All Mosquitoes are Not the Same When it Comes to Zika

By now, we all know that Zika virus can be spread to humans through pesky mosquito bites. But why should we care only about specific mosquitoes? Aren’t all mosquitoes the same? Actually, there are more than 3,500 species of mosquitoes, 175 of which are found in the United States, and each one is different. The most commonly found species in the U.S. include the Anopheles quadrmaculatus, Culex pipiens, Aedes aegypti, and Aedes albopictus mosquitoes.

Do I need to be scared of all mosquito species transmitting Zika virus? No. If Zika virus were spread purely by bites, then any blood-sucker (mosquitoes, ticks, fleas, etc.) could spread the virus. However, this is not what we have observed. Currently, the Aedes aegypti and Aedes albopictus mosquito species have proven to be highly efficient at spreading Zika virus. Once a mosquito is infected, the virus actually has to replicate (or reproduce) inside the mosquito before entering its salivary glands. Once the virus is present in the salivary glands, the mosquito can then transmit the disease when it bites a human.

Are there other mosquito species that can effectively transmit Zika virus? Zika cannot survive in all mosquito species because mosquitoes, like humans, have an immune system that provides protection from germs. The Zika virus is not able to replicate in some mosquito species because those mosquitoes’ immune systems protect them against the virus, thereby limiting their ability to spread Zika to humans. For example, an initial report stated that Zika virus was found in Culex pipiens mosquitoes. A later study confirmed that Zika virus can be detected in this species and one other immediately after a bloodmeal containing the virus. No trace of Zika virus, however, was found in these mosquitoes 7 or 14 days after the bloodmeal. This suggests that the immune system of Culex pipiens prohibited the virus from replicating in the mosquito. That is good news for us! That means current mosquito control programs can target Aedes aegypti and Aedes albopictus mosquitoes in an effort to prevent local transmission of Zika virus. In the meantime, more research is being conducted to identify other mosquito species that may effectively transmit Zika virus. Stay tuned…

Author: Sid Baccam, Computational Epidemiologist, IEM