Blue Sky Science: Can all mosquitos transmit viruses like Zika?

Mike Corry

Can all mosquitos transmit viruses like Zika?

Not all mosquitos can transmit the Zika virus, and that’s the case with any mosquito-borne pathogen. There are about 3,000 species of mosquitos in the world and only a handful—about 150—are considered vectors of pathogens, capable of spreading viruses.

In terms of the Zika virus and the outbreak in the Americas, two mosquito species are involved: Aedes aegypti and Aedes albopictus.

These mosquitos feed indoors during the daytime, their breeding habitats develop around human dwellings and in any small amount of water. They are good at transmitting human pathogens because they have this close proximity to and association with humans.

The mosquito and virus have a compatible relationship where the mosquito has an innate ability to ingest the virus, support its development or replication, and then transmit the virus to a new host.

When a mosquito ingests a virus, the first site of replication is in the mosquito’s midgut, basically its stomach. Lining that gut are a number of receptors, similar to a lock-and-key relationship. The cells in the mosquito’s gut have the lock, and the virus needs a specific key to open that lock and get into the cell.

The virus has to travel all through the mosquito’s body from the midgut to the circulatory system and other tissues. Each point along the way is an opportunity to stop the virus, but in a compatible system like Zika virus and Aedes aegypti mosquitos, the virus gets through all the checkpoints.

Eventually the virus needs to make it to the mosquito’s salivary glands if it wants to spread to another host.

When a mosquito feeds, it inserts its mouth parts into a human or animal. It’s not only ingesting blood, it’s actually spitting back into the human or animal. If that mosquito is infected with a virus, it’s actually spitting out saliva and the virus. That’s how the viral infection spreads.