High Occurrence of Methicillin-Resistant Staphylococcus aureus in Horses at Slaughterhouses Compared with Those for Recreational Activities: A Professional and Food Safety Concern?

This study investigates the prevalence and genetic characteristics of Methicillin-Resistant Staphylococcus aureus (MRSA) in horses, and its potential transmission to humans. The study found a high occurrence of MRSA in horses at slaughterhouses compared to those at farms or racecourses, and also identified MRSA carriers among people working closely with horses.

Research Objective

• The objective of this study was to better understand the epidemiology of MRSA in horses and its potential for zoonotic transmission – in other words, its ability to pass from animals to humans. This was done by examining the prevalence of MRSA in horses in several environments (farms, racecourses, and slaughterhouses) and in people working closely with horses. The research also aimed to identify the genetic characteristics of the MRSA strains present.

Methods Used

• The researchers used standard and molecular methods to test for MRSA in horses. They took nasal swabs from 388 horses across various environments – farms, racecourses, and slaughterhouses – and carried out laboratory analysis on these samples to determine the presence of MRSA.
• They also tested 67 humans who had close contact with horses, such as those working in slaughterhouses, riding stables, or racecourses.

Research Findings

• A total of 7% of the tested horses were found to carry MRSA. Most significantly, the prevalence of MRSA was found to be much higher in horses at slaughterhouses compared to those at farms or racecourses.
• The MRSA strains identified in horses were ST398 (t011, t899, t1255) and ST1 (t127), while the strains identified in humans were ST398 (t011, t034) and ST1 (t127).
• A small number of the staff members tested (7%) were also found to be carriers of MRSA. These individuals worked across all three environments studied: slaughterhouses, riding stables, and racecourses.
• The MRSA strains identified in both horses and humans carried the SCCmec IVa or V gene, were pvl negative and pia positive, and demonstrated resistance to at least two classes of antimicrobials. This suggests that these strains could be difficult to treat if they cause infections.

Conclusion and Implications

• The researchers concluded that the presence of MRSA in horses and in humans working closely with them is an emerging public health issue. This is due to the risk of MRSA being transmitted from horses to humans, particularly those working in close contact with horses. There is also a potential risk for people who consume horse meat.
• The high prevalence of MRSA in horses at slaughterhouses is a particular concern, from both a professional and food safety perspective.