Brucella abortus

Brucellosis in cattle is a disease caused by Brucella abortus (B. abortus), a facultative, intracellular bacterium. The major mode of disease transmission is ingestion of B. abortus organisms that may be present in tissues of aborted fetuses, fetal membranes and uterine fluids. In addition, infection may occur as the result of cattle ingesting B. abortus-contaminated feed or water. Infection in cows has also occurred through venereal transmission of the organism by infected bulls.

Abortion is the outstanding clinical feature of the disease. If the carrier state develops in a majority of infected cows in a herd, the clinical manifestations may be reduced milk production, dead calves at term and a higher frequency of retained placentas. Disease in the bull may produce infections of the seminal vesicles and testicles, resulting in shedding of the organisms in semen.

Diagnosis is based on serological (serum/milk) and bacteriological procedures. While a positive bacteriological finding is the most definitive diagnosis, several weeks may be required to obtain final culture results. The success of disease eradication depends upon rapid and accurate identification.