Aim: The study was undertaken to assess presence of sub-clinical 
bluetongue in the state of Assam, one of the un-affected north-eastern state of 
India. 
Materials and Methods: Serum samples were collected from 
apparently healthy as well as suspected sheep, goat and cattle from different 
districts of Assam encompassing various agro-climatic zones. Anti-BT antibodies 
were screened in sera using indirect enzyme linked immunosorbent assay (iELISA). 
Results: Out of total 313 animal serum samples screened (sheep-68, 
goat-195, cattle-50), 58.82% of sheep, 31.79% of goat and 70.00% of cattle serum 
samples were found positive. The prevalence of anti-BT antibodies in different 
agro climatic zones ranged between 31-50%. 
Conclusion: This study 
revealed high seroprevalence of bluetongue in cattle, sheep and goats in Assam. 
Incidence of bluetongue in animals of Assam being not reported so far; the 
present seroprevalence status of bluetongue in Assam indicates presence of 
sub-clinical infection in the state for the first time. 
Keywords: 
Antibodies, Assam, bluetongue, iELISA, seroprevalence, virus