Vector Competence of Selected African Mosquito (Diptera: Culicidae) Species for Rift Valley Fever Virus

Abstract

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Prediction of a Rift Valley fever outbreak

“…The flooding of dambos induces the hatching of transovarially infected Aedes mcintoshi mosquito eggs that are dormant in the soil, producing infected adult females in 7-10 days that can transmit RVF virus to domestic animals (1,22,25). After a blood meal, the Aedes mosquitoes will lay infected eggs on moist soil at the edge of mosquito habitats, but appear to not be an efficient secondary vector of the virus between infected and noninfected domestic animals and humans (25,26). However, Culex species mosquito vectors subsequently colonize these flooded dambos and, with a delay of several weeks, large populations of these mosquitoes emerge and efficiently transmit the virus from domestic animals, which amplify the virus, to noninfected domestic animals and humans (22,25,26).…”

“…After a blood meal, the Aedes mosquitoes will lay infected eggs on moist soil at the edge of mosquito habitats, but appear to not be an efficient secondary vector of the virus between infected and noninfected domestic animals and humans (25,26). However, Culex species mosquito vectors subsequently colonize these flooded dambos and, with a delay of several weeks, large populations of these mosquitoes emerge and efficiently transmit the virus from domestic animals, which amplify the virus, to noninfected domestic animals and humans (22,25,26). By using information gained from previous RVF outbreaks (2, 12, 25, Fig.…”

Rift Valley fever virus: strategies for maintenance, survival and vertical transmission in mosquitoes

“…This is supported by studies of RVFV although no significant decrease in detection has been observed from adult pools [94]. Therefore the use of pooled larvae in previous studies may have limited the potential to detect virus and caused the negative results [42,73,95]. If the testing of pooled larvae is considered necessary, a combination of assays can be used.…”

“…Infection can be performed orally via feeding on a viraemic animal or artificial blood meal, or intrathoracic inoculation, by injecting virus through a soft area of cuticle in the thorax directly into the haemocoel. Inoculation bypasses the midgut resulting in near 100 % infection rates, circumventing problematic feeding rates [42]. It can be performed directly with quantified…”

“…This may be linked to the increase in size and development time of the progeny allowing increased viral titres, and time for dissemination to the ovaries. Therefore, negative results for RVFV from eggs hatched and reared at 26 C may have been limited by the temperature [42,73] (Table 2). The species-specific impact of temperature on fecundity and duration of gonotrophic cycles will further impact VT, highlighting the need to test a range of temperatures representative of diurnal range within the mosquito's natural habitat.…”