Patterns of Host Use in Mosquitoes: Implications for Virus Transmission

Abstract

Mosquitoes do not feed indiscriminately among hosts, but demonstrate various patterns of host use. Each mosquito species may specialize in feeding within a group of related hosts or may utilize a wide variety of hosts. Mosquito host use may vary with season, habitat or weather and may be affected by factors, such as age, defensive behavior, and daily activity period. Patterns of host use by mosquitoes drive the transmission of mosquito-borne viruses. For zoonotic diseases, a vector must first acquire a pathogen from a reservoir host prior to infecting a human. Birds, for example, are reservoirs for many mosquito-borne viruses such as West Nile virus and eastern equine encephalomyelitis virus. Epidemics of West Nile virus and eastern equine encephalomyelitis virus in humans and horses usually occur in the summer and early fall, when mosquito populations shift from feeding on avian hosts. The work presented here reports on studies examining host use by mosquitoes and the impact of patterns of host use on the transmission of mosquito-borne viruses. To determine host preference of ectotherm-feeding mosquitoes, host use and host abundance data were analyzed to determine whether mosquitoes select some host species over others. Culex peccator was a generalist in its feeding patterns within ectotherms, and Culex territans appeared to select Bullfrogs and Spring Peepers. To determine the importance of nestling birds as hosts for mosquitoes, I examined patterns of host use in adult and nestling birds, by introducing mosquitoes into nest boxes of eastern bluebirds, and then determining which birds were fed upon by comparing microsatellite loci in mosquito blood meals. Mosquitoes did not target nestling birds, but fed on nestlings in proportion to their abundance. I tested the hypothesis that temporal patterns of host selection by mosquitoes reflect reproductive phenology of hosts by comparing seasonal patterns of host use with host reproductive phenology. Regardless of host group, mosquitoes fed on host species that were in the process of mate attraction or recruitment. I investigated the relationship between epidemiology of eastern equine encephalitis virus (EEEV) and host shift by vectors in southeastern states. Mammal-feeding intensity by mosquitoes was highly correlated with EEEV cases in horses, indicating that host shifts in vector mosquitoes is critically important in the initiation of epizootics of EEEV in nature.