Diurnal Temperature Range and Chikungunya Virus Infection in Invasive Mosquito Vectors

Abstract

Climate strongly influences the geographic distribution and timing of mosquito-borne disease outbreaks. Environmental temperature affects phenotypic traits of mosquitoes including vector competence for arboviruses mediated by changes in infection, extrinsic incubation period and in rates of transmission. Most experiments, however, are done at constant temperatures. In nature, mosquitoes are more likely to experience daily fluctuations in temperature. Here we compare disseminated infection (leg infection) and saliva infection of Aedes aegypti (L.) (Diptera: Culicidae) and Aedes albopictus (Skuse) (Diptera: Culicidae) from Florida following oral exposure to an Asian genotype of chikungunya virus emergent in the Americas. We evaluated experimentally the effect of variable temperature regimens on disseminated infection and saliva infection of these Aedes species. Each of three temperature regimes had approximately the same average temperature (27-28°C), but differed in the magnitude of the diurnal temperature range (DTR). The large DTR was 8.0°C (range 23-31°C) and the small DTR was 4.0°C (range 26-30°C) which approximate ranges in different locations of Florida during July-October when risk of transmission is highest. The constant temperature was set at 27°C. Testing three geographic populations of each mosquito species, significant effects on disseminated infection were detected for an interaction between temperature regime and geographic population for both Ae. aegypti and Ae. albopictus. There were no significant treatment effects of temperature, geographic population, or temperature by geographic population interaction on saliva infection for either mosquito species. Constant temperature resulted in a higher viral load in the saliva of Ae. albopictus, but not Ae. aegypti, compared to conditions where the temperature fluctuated.

Keywords: disseminated infection; emergent arbovirus; environmental variation; invasive mosquitoes; transmission.