RAPID DIAGNOSIS OF EQUINE INFLUENZA BY THE DIRECTIGEN FLU-A ENZYME-IMMUNOASSAY

The Directigen FLU-A enzyme immunoassay was tested for its ability to detect equine-2 influenza viruses in nasopharyngeal fluids from horses and ponies. A total of 125 swabs from experimental infections and fro m different sources of natural infection in the USA and Hong Kong were examined. The assay results were compared with the results of standar d virus culture in embryonated chicken eggs or Madin-Darby canine kidn ey cells, and with the serology of the horses sampled. In comparison w ith virus culture the enzyme immunoassay exhibited 83 per cent sensiti vity, 78 per cent specificity, 70 per cent positive predictive value a nd 88 per cent negative predictive value. The test appeared to be more sensitive than haemagglutination for the detection of low levels of v irus in embryonated egg cultures. It also detected equine-1 influenza virus in culture. The test is rapid (15 minutes), simple, and should b e a convenient method for the rapid diagnosis and screening of horses for equine influenza infection.