A total of 16 vaginal swaps, 18 sera, 1 hygroma fluid and 14 milk samples were screened for the possible presence of Brucella abortus after one clinical case typified by hygroma was observed in a herd of 108 cattle from Logo, Benue state, Nigeria. Of all the samples screened, only one female cow returned positive for Rose Bengal plate test(RBPT), Milk Ring test (MRT) and upon culture, only same female cow was positive. The isolate grew on Serum Dextrose Agar (SDA) in atmosphere containing 10% CO2 and appeared as tiny Gram-negative, coccobacilli organism that were non- motile non-bipolar and non-spore forming. It produced hydrogen sulphite, and was urease positive. It agglutinated with positive control serum for Brucella while negative with the negative control serum. The organism grew in the presence of basic fuchsin and not in thionin dye. It was lysed by Tbilisi phage, hydrolyzed urea and agglutinated in polyclonal sera anti-A and not anti-M. The organism was therefore identified as Brucella abortus biotype 1.
Key words: Occurrence, Brucella abortus, Cattle, Logo, Benue State and Nigeria.