Responses of ewes to B. melitensis Rev1 vaccine administered by subcutaneous or conjunctival routes at different stages of pregnancy.

An experiment to determine the innocuousness and the humoral immune response of B. melitensis Rev1 vaccine was carried out in pregnant ewes. Thirty-three ewes were vaccinated on day 55 of pregnancy: 9 ewes received 2 X 10(9) Rev1 of French origin by the subcutaneous route, 9 ewes were conjunctivally vaccinated with 5 X 10(8) of the same strain, 7 ewes were subcutaneously vaccinated with 10(9) Rev1 of Spanish origin and 8 ewes received 1.8 X 10(9) Spanish strain Rev1 by conjunctival route. Another group (8 animals) were subcutaneously vaccinated with a reduced dose (10(6) of the French strain between days 90 and 120 of pregnancy. Finally, 20 ewes were vaccinated on day 120 of pregnancy with the French strain of which 11 received 10(9) Rev1 by the subcutaneous route and 9 were conjunctivally vaccinated with the same dose. Rev1 strain was isolated from the vaginal discharge of a significantly higher number of ewes vaccinated subcutaneously than in conjunctivally vaccinated ewes (24/35 versus 9/26 respectively; P less than 0.001). No difference between the two vaccine strains was recorded in the number of ewes excreting Rev1. Ewes subcutaneously vaccinated on day 55 of pregnancy aborted more frequently than conjunctivally vaccinated ewes (11/16 versus 2/17, respectively), hence a significantly reduced (P less than 0.001) length of pregnancy. Although 10 of the 11 animals subcutaneously vaccinated on day 120 of pregnancy excreted Rev1 strain, only one aborted. There was no significant effect of the time of vaccination on both abortions and length of pregnancy in ewes conjunctivally vaccinated with the French strain.(ABSTRACT TRUNCATED AT 250 WORDS)