Q fever: A long-term strategy of vaccination requires a reasonable compromise

Coxiella burnetii causes Q fever and Coxiellosis, respectively. An inactivated vaccine (Coxevac (R), Ceva) is registered in Germany for cattle and goats. It a zoonotic pathogen; therefore the risk of infections of humans (e.g. holidays on farms) should be minimized. The presence of C. burnetii in milk is of economic importance; however, so far pasteurization of milk is regarded as safe and the oral route of infection is regarded to be of subordinated importance. Finally, vaccination is done to protect animals from clinical disease. Considerations in favour of vaccination need to be balanced by the risk of side effects due to vaccination and the costs of vaccination. On the basis of a case it is demonstrated that vaccination reduces the concentration of C. burnetii at herd level. Shedding of the pathogen at calving was detected 8 months after vaccination, thereafter only sporadic cases were observed. Vaccination had no effect on pathogen shedding by chronically infected cows (e.g. milk). These animals need to be identified prior to vaccination and should be removed from the herd in a coordinated manner. An existing immunity got boostered by vaccination. The control of C. burnetii results in a growing number of susceptible heifers. Therefore vaccination at the age of 12-15 months is recommended. Revaccination every 9 months increases the risk of side-effects and costs both are decreasing the acceptance to maintain long-term vaccination. As a consequence we decided to revaccinate once prior to the second pregnancy. A single revaccination 16 months after first vaccination resulted in a strong increase of phase II-specific-Interferon gamma-response and phase II-antibody titres which is typical for a boostered immunity. The proposed concept in this herd is still controlled by regularly tested vaginal swabs collected at calving.