Use of the indirect fluorescent antibody technique for the detection of bluetongue virus antigen in tissue smears from Culicoides variipennis (diptera,ceratopogonidae)

An indirect fluorescent antibody test was used to detect Bluetongue virus (BTV) antigen in tissue smears prepared from laboratory-infected Culicoides variipennis. Insects were infected by intrathoracic inoculation and virus was detected in head, thorax and abdomen, in general increasing in titre over a period of 9 days, at which time the experiment was terminated. Reliable positive results by fluorescence were obtained from the fifth day post infection in head, thorax and abdomen smears. Since high titres of virus were found in the head, smears could therefore be prepared from the head alone, leaving the remainder of the insect for further tests.The technique iis useful in experiments involving the screening of large numbers of insects for possible BTV infection, although further work would be necessary to establish the reliability of the method for routine use.