EFFICACY OF BRUCELLA-SUIS STRAIN-2 VACCINE AGAINST BRUCELLA-OVIS IN RAMS

The protective efficacy against Brucella ovis of live vaccine Brucella suis strain 2 (S2) and Brucella melitensis strain Rev 1 has been eval uated in rams. Fourteen 4-month-old Brucella-free Aragonesa rams were vaccinated conjunctivally with 2 x 10(9) c.f.u. S2. Sixteen rams of th e same breed, condition and age were conjunctivally vaccinated the sam e day with 1.6 x 10(9) Rev 1. Thirteen rams were unvaccinated controls . Eight months after vaccination all rams were challenged with 6 x 10( 9) cfu. B. ovis and slaughtered 2 months thereafter for bacteriologica l and pathological studies. The percentage of infection in the group v accinated with Rev 1 (43.7%) was significantly lower (p < 0.05) than t hat of the S2-vaccinated animals (78.6%) and unvaccinated controls (84 .6%). No significant differences were found when comparing the percent ages of infection corresponding to S2-vaccinated and con trol groups. The degree of infection (percentage of necropsy samples infected) was significantly lower in Rev 1-vaccinated (13%) than in S2-vaccinated (3 6.9%) or control groups (47.4%) (p < 0.001). However, no significant d ifferences were found when comparing S2-vaccinated and control groups.