Screening for methicillin-resistant Staphylococcus aureus (MRSA) upon arrival to a veterinary hospital is useful for detecting cases of the “superbug” early so affected horses can be isolated, said Scott Weese, DVM, DVSc, Dipl. ACVIM, an associate professor at the University of Guelph’s Ontario Veterinary College (OVC). This practice reduces the chance that the emerging antibiotic-resistant zoonosis (disease transmissible from a non-human animal to humans) will be spread to horses and personnel.

Weese said OVC detected its first case of MRSA in 2000. Since then, he and colleagues have made it policy to swab the nasal passages of every horse admitted to the hospital. Weese presented an abstract on MRSA data collected between Oct. 4, 2002, and June 15, 2004, at the annual meeting of the American College of Veterinary Internal Medicine (ACVIM) held June 1-4 in Baltimore, Md.

“Screening programs are very important in human hospitals,” said Weese, saying OVC took their lead. “Every horse at OVC gets swabbed coming in, weekly, and leaving.” Not only does this allow for isolation of infected horses, it differentiates community-acquired (picked up outside the hospital) from nosocomial (caught in the hospital) infections.

Hospital personnel swabbed 2,283 of 3,056 admitted horses (74.7%) at least once in the study. MRSA was isolated from 120 of the 2,283 (5.3%). Of those, 61 (50.8%) were community-associated and 53 (44.2%) were nosocomial. The origin of six of the infections was unclear. Clinical infections (including anything from septic arthritis to an incision or wound infection) were present or developed in 14 of the 120 horses (11.7%)