Role of Anopheles quadrimaculatus and Coquillettidia perturbans (Diptera: Culicidae) in the transmission cycle of Cache Valley virus (Bunyaviridae: Bunyavirus) in the midwest, USA.

Midwestern populations of Coquillettidia perturbans (Walker) and Anopheles quadrimaculatus (Say) were tested for their ability to transmit Cache Valley virus (CV), a recognized human and animal pathogen. Field-collected mosquitoes were fed artificial blood meals containing 5.2-6.2 log10 pfu/ml of CV. After 9-23 d at 28 degrees C, 75-93% of blood-fed Cq. perturbans had disseminated infections and 6-62% transmitted the virus to suckling mice. However, when infected with a lower virus titer (3.3 log10 pfu/ml), only 10-36% of the mosquitoes had disseminated infections and 0-10% transmitted the virus to suckling mice. A similar infection rate (21%) was observed in Cq. perturbans fed on viremic (3.2 log10 pfu/ml) hamsters. An. quadrimaculatus were infected (81-100%) by both doses used, with transmission rates ranging from 13-67% after 16-23 d of incubation. Transmission rates for the laboratory strain An. quadrimaculatus SAVANNAH ranged from 20 to 33% after 7-14 d of incubation. Our data show that although An. quadrimaculatus is more susceptible to CV infections than Cq. perturbans, both mosquito species could be involved in the midwestern transmission cycle of the virus.