Molecular detection and epidemiology of Brucella in dairy cattle of Bangladesh

Abstract

Brucella, a Gram-negative bacterium, causes late abortion in dairy cattle. The genus Brucella has six recognized species based on host specificity, but the greatest economic impact results from Brucella abortus. Brucellosis is considered one of the most widespread zoonoses in the world by the Food and Agriculture Organization (FAO), the World Health Organization (WHO), and the Office International des Epizooties (The World Organization for Animal Health, OIE). It is an important zoonotic disease that causes significant losses in the reproduction of sexually mature animals. In pregnant cows, brucellosis is characterized by late abortion, the birth of weak calves, stillbirths, and infertility. Therefore, a cross-sectional study was conducted in commercial dairy cattle in Bangladesh to describe the epidemiological scenario of Brucella. Nineteen upazillas (sub-districts) from 12 districts of 7 divisions were randomly chosen for the study. A total of 44 dairy cattle farms, 1–6 farms per upazilla, were recruited based on the presence of abortion history within the past six months. A pretested questionnaire was used to collect epidemiological information through face-to-face interviews and direct observation. Blood samples and aborted fetuses were collected for laboratory evaluation. Aborted fetuses were collected only from Chattogram Metro. Sero-positivity for Brucella abortus was evaluated on the samples obtained using OIE protocol-based iELISA technique. Aborted fetus was evaluated through bacteriological culturing followed by PCR. The overall sero-prevalence of Brucella was 1.50 in dairy cattle in Bangladesh (Herd level and individual level). In this study, iELISA is more specific and sensitive for detecting Brucella antibodies. PCR gives more accurate and precise results for detecting Brucella abortus.