Mosquitoes and other biting insects can’t spread SARS-CoV-2, researchers reported, even if the blood suckers have had plenty of opportunity over the summer with everyone spending more time outside.
Unlike dengue, malaria, and Zika virus, the virus behind COVID-19 couldn’t replicate after being ingested by mosquitoes, Dana Mitzel, PhD, of the U.S. Department of Agriculture in Manhattan, Kansas, and colleagues reported on the preprint server bioRxiv without peer review.
“For arthropods to be transmission-competent vectors, the respective pathogen must be acquired from a host during blood feeding, then infect the midgut, escape the midgut barrier, disseminate to and infect the salivary glands, and finally be transmitted to a susceptible host during subsequent blood feeding,” they wrote.
The group fed SARS-CoV-2 spiked blood to a variety of common biting insects found in the U.S. that spread other RNA viruses — Culicoides sonorensis biting midges (important in spreading disease to farm animals), as well as Culex tarsalis and Culex quinquefasciatus mosquitoes (important in spreading disease to humans) — and then watched them for 10 days to mimic natural infection routes.
While most of the midges (85%) had detectable coronavirus RNA, only 17% of the Cx. tarsalis mosquitoes and 50% of the Cx. quinquefasciatus mosquitoes did at 10 days. But no structural changes were seen in any of their cells that would be expected with viral invasion, indicating they were not infected and would not be able to transmit replicating virus.
Testing cell lines derived from C. sonorensis midges, Aedes aegypti mosquitoes, Cx. quinquefasciatus mosquitoes, and Cx. tarsalis mosquitoes also showed no SARS-CoV-2 susceptibility.
The findings square with those of Italian researchers, who found no evidence of replication of the virus after it was fed to common or tiger mosquitoes, and another study affirming no infection or replication in Ae. aegypti or albopictus mosquitoes, which are also common in the U.S. The World Health Organization and CDC have also pointed to no evidence of mosquito-borne spread.
The researchers disclosed no relevant conflicts of interest.
Note that bioRxiv is a preprint server for posting manuscripts prior to undergoing formal peer review. As such, the data and conclusions should be regarded as preliminary until published in a peer-reviewed journal.