MRSA and swine veterinarians ? results from AASV member survey

May 13, 2008 — Peter Davies, Matt Allerson, Sri Sreevatsan, Jeff Bender

To estimate the prevalence of methicillin-resistant Staphylococcus aureus (MRSA) in US swine veterinarians, at the 2008 AASV Annual Meeting in San Diego we collected nasal swabs from 150 volunteers. The survey is part of a study of MRSA in pigs, pork products and swine veterinarians sponsored by the National Pork Board.

Eight (7.1%) positive culture results were obtained from the 113 swine veterinarians (37 volunteers who were not veterinary graduates, mostly students, tested negative). Six (7%) positive results were obtained from 87 US swine veterinarians, and 2 from 26 veterinarians from other countries (published estimates for the US population indicate a prevalence of the order of 1%). Based on spa typing, 5 of the 8 isolates were closely related to the 'livestock associated' MRSA clone that appears to be widespread in the Dutch and Canadian swine industries. Three of these were isolated from US veterinarians (n = 87) from 3 different states, and the other 2 from Canadian veterinarians (n = 23). Together with a recent report of the detection of this clone on a swine farm in Iowa, these findings indicate that this clone is present in the US industry and may be widespread (given veterinarians from 3 states were positive).

The pig associated clone can certainly cause human infections - a small number of cases, including some severe infections, have been reported from Holland. However, there is no report yet of fatal disease. As yet, this clone has not occurred in human cases in the USA that have been collected as part of CDC surveillance activities. Dutch authorities have concluded that foodborne transmission is not a significant concern, and are focusing on occupational risk. Given that Holland (which has a rigorous surveillance system for MRSA) is an important pig producing country and has been aware of high prevalence of exposure of workers for several years, this indicates that we are not likely facing any imminent crisis for occupational health in the industry. Together with Tara Smith (University of Iowa) and Wondwossen Gebreyes (Ohio State University), we will be pursuing further research to try and understand the epidemiology of MRSA in the US swine industry.

Farms are places where minor injuries (e.g. skin cuts) are frequent. Recognition that our workers may have an above average risk of MRSA exposure should make us ensure that proper procedures are in place for rapid treatment of workplace injuries. It is important to practice good hygiene - regular hand washing with soap and water; pay attention to existing and new skin wounds (clean and cover with bandages until healed); do not share personal items. Also, seek medical attention if concerned about any infections that develop.

We would like to thank everyone who participated, and commend the willingness of the AASV members to be involved. All participants who requested to receive their results should soon receive notification by email or mail.

[Ed. Note: For more information on MRSA visit the AASV Human Health Committee web page for a Fact Sheet on MRSA and additional references.]

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Peter Davies, Matt Allerson, Sri Sreevatsan, Jeff Bender University of Minnesota