An integrated study on Q fever in livestock farmers and ruminant animals in the Netherlands

Q fever seems to be re-emerging among ruminants and humans in the Netherlands
leading to a growing public health concern. This disease, caused by Coxiella
burnetii, is a zoonosis with a worldwide distribution that affects both humans
and animals. Internationally, the most frequent sources of human Q fever are
domestic ruminants, such as cattle, goats and sheep. Transmission to humans is
primarily through the aerosol route. The clinical presentation in humans varies
from asymptomatic to severe pneumonia. Chronic infection and reproductive
disorders may also develop. Infections in ruminants are mainly subclinical, but
abortions and preterm birth of stillborn animals can occur.

Since May/June 2007, the number of human cases has been increasing (2007: 160,
2008: 1000, 2009 up to early June about 900). Since 2005, abortion waves due
to Q fever occurred on several dairy goat farms in the same region. A study on
the seroprevalence of C. burnetii in the general human population is ongoing.
However, the current prevalence of C. burnetii in sheep and goats and in
high-risk human populations is unknown. Old data from the 1980's demonstrated a
high seroprevalence in farmers and veterinarians. Currently, no evidence-based
effective control measures are available. Therefore, a concerted action of
human and veterinary experts is taken to identify individual and farm-related
risk factors,*high-risk* regions and consider the risk of occupational exposure
to C. burnetii in the agriculture sector.

From a public health perspective, the development towards large-scale farming
(so called 'megastallen'), also observed among goat farms, raises concern among
the public and health professionals about the infection risks of neighbouring
communities, for which scientific evidence is lacking. This integrated approach
can further elucidate the role of herd size on infection risk in both animals
and humans.

Overall aim: to determine the extent and risk factors for farm-based and
individual acquisition of Coxiella burnetii infections on ruminant farms to
improve veterinary, occupational and public health by providing leads for
primary (reduce circulation in the ruminant reservoir) and secondary (reduce
transmission from infected animals to humans) prevention.

To achieve this, the following objectives are formulated:

1. To determine C. burnetii serostatus in small ruminants (sheep and goats) and
livestock farmers (sheep, goats), their adult family members and (preferably
young trainee) farm workers.

2. To determine farm-based and individual risk factors for positive serostatus
for C.burnetii in small ruminants and humans working or living on livestock
farms.

3. To develop laboratory-based tools for source investigation in future
outbreaks by creating a baseline database of circulating subtypes of C.burnetii
in human (if possible), small ruminants and the farm environment in the
Netherlands.

A cross-sectional seroprevalence and risk factor study among livestock farmers,
adult family members, farm workers and livestock on ruminant farms. A random
sample will be drawn from the UBN-database of the Animal Health Service (GD)
stratified by ruminant type (goat, sheep, dairy cattle) based on sample size
calculations and expected participation (40%).
All eligible farms in the sample will receive a letter and an information
leaflet explaining the purpose of the study, the way their data will be used
and a response card. All approached farms will be asked to sign a written
informed consent before actual enrolment in this study. Individual participants
(adults, and youth (12-17 years) will be requested to provide a blood sample,
with a maximum of three persons per farm. A self-administered farm-based
questionnaire will be obtained to identify risk factors and the farm history,
as well as a questionnaire for each individual providing blood to assess
individual exposure and risk factors. In a subset of 30 Q-fever positive and 10
Q-fever negative farms, a more indepth analyses of environmental samples will
be investigated to study the spread in the farm environment.

For this study, data will be collected through farm visits performed by a
research assistant. Individual self-administered questionnaires (about 15
minutes) and a blood sample will be obtained (about 10 minutes) from a maximum
of three adults per farm by the research assistant, who gave informed consent
The visit will take about an hour, dependent on the number of study
participants, and to check the completeness of the questionnaires (1 individual
questionnaire per study participant, and 1 farm-based questionnaire per farm
visited). The farm-based questionnaire will be self-administered by the farmer
(about 30 minutes) and checked for completeness.