COUNTERMEASURES TO CONTROL AND ERADICATE RIFT VALLEY FEVER (RFV)
Location: Arthropod-Borne Animal Diseases Research
Title: Factors Affecting the Ability of American Mosquitoes to Transmit Rift Valley Fever Virus
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: December 19, 2008
Publication Date: January 27, 2009
Citation: Turell, M.J., Bennett, K.E., Wilson, W.C. 2009. Factors Affecting the Ability of American Mosquitoes to Transmit Rift Valley Fever Virus. Meeting Abstract.
The recent outbreaks of disease caused by Rift Valley fever virus (RVFV) in Kenya, Mauritania, Yemen, Tanzania, Somalia, and Madagascar indicate the potential for RVFV to cause severe disease in both humans and domestic animals and its potential to be introduced into new areas, including North America. Because mosquito control methods are often species specific, measures that are effective for one species may have little or no effect on others. Thus, it is important to determine which mosquito species are capable of transmitting RVFV so that appropriate control measures can be instituted rapidly and efficiently, should this virus be introduced into North America. Therefore, we evaluated Aedes dorsalis, Ae. vexans, Culex tarsalis, and Culicoides sonorensis from the Midwestern United States for their ability to serve as potential vectors for RVFV. Specimens were allowed to feed on adult hamsters inoculated with RVFV, incubated for 7-21 days at 26oC, and then allowed to refeed on susceptible hamsters and tested to determine infection, dissemination, and transmission rates. When exposed to hamsters with viremias >108.8 plaque-forming units/mL of blood, Cx. tarsalis transmitted RVFV efficiently (infection rate = 93%, dissemination rate = 56%, and estimated transmission rate = 56%). In contrast, when exposed to the same virus dose, none of the other species tested was able to transmit RVFV efficiently under laboratory conditions. Although Ae. dorsalis was susceptible to infection (78%) and had a moderate dissemination rate (33%), this species had a salivary gland barrier and rarely transmitted RVFV by bite. In contrast, only 30% of Ae. vexans became infected and 3% developed a disseminated infection. However 32% of those with a disseminated infection transmitted virus by bite, so ~1% of orally exposed Ae. vexans would be expected to transmit RVFV by bite. None of the C. sonorensis became infected, even after intrathoracic inoculation, and none of the Anopheles quadrimaculatus tested transmitted RVFV by bite, even after intrathoracic inoculation, indicating that these species would not be competent vectors of RVFV. In addition to laboratory vector competence, factors such as seasonal density, feeding preference, longevity, and foraging behavior also need to be considered when determining the role these species could play in RVFV transmission.