The seroprevalence of foot-and-mouth disease in the sedentary livestock herds in four districts of Bhutan.

Cross sectional serological surveys were conducted between March and December 2009 to determine the distribution of foot-and-mouth disease and also to validate the current passive surveillance system in Bhutan. A total of 1909 sera collected from cattle, goats, sheep, and pigs, from 485 herds in 106 villages, were tested using a foot-and-mouth disease non-structural protein 3ABC ELISA. The true prevalence at the animal-level for all species was 15% (95% CI: 13.5, 16.7) using the sensitivity (97.2%) and specificity (99.5%) for cattle. The true prevalence for cattle, goats, sheep and pigs were 17.6 (95% CI: 15.6, 19.5), 11.9% (95% CI: 5.6, 18.3), 11.9% (95% CI: 1.3, 25.1), and 1.9% (95% CI: 0.0, 3.8), respectively. The sub-districts that shared border with India had significantly (p=0.03) higher seroprevalence than the interior sub-districts. Villages located in the sub-tropical zone had significantly (p<0.0001) higher seroprevalence than those located at high altitude zones. Herds with known outbreaks of FMD were 3.6 times more likely (p<0.001) to be seropositive than those with no history of outbreaks of FMD. The study showed the usefulness of population-based serological surveys in detecting circulation of active infection in populations which were, until now, considered to be free of disease based on a passive surveillance system. The study also highlighted the benefits of conducting serological and questionnaire surveys, simultaneously, to ascertain the infection status of herds and animals. Some of the findings from this study could be considered for strengthening of the current FMD control program in Bhutan.