Brucellosis seropositivity and risk factors in small ruminants and livestock workers: A cross-sectional study in Punjab, Pakistan.

Brucellosis is a major zoonotic disease worldwide. This cross-sectional study aimed to determine the seropositive proportion of brucellosis and identify associated risk factors in small ruminants (sheep and goats) and livestock workers in Punjab, Pakistan. A total of 1783 blood samples were collected from unvaccinated sheep and goats across 219 flocks, along with 122 blood samples from occupationally exposed humans using convenience sampling of villages and flocks. Serum samples were tested using a commercial indirect-ELISA kit. Overall, 2.0 % of animals were seropositive, 9.1 % of flocks had at least one seropositive animal, and 9.8 % of livestock workers were seropositive. Significant animal-level risk factors included flock sizes > 50 (OR: 6.5), extensive production systems (OR: 5.6), introduction of new animals without quarantine (OR: 17.1), and mixed farming with large ruminants (OR: 4.0). In humans, contact with seropositive animals (OR: 8.2), animal abortions (OR: 16.2), and unpasteurized milk consumption (OR: 23.3) were key predictors. Real-time PCR confirmed Brucella abortus in sheep and goats, but no Brucella DNA was detected in humans. These findings underscore the importance of integrated surveillance, farmer education, and biosecurity measures to mitigate zoonotic transmission. Further large-scale studies using advanced molecular tools are recommended to validate these findings and support targeted brucellosis control programs.