APPLICATION OF A COMPETITIVE ELISA FOR THE DETECTION OF BLUETONGUE VIRUS-ANTIBODIES IN LLAMAS AND WILD RUMINANTS

A competitive enzyme-linked immunosorbent assay (C-ELISA), using a gro up-specific monoclonal antibody against bluetongue virus (BTV), was ap plied to detect anti-BTV antibodies in serum samples from two llamas ( Llama glama) experimentally infected with BTV serotype 10. Antibodies were detected in both llamas by 1 wk or 2 wk post-infection. Antibodie s to BTV increased exponentially during the first 4 wk in both llamas and stabilized at an elevated level during the remaining 5-wk-period o f the experiment. We evaluated the C-ELISA for 1,442 field sera from b luetongue-free areas, collected from 398 llamas in New Zealand as well as 451 elk (Cervus elaphus canadensis), 323 bison (Bison bison) and 2 70 reindeer (Rangifer tarandus tarandus) in Canada. Based an the frequ ency distribution of the C-ELISA values, we propose that the current n egative cut-off value of 50% inhibition established for bovine held se ra also can be applied to the sera from these wild ruminants. The C-EL ISA values for other wild ruminant field sera collected in bluetongue- free areas of Canada from 98 native caribou (Rangifer tarandus caribou ), 32 white-tailed deer (Odocoileus virginianus), 14 moose (Alces alce s), and nine muskoxen (Ovibos maschatus) and 15 yak (Bos grunniens) al so were less than 50%, with the exception of three caribou samples. Ba sed on our results, we propose that the C-ELISA be used as a rapid and specific test for serodiagnosis of BTV infection in llamas and possib ly other wild ruminants.