Should I Test My Horse For MRSA?
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Methicillin-resistant Staphylococcus aureus (MRSA) is an emerging problem in horses. Owners often ask if they should have their horses tested to see if they are MRSA carriers. There's no simple answer that applies to all farms, but basic points that need to be considered include:
- MRSA is endemic in the horse population. A small percentage (<5%) of healthy horses carry MRSA at any given time, and it likely circulates regularly between groups of horses.
- MRSA infection only occurs in a small percentage of the horses that are exposed to the bacterium - most horses never develop signs of illness.
- MRSA can be transmitted to between horses and people.
So you can see why people might want to test their horses and there are few situations where screening really makes sense. Remember, though, that screening is only useful if you plan to do something about the results. If your horse is MRSA positive, what will you do? If the answer is nothing, or you'll just make sure you wash your hands well after handling your horse, I'd tell you that you should be doing that anyway and not bother with the test. However, there are a few scenarios when screening horses for MRSA is a good idea:
- Screening is a key component to any plan to eliminate MRSA from the farm. Eradication of MRSA can usually be accomplished quite effectively using screening and good infection control practices (and, if there are no clinically infected horses, not one dose of antibiotics!).
- Some farms routinely screen incoming horses for strangles before they are allowed to have contact with resident horses. This can be done for MRSA as well, to reduce the risk of MRSA getting onto the farm and silently spreading from horse to horse. It's not as straightforward for MRSA as it is for strangles, because we know less about the best screening methods and, probably more importantly, people (not just horses) can bring MRSA onto the farm.
- When an MRSA outbreak is underway, or when efforts are being made to determine why a particular horse developed an MRSA infection, screening can be useful - but again, only if there's a plan to use the results.
- Our equine hospital screens horses for MRSA on admission, so that we can isolate carriers and reduce the risk of transmission to our highly susceptible hospitalized patients. It also helps us identify farms with MRSA problems that might benefit from implementing an eradication program. We also screen horses at the time of discharge to make sure MRSA has not been transmitted to them while they were in hospital.
Screening your average horse on your average farm is harder to justify. A single negative result might give you a false sense of security, because a horse that is negative today might be positive tomorrow, or it might positive already but the current testing methods couldn't detect it. The use of good infection control practices is much more important than testing for day-to-day MRSA control. Screening for MRSA is something that is usually only considered in specific circumstances.
More information about MRSA can be found on the equIDblog Resources page.
