Larval environmental stress altersAedes aegypticompetence for Sindbis virus

Abstract

Summaryobjective To evaluate how stress at the larval stage alters adult mosquito performance and susceptibility to viral infection.methods We used a model system consisting of Sindbis virus (SINV) and the yellow fever mosquito Aedes aegypti. Larvae were either reared under optimal conditions (control) or exposed to one of four types of stressors; suboptimal nutrients, starvation, elevated temperature, and a low dose of the insecticide malathion and adult females were fed SINV infectious blood meal. Differential expressions of stress, immune-specific and detoxification genes was measured in fourth instar larvae (HSP70, HSP83, cecropin, defensin, transferrin and CYP6Z6) and 3-day-old females (cecropin, defensin, transferrin) to identify plausible molecular mechanisms associated with mosquito response to stress.results There were stress-specific variations in mosquito performance (survival, development time, female size), but all stressors had a consistent effect of significantly increasing susceptibility to viral infection and dissemination relative to the controls. Three genes were up-regulated in fourth instar larvae exposed to temperature stress (cecropin, defensin and CYP6Z6) compared to single genes in suboptimal nutrient (cecropin) and malathion (transferrin) stress treatments and down-regulation of all the six genes in starvation treatments. In adult samples, transferrin was up-regulated in all but starvation treatments while defensin was up-regulated in starvation and temperature stress treatments.conclusions Stress during larval development may cause alterations in adult mosquito phenotype and immunity that can increase their susceptibility to pathogens.

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

“…Along the same lines, nutrient-deprivation during the larval stages enhanced infection and transmission (horizontal and vertical) of LaCrosse encephalitits virus by Aedes triseriatus (Say; Grimstad and Haramis 1984, Patrican and DeFoliart 1985, Grimstad and Walker 1991. Together these observations are consistent with observations that temperature and nutrition may alter the expression of immunity-related genes and viral competence (Telang et al 2012, Muturi et al 2011c. Specifically, cooler rearing conditions may compromise the immune system in Ae.…”

“…albopictus development time contrasts with other studies that have documented higher larval temperature decreasing Ae. albopictus development time (Muturi et al 2011c, Yoshioka et al 2012, Alto and Bettinardi 2013. As predicted, more food led to a significantly shorter development time only at the elevated larval temperature in Ae.…”

La Crosse Virus Field Detection and Vector Competence of Culex Mosquitoes

“…aegypti infected with Sindbis virus. 57 Our findings agree with these in that larval nutritional stress and smaller adult Cx. restuans were more likely to transmit LACV than larger adults.…”

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

“…Given these observations, it is tempting to draw the conclusions that warmer rearing conditions may enhance competence of mosquitoes for Flaviviruses but depress competence for other arboviruses (Alphaviruses and Bunyaviruses). However, caution is advised in interpreting potential fundamental differences in the influence of temperature on mosquitovirus interactions because of inconsistencies in observed temperature effects (e.g., warm larval-rearing conditions increased susceptibility to infection and dissemination for Alphavirus Sindbis 33,62 ; cool larval-rearing conditions enhanced horizontal and vertical transmission of St. Louis encephalitis and Murray Valley encephalitis Flaviviruses 22,31 ). The constant temperatures used here do not capture the daily temperature regimen in nature known to influence dengue virus 63 and malaria transmission, 64,65 an important consideration for predictive models and control efforts.…”