The rise and control of the 2007–2012 human Q fever outbreaks in the Netherlands

Abstract

Q fever is an almost ubiquitous zoonosis caused by Coxiella burnetii, which is able to infect several animal species, as well as people. Cattle, sheep and goats are the primary animal reservoirs. In small ruminants, an infection may result in abortion and stillbirth. Infected animals can shed the organism in faeces, milk and mainly in foetal membranes and foetal fluids. Transmission to humans mainly occurs through the aerosol route.Q fever was described as a febrile illness, which had started to occur in 1933 in abattoir workers in Brisbane, Australia. Since the first documented outbreaks, Q fever has been described in many countries all over the world, and in 1955 its existence was reported in 51 countries on five continents. In the Netherlands, Q fever was diagnosed for the first time in humans in 1956, and became a notifiable disease in 1978. Between 1978 and 2006, the average number of notifications per annum was seventeen. In 2007, the first year of what later turned out to be one of the largest recorded community outbreaks of Q fever, an outbreak occurred with 168 human patients notified, and in 2008 and 2009, 1000 and 2354 human Q fever patients were notified, respectively, and dairy goats were suspected to be the source.In 2005, C. burnetii was diagnosed for the first time as a cause of abortion at two dairy goat farms in the Netherlands. In 2006, 2007, 2008, and 2009, six, seven, seven, and six new abortion waves at dairy goat farms were confirmed, respectively. The infected dairy goat farms were mainly located in the same area where human cases occurred and they were considered the most plausible source of human infection. In the same period, cases of abortion caused by C. burnetii were confirmed at two dairy sheep farms.Since 2007, a large multidisciplinary research portfolio has started, aimed at generating better knowledge about this disease. In June 2008, Q fever in small ruminants kept for milk production became notifiable in the Netherlands for farms with an abortion rate of more than five per cent. In the autumn of 2008, a voluntary vaccination campaign in goats was made possible in the high-risk Q fever area in the south of the Netherlands with the so far unregistered phase I vaccine containing inactivated C. burnetii (Coxevac®, CEVA Santé Animale). From 2009 onwards, vaccination became compulsory for dairy sheep and dairy goat farms in the south of the country, and was compulsory in the whole country from January 2010 onwards for dairy sheep and dairy goat farms, and for small ruminant farms offering recreational activity. Since February 2009, a stringent hygiene protocol became mandatory for all dairy goat and dairy sheep farms, and on 1 October 2009, bulk milk monitoring became mandatory on farms with more than fifty dairy goats or dairy sheep, and C. burnetii PCR positive bulk milk has since been used as an additional criterion for veterinary notification of Q fever. At the end of 2009, it was decided to cull all pregnant animals on farms with a C. burnetii PCR positive bulk tank milk. Since 2010, there was a sharp decline in the number of notified human cases with 504, 81, and 66 cases notified in 2010, 2011, and 2012, respectively. In combination with a rise in the human population with antibodies against C. burnetii, the implemented control measures most likely have ended this large outbreak.