Department of Veterinary Microbiology, College of Veterinary Science, Acharya N.G. Ranga Agricultural University, Tirupati - 517 502 (A.P.)
Fluorescence inhibition test (FIT) was employed as a rapid method for serotyping of bluetongue virus (BTV) and compared with serum neutralization test (SNT). BTV-2 serotype was used to standardize the test, and using this test a field isolate, MBN, was serotyped. Anti-BTV rabbit serum at 1: 100 dilution was found to be optimum to get maximum fluorescence in the infected Vero cells. In the present investigation the BTV antigens were detected in the infected cells as early as 16 hr post infection (PI). Anti BTV-2 and anti-MBN sheep sera at a dilution of 1: 10 and 1: 20, respectively, were found to inhibit the fluorescence completely with homologous viruses. BTV reference sera against serotypes 1, 2, 9, 11, 18 and 23 used for serotyping by FIT and SNT revealed that MBN isolate could be BTV-9. Comparable results were obtained both in the FIT and SNT, but the former test is more rapid and less cumbersome.
