The transmission of blue-tongue and horse-sickness by Culicoides

Abstract

An account is given of an investigation into the transmission of blue-tongue and horse-sickness conducted at Onderstepoort during 1942 and 1943. Three positive infections with blue-tongue and one with horse-sickness, following the injection of emulsions of wild-caught Culicoides into susceptible animals, are recorded. The successful transmission of blue-tongue by the bites of Culicoides, which fed on experimentally sheep 10 days previously, is described. The identity of the diseases in question had been established clinically, by subinoculations into susceptible animals and by immunity tests with homologous strains of the particular virus where possible. The author is quite confident of the correctness of the diagnoses of the disease conditions produced. The special light trap used in the investigation for the trapping of Culicoides and the technique of handling and storing these insects are briefly described. It is concluded that certain species of the genus Culicoides are capable of becoming infected with and transmitting to susceptible animals by bite the virus of blue-tongue of sheep. From the evidence advanced it is anticipated that the transmitter or transmitters of horse-sickness will be found within the genus Culicoides.