Seroepidemiologic and risk factor survey for Coxiella burnetii antibodies among Dutch veterinarians working with livestock.

Q fever, caused by Coxiella burnetii, is a worldwide zoonosis affecting both
humans and animals, and a re-emerging public health problem in the Netherlands.
In 2007, 2008 and 2009, there were large and prolonged outbreaks of Q fever. In
2007, a community outbreak with 176 laboratory-confirmed cases occurred in a
rural area in the south of the Netherlands and in 2008 this number raised with
a total of 1000 confirmed cases. In 2009 the epidemic is even larger and until
2 September 2009 a total of 2110 persons are notified with diagnosed acute
Q-fever.
Dairy goats are considered an important source and Q fever-induced abortion
wave have occurred at farms located near human Q-fever clusters in the South of
the Netherlands. Veterinarians have a high level of exposure to Coxiella
Burnetii, the causative organism of Q fever, especially those veterinarians who
treat livestock.
Dutch data on veterinarians date from the 1980*s when Richardus et al. measured
IgG antibodies against Coxiella burnetii among veterinarians and found a
seroprevalence of 84%. Even though other studies used a different laboratory
test and found lower seroprevalences, varying from 9.5%-63%, the veterinarian
populations is considered a high-risk group for acquisition of Q-fever. This
clearly stresses the need for research study assessing recent data about
occurrence and risk factors of Q-fever among veterinarians in the Netherlands.
As a consequence of the research study and knowledge transfer, greater
awareness of Q fever in this high-risk occupational group can prevent delays in
diagnosis and treatment and help identify chronic forms at an early stage.
Also, increased awareness may enhance efforts to control further transmission
between animals and humans.

The aim of this study is to estimate the seroprevalence of past C. burnetii
infection among veterinarians working with livestock and to identify
(coccupational) risk factors associated with Q fever seropositivity in
veterinarians. This will give insight into the epidemiological links and
transmission routes, making it possible to recommend preventive measures to
reduce transmission from infected animals to humans.

For this study, an individual self-administered questionnaire and a blood
sample will be obtained from veterinarians attending the 3-day GGL conference
in Doorn mid-November 2009. The questionnaires contain questions about
person-based risk factors (age, gender, individual exposure to ruminants and
pets, clothing protection measurements, consumption of raw milk or fresh dairy
products, medical history, outdoor activities, tick-bites and contact with
agricultural products such as hay and straw). The questionnaire will be
self-administered by the veterinarian at home before visiting the GGL
conference and after receipt at the GD and RIVM checked for completeness. If
incomplete, additional information will be collected during the conference or
by phone.
The blood samples will be collected during the GGL conference by a medical
research assistant, with expertise and authorisation in blood sampling. Through
a single venapuncture 2 tubes (4 ml) of serum will be obtained for
determination of Coxiella burnetii serostatus with Q-Fever IgG
immunofluorescence assay (Focus Diagnostics) for phase 1 and 2 IgG, using a cut
off value of 1:32. End point IgG titers will be determined for samples with
positive results. The Jeroen Bosch Hospital in Den Bosch will analyse the blood
samples. The test result of the IgG test (IFA) does not have individual
therapeutical implications as it represents historical exposure to Coxiella
burnetii only. If indicated on the individual informed consent form,
participants can request their test result with microbiological interpretation
and guidance from their general practitioner; or receive the test result
directly by post within 8 weeks after the blood sample was taken.

The burden for the participation of this study consist of:
-Blood sampling through a single venapuncture to obtain a serum sample 2 tubes
(4 ml) by a research assistant (maximum 10 minutes per person). The research
nurse will take the blood sample at the GGL conference in order not to burden
the study participants with extra travel time. Blood sampling will be divided
in different time slots. The participants get information about the exact blood
sample time in advance to minimize the waiting time at the blood sample spot.
-Completion of a questionnaire for those providing a blood sample (approx 15
minutes). This will be checked by the research assistant on completeness.
The risk are negligible as the study entails a single venapuncture during a
farm visit carried out by a research assistant experienced in taking blood
samples from all age groups and the completion of a hard-copy or online
questionnaire. Study participants will be assigned an anonymous study ID which
will be use to analyze and store the data. Results of the study will only be
reported on a group level and cannot be deducted to the individual or to
individual practices. If indicated on the individual informed consent form,
participants can request their test result with microbiological interpretation
and guidance from their general practitioner; or receive the test result
directly by post within 8 weeks after the blood sample was taken.