Clinical aspects and prevention of Q fever in animals.

The natural reservoir of Coxiella burnetii encompasses many free-living vertebrates but the major risk of human infection arises through contact with infected ruminant livestock and their contaminated products. The organism has a remarkable affinity for the ruminant placenta and mammary gland but the great majority of naturally-occurring infections are asymptomatic. However, the potential of C. burnetii to cause abortion has been demonstrated experimentally and observed in the field while more recent evidence has implied a contributory role in bovine infertility. Empirical vaccines incorporating inactivated whole cells of C. burnetii or derivatives have induced varying degrees of protection of cattle and sheep against both natural and experimental challenge but, in some cases, severe reactions have occurred at inoculation sites. Modifications in processes of antigen preparation seem to overcome this problem. Discrimination between antibodies resulting from natural infection and those induced by vaccination is possible using ELISAs with specificity for individual immunoglobulin isotypes.