Seroprevalence and risk factors associated with bovine tuberculosis in cattle in Eastern Bhutan.

Bovine tuberculosis (bTB) is a chronic zoonotic disease affecting cattle of all age groups including wild animals. It poses a significant threat to public health and high economic losses to dairy farmers. While the disease has been eradicated from most of the developed countries through extensive surveillance, testing and culling strategy, it is endemic in Africa, Asia, and the Middle East countries. Currently, there is limited research regarding the prevalence of bTB in cattle in Bhutan. This study aimed to determine the seroprevalence of bTB in cattle in six districts of eastern Bhutan. A two-stage probability proportional to size (PPS) sampling strategy was used to determine the number of animals from which serum samples needed to be collected in each district and sub-district. All farms and cattle for sampling were randomly selected from the data in the annual livestock census of 2020. The samples were tested using bTB ELISA test kit. The seroprevalence and their 95% confidence intervals were calculated. Logistic regression models were constructed to assess the influence of various individual animal and environmental risk factors (breed, age, sex, source of animal, body condition scores of animals, respiratory system status) associated with sero-positivity in animals. The study revealed an apparent seroprevalence of 2.57% (25/971 cattle; 95% CI:1.58–3.57), with an estimated true seroprevalence of 0.91% (95% CI: 0.0–2.81). However, none of the variables were found to be significantly associated with bTB seroprevalence in cattle. We recommend, further sampling and employment of confirmatory testing to fully ascertain the extent of bTB in the cattle herds in eastern Bhutan for prevention and control. Author summary: Bovine tuberculosis (bTB) is a bacterial zoonotic disease caused by Mycobacterium bovis, affecting cattle of all ages. Mycobacterium bovis imposes significant economic burdens on livestock farmers, primarily through reduced production, trade restrictions for live animals and animal products, and the costs of control measures. The disease can be transmitted to humans via consumption of raw milk or through inhalation of infected aerosols. Worldwide, the bovine tuberculosis accounts for 10% of the human tuberculosis cases. In Bhutan, the prevalence and incidence of bTB in both cattle and humans are unknown. In this study, we estimated the seroprevalence of bTB among cattle in six eastern districts of Bhutan. We collected serum samples from 971 cattle and tested them for bovine tuberculosis using ELISA. Our study demonstrated an apparent prevalence of 2.57% (95% CI:1.58–3.57) and a true prevalence of 0.91% (95% CI: 0.0–2.81). Additionally, we assessed factors such as age, breed and farm location that could affect the prevalence of bTB, but none of these factors were significantly associated with the prevalence of bTB. Our study revealed a very low seroprevalence of bTB, among cattle in eastern Bhutan. The findings from this study will contribute to design prevention and control measures for bTB in cattle in Bhutan. [ABSTRACT FROM AUTHOR]