Coxiella burnetii DNA in goat milk after vaccination with Coxevac®

Q fever is a zoonotic disease caused by Coxiella burnetii, a species of bacteria that is distributed globally. A large Q fever epidemic is currently spreading throughout the Netherlands with more than 3500 human cases notified from 2007 to 2009. Governmental measures to prevent further spread of the disease imposed in December 2009 included vaccination of all dairy goats and sheep and, in parallel, bulk tank milk testing to identify contaminated goat and sheep farms. When bulk tank milk was found to contain C. burnetii DNA, pregnant ruminants were culled. An important, but unsolved issue in this policy was whether vaccine-derived C. burnetii DNA is excreted in milk after vaccination. Using real time PCR and single nucleotide polymorphism (SNP) genotyping techniques, we show here that within hours and up to 9 days after vaccination with Coxevac®, vaccine-derived C. burnetii DNA can be detected in the milk of dairy goats. This is the first report describing DNAlactia of vaccine-derived DNA after vaccination with a completely inactivated vaccine. This finding had implications for the Dutch policy to combat the Q fever epidemic. A 2-week interval was introduced between vaccination and bulk tank milk testing to identify infected farms.