Efficacy of Phase I and Phase II Coxiella burnetii Bacterin Vaccines in a Pregnant Ewe Challenge Model.

The bacterium can cause the disease Q-fever in a wide range of animal hosts. Ruminants, including sheep, are thought to play a pivotal role in the transmission of to humans; however, the only existing livestock vaccine, namely, Coxevac (Ceva Animal Health Ltd., Libourne, France), a killed bacterin vaccine based on phase I strain Nine-Mile, is only approved for use in goats and cattle. In this study, a pregnant ewe challenge model was used to determine the protective effects of Coxevac and an experimental bacterin vaccine based on phase II against challenge. Prior to mating, ewes ( = 20 per group) were vaccinated subcutaneously with either Coxevac, the phase II vaccine, or were unvaccinated. A subset of pregnant ewes ( = 6) from each group was then challenged 151 days later (~100 days of gestation) with 10 infectious mouse doses of , Nine-Mile strain RSA493. Both vaccines provided protection against challenge as measured by reductions in bacterial shedding in faeces, milk and vaginal mucus, and reduced abnormal pregnancies, compared to unvaccinated controls. This work highlights that the phase I vaccine Coxevac can protect ewes against infection. Furthermore, the phase II vaccine provided comparable levels of protection and may offer a safer and cost-effective alternative to the currently licensed vaccine.