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Researchers identify three new mosquito vectors of Zika in Mexico

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January 25, 2018

Image of a female Culex tarsalis mosquito.
A female Culex tarsalis mosquito, newly identified as a potential vector of Zika virus.
Source: CDC/James Gathany

Researchers identified three new mosquito carriers of Zika virus in Mexico and say all three are potential vectors of the disease.

Writing in Scientific Reports, the researchers reported isolating Zika virus from the salivary glands of wild-caught female Culex coronator, C. tarsalis and Aedes vexans mosquitoes, as well as other previously reported vectors, including A. aegypti, the primary driver of the recent Zika virus epidemic in the Americas. They also isolated Zika from different body parts of wild-caught female C. quinquefasciatus mosquitoes and whole males from the A. aegypti and C. quinquefasciatus species.

“Our findings strongly suggest that all the species reported herein are potential vectors for [Zika virus],” they wrote.

According to the report, past research has indicated that Zika arrived in Mexico from Brazil in the second half 2014 or early 2015. The mosquitoes that tested positive in the new study were collected in a neighborhood in Guadalajara, in the western Mexican state of Jalisco.

According to the CDC, there is still a risk for Zika infection in Mexico, where mosquitoes may be transmitting the virus to people. Zika can cause a pattern of birth defects called congenital Zika syndrome — which includes severe microcephaly — in children whose mothers were exposed to the virus.

The researchers said their findings support some past studies showing that C. quinquefasciatus is a competent vector of Zika but conflict with other publications reporting that Culex mosquitoes are poor vectors of Zika.

They said A. aegypti “is more likely the primary vector of the disease” in Jalisco, as it has been in other places that have experienced locally transmitted Zika. – Gerard Gallagher

Disclosures: The authors report no relevant financial disclosures.

itj+ Perspective

Photo of Peter Hotez

The findings are important because they suggest Culex mosquitoes could be a possible vector for human Zika virus infection. In the United States, Culex mosquitoes have a much broader distribution compared with Aedes aegypti, the classical Zika vector. This explains why we can see (Culex-transmitted) West Nile virus cases across the U.S. However, these findings, while provocative in suggesting Culex mosquitoes are potential vectors, do not necessarily mean that Culex mosquitoes are efficient Zika virus transmitters. This might explain why human Zika virus cases occurred only in Puerto Rico, South Florida and South Texas, where A. aegypti are found. If it turns out that Culex mosquitoes can easily transmit Zika, then women across the U.S. would need to be considered vulnerable to pregnancy-associated infection and congenital transmission.

Peter J. Hotez, MD, PhD

Dean, National School of Tropical Medicine at Baylor College of Medicine
Endowed chair in tropical pediatrics, Texas Children’s Hospital

Disclosure: Hotez reports no relevant financial disclosures.