Methicilline Resistant Staphylococcus aureus in calves and calve owners

Staphylococcus aureus represents a colonizer and pathogen for human as well as
for various animal species. Prevalence of methicilin-resistant S. aureus (MRSA)
in human medicine has constantly increased in many parts of Europe. In the
Netherlands the occurrence of MRSA among clinical isolates is still <1%, among
the lowest in Europe. In the south of Europe this can be 20-50%. The low
prevalence in The Netherlands can largely be explained by our national search
and destroy policy, in combination with restrictive antibiotic use. This low
antibiotic pressure in the Netherlands, probably limits the selection of
resistant micro-organisms, including S. aureus. Since 1995, the Netherlands has
been confronted with a few MRSA outbreaks that could not be related to patients
with known risk factors for MRSA carriage as indicated. If MRSA strains are
circulating in the community outside the hospitals, the risk factors would not
be sufficient for a successful search and destroy policy, and further outbreaks
might be the consequence.
Companion animals such as dogs, cats an horses, have been implicated more
frequently in recent years as potential reservoirs of MRSA. Initially, MRSA
infections were sporadically described in companion animals but the number of
reports has markedly increased in the last few years. Various case reports have
documented MRSA infections in dog owners associated with colonization by
genetically related strains in their dogs. Genetically related MRSA isolates
have also been reported in horses and pigs in-contact humans. Transmission of
Staphylococcus Aureus has been reported between owners and their pets. The
occurrence of MRSA in dogs and cats has been reported with frequencies between
1% and 10% of samples . Although mucosal carriage of MRSA has been demonstrated
in individual pets, horses and veterinary staff few data exist on the
prevalence of MRSA in these
groups.
In 2004 a possible relationship
between pig and calve farming and a higher risk of MRSA carrier ship was found
in the Netherlands. A recent study of slaughterhouse pigs showed a prevalence
of 39%. In France also a relation between pig farming and MRSA carrier ship
was found because of strain exchanging with swine. Wulf et al., found recently
a prevalence of 3.9% in veterinary students and 4.6% in veterinarians which
indicate that people who are in close contact with livestock are at higher
risk.
The transmission of MRSA primarily takes place of colonized or infected persons
to others. The bacteria spread between air channels, dust and skin particles.
Infection is especially dangerous for people with diminished resistance e.g.
operated people. A healthy person can be infected with MRSA but most probably
will not notice the infection. This healthy person can become a carrier. The
potential source of contamination of animal and farmers by MRSA strains is not
yet investigated. Possibly personal hygiene may play a role.
Another explanation of MRSA transmission could be the fact that MRSA organisms
can travel within bioaerosols. Chapin et al., found a high level of
multidrug-resistant bacteria in the air of a concentrated swine feeding
operation. These findings therefore suggest that inhalation of air from these
facilities may serve as an exposure pathway for the transfer of multi-resistant
bacterial pathogens from swine to human. Recently Gibbs et al found that high
levels (comparable as within the facility) of antibiotic resistant bacteria
(inclusive MRSA) persist to (at least) 150 meter downwind of the swine
facility. This indicate that those who working inside the facility and those
living in close proximity downwind of the facility could be at risk for adverse
human health effects associated with exposure to large numbers of antibiotic
resistant organisms.

Little is known about the epidemiology of MRSA-infections in animals in the
Netherlands. Also not much is known about the risks of transmission of MRSA
between animals and humans. Therefore an epidemiological study in a defined
population of calvefarmers. Risk factors should be determined including the
prevalence of MRSA in animals. This could lead to a risk assessment of the MRSA
spread of animals to humans.
The main aim of this study is to assess the prevalence of MRSA carrier ship in
these study population and to determine the risk factors and transmission
patterns.

1. estimate the prevalence of MRSA among calve farmers, their families and
relevant co-workers at the calve farm;

2. determine potential risk factors for MRSA carriage for these groups

3. determine the association between MRSA prevalence and types of MRSA in calve
farmers and calves

4. Is the nasal swab sufficient enough to detect MRSA contamination in calves?

5. Is there an association between specific facility characteristics and MRSA
contamination.
6. What are the transmission pathways of MRSA?
7. When is a facility contaminated with MRSA?
8. How develops a MRSA contamination on a calve facility over time?

A Random sample of 100 calve farmers out of all Dutch calve farmers will be
taken. Calve farmers will be invited to participate to the study using a letter
signed by the researcher and theri own proffesional bodies. A brochure with
information about the study and an informed consent form will be attached. The
farmers will be asked to join the study by telephone. At a preffered time, an
appointment will be made to take noseswabs of study subjects, to complet the
questionnaire and doing the air sampling in and outside the calve barns.

A researher will vistit the farm and swab all persons who gave informed
consent. The visit will take 30 min, depending on the number of study
participants, to complete the questionnaires. (1 per participant).