Methicillin resistant Staphylococcus aureus (MRSA) in pigs

Updated 05.01.2023

There are several varieties of Methicillin resistant Staphylococcus aureus (MRSA) some of which are associated with animals (especially pigs), and are collectively referred to as LA-MRSA (Livestock Associated - MRSA).

Within a few years, LA-MRSAs have become widespread in swine populations around the world, thereby representing a risk for dissemination to the human population.

Methicillin resistant Staphylococcus aureus (MRSA) has been surveyed yearly in pigs in Norway since 2014. The objective of the surveillance is to identify LA-MRSA positive swine herds with the intention of contact tracing and eradication, with an overall goal of keeping the Norwegian pig population free of LA-MRSA.

Background

All types of MRSA can be transmitted between humans and animals and vice versa. However, not all types are well adapted for establishing in other species than their original host specie. MRSA is not typically associated with disease in animals and healthy humans, but it is important to prevent transmission especially to health institutions such as hospitals and nursing homes where the bacteria can cause severe infections that are difficult to treat.

Surveys conducted in 2008, 2011 and 2012 indicated a very low prevalence of MRSA-positive swineherds in Norway. The MRSA belonging to the animal associated clonal complex CC398 spa-type t034 was detected in swine samples for the first time in 2011. In 2013/14, three clusters of MRSA CC398 positive swine herds were detected, in eastern and southwestern Norway, respectively, and measures to eradicate LA-MRSA from positive swineherds were imposed. The rationale behind this strategy was to avoid the swine population becoming a reservoir of MRSA with the potential of zoonotic transmission. The LA-MRSA eradication strategy includes restrictions on trade of live animals upon suspicion, depopulation of pigs in LA-MRSA positive swineherds, thorough cleaning and disinfection of premises, negative samples from the environment and mandatory down-time before restocking with pigs from MRSA negative herds. After restocking, samples were collected from animals and the environment several times to assess the effectiveness of MRSA eradication.

Since 2013/14 a number of herds have been subjected to MRSA eradicated and the strategy is considered successful though expensive and time-consuming for all involved (authorities, management support institutions and the pig production sector itself).

2021

The surveillance programme in 2021 did not detect any pig herds with MRSA. In total, 763 herds were included in the survey, of which 73 were genetic nucleus or multiplier herds, 11 herds were central units of the sow pool herds, 27 were of the largest farrow to grower or farrow to finish herds, and the remaining 652 were fattening herds.

Download report

MRSA in pigs 2021 (pdf 829kb)

Previous reports

MRSA in pigs 2020 (pdf 856kb)
MRSA in pigs 2019 (pdf 848kb)
MRSA in pigs 2018 (pdf 898kb)
MRSA in pigs 2017 (pdf 840kb)
MRSA in pigs 2016 (pdf 975kb)
MRSA in pigs 2015 (pdf 1mb)
MRSA in pigs 2014 (pdf 2mb)