Seroepidemiological and risk factor survey among Dutch livestock farmers (SBV-I) and veterinarians (SBV-II) exposed to Schmallenberg virus

In early November 2011 a new orthobunyavirus, provisionally named the
Schmallenberg virus (SBV), was detected in cattle with diarrheal disease in
Germany. Early December, this virus was found in association with malformed
lambs in The Netherlands. Since then, similar findings have been observed in
sheep and cattle in the Netherlands, France, Belgium and the UK. Viruses of the
family Orthobunyaviridae are segregated into genotypes and serogroups as
taxonomic units. The SBV belongs to the Simbu serogroup, that contains several
other viruses causing similar syndromes in ruminants, but also some viruses
that cause febrile illness (reportedly without congenital malformations) in
humans. Therefore, the possibility that this virus would cause disease in
humans cannot be excluded at this stage, although there are no indications
from regular surveillance . Transmission of SBV most likely occurs through
vectors such as midges and possibly mosquitos, and the current problems in
cattle and sheep are related to a peak of infections during late summer. Humans
may have been exposed during that time period as well. The birth of malformed
sheep and cattle leads to increased manual contact of farmers and veterinarians
during delivery, adding a second source of exposure as birthing material
contains genetic material of SBV. If human infection would be possible,
farmers and veterinarians in close contact with or living and working in the
same area as infected animals are most likely to have been at risk.

The aim of this study is to do a sero-survey among farmers - including their
family and employees - and veterinarians living and/or working with livestock
and - if sero-positive cases would be found - to identify risk factors for
sero-positivity and to evaluate the association of seropositivity with reported
health complaints.

This is a cross-sectional study among farmers - including their family members
and employees - and veterinarians living around and/or working with livestock.
Questionnaires and serum samples will be obtained from farmers from
SBV-infected farms and veterinarians that worked at SBV-infected farms. Farmers
will be enrolled in cooperation with the Animal Health Service; veterinarians
attending the GGL conference in Doorn on March 28th 2012 will be enrolled if
they report to have worked at SBV-infected farms. Samples will be screened
using a SBV neutralisation test on Vero-e6 cells with SBV antigen. If positive
samples are found, by the use of the questionnaires the risk factors associated
with SBV seropositivity will be studied in this occupational group. Results
will be compared with a historic reference sample set from the same risk
groups.

For the farmers, the burden for the participation of this study consists of:

- blood sampling through a single venapuncture to obtain a serum sample (2
tubes of 5 ml) per person at the participating farm by a research assistant
from a municipal health service (maximum 10 minutes per person). The research
assistant will make an appointment for the farm visit by phone. Research
assistants will perform blood sampling at the farm location in order not to
burden the study participants with extra travel time.
- completion of an individual questionnaire for those providing a blood sample
(approx 10 minutes). The research assistant will hand out the questionnaire
during the farm visit and collect them at the end of the visit after checking
for completeness..
-The complete farm visit of the research assistant will take approximately 1
hour (blood sampling and check for completeness of the individual
questionnaires for 2 participants per farm).

For the veterinarians, the burden for the participation of this study consists
of:
- Blood sampling through a single venapuncture to obtain a serum sample (2
tubes of 5 ml). In order not to burden the study participants with extra travel
time, blood sampling will be performed at the GGL conference March 28th in
Doorn by two research assistants. The participants receive study information at
least one week in advance of the GGL conference, completion of a questionnaire
(approximately 10 minutes). This will be checked by a research assistant for
completeness.

Participation to the study is on a voluntary basis. The burden associated with
participation is marginal. The risks are negligible as the study entails a
single venapuncture carried out by a research assistant experienced in taking
blood samples and the completion of a questionnaire. Physical examinations or
other tests are not part of the study design. Study participants will be
assigned an anonymous study ID which will be used 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 farms or practices. As indicated on
the informed consent form, upon request participants can receive their test
result if it is positive from the GGD, with microbiological interpretation and
explanation.