Background: A Q-fever outbreak occurred in an urban area in the south of the Netherlands in May 2008. The distribution and timing of cases suggested a common source. We studied the spatial relationship between the residence locations of human cases and nearby small ruminant farms, of which one dairy goat farm had experienced abortions due to Q-fever since mid April 2008. A generic geographic information system (GIS) was used to develop a method for source detection in the still evolving major epidemic of Q-fever in the Netherlands. Methods: All notified Q-fever cases in the area were interviewed. Postal codes of cases and of small ruminant farms (size >40 animals) located within 5 kilometres of the cluster area were geo-referenced as point locations in a GIS-model. For each farm, attack rates and relative risks were calculated for 5 concentric zones adding 1 kilometre at a time, using the 5-10 kilometres zone as reference. These data were linked to the results of veterinary investigations. Results: Persons living within 2 kilometres of an affected dairy goat farm (>400 animals) had a much higher risk for Q-fever than those living more than 5 kilometres away (Relative risk 31.1 [95% CI 16.4-59.1]). Conclusions: The study supported the hypothesis that a single dairy goat farm was the source of the human outbreak. GIS-based attack rate analysis is a promising tool for source detection in outbreaks of human Q-fever.

SUMMARY: A Q fever outbreak occurred in the southeast of The Netherlands in spring and summer 2007. Risk factors for the acquisition of a recentCoxiella burnetiiinfection were studied. In total, 696 inhabitants in the cluster area were invited to complete a questionnaire and provide a blood sample for serological testing of IgG and IgM phases I and II antibodies againstC. burnetii, in order to recruit seronegative controls for a case-control study. Questionnaires were also sent to 35 previously identified clinical cases. Limited environmental sampling focused on two goat farms in the area. Living in the east of the cluster area, in which a positive goat farm, cattle and small ruminants were situated, smoking and contact with agricultural products were associated with a recent infection. Information leaflets were distributed on a large scale to ruminant farms, including hygiene measures to reduce the risk of spread between animals and to humans.

The Netherlands is again facing a sharp increase in Q fever notifications, after the unprecedented outbreaks of 2007 and 2008. The most affected province of Noord Brabant has a high density of large dairy goat farms, and farms with abortion waves have been incriminated. Mandatory vaccination of small ruminants has started and should have an effect in 2010. A large multidisciplinary research portfolio is expected to generate better knowledge about transmission and additional control measures.

Q fever is a worldwide zoonosis caused by the bacterium Coxiella burnetii which is common in a wide range of wild and domestic animals. Cattle and small ruminants, in particular sheep and goats, have been associated with large human outbreaks. Humans become infected primarily by inhaling aerosols that are contaminated by C. burnetii. Most infections remain asymptomatic but in about 40% lead to a febrile disease, pneumonia and/or hepatitis. Chronic infections, mainly endocarditis, are observed in 3 to 5% of cases, with an increased risk for pregnant women and persons with heart valve disorders or impaired immunity. Q fever in pregnancy, whether symptomatic or asymptomatic, may also result in adverse pregnancy outcomes [1]. Q fever in humans is a notifiable disease in The Netherlands. The notification criteria for a confirmed case of acute Q fever are clinical symptoms consistent with Q fever and a positive serology defined by immunofluoresence assay (IFA) test or a C. burnetii complement fixation test [2]. Also clinical patients diagnosed by PCR are considered as confirmed cases. Between 1997 and 2006, Q fever was notified rarely with an average of 11 (range 5-16) cases annually [3]. In 2007, we reported in this journal the first community outbreak of Q fever in the south of The Netherlands [4].

The aim of this study was to estimate the seroprevalence of Coxiella burnetii in dairy goat farms in the Netherlands and to identify risk factors for farm and goat seropositivity before mandatory vaccination started. We approached 334 eligible farms with more than 100 goats for serum sampling and a farm questionnaire. Per farm, median 21 goats were sampled. A farm was considered positive when at least one goat tested ELISA positive.

Q fever, caused by Coxiella burnetii, is a recognized occupational infection in persons who have regular contact with ruminants. We determined C. burnetii seroprevalence in residents living or working on dairy cattle farms with >50 adult cows and identified risk factors for seropositivity. Serum samples from farm residents, including employees, were tested for C. burnetii IgG and IgM; seroprevalence was 72.1% overall and 87.2%, 54.5%, and 44.2% among farmers, spouses, and children, respectively. Risk factors included farm location in southern region, larger herd size, farm employment, birds in stable, contact with pigs, and indirect contact with rats or mice. Protective factors included automatic milking of cows and fully compliant use of gloves during and around calving. We recommend strengthening general biosecurity measures, such as consistent use of personal protective equipment (e.g., boots, clothing, gloves) by farm staff and avoidance of birds and vermin in stables. <!-- link to audio presentation here --> <!--[if!IE]><!--> Download MP3 <!--><![endif]--><!--[if IE]> Download MP3 <![endif]--> Length: 1:34