An epidemiological survey was conducted to identify probable risk factors and prevalence of brucellosis in commercial and backyard dairy cows at Chittagong, Bangladesh. A total of 500 milk samples were collected (250 commercial and 250 backyards) for Milk Ring Test (MRT). The MRT positive cows were subjected to sera collection and Rose Bengal Plate Test (RBPT) and indirect ELISA were done for confirmatory diagnosis. The overall seroprevalence in cattle was 5% (7.6% in commercial and 2.4% in backyard). Significantly higher (P<0.05) prevalence was found in the zero grazing (5.74%), pregnant cows (7.53%) and cows with history of retained placenta (7.89%) or abortion (5.88%) or both (11.76%) than non-pregnant (2.68%) and without any reproductive disorder (4.44%). A total of 420 farm attendants and owners were interviewed where 93.55 and 99.08% commercial and backyard personnel found to have no knowledge of brucellosis and 9.67 and 87.77% consume raw milk as yogurt respectively were highly vulnerable to zoonotic brucellosis, respectively. The results showed that brucellosis is widely distributed locally, underscoring the need for further studies including biovar determination.

Key words: Bovine brucellosis, Chittagong, iELISA, Milk Ring Test, Prevalence, Rose Bengal Plate Test