Submitted to: Journal of Medical Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/13/2021
Publication Date: 7/16/2021
Citation: Balaraman, V., Drolet, B.S., Gaudreault, N.N., Wilson, W.C., Owens, J.L., Bold, D., Swanson, D.A., Jasperson, D.C., Noronha, L.E., Richt, J.A., Mitzel, D.N. 2021. Susceptibility of midge and mosquito vectors to SARS-COV-2 by natural route of infection. Journal of Medical Entomology. 58(4):1948-1951. https://doi.org/10.1093/jme/tjab013.
DOI: https://doi.org/10.1093/jme/tjab013

Interpretive Summary: SARS-CoV-2 is a recently emerged, highly contagious virus causing the current 2019 coronavirus (COVID-19) disease pandemic. SARS-CoV-2 was transmitted from animals to humans; however, the animal origin remains unknown. Once in humans, transmission between persons occurs by breathing in infected particles or by contacting contaminated surfaces and then touching your eyes, nose or mouth. Although SARS-CoV-2-related viruses are not transmitted by arthropods, both the public health and agricultural sectors have raised concerns regarding the potential role of arthropods in spreading SARS-CoV-2 among humans and animals. Currently, few studies have demonstrated that SARS-CoV-2 replication is not supported in cells from certain insect species nor in certain species of mosquitoes. This study expands on the current knowledge by including additional insect species (Culex tarsalis). The insects added to this study include biting midges and an additional mosquito species, both insects are known to be important vectors in the transmission of virus to humans and animals in North America. In addition, this study examines the susceptibility of these biting insects to SARS-CoV-2 following ingestion of an infected blood meal, representing a natural infection. Thus, this is the first susceptibility study of SARS-CoV-2 infection using three critical insect vectors following ingestion of SARS-CoV-2 infected blood meal. The results from this study indicate that none of the biting insects, nor their representative cell lines support SARS-CoV-2 replication. We conclude that these biting insects do not pose a risk for transmission of SARS-CoV-2 to humans or animals following ingestion of a SARS-CoV-2 infected blood meal.

Technical Abstract: SARS-CoV-2 is a recently emerged, highly contagious virus and the cause of the current pandemic. It is a zoonotic virus, although its animal origin is not clear yet. Person-to-person transmission occurs by inhalation of infected droplets and aerosols, or by direct contact with contaminated fomites. Arthropods transmit numerous viral, parasitic, and bacterial diseases; however, the potential role of arthropods in SARS-CoV-2 transmission is not fully understood. Thus far, a few studies have demonstrated that SARS-CoV-2 replication is not supported in cells from certain insect species nor in certain species of mosquitoes after intrathoracic inoculation. In this study, we expanded the work of SARS-CoV-2 susceptibility to biting insects after ingesting a SARS-CoV-2infected blood meal. Species tested included Culicoides sonorensis biting midges, as well as Culex tarsalis and Culex quinquefasciatus mosquitoes, all known biological vectors for numerous RNA viruses. Arthropods were allowed to feed on SARS-CoV-2 spiked blood and at various time points post infection analyzed for the presence of viral RNA and infectious virus. Additionally, cell lines derived from C. sonorensis (W8a), Ae. aegypti (C6/36), Cx. quinquefasciatus (HSU), and Cx. tarsalis (CxTrR2) were tested for SARS-CoV-2 susceptibility. Our results indicate that none of the biting insects, nor the insect cell lines support SARS-CoV-2 replication. We conclude, that biting insect do not pose a risk for transmission of SARS-CoV-2 to humans or animals following a SARS-CoV-2 infected blood meal.