Laboratory infection of the mosquito, Toxorhynchites brevipalpis (Diptera, Culicidae), with bluetongue virus.

The use of Toxorhynchites brevipalpis as a system for the propagation and isolation of bluetongue virus (BTV) was investigated. BTV was found to multiply in T. brevipalpis after infection by intrathoracic inoculation. Virus concentrations of up to 6.9 log 10 TCID50 per mosquito were found within 7 days of infection and were maintained for at least 6 days. Virus could be detected by an indirect fluorescent antibody test applied to head and thorax tissue smears. These results are comparable to those obtained after inoculation of Culicoides variipennis with the same virus. Comparison of T. brevipalpis and baby hamster kidney (BHK) cells as systems for isolation of BTV showed that there was little difference in sensitivity between the two systems for the stock BTV used. Field samples were not available for test. It was concluded that the use of T. brevipalpis as an isolation system for BTV would have no apparent advantage if BHK cells were available.