September 2020 - Volumes

Mosquitos Not a Threat to Vector COVID-19

Mosquitos can’t transmit the coronavirus, according to a Kansas State University study published in Scientific Reports, the first to produce conclusive evidence on the relationship between SARS-CoV-2 and mosquitos.

SARS-CoV-2, the virus that causes COVID-19, is unable to replicate in mosquitos even if they bite an infected host, the study found. This means mosquitoes can’t spread the infection any further, even in extreme circumstances.

The KSU study tested the ability of the virus to replicate in three of the most common mosquito species: Aedes aegypti, Ae. albopictus and Culex quinquefasciatus. These species are among the most significant vectors of arboviruses, but fortunately, they won’t become vectors for COVID-19.

WHO’s initial assumption was supported by existing information about the behavior of similar coronaviruses. Mosquitos transmit diseases through the exchange of blood, and coronaviruses are not spread through blood—they’re respiratory.

This assumption was supported by the fact that SARS-CoV-2 hasn’t been detected in the blood of infected humans, and it hasn’t been transmitted from human to human through blood transfusions.

Additionally, other coronaviruses have typically been too weak to infect mosquitoes even when they feed on infected hosts.

However, the conclusive evidence provided by KSU’s testing is still crucial in minimizing the potential unknowns about COVID-19. In past experiments, viruses that are too weak to detect have managed to infect mosquitos, so it’s dangerous to rely on assumptions about how the coronavirus travels.

During KSU’s tests, scientists used intrathoracic inoculation, the most effective mode of delivering a virus to a mosquito, to infect each species with SARS-CoV-2. By using this mode of infection, scientists removed as many obstacles as possible to see if the virus would replicate. Since the transmission was unsuccessful in a controlled lab setting, transmission in the wild is even less likely.

Mosquitoes of all three species successfully received the virus within two hours of inoculation, but the virus did not survive or replicate in any of the mosquitoes, leading scientists to the conclusion that mosquitoes will not be furthering the spread of COVID-19.

Source: https://doi.org/10.1038/s41598-020-68882-7