Status of brucellosis in a dairy cattle herd with history of abortion in Morogoro District, Tanzania

Abstract

Bovine brucellosis, caused by Brucella bacteria, is a zoonotic disease with major public health and economic impacts, including decreased milk production and reproductive losses such as abortion. It can spread through milk consumption, posing health risks to humans. This study aimed to investigate the presence of Brucella infection in a dairy herd with a history of abortions and the risk practices associated with bovine brucellosis. A cross-sectional study, conducted from January to March 2024, investigated a dairy herd of 36 cattle, with 47.22% (17/36) identified as adult cows. Milk, blood, and serum samples were collected.  Cattle over six months old (n=31) were tested for brucellosis using both the Rose Bengal Plate Test (RBPT) and competitive ELISA (c-ELISA), with both tests performed on the same samples. Brucella DNA was detected using Real-time Polymerase Chain Reaction (qPCR) targeting the IS711 insertion sequence. Specific genes, BruAB_0168 and BMEII0466, were amplified to identify Brucella abortus and Brucella melitensis, respectively. Cohen’s Kappa statistic was used to assess the level of agreement between RBPT and c-ELISA results. A focus group discussion used to assess potential risk practices associated with brucellosis focusing on abortion history, handling and disposal of aborted materials, management of aborting and sick cows, contact with other livestock and wildlife, routine health monitoring, and biosecurity practices. As the study targeted a single farm, potential risk practices were evaluated qualitatively rather than statistically.  Serological testing revealed Brucella exposure in the herd, with 41.94% (13/31) testing positive using the RBPT and 74.19% (23/31) testing positive using c-ELISA. qPCR identified Brucella DNA in three out of 36 serum samples, with one sample specifically confirmed as Brucella abortus. These findings confirm Brucella infection in the herd. A comprehensive reproductive health strategy and ongoing monitoring are needed to improve herd health and reduce economic losses.