Zika Found in Common Backyard Asian Tiger Mosquito

A common backyard mosquito can be infected with the Zika virus and it may pass the virus along in its eggs, researchers reported Friday.

The findings add to worries that the Asian tiger mosquito, scientifically known as Aedes albopictus, could help spread the virus as mosquito season hits temperate regions of the world.

Image: Estimated range of Aedes aegypti and Aedes albopictus in the United States, 2016
Estimated range of Aedes aegypti and Aedes albopictus in the United States, 2016. CDC

The study, published in the Journal of Medical Entomology, doesn’t prove that tiger mosquitoes can spread Zika, which causes severe birth defects. But it adds to evidence that they might.

Chelsea Smartt of the Florida Medical Entomology Laboratory and the University of Florida and colleagues hatched eggs from Aedes albopictus mosquitoes gathered during a 2015 outbreak of Zika in Brazil. When they ground up the mosquitoes that grew from those eggs — male and female — they found genetic pieces of Zika.

“Our results mean that Aedes albopictus may have a role in Zika virus transmission and should be of concern to public health,” Smartt said in a statement.

“This mosquito is found worldwide, has a wide range of hosts and has adapted to colder climates.”

The main carrier of Zika is Aedes aegypti, or the yellow fever mosquito. It needs warm, tropical climates to thrive.

Aedes albopictus, easily identified by its stripey white legs and daytime biting habits, arrived in Texas in 1985. It’s much more tolerant of cold temperatures, thrives more in the suburbs than in the cities and now lives in 40 U.S. states.

So far, home-grown Zika has only been found in the U.S. in two places – south Florida and south Texas. But travelers infected with Zika have been diagnosed all across the country.

It takes people plus mosquitoes to spread a virus like Zika. The mosquitoes bite actively infected people, incubate the virus for a while, and then bite other people to spread it.

Mosquitoes don’t go far, so outbreaks die out unless many people become infected and keep spreading it back to mosquitoes. Sometimes an animal can act as a reservoir — birds can keep West Nile Virus spreading, for instance.

Now the question is how well the virus lives in the bodies of the Asian tiger mosquito. Simply finding a virus in a mosquito does not necessarily mean the mosquito spreads the virus. The virus must replicate in the insect’s salivary glands to be transmitted in a bite.

“The fact that you find it in Aedes albopictus is not surprising,” said Dr. Peter Hotez, dean of the School of Tropical Medicine at Baylor College of Medicine.

“The question is how important it is for transmission.”

More study is needed, the University of Florida team said.

“The detection of Zika virus RNA from five adult Ae. albopictus reared from eggs collected during the 2015 outbreak in Camaçari, Bahia, Brazil, is consistent with the potential for vertical or sexual transmission of Zika virus by Ae. albopictus; however, evidence supporting this was not conclusive,” they wrote.

But related viruses, including dengue, yellow fever, West Nile, Japanese encephalitis, and St. Louis encephalitis viruses, have been spread from parents to eggs in several species of mosquitoes.

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