Tripartite interactions among insect vectors, midgut bacteria, and viruses may determine the ability of insects to transmit pathogenic arboviruses. Here, we investigated the impact of gut bacteria on the susceptibility of Culicoides nubeculosus and Culicoides sonorensis biting midges for Schmallenberg virus, and of Aedes aegypti mosquitoes for Zika and chikungunya viruses. Gut bacteria were manipulated by treating the adult insects with antibiotics. The gut bacterial communities were investigated using Illumina MiSeq sequencing of 16S rRNA, and susceptibility to arbovirus infection was tested by feeding insects with an infectious blood meal. Antibiotic treatment led to changes in gut bacteria for all insects. Interestingly, the gut bacterial composition of untreated Ae. aegypti and C. nubeculosus showed Asaia as the dominant genus, which was drastically reduced after antibiotic treatment. Furthermore, antibiotic treatment resulted in relatively more Delftia bacteria in both biting midge species, but not in mosquitoes. Antibiotic treatment and subsequent changes in gut bacterial communities were associated with a significant, 1.8-fold increased infection rate of C. nubeculosus with Schmallenberg virus, but not for C. sonorensis. We did not find any changes in infection rates for Ae. aegypti mosquitoes with Zika or chikungunya virus. We conclude that resident gut bacteria may dampen arbovirus transmission in biting midges, but not so in mosquitoes. Use of antimicrobial compounds at livestock farms might therefore have an unexpected contradictory effect on the health of animals, by increasing the transmission of viral pathogens by biting midges.

昆虫媒介、中肠细菌和病毒之间的三方相互作用可能决定昆虫传播致病性虫媒病毒的能力。在这里，我们研究了肠道细菌对库蠓和声库蠓对施马伦贝格病毒的敏感性以及埃及伊蚊对寨卡病毒和基孔肯雅病毒的敏感性的影响。通过用抗生素处理成年昆虫来控制肠道细菌。使用 Illumina MiSeq 对 16S rRNA 进行测序来研究肠道细菌群落，并通过用传染性血粉喂养昆虫来测试对虫媒病毒感染的敏感性。抗生素治疗导致所有昆虫的肠道细菌发生变化。有趣的是，未经处理的伊蚊的肠道细菌组成。埃及伊蚊（aegypti）和核伊蚊（C. nubeculosus）显示阿萨伊亚属（Asaia）为优势属，抗生素治疗后其数量急剧减少。此外，抗生素治疗导致两种叮蠓物种中的代尔夫特氏菌数量相对较多，但蚊子中却没有。抗生素治疗和随后肠道细菌群落的变化与 Schmallenberg 病毒感染率显着增加 1.8 倍，但与C. sonorensis无关。我们没有发现伊蚊感染率有任何变化。携带寨卡病毒或基孔肯雅病毒的埃及蚊子。我们得出的结论是，肠道常驻细菌可能会抑制虫媒病毒在蠓中的传播，但在蚊子中则不然。因此，在畜牧场使用抗菌化合物可能会增加蠓叮咬引起的病毒病原体的传播，从而对动物的健康产生意想不到的矛盾影响。