Comparative efficacy of ten commercial Campylobacter fetus vaccines in the pregnant guinea pig: challenge with Campylobacter fetus serotype A.

Efficacy of ten commercial Campylobacter fetus vaccines was tested in pregnant guinea pigs and compared with that of an experimental vaccine prepared from the challenge-exposure strain. If the first lot of vaccine failed to protect 50% of the guinea pigs, one or two additional lots of that vaccine were purchased and retested. Three vaccines for cattle, evaluated, as the most effective of those tested, protected 62%, 72%, and 89% of the guinea pigs from abortion; the experimental vaccine protected 98%. The two vaccines for sheep protected 50% and 61% of the guinea pigs from abortion. With the other five vaccines produced for immunizing cattle, protection was from 0% to 36%, with the exception of one lot of a vaccine that protected 74%. Blood infection was found at necropsy in only 6% of the guinea pigs given vaccines that protected 50% or more from abortion, but was found in 66% of those given vaccines that protected less than 50%. Similarly, tissue infection was found at necropsy in only 18% of the guinea pigs given vaccines that protected more than 50%, but was found in 91% of those given vaccines that protected less than 50% from abortion. Oil-emulsion adjuvants appeared to enhance protection from abortion and infection. Nodules persisted at the injection site in most of the guinea pigs immunized with vaccines containing oil-emulsion adjuvants, but rarely persisted in guinea pigs given aqueous-phase adjuvant vaccines. Comparison of efficacy of the vaccines in guinea pigs with efficacy in sheep and cattle remains to be made.