Impact of Extrinsic Incubation Temperature and Virus Exposure on Vector Competence ofCulex pipiens quinquefasciatusSay (Diptera: Culicidae) for West Nile Virus

Abstract

Culex pipiens quinquefasciatus Say mosquitoes from a laboratory colony were exposed to artificial blood meals containing West Nile virus (WNV) and held at incubation temperatures approximating average daily temperatures that occur during Florida arboviral periods. Mosquitoes fed blood meals containing 6.2 logs plaque-forming units (pfu) WNV/mL and held at 25 degrees C, 28 degrees C, or 30 degrees C for 13 days exhibited significantly different rates of infection (30%, 52%, 93%) and dissemination (33%, 22%, 81%) across temperatures. In a separate experiment, Cx. p. quinquefasciatus mosquitoes were provided artificial blood meals with graded doses of WNV from 3.7 to 5.8 logs pfu/mL and maintained at 28 degrees C for 13 days. Rates of infection increased as a function of virus dose, but neither body titers nor dissemination rates were significantly different for mosquitoes that were infected by ingesting different amounts of WNV. Our findings indicate that efficiency of WNV infection and dissemination, and thereby transmission, in Cx. p. quinquefasciatus populations similar to our tested colony may also be diminished when fed blood meals containing less than 5.8 logs pfu WNV/mL and when environmental temperature falls below 30 degrees C. The relationship between the infection rate and dissemination rate changed at different temperatures. This relationship is likely complex and dependent on diverse interactions between factors such as incubation temperature and viremia, which should also be assessed for field populations.

West Nile Virus Vector Competency of Culex quinquefasciatus Mosquitoes in the Galápagos Islands

“…quinquefasciatus . 39,40 Contrary to evidence of vertical transmission in North American Cx. quinquefasciatus , 42,50 Galápagos populations showed no transmission to progeny, which suggests that vertical transmission may have a limited role in maintenance of WNV in Galápagos.…”

“…32,[36][37][38] Generally, longer incubation periods, higher viral doses, and higher temperatures are expected to yield higher rates of infection. 30,32,39 However, Cx. quinquefasciatus in Australia was shown to be a highly competent vectors when exposed to a dose of only 10 4.0±0.…”

Sources of Error in the Estimation of Mosquito Infection Rates Used to Assess Risk of Arbovirus Transmission

“…pipiens quinquefasciatus -WNV system. 5,6 Data on WEEV transmission by Cx . tarsalis in the laboratory were available.…”

“…pipiens quinquefasciatus and WNV, 33% of infected mosquitoes will develop disseminated infections after 13 days of incubation at 25°C, and 81% will have disseminated infections after 13 days at 30°C. 6 Dissemination is necessary for viral transmission, and some studies report that 90% of Cx . pipiens mosquitoes with disseminated WNV infections transmit the virus by bite.…”

Larval Temperature–Food Effects on Adult Mosquito Infection and Vertical Transmission of Dengue-1 Virus

“…An expansive literature demonstrates that the environmental factors experienced by an adult female mosquito can affect her vector competence, the innate ability of the vector to support replication and transmission of a pathogen (Turell 1993, Richards et al 2007). Additionally, growing evidence suggests that effects of the larval environment can continue through the adult stage to also influence vector competence, because innate immunity, infection barriers, and escape barriers develop during larval stages (Grimstad and Walker 1991;Reiskind and Lounibos 2009;Muturi et al 2011aMuturi et al , 2012Alto and Lounibos 2013).…”