Comparison between subcutaneous and conjunctival route of vaccination with Rev. 1 strain against Brucella melitensis infection in ewes.

In areas where the prevalence of Brucella melitensis infection in sheep is high, control of the disease cannot be led without the help of vaccination. The use of Brucella melitensis strain Rev. 1 vaccine affords a very good protection. The drawback is that this vaccine, giving rise to long-lasting antibody titers, may disturb serological screening when a return is made to a test and slaughter policy, after several years of vaccination. There is a great need for another mode of vaccination which would avoid this disadvantage. In this experiment, the potency of a vaccination by conjunctival route with 1.4 X 10(8) Rev. 1, plus a recall of 2.9 X 10(8) six months later, was compared with that of the normal subcutaneous vaccination with 1.4 or 2.7 X 10(9) Rev. 1. The vaccination by conjunctival route afforded a somewhat better protection than the subcutaneous one, and with a shorter serological response. It may be possible that a single conjunctival vaccination, avoiding the difficulties of vaccinating twice in ovine flocks and giving few antibodies, could also afford a good protection. Research in progress should include investigation of this point.