Study Suggests Culex Mosquitoes Are Unable to Transmit Zika in the U.S.
Researchers have identified the Zika virus in mosquito species other than Aedes aegypti, which is largely responsible for the current outbreaks of Zika infection, raising concerns that other mosquitoes may be capable of transmitting the virus. However, a new study demonstrates that mosquitoes in the genus Culex are highly unlikely to transmit the infection to humans in the United States. The study was published in Vector-Borne and Zoonotic Diseases.
The report demonstrates that the most widespread and abundant Culex species in the United States are very resistant to Zika virus infection, even when exposed to high levels of the virus in bloodmeals. The study showed that the southern house mosquito (Culex quinquefasciatus), for example, is refractory to infection with Zika virus. This finding has important implications for Florida and other emerging areas of Zika virus infection, and the authors recommend that mosquito-control efforts in areas of Florida with non-travel-related cases of infection should continue to focus on Aedes species.
According to University of Aix-Marseille visiting Professor Ernest Gould, who was not involved in the study, “[This paper] describes laboratory experiments to assess the transmission competence of Culex species and provides strong evidence to support the view that Culex species mosquitoes are highly unlikely to be important vectors of Zika virus. This report provides very helpful guidance for health agencies charged with the responsibility of controlling local mosquito populations in regions of North America where Zika virus presents a potential threat.”
However, an unpublished study from Brazil has shown that Brazilian Culex quinquefasciatus can be infected with Zika virus, and that Culex quinquefasciatus has been found in the city of Recife, where Zika is known to occur.
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Editor’s note (Sept 12, 2016): It’s been brought to our attention that, according to a recent article in Emerging Microbes & Infections, Chinese researchers were able to successfully infect Culex pipiens quinquefasciatus with the Zika virus, and that the mosquitoes were able to transmit the virus to mice. Then again, other researchers from Brazil have published an article in PLOS Neglected Tropical Diseases that claims that Culex quinquefasciatus from Rio de Janeiro Is Not Competent to Transmit the Local Zika Virus. Why the discrepancies? It could be differences in the virus strains, geographical variations in populations of the mosquitoes, methodology problems, or a combination of all three. Time will tell as more research is conducted and published.