Submitted to: Research Workers in Animal Diseases Conference Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: November 13, 1995
Publication Date: N/A
To determine placental tropism and abortigenicity of the vaccine candidate, B. abortus strain RB51, a rough mutant of the virulent strain 2308, 10 Polled Hereford heifers were inoculated intravenously in the sixth month of gestation. Heifers were euthanized and examined at 8 weeks p.i.(n=5) or at full term (n=5). Four of five heifers sampled at 8 weeks p.i. and 3/4 heifers at term had placentitis. Trophoblastic epithelium of the placentomal arcade zone had abundant intracytoplasmic bacteria that were immunoreactive for RB51 antigen. Tips of maternal septae had a lymphoplasmacytic infiltrate with small multifocal erosions and ulcerations of maternal epithelium. RB51 was cultured from all tissues in which lesions were seen. Placentae of one cow from each group had no placentitis and were culture negative for RB51. Four of five fetuses from heifers examined at 8 weeks p.i. and 3/4 full term calves had RB51 in liver, spleen, lung and bronchial lymph nodes but no lesions were seen. One heifer in the full term group delivered a premature weak fetus. The dam had severe placentitis and lymphoplasmacytic endometritis. All tissues and fluids sampled from the heifer and calf contained RB51. These results establish that B. abortus strain RB51 can infect the bovine placenta and fetus and can induce placentitis which in some cases can lead to preterm labor.