zika west nile mosquito

Since the 2016 Zika outbreak was first linked to cases of microcephaly, epidemiologists have been vigilant about the virus’ spread, watching mosquito migration patterns as they push further north in the United States. The latest study from PLOS Neglected Tropical Diseases confirms that California’s Aedes genus of mosquitoes can, in fact, carry and transmit the virus.

The seasonal rise in temperatures yields a mosquito migration that can come with risks, and the capabilities of some species were still unknown, such as the Aedes aegypti, whose bite doesn’t always lead to infection and whose infection doesn’t always lead to symptoms. Whereas prior investigations were “cautiously optimistic” that Zika-carrying mosquitoes would not take root in California, the latest report published in the science journal PLOS on Thursday confirmed that several species of Aedes mosquitoes are vectors of the Zika virus, or ZIKV.

A collection of Aedes saliva for Zika virus testing
A collection of Aedes saliva for Zika virus testing

To reach this conclusion, Drs. Lark Coffey and Chris Barker of the University of California, Davis, infected Aedes aegypti, Culex tarsalis, and Culex quinquefasciatus mosquitoes with three different strains of Zika. These variations on the disease included the ancestral strain from Malaysia in 1966, as well as variants from the 2015 outbreaks in Puerto Rico and Brazil. Coffey, Barker, and their team of researchers let each mosquito take a bite out of an infected mouse and then followed the pest to see if it transmitted ZIKV.

Trials conducted 14 and 21 days after the infection found no trace of ZIKV detected in the saliva of either Culex mosquito species. However, 85 to 90 percent of the Aedes mosquitoes had Zika RNA in their saliva, for all strains of the virus.

As of June 6, there have been 5,701 reported in the United States and an additional 37,250 reported in US territories, according to the Centers for Disease Control and Prevention. The CDC continues to surveil the virus and its resulting cases of microcephaly, the rates of which have calmed since the 2016 outbreak. However, the health agency warns that the warmer season, as well as the aftermath of potential hurricanes, will contribute to an increased risk of infection this summer.

“Understanding the mosquito species that vector ZIKV is important for estimating regional outbreak potential and for informing local mosquito control strategies,” Coffey and Barker’s team said. While Zika is no longer captivating headlines, the virus able to reemerge every summer, forcing scientists to remain vigilant for its next move.

Photos via Olivia Winokur and Brad Main, Wikimedia