"Pig MRSA" in Horses
Methicillin-resistant Staphylococcus aureus (MRSA) is an emerging problem in horses. This antibiotic-resistant bacterium can cause disease in both horses and the people in contact with them. In the early 2000s, virtually all reports of MRSA in horses in North America, and many from Europe, involved one particular "strain" of MRSA. This strain goes by different names in different places, but in Canada its called CMRSA-5, and in the US it's called USA500. This is actually a strain that originated in people but which seems to be well adapted to horses.
Recently, there was a report in the journal Veterinary Microbiology describing the isolation of a different MRSA strain from 10.9% of horses tested on admission to a veterinary teaching hospital in Belgium. This strain, called ST398, is getting a lot of attention lately, because it is being commonly found in pigs (and perhaps cattle). It is also emerging as an important cause of disease in people in Europe. In the Belgian study, the horses carrying ST398 were from different areas (not just one farm or town), which suggests that the strain is widespread in the horse population in that region. The source of ST398 in these horses is unknown, but it is reasonable to suspect that it may have moved from pigs to horses. The impact this will ultimately have on horses and people that work with horses, in Belgium, Europe and other parts of the world, is unclear, but one has to assume that this strain could become a problem, just like CMRSA-5.
More information on this topic can be found in the previous equIDblog post entitled "Horses and MRSA". More information about MRSA can also be found on the equIDblog Resources page.
