Page Banner

United States Department of Agriculture

Agricultural Research Service

Research Project: COUNTERMEASURES TO CONTROL AND ERADICATE RIFT VALLEY FEVER (RFV)

Location: Arthropod-Borne Animal Diseases Research

Title: Potential for North American mosquitoes to transmit Rift Valley fever virus

Authors
item Turell, Michael - USAMRIID
item Bennett, Kristine
item Wilson, William

Submitted to: American Society of Tropical Medicine and Hygiene
Publication Type: Abstract Only
Publication Acceptance Date: September 8, 2008
Publication Date: December 7, 2008
Citation: Turell, M.J., Bennett, K.E., Wilson, W.C. 2008. Potential for North American mosquitoes to transmit Rift Valley fever virus. American Society of Tropical Medicine and Hygiene.

Interpretive Summary: The recent outbreaks of disease caused by Rift Valley fever virus (RVFV) indicate the potential for RVFV to cause severe disease in both humans and domestic animals and its potential to be introduced into new areas, possibly even North America. Because mosquito control methods are often species specific, 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. We evaluated Aedes dorsalis, Ae. vexans, and Culicoides sonorensis from the midwestern United States for their ability to serve as potential vectors for RVFV. Specimens were allowed to feed on RVFV infected adult hamsters, incubated for 7-21 days, and then allowed to refeed on susceptible hamsters and tested to determine infection, dissemination, and transmission rates. None of the species tested was able to transmit RVFV efficiently under laboratory conditions. Although Ae. dorsalis was the most susceptible to infection (78%) and had the highest dissemination rate (33%), this species had a salivary gland barrier and rarely transmitted RVFV by bite. In contrast, only 26% and 6% of Ae. vexans became infected and developed a disseminated infection, respectively. However about 50% of those with a disseminated infection transmitted virus by bite. None of the C. sonorensis became infected, even after intrathoracic inoculation, indicating that this species would not be a competent vector. 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.

Technical 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, possibly even 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, 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. None of the species tested was able to transmit RVFV efficiently under laboratory conditions despite feeding on a hamster with a viremia of 108.8 plaque-forming units/ml of blood. Although Ae. dorsalis was the most susceptible to infection (78%) and had the highest dissemination rate (33%), this species had a salivary gland barrier and rarely transmitted RVFV by bite. In contrast, only 26% and 6% of Ae. vexans became infected and developed a disseminated infection, respectively. However about 50% of those with a disseminated infection transmitted virus by bite. None of the C. sonorensis became infected, even after intrathoracic inoculation, indicating that this species would not be a competent vector. 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.

Last Modified: 4/16/2014
Footer Content Back to Top of Page