Long-term monitoring of a Coxiella burnetii-infected sheep flock after vaccination and antibiotic treatment under field conditions.

The purpose of this study was to pursue the development of a sheep flock for a period of 18 months after a Q fever outbreak. In a flock with approximately 250 ewes losses of 18% were caused by abortions and weak offspring. Q fever was diagnosed in April 2009 after detection of Coxiella (C.) burnetii in one placenta and two aborted fetuses by PCR. Shortly afterwards Q fever was diagnosed in humans. Between July 2009 and December 2010 the sheep were sampled regularly. Six weeks before lambing the flock was initially immunised with Coxevac. Moreover, pregnant ewes were treated with oxytetracyclines during late gestation until lambing. Seroprevalence increased from 39% before vaccination up to 98% afterwards. After these measures bacteraemia and shedding of C burnetii decreased significantly, indicating that during an acute outbreak the vaccination with Coxevac can reduce the shedding of C burnetii effectively, although vaccination is performed without medical approval for sheep and in late pregnancy. Both measures should be taken into consideration in acute Q fever outbreaks to reduce or even avoid transmission to humans.