MRSA in pigs and pork in Europe and N. America

08.nov.08
Pig Disease Information Centre
Dr. Michael Meredith
www.pighealth.com

At the recent International Pig Veterinary Society Congress in South Africa (a biennial event), a number of swine-specialist veterinarians gave papers given on MRSA (Methicillin-resistant Staphylococcus aureus) infection in pigs. MRSA is causing increasing concern to swine breeders and pork producers around the world, especially since it was reported to be spreading in breeding pyramids in The Netherlands.

A European survey of MRSA infection in pigs is currently in progress, supported by the European Food Safety Authority (EFSA). There has been mounting concern in the European Union after discovery of MRSA in Dutch and German pigs and EU farm workers and vets. Canada and USA pig herds have also been affected.

The main concern about MRSA in swine is the risk it poses as a zoonosis risk to farmers, vets and meat industry personnel who may come into contact with infected animals. There is also concern about the effect on consumer confidence, although the real risk to consumers is very small, because the organism is easily destroyed by cooking and the main risk to humans comes from other human beings (hospital or community-acquired infection) and, to a lesser extent, from close contact with pets and horses. It is likely that some, or even many, animal infections may have come humans in the first place.

Veterinarian David Burch, of the Octagon Services farm animal health consultancy in the UK, says that MRSA probably mostly has little to no effect on pigs themselves - S. aureus is not commonly a primary pathogen, more of an opportunist infection. Piglets which acquire skin damage from rough flooring, fighting wounds, or develop infected navels or gum damage after teeth clipping, are at risk of developing MRSA bacteremia and blood-borne spread of infection to other locations. In a survey of 4,000 submissions to a diagnostic laboratory in the Netherlands, 97 isolates (2.4% of cases) of S. aureus were found. Affected organs were: joints (48%), lungs (12%), heart and pericardium (8%), spleen (8%). The incidence of brain, abscess, kidney and blood infections was below 5%. Only 16 of these (0.4% of submissions) involved MRSA, demonstrating the low clinical impact the infection has in the pig, despite surveys indicating 39% infection of Dutch pigs and 81% of pig farms being infected.

Apart from hygienic precautions, especially thorough hand-washing after handling potentially infected animals or equipment, Burch recommends that pig keepers should ask the breeder about MRSA checks before purchasing breeding stock.

He suggests that MRSA-related biosecurity at both national and farm level also has to be increased. More information about MRSA in pigs can be found at: www.pighealth.com