THE CONTRIBUTION OF CULEX PIPIENS COMPLEX MOSQUITOES TO TRANSMISSION AND PERSISTENCE OF WEST NILE VIRUS IN NORTH AMERICA

Theodore G. Andreadis

Department of Entomology and Center for Vector Biology and Zoonotic Diseases

The Connecticut Agricultural Experiment Station

123 Huntington St.

New Haven, CT06511

theodore.andreadis@ct.gov

ABSTRACT

Mosquitoes within the Culex pipiens complex have been implicated as major vectors of West Nile virus (WNV) in North America due to their seasonal abundance, vector competence and high field infection rates. However, the role of Cx. pipiens complex mosquitoes in enzootic amplification of WNV among avian hosts and epidemic transmission to humans varies throughout its geographical distribution. In the northeastern US, Cx. p. pipiens is recognized as the primary enzootic vector responsible for amplification of virus among wild bird populations. However, because it is strongly ornithophilic, its role in transmission to humans appears to be limited. In the north central and Mid-Atlantic States by contrast, Cx. p. pipiens shows an increased affinity for human hosts and has been incriminated as a key bridge vector. In southern regions of the US, Culex p. quinquefasciatus and their hybrids are more opportunistic feeders, and are thought to be principal enzootic and epidemic vectors. In western regions of the US where Culex tarsalis predominates, especially in rural areas, Cx. p. pipiens and Cx. p. quinquefasciatus play roles that are more limited and are recognized as secondary vectors. The involvement of underground populations of Cx. p. pipiens form “molestus” in WNV transmission is largely unknown, but human-biting Cx. p. pipiens are more likely to have a molestus genetic signature. The detection of WNV from overwintering populations of Cx. p. pipiens and their role in local overwintering of WNV are addressed.