Following tests that found livestock-associated Methicillin-resistant Staphylococcus aureus (LA-MRSA) in pork of Danish and Irish origin, and possibly even British as well, in UK supermarkets, Digby Scott takes a look at this high-profile bacteria.
Cases of LA-MRSA have exploded on Danish pig farms, and the disease is now prevalent on the majority of units. Only 3.5% of Danish pig herds had MRSA in 2009, but a survey carried out by the Danes last year found more than 60% of herds were now positive (63% of breeding herds and 68% of finisher herds).
If Britain drops its guard when importing live pigs, the disease could become a commonplace occupational hazard for pig unit staff in this country. Until last year the United Kingdom was deemed free from the disease, but then imported pigs caused an outbreak in Northern Ireland. This was then followed by an unexplained outbreak in two piglets in East Anglia at the beginning of this year.
In Denmark, cases of LA-MRSA in humans have increased from 14 in 2007 to 643 in 2013, and those showing not only colonisation of the nose, but infections increased from six in 2007 to 156 in 2013. Of the human cases, the overwhelming majority (87 percent) were people working closely with pigs — farmers and farm staff, and their families.
If LA-MRSA does spread widely into Britain, like it has in Denmark, The Netherlands, Spain and other countries where there’s a high prevalence, the Soil Association is likely to accuse farmers of over-using antibiotics that select for the MRSA bacteria.
What it means for pigs
Most pigs (and cattle, goats, sheep and turkeys) show no clinical signs when infected by LA-MRSA, and swabbing is necessary to determine if the bacteria is present.
LA-MRSA can persist in dust in animal housing for several months, so a full depopulation may be necessary to get rid of it. This is what happens in Norway, but such a measure would be impractical in a major pig-producing country such as Denmark.
The most recent survey for LA-MRSA in Britain was seven years ago, when no cases were found, but the Animal and Plant Health Agency acknowledges it could now be “more prevalent” in British livestock.
What it means for farm staff
People in close contact with affected livestock can be colonised by LA-MRSA, and it may then spread to those they are in close and regular contact with. If exposure to infected livestock is short-term, however, in most cases human colonisation will disappear after 24 hours away from the animals.
Most people who are colonised will have no disease and no symptoms, but it can cause opportunistic infections such as boils and abscesses, particularly in immunocompromised people.
Bearing in mind that LA-MRSA may now be present to some degree on British livestock farms, it’s sensible for pig unit staff to step up personal biosecurity measures.
- cover any open wounds and cuts;
- wash hands thoroughly after handling animals;
- if undergoing medical treatment, including surgery, tell your doctor of your occupational exposure to livestock.
What it means for consumers
The risk of a human catching LA-MRSA from meat is very low if good food hygiene is observed and the meat is properly cooked.
The NPA’s position statement on LA-MRSA is available for download at: www.npa-uk.org.uk.