Experimentally induced Brucella abortus infection in pregnant goats

SUMMARY Pregnant goats in midgestation (7 to 16 weeks) were conjunctivally exposed to Brucella abortus strain 2308 to evaluate their applicability as an animal model for bovine brucellosis. Brucellae were isolated from uterine fluid and/or placental specimens of 10 of 12 does at parturition. Six of the 10 infected does delivered dead fetuses and 1 of the 10 delivered live, premature twins. Dead fetuses typically contained brucellae in multiple tissues, whereas brucellae generally were not isolated at birth from live kids. After parturition, B abortus was excreted in the milk and uterine fluids of the infected does. At necropsy (6 weeks after parturition), organisms in the doe were primarily in the uterus and in the lymph nodes that drained the mammary glands, uterus, and head. Brucella abortus was most often isolated from the cranial lymph nodes of neonates that had remained with their dam for 6 weeks after parturition. Serum anti-Brucella antibody concentrations were determined by use of standard tube agglutination, mercaptoethanol agglutination, Rivanol plate tests, card tests, complement fixation, hemolysis-in-gel tests, and an enzyme-linked immunosorbent assay. Serologic responses were detected 2 to 3 weeks after exposure and remained detectable until parturition. Antibody titers increased after parturition in does shedding B abortus at parturition. Anti-Brucella antibody was not detected in neonates before colostrum intake. The neonate’s postcolostral titers were similar to those in the dam at the time of parturition. Milk anti-Brucella antibody was detected in milk (milk ring test) from infected and noninfected mammary glands. Results of the study indicated that goats are susceptible to a bovine pathogenic strain of B abortus and should be a suitable animal model for the study of bovine brucellosis.