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

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... ned (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.