Environmental and Biological Factors Influencing Culex pipiens quinquefasciatus Say (Diptera: Culicidae) Vector Competence for Saint Louis Encephalitis Virus

Abstract

Complex interactions between environmental and biological factors influence the susceptibility of Culex pipiens quinquefasciatus to St. Louis encephalitis virus and could affect the epidemiology of virus transmission. Similar interactions could have epidemiologic implications for other vector-virus systems. We conducted an experiment to examine four such factors in combination: mosquito age, extrinsic incubation temperature (EIT), virus dose, and colony. The proportion of mosquitoes with body infections or disseminated infections varied between colonies, and was dependant on age, EIT, and dose. We also show that the probability of a body or leg infection interacted in complex ways between colonies, ages, EITs, and doses. The complex interactive effects of environmental and biological factors must be taken into account for studies of vector competence and epidemiology, especially when laboratory studies are used to generalize to natural transmission dynamics where the extent of variation is largely unknown.

Temperature and Dengue Virus Infection in Mosquitoes: Independent Effects on the Immature and Adult Stages

“…Increases in adult-holding temperatures have usually been associated with enhanced vector competence. [19][20][21][22][23][24][25][26][27] However, some studies have identified reduced vector competence and activity in nature associated with increases in temperature (western equine encephalitis virus [WEEV] and St. Louis encephalitis virus [SLEV]). [28][29][30][31] Additionally, cool rearing temperature of the immature stages may be associated with reduced virus infection and dissemination in the adult stage.…”

Environmental and Biological Factors Influencing Culex pipiens quinquefasciatus (Diptera: Culicidae) Vector Competence for West Nile Virus

“…[1][2][3][4][5][6] Although it is well-established that different environmental or biological factors influence mosquito vector competence for arboviruses, there has been little work to determine how various biological and environmental factors interact with one another to influence vector competence. Culex pipiens quinquefasciatus Say vector competence for St. Louis encephalitis virus (SLEV) is dependent on complex interactions between the biological factors of age and mosquito population and the environmental factors of EIT and virus dose.…”

“…p. quinquefasciatus vector competence for SLEV. 6 Female mosquitoes with no infection of the body show a midgut infection barrier (MIB), whereas females with an infected body and no dissemination to the legs show a midgut escape barrier (MEB). 15 We characterized virus titers in the body and legs as a quantitative measure of the ability of the virus to replicate in mosquito tissues.…”

“…Culex pipiens quinquefasciatus Say vector competence for St. Louis encephalitis virus (SLEV) is dependent on complex interactions between the biological factors of age and mosquito population and the environmental factors of EIT and virus dose. 6 West Nile virus (WNV; family Flaviviridae : genus Flavivirus ) is maintained in an enzootic cycle involving ornithophilic mosquitoes and avian populations, and it threatens humans whenever large numbers of infectious mosquitoes exhibiting opportunistic feeding coincide with amplification hosts and human populations. 7 Culex p. quinquefasciatus feeds on both avian and mammalian hosts, [8][9][10] has been shown to be a competent vector of WNV in the laboratory, 3,11,12 has been found in nature to be infected with WNV, 13,14 and is considered a prominent WNV vector in the United States.…”

Mosquito-Borne Arboviral Surveillance and the Prediction of Disease Outbreaks

“…Intrinsic factors in all mosquitoes regulate viral escape from infected organs, the penetration of virus into new organs, and viral replication within those organs (Black et al 2002). Extrinsic factors including the amount of virus ingested by the mosquito with its first infective blood meal and ambient temperature, which determines how quickly the virus replicates in the mosquito and infects the salivary glands (a process known as the extrinsic incubation period (EIP)), also influence mosquito vector competence (Anderson et al 2010, Richards et al 2009. Most mosquito species are poor arboviral vectors, primarily because of intrinsic and extrinsic factors that disfavor viral replication and mosquito infection processes.…”