Understanding MRSA infections in horses

Vets are faced with horses suffering from infections on a daily basis. Some of these are incredibly serious — if the infection is not rapidly resolved, the horse may die. But since the advent of antibiotics more than 50 years ago, vets have been able to treat most bacterial infections effectively and with confidence.

Almost as soon as antibiotics were developed, it became clear that their ability to work was likely to alter with the passage of time. This was due to the evolution of resistance by bacteria to the actions of the drugs.

Bacteria have an amazing ability not only to develop resistance to antibiotics, but also to transfer this resistance to different populations of bacteria. The end result is that, with time, antibiotics have become less efficient at killing bacteria. Consequently, diseases caused by bacterial infections become more difficult to treat.

While antibiotic drug resistance is not yet at crisis point among horses, but there are some specific areas of concern. The increasing diagnosis of MRSA infections in the horse, many of which occur in those that have recently undergone surgical treatments in equine hospitals, is a big worry.

MRSA — methicillin-resistant Staphylococcus aureus — is responsible for creating potentially fatal infections in humans, but in horses it can be treatable, which is fortunate given that vets are seeing it more frequently.

Equine MRSA can be resolved with appropriate, sometimes rather aggressive, treatment. Depending where the infection is, surgical drainage and the removal of infected tissue may be carried out. The infected horses should be quarantined while the infection is active.

A study carried out in the US in 2009 found that 84% of 115 horses with MRSA infection made a full recovery.

To read more about the growing problem of resistance to antibiotics in horses, and find out what you can do to help, see p16 Horse & Hound (31 January, 2012)