SUMMARYThe 2007-2009 human Q fever epidemic in The Netherlands attracted attention due to its magnitude and duration. The current epidemic and the historical background of Q fever in The Netherlands are reviewed according to national and international publications. Seroprevalence studies suggest that Q fever was endemic in The Netherlands several decades before the disease was diagnosed in dairy goats and dairy sheep.

Coxiella burnetii is an intracellular bacterial pathogen that causes Q fever. Infected pregnant goats are a major source of human infection. However, the tissue dissemination and excretion pathway of the pathogen in goats are still poorly understood. To better understand Q fever pathogenesis, we inoculated groups of pregnant goats via the intranasal route with a recent Dutch outbreak C. burnetii isolate. Tissue dissemination and excretion of the pathogen were followed for up to 95 days after parturition. Goats were successfully infected via the intranasal route. PCR and immunohistochemistry showed strong tropism of C. burnetii towards the placenta at two to four weeks after inoculation. Bacterial replication seemed to occur predominantly in the trophoblasts of the placenta and not in other organs of goats and kids. The amount of C. burnetii DNA in the organs of goats and kids increased towards parturition. After parturition it decreased to undetectable levels: after 81 days post-parturition in goats and after 28 days post-parturition in kids. Infected goats gave birth to live or dead kids. High numbers of C. burnetii were excreted during abortion, but also during parturition of liveborn kids. C. burnetii was not detected in faeces or vaginal mucus before parturition. Our results are the first to demonstrate that pregnant goats can be infected via the intranasal route. C. burnetii has a strong tropism for the trophoblasts of the placenta and is not excreted before parturition; pathogen excretion occurs during birth of dead as well as healthy animals. Besides abortions, normal deliveries in C. burnetii-infected goats should be considered as a major zoonotic risk for Q fever in humans.

Q fever is a zoonosis caused by the bacterium Coxiella burnetii. One of the largest reported outbreaks of Q fever in humans occurred in the Netherlands starting in 2007; epidemiologic investigations identified small ruminants as the source. To determine the genetic background of C. burnetii in domestic ruminants responsible for the human Q fever outbreak, we genotyped 126 C. burnetii–positive samples from ruminants by using a 10-loci multilocus variable-number tandem-repeat analyses panel and compared them with internationally known genotypes. One unique genotype predominated in dairy goat herds and 1 sheep herd in the human Q fever outbreak area in the south of the Netherlands. On the basis of 4 loci, this genotype is similar to a human genotype from the Netherlands. This finding strengthens the probability that this genotype of C. burnetii is responsible for the human Q fever epidemic in the Netherlands.

Recently, the number of human Q fever cases in the Netherlands increased dramatically. In response to this increase, dairy goats and dairy sheep were vaccinated against Coxiella burnetii. All pregnant dairy goats and dairy sheep in herds positive for Q fever were culled. We identified the effect of vaccination on bacterial shedding by small ruminants. On the day of culling, samples of uterine fluid, vaginal mucus, and milk were obtained from 957 pregnant animals in 13 herds. Prevalence and bacterial load were reduced in vaccinated animals compared with unvaccinated animals. These effects were most pronounced in animals during their first pregnancy. Results indicate that vaccination may reduce bacterial load in the environment and human exposure to C. burnetii.

Coxiella burnetii is the causative agent of Q fever, a well-known zoonosis. The clinical presentation of Q fever is non-specific in most animals, with the exception of ruminants where Q fever is responsible for late abortion and stillbirths. Q fever has only recently been included in the Community Summary Reports on Zoonoses. Reporting from the European Union Member States is not harmonised and the level of information available varies considerably. Therefore, a project on the development of harmonised schemes for the monitoring and reporting of Q fever in animals in the European Union was launched. More than 30 different animal species susceptible to Q fever have been recorded in Europe. However, domestic ruminants (cattle, sheep and goats) represent the source most often associated to human outbreaks. Thus, it is proposed to focus monitoring schemes on domestic ruminants. A standardised definition is suggested for a herd/flock considered as clinically affected with Q fever. This includes the occurrence of serial abortions, confirmation of the presence of C. burnetii by Polymerase Chain Reaction and positive serology by Enzyme-Linked Immunosorbent Assay. It is further proposed that the monitoring of Q fever should mainly rely on a passive system aiming at the identification of clinically affected herds and flocks and diagnostic methods should include a combination of Enzyme-Linked Immunosorbent Assay and Polymerase Chain Reactions. Guidelines for the interpretation of the test results are presented for cattle and small ruminants. Active monitoring schemes may be applied in countries that need to evaluate Q fever prevalence in their animal populations when the disease frequency in humans or animals is suspected to be high. Active monitoring can involve either bulk tank milk testing or sero-surveys. Harmonised reporting forms are suggested for submitting the information at Community level.