Although the number of MRSA-positive pig herds is on a par with 2010 levels, significantly more pigs at slaughter were found to be infected with pig MRSA, and the number of people infected with the bacteria is increasing, according to a Danish surveillance report, DANMAP, for 2011.
MRSA bacteria are resistant to antimicrobial agents that are essential to treating life-threatening infections in humans. The number of people diagnosed with MRSA continues to rise, but compared with other countries, Denmark still experiences a low occurrence of infections caused by MRSA bacteria.
In 2011, the occurrence of MRSA was studied in approximately 80 pig farms and about 800 pigs and 180 cattle in slaughterhouses. MRSA was not found in cattle, but in 16 percent of pig herds, which was the same level as in 2010.
Approximately 44 percent of the pigs tested positive for MRSA at slaughter, which was higher than in 2009, when the last survey of pigs in slaughterhouses was conducted. This suggests that there was a higher occurrence in the positive herds than previously which means that MRSA more frequently was transmitted between pigs during transport and before slaughter.
The number of people infected with MRSA of the so-called pig type, CC398, increased from 109 in 2010 to 164 in 2011. MRSA CC398 constituted 12.5 percent of all MRSA cases in 2011. The vast majority of new cases were still seen in persons in direct contact with pigs.
"We need to prevent increasing occurrence of MRSA in pigs because we have a large pig production in Denmark and pigs are the main source of MRSA CC398", says Yvonne Agersø, Senior Researcher at the National Food Institute, Technical University of Denmark.
As a consequence of the increasing occurrence of MRSA CC398 contact with live pigs is now included as a risk factor in the revised MRSA guideline for healthcare professionals which will be published this autumn.
"The continued increase of community acquired MRSA and the increasing occurrence in agriculture should be taken seriously and combated as it could otherwise lead to increased hospital incidence. The fact that contact with live pigs is added as a risk factor in the revised MRSA guideline and is an important step in the right direction", says Robert Skov.