Culex Mosquitoes and Zika Virus Infection? Nah.

PLOS Neglected Tropical Diseases co-Editors-in-Chief Peter J Hotez and Serap Aksoy discuss new research reporting that Culex mosquitos apparently cannot transmit Zika.

As Zika infects large numbers of immunologically naïve populations in the Americas, significant concern has been raised about the possibility that Culex mosquitoes could be responsible for transmitting the virus.  In the continental United States, this is of particular concern given that Culex are far more numerous and widely distributed than Aedes mosquitoes, explaining why West Nile Virus transmission has been observed in most US states.

Could Culex mosquitoes transmit Zika virus and spread microcephaly cases across the US?  This week’s PLOS Neglected Tropical Diseases article by Ricardo Lourenco-de-Oliveira and his colleagues at Brazil’s Instituto Oswaldo Cruz so far indicates that Culex quinquefasciatus, the “southern house mosquito,” is not competent to transmit local strains of Zika and “there is no experimental evidence that Cx. quinquefasciatus likely plays a role in [Zika] transmission”.  In this study they determined that Zika virus infection rates were minimal to totally absent in all Cx. quinquefasciatus, whereas they were significantly higher for Aedes aegypti mosquitoes, which exhibit the ability to disseminate and transmit Zika Virus [1].

So the good news is that Cx quinquefasciatus, which is responsible for WNV transmission in the southern US, is not a competent vector for Zika.  The bad news of course is that Ae. aegypti  remains an important vector, currently responsible for Zika transmission in South Florida and possibly elsewhere in other areas known to host this species, especially Texas,  Louisiana, and Arizona, and even in small pockets in Southern California.   We still have several weeks left of arbovirus transmission season in the southern US and the possibility remains that outbreaks will continue in Florida and may have already begun on the Gulf Coast or elsewhere.

Featured image credit: James Gathany, William Brogdon, USCDCP