Submitted to: American College of Veterinary Pathologists Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: November 17, 1995
Publication Date: N/A
Technical Abstract: To determine the abortigenicity of the vaccine candidate, RB51, a rough mutant of the virulent strain 2308, 10 Polled Hereford heifers were inoculated i.v. in the sixth month of gestation. Heifers were euthanized and examined at 8 wks. post-inoculation (n=5) or at full term (n=5). Four of five heifers sampled at 8 wks. p.i. and 2/4 heifers at term had suppurative placentitis of the arcade zone with abundant intratrophoblastic bacteria as well as lymphoplasmacytic endometritis. In mammae, lymphoplasmacytic infiltrates in intersti- tial septae and suppurative infiltrates in alveoli were seen in 2/5 heifers at 8 wks. p.i. RB51 was cultured from all tissues in which lesions were seen. Four of five fetuses from heifers examined at 8 wks. p.i. and 2 full term calves had RB51 in liver, spleen, lung and bronchial lymph node but no lesions were seen. One heifer delivered a premature weak fetus 9 wks. p.i. The dam had severe suppurative placentitis as well as lymphoplasmacytic endometritis while the calf had mild multifocal interstitial hypercellularity with cells immuno- reactive for the macrophage marker CD68(EBM11). All tissues and fluids sampled from the heifer and calf contained RB51. These re- sults suggest that RB51 can colonize the bovine placenta, mammary gland and fetus and can induce placentitis which in turn can rarely lead to premature expulsion of the fetus.