Brucella suis infection in pregnant cattle

Abstract

Six pregnant cows in 11 to 33 weeks of gestation were each inoculated into the right conjunctival sac with 0.2 ml of a smooth culture of Brucella suis type I containing 27 million viable organisms. The 6 cows produced 7 calves, of which one single calf and one twin calf were stillborn (cause not determined). Br. suis was not isolated from any cow or calf using either special media or guinea-pig inoculation. No abnormality was found in any cow or calf at autopsy. Microscopic examination of placentas and tissues from stillborn calves revealed no abnormality. Serologically, 2 weeks after inoculation all 6 cows had positive reactions to the rose bengal test (RBT) and serum agglutination (SAT) titres of 25 iu to 116iu. However, these reactions disappeared within 11 weeks. Only 2 cows had a complement fixation (CFT) titre which lasted a maximum of 5 weeks and reached a titre of 4/4. Following the anamnestic use of Br. abortus strain 45/20 vaccine on 3 of the cows, positive RBT reactions, SAT titres of 33, 29 and 58 iu, and CFT titres of 4/16, 1/8 and 3/8 (respectively) were recorded 6 weeks after vaccination.