Sero‐Epidemiology and Molecular Detection of Bluetongue Virus in Goats in Bangladesh

BACKGROUND: Bluetongue (BT) is an arthropod-transmitted, non-contagious viral disease of domestic ruminants caused by bluetongue virus (BTV). The incidence of BT in Bangladesh is poorly understood, and there is no molecular evidence of BTV in the country. OBJECTIVES: This study aimed to determine the seroprevalence of BTV, identify associated risk factors and confirm BTV infection in goats in Bangladesh using reverse transcription polymerase chain reaction (RT-PCR). MATERIALS AND METHODS: A total of 460 goat serum samples were randomly collected from ten goat-rich districts of Bangladesh from July 2023 to June 2024. Farmers were interviewed using a structured questionnaire to determine potential risk factors. Serum samples were screened for anti-BTV antibodies using competitive enzyme-linked immunosorbent assay (c-ELISA), and logistic regression models were applied to identify potential risk factors. Nested RT-PCR was performed on ELISA-positive pooled blood samples for molecular detection of BTV using VP7 and NS1 gene-specific primers. RESULTS: The overall seroprevalence was 63.04% (95% confidence interval [CI]: 58.63-67.45). Multivariate logistic regression analysis revealed that breed (crossbred; OR: 3.4, 95% CI: 1.34-8.63), sex (female; OR: 1.97, 95% CI: 1.15-3.40), age (over 2 years; OR: 6.32, 95% CI: 2.42-16.81), biosecurity (poor; OR: 26.48, 95% CI: 1.72-405.6), farm type (household; OR: 33.72, 95% CI: 3.02-375.5), flock size (large; OR: 30.53, 95% CI: 2.91-319.6) and vector control (no; OR: 27.56, 95% CI: 8.60-88.28) were the major risk factors associated with the seroprevalence of anti-BTV antibodies. Nested RT-PCR successfully amplified the VP7 (770 bp) and NS1 (101 bp) genes. Among the 58 pooled samples (each pool containing 5 of the 290 ELISA-positive samples), 13 pools (22.4%) tested positive for BTV RNA, confirming the detection of the virus in goats by PCR. CONCLUSION: This study provides the first large-scale evidence of BTV exposure and PCR-based detection in goats in Bangladesh and highlights important epidemiological risk factors for BTV transmission.