"Bird biting" mosquitoes and human disease: a review of the role of Culex pipiens complex mosquitoes in epidemiology

Abstract

The transmission of vector-borne pathogens is greatly influenced by the ecology of their vector, which is in turn shaped by genetic ancestry, the environment, and the hosts that are fed on. One group of vectors, the mosquitoes in the Culex pipiens complex, play key roles in the transmission of a range of pathogens including several viruses such as West Nile and St. Louis encephalitis viruses, avian malaria (Plasmodium spp.), and filarial worms. The Cx. pipiens complex includes Culex pipiens pipiens with two forms, pipiens and molestus, Culex pipiens pallens, Culex quinquefasciatus, Culex australicus, and Culex globocoxitus. While several members of the complex have limited geographic distributions, Cx. pipienspipiens and Cx. quinquefasciatus are found in all known urban and sub-urban temperate and tropical regions, respectively, across the world, where they are often principal disease vectors. In addition, hybrids are common in areas of overlap. Although gaps in our knowledge still remain, the advent of genetic tools has greatly enhanced our understanding of the history of speciation, domestication, dispersal, and hybridization. We review the taxonomy, genetics, evolution, behavior, and ecology of members of the Cx. pipiens complex and their role in the transmission of medically important pathogens. The adaptation of Cx. pipiens complex mosquitoes to human-altered environments led to their global distribution through dispersal via humans and, combined with their mixed feeding patterns on birds and mammals (including humans), increased the transmission of several avian pathogens to humans. We highlight several unanswered questions that will increase our ability to control diseases transmitted by these mosquitoes.

Figure 1

Global distribution of the Cx. pipiens complex mosquitoes. Geographic range for Cx. p. pipiens may include both forms (pipiens and molestus) and in temperate Asia and Australia although Cx. p. pipiens form molestus can be found in urban environments we omitted it for clarity. Note that Cx. australicus and Cx. globocoxitus are restricted to Australia. (Adapted from (Mattingly, 1965; Smith and Fonseca, 2004; Vinogradova, 2000).

Figure 2

Feeding patterns of four species of Culex mosquitoes. Left axis shows the fraction of feedings from mammals and birds (first eight columns) represented by the mean (column height), 95% confidence interval (whiskers), and raw data (points). Right axis and last four columns show the fraction of feedings from humans (a subset of the mammals) on a different scale. See Supplemental Online Table 1 for sources and raw data.