Sero-survillence of blue tongue virus antibody and their associated risk factors among domesticated ruminants of Chitwan district of Nepal

Background Bluetongue virus (BTV) affects domestic ruminants. Although no recent clinical outbreaks have been reported in Nepal, previous serosurveys have indicated a high seroprevalence of BTV antibodies. This study aimed to determine the seroprevalence of BTV antibodies in livestock of the Chitwan District, Nepal, and to identify associated risk factors. Methods Serum samples were collected from 382 domestic ruminants (121 cattle, 132 goats, 103 sheep, and 26 buffalo) across the Chitwan district. The samples were tested for BTV antibodies using a commercial competitive ELISA kit. Data on animal species, age, sex, breed, and housing practice were recorded. Associations between these variables and seropositivity were assessed using chi-square tests and multivariate logistic regression, with p  < 0.05 considered statistically significant. Results The overall seroprevalence of BTV antibodies was 59.69%. Cattle exhibited the highest seroprevalence (95.87%), followed by goats (49.24%), buffalo (46.15%), and sheep (33.98%). Seroprevalence among older animals (> 24 months) was significantly higher (78.1%) than in younger animals (≤ 24 months; p  < 0.001). Females had higher seroprevalence (67.01%) than males ( p  < 0.001). Crossbred animals had higher seroprevalence (71.77%) than indigenous breeds ( p  < 0.001). Animals kept in intensive housing systems had higher seroprevalence (62.24%) than those in semi-intensive systems, although this difference was marginal ( p  ≈ 0.07). In multivariate analysis, cattle had markedly higher odds of seropositivity than sheep (adjusted odds ratio = 42.73; p  < 0.001). Additionally, female goats and goats raised under intensive systems had significantly higher odds of seropositivity. Conclusion The high seroprevalence indicates widespread, likely enzootic, circulation of BTV in the livestock of Chitwan, despite no reported clinical outbreaks. Cattle appear to be key hosts in maintaining the virus. These findings underscore the need for improved surveillance, vector control, and further investigation of circulating BTV serotypes in Nepal.