Spatial epidemiology and socio-economics of bovine brucellosis in selected districts of the Northern Province of Sri Lanka

This study was conducted to characterize the spatial epidemiology and socio-economics of bovine brucellosis on dairy farms in the Kilinochchi and Mullaitivu Districts of Northern Province, Sri Lanka. A cross-sectional study involving bulk milk sampling and interviews using a structured questionnaire was conducted at 214 dairy farms. Milk samples were tested for Brucella antibodies using an indirect enzyme-linked immunosorbent assay. Global spatial clustering statistics and SaTScan were also performed. The association between milk sero-positivity and socio-economic variables was evaluated using univariable analysis. Multi-variable spatial risk factor analysis was conducted using the integrated nested Laplace approximation selecting principal components (PCs) of land use and socio-economic and ecological variables with P<0.2 in the univariable analyses as explanatory variables. The crude and true herd-level prevalence was estimated at 12.1% (26/214; 95% confidence interval [CI]: 8.4-17.2%), and 11.2% (95% CI: 7.3% to 16.3%), respectively. The Cuzick and Edward's k-nearest neighbor test found significant clustering at 8, 10, and 11 nearest neighbors; however, no local cluster was suggested by SaTScan. In the final multivariable model, the PC representing agricultural land as positive loading and forest land as negative was positively associated with brucellosis sero-positivity, whereas barn cleaning was negatively associated, suggesting good farm hygiene is important for preventing bovine brucellosis.