Prevalence and risk factor investigation for exposure to Brucella species in surrogate stray cattle population reared in cow shelters in Punjab, India.

Abstract

Bovine brucellosis is endemic in cattle in India, however not much is known on the prevalence of this disease in stray cattle populations of the country. This study aimed to estimate the prevalence and identify risk factors associated with brucellosis in the stray cattle populations reared in cow shelters (gaushalas) of Punjab, India. Blood samples were collected from 587 cattle reared in 23 cow shelters in 23 districts (one per district) of the Punjab and were tested using Rose Bengal plate test (RBPT), standard tube agglutination test (STAT) and Indirect Enzyme Linked Immunosorbent Assay (i-ELISA). Information on the sex and breed of the animal, total cattle population and presence of a separate shed for parturition were collected. An animal was considered exposed to Brucella infection based on a positive RBPT or STAT test and a positive i-ELISA test. Explanatory variables for the animal level disease status outcome variable were sex and breed of the animal and at the shelter level were shelter cattle population size and presence of a separate shed for parturition. Univariable binomial exact logistic regression analysis was conducted to assess the association of each explanatory variable with the binary outcome variable. Sixty-two animals were seropositive on RBPT, with an apparent seroprevalence of 10.56% (95% confidence interval [CI]: 8.33%, 13.31%) and the estimated true seroprevalence of 11.48% (95% CI: 8.9%, 14.64%). Sixty three animals were seropositive using STAT [apparent seroprevalence of 10.73% (95% CI: 8.48%, 13.50%) and the estimated true seroprevalence of 10.69% (95% CI: 8.27%, 13.67%)], and 68 using i-ELISA [an apparent seroprevalence of 11.58% (95% CI: 9.24%, 14.43%) and the estimated true seroprevalence of 13.28% (95% CI: 10.50%, 16.66%)]. Cross bred cattle had a lower risk of being test positive (odds ratio 0.16, p=0.04) as compared to indigenous cattle. Due to a ban on cow slaughter in the country, roaming stray cattle infected with brucellosis present a permanent risk of introduction of disease to the dairy farms and other vulnerable populations.