Culex Mosquitoes Do Not Transmit Zika Virus

    Being one of the most widespread mosquito genera in the United States and globally, Culex is a constant concern for public health because several species serve as vectors for important diseases of humans and animals, such as West Nile virus, filariasis, and avian malaria. However, a new research study led by investigators at the Kansas State University’s Biosecurity Research Institute has provided some encouraging results, finding that Culex mosquitoes are seemingly unable to transmit the Zika virus (ZIKV).

    The results of this study were published recently in Vector-Borne and Zoonotic Diseases, a Mary Ann Liebert publication, in an article entitled “Culex Species Mosquitoes and Zika Virus” and involved researchers from Rutgers University, the University of Florida, and the U.S. Department of Agriculture.

    “It’s very important to know that Culex mosquitoes are not able to transmit Zika,” explained senior study investigator Dana Vanlandingham, Ph.D., assistant professor of virology in the College of Veterinary Medicine at the Kansas State University. “It enables people to target their control strategies so that they aren’t wasting time and effort on a mosquito that isn’t transmitting Zika virus.”

    Before the current study, Culex mosquitoes’ role in ZIKV transmission was unclear. By studying Culex mosquitoes from various areas across the country and over a period of time, the researchers found that ZIKV did not multiply, but instead disappeared within the species.

    “This is great news,” remarked co-author Stephen Higgs, Ph.D., director of the Biosecurity Research Institute at Kansas State University. “We can check this particular group of mosquitoes off the list here in the U.S. and focus efforts of control on the mosquitoes that we know can infect, like Aedes aegypti and Aedes albopictus.”

    The Centers for Disease Control and Prevention has identified A. aegypti, or yellow fever mosquito, and A. albopictus, or Asian tiger mosquito, as two species that transmit ZIKV—both of which are widely distributed in the U.S.

    Visually distinct from each other, Culex mosquitoes are brown, whereas A. aegypti are black and A. albopictus are black and white. Moreover, Culex species transmit West Nile virus and Japanese encephalitis and are considered permanent water mosquitoes, residing outside in wild habitats. Conversely, A. aegypti and A. albopictus are often considered floodwater mosquitoes and can live in and around houses, in plant trays, spare containers, or gutters.

    The authors wrote that their results “showed a high degree of refractoriness among members of Culex pipiens complex to ZIKV even when exposed to high-titer bloodmeals. Our finding suggests that the likelihood of Culex species mosquitoes serving as secondary vectors for ZIKV is very low, therefore vector control strategies for ZIKV should remain focused on Aedes species mosquitoes. Our demonstration that Culex quinquefasciatus from Vero Beach, FL, is refractory to infection with ZIKV is especially important and timely. Based on our data, we would conclude that the autochthonous cases of Zika in Florida are not due to transmission by C. quinquefasciatus.”

    “We need to know which mosquitoes to target and which mosquitoes not to target because mosquitoes live in different environments,” noted Dr. Vanlandingham, whose research focuses on zoonotic viruses—such as Japanese encephalitis and chikungunya. “Some mosquitoes are found outside, and some are more in people’s homes. You need to know this in order to target your efforts.”

    The authors were excited by their findings but stressed the importance of vigilance in combating the spread of the ZIKV. Homeowners can get rid of small pools of water where mosquitoes breed and should use mosquito repellent as personal protection.