BIONOMICS AND CONTROL OF RIFT VALLEY FEVER VIRUS VECTORS IN KENYA
Mosquito and Fly Research Unit
2012 Annual Report
1a.Objectives (from AD-416):
1. Determine the animal and mosquito species that serve as the inter-epizootic maintenance hosts of Rift Valley fever virus (RVFV) virus.
2. Test candidate repellents for biting insects.
3. Test and evaluate efficacy of control treatments.
1b.Approach (from AD-416):
1. Determine mosquito blood meal sources for blood-fed females collected during an outbreak (previously collected) and during an inter-epidemic period. Test collected mosquitoes for the presence of RVFV using RT-PCR. Determine mosquito succession from the onset of rain events leading to flooding until flooded areas are dry.
2. Evaluate the efficacy of a candidate repellent for use on humans in terms of how well it protects against insect bites and how well it would be received and actually used in an emergency distribution situation.
3. Evaluate the efficacy of chemical mosquito control that is applied prior to rain events.
This research relates to the inhouse project Objective 6: "Discover and characterize environmental predictors of the distribution of mosquitoes in order to assess the risk of invasive species and pathogen transmission." Apply to the development of methods and techniques to accurately assess mosquito population density, to deploy vector surveillance systems, and to detect exotic invasive species.
Blood fed mosquitoes (from Garissa, Baringo and Kilifi) were analyzed for Rift Valley Fever Virus (RVFV) in the blood meals and the vertebrate source of the blood meals determined. Blood meals of mosquitoes from Garissa and Baringo were found infected with RVFV, and none from Kilifi. Of the Garissa mosquitoes, 8 were Aedes ochraceus while 1 was Ae. mcintoshi. Of the mosquitoes from Baringo, 6 were Mansonia uniformis while 1 was Hodgesia spp. One of the three Ae. ochraceus mosquitoes that fed on goat and 3 of the 4 that fed on sheep had a disseminated RVFV infection. The 1 Ae. ochraceus that fed on human had infection localized to the abdomen. The 4 Ma. uniformis that fed on sheep had disseminated infection while 1 that fed on goat had localized infection. One whose blood meal source could not be determined had disseminated infection.