Genetic Variation Associated with Mammalian Feeding inCulex pipiensfrom a West Nile Virus Epidemic Region in Chicago, Illinois

Abstract

Mosquitoes of the Culex pipiens complex are important vectors of West Nile virus in the United States. We examined the genetic variations of Cx. pipiens mosquitoes from Chicago, Illinois that were determined to be principally ornithophilic but exhibited a relatively higher inclination for mammalian hosts including humans. Microsatellite analysis of 10 polymorphic markers was performed on 346 engorged Cx. pipiens specimens with identified avian or mammalian blood meals. Our results indicated that there were no significant differences in allelic richness, the pattern of conformity to Hardy-Weinberg equilibrium, and linkage disequilibrium, nor was there overall genetic differentiation between specimens with avian- and mammalian-derived blood meals. However, Cx. pipiens form pipiens with mammalian- (including human-) derived blood meals had significantly higher ancestry (p < 0.001) and proportion of hybrids (p < 0.01) from the Cx. pipiens form molestus (population from New York City) than did those with avian-derived blood meals. By contrast, there were no significant differences in the ancestry (p > 0.05) and the proportion of hybrids (p > 0.05) from Cx. quinquefasciatus (population from Harris Country, Texas). No temporal genetic variation was detected in accordance with the observation that there was no shift in blood feeding from birds to mammals. The results of this study in conjunction with regional host-feeding behavior suggest that the probability of genetic ancestry from Cx. pipiens f. molestus may predispose mosquitoes to feed more readily on mammals; however, the genetic mechanisms are unknown.

Host compatibility rather than vector–host-encounter rate determines the host range of avian Plasmodium parasites

“…Engorged mosquitoes were sampled in the same study sites at which both avian hosts and mosquito vectors were surveyed for parasites. While C. pipiens represents a well-known species complex, previous study showed that introgression of molestus and quiquefasciatus forms is minimal in the Chicago population [47]. Thus, the numerous behavioural and physiological differences between these forms [48] are unlikely to influence the patterns presented here.…”

Autogeny in Culex pipiens Complex Mosquitoes from the San Francisco Bay Area

“…pipiens complex with respect to autogeny (this study) and host preference. 45,46 Although temperatures in coastal Santa Clara County are mild in the winter, cool temperatures may persist for many weeks (Figure 2A). Egg rafts deposited very early in the fall may experience relatively warm temperatures during development, but the temperature decreases rapidly in September and October, exposing the larvae hatching from later egg rafts to cold developmental temperatures.…”

Phenotypic Variation among Culex pipiens Complex (Diptera: Culicidae) Populations from the Sacramento Valley, California: Horizontal and Vertical Transmission of West Nile Virus, Diapause Potential, Autogeny, and Host Selection

“…Although studies have noted a significant association between f. molestus hybrid ancestry in Cx. pipiens individuals and a high proportion of mammalian 34 and human 33 blood feeding, no study has directly assessed blood feeding patterns from known f. molestus populations in the United States. Previous studies have noted frequent human biting by f. molestus females in underground railway tunnels in Europe, 6,79 but did not directly evaluate host preferences of surface or subterranean populations.…”

“…pipiens females were more likely to feed on mammals if they had a higher genetic ancestry from f. molestus. 33,34 However, three recent bloodmeal identification studies done in California showed that Cx. pipiens complex females fed infrequently on mammals, including humans, even in highly urbanized areas [35][36][37] ; however, these studies did not evaluate the genetic ancestry of the individual females tested.…”