Effects of oral or intravenous inoculation with Brucella abortus strain RB51 vaccine in Beagles

Abstract

Objectives - To determine whether the vaccine Brucella abortus strain RB51 (SRB51) would infect dogs, be shed in urine or feces, or cause placentitis and abortion. Animals - 18 Beagles. Procedure - Males (n = 3), nonpregnant females (n = 3), and pregnant females (n = 4) were inoculated orally with SRB51; control dogs (n = 2) were fed sterile saline solution. A separate group of pregnant females (n = 5) received SRB51 IV, and their controls (n = 1) received sterile saline solution IV. Dogs were observed twice daily for evidence of abortion. Urine and feces were collected periodically for bacteriologic culture, and blood was collected for bacteriologic culture and serologic analysis. At full gestation (oral and IV inoculated pregnant females) or on postinoculation day 49 (nonpregnant females and males), dogs were euthanatized and samples were collected for bacteriologic culture and microscopic examination. Results - Abortion was not apparent during the study, and SRB51 was not found in samples of urine or feces from any dog. Strain RB51 was isolated from retropharyngeal lymph nodes from all orally inoculated dogs (9/9). One orally inoculated and 1 IV inoculated pregnant dog had SRB51 in placental tissues. Strain RB51 was also isolated from 1 fetus from the orally inoculated female dog with placentitis, but lesions were not detected in the fetus. Conclusions and Clinical Relevance - Oral inoculation of nonpregnant female or male dogs with SRB51 did not result in shedding in urine or feces, although oropharyngeal lymph nodes became infected; in pregnant females, it caused infection of the placenta, with resulting placentitis and fetal infection, but abortion was not apparent. Intravenous inoculation resulted in infection of maternal spleen, liver, and placenta; however, fetal infection and abortion were not observed. Infected canine placental membranes or fluids may be a source of infection for other animals and human beings.