensis was the most commonly found species in Kansas followed by C. stellifer, C. crepuscularis, and C. haematopotus. The dominant bacterial genus in the gut and larval habitat of C. sonorensis was Aeromonas sp. and Pseudomonas sp., respectively. A. veronii population reached its peak on day 1 post-blood feeding (~10⁸ CFU per midge), then declined and stabilized (~10⁶ CFU per midge). CONCLUSIONS: Aeromonas sp. is a candidate for paratransgenic approach to minimize EHDV transmission and Pseudomonas sp. for the midge larval development inhibition studies.