Link: D3 MRSA 2003.
RESULTS: MRSA was identified from 82 horses and 29 human contacts: 29 (35%) of equine cases were from the VH, and 41 (50%) from one thoroughbred farm. 16% of horses were clinically infected compared to only one human. Typing found 95% of equine and 93% of human MRSA to be Canadian MRSA-5/spa type 7 (related to the “Archaic” strain). Uncommon in humans in Ontario, these strains were typically resistant (R) to tetracycline and gentamicin, variably R to erythromycin, co-trimoxazole and rifampin, invariably susceptible to fluoroquinolones and frequently exhibited borderline oxacillin-R at 24h (MIC, 1-8mg/L) increasing to MIC 32mg/L at 48h. Another uncommon MRSA, PFGE clone X, identified at the VH and thoroughbred farm from 3 horses and 2 humans, was shown to harbor an indistinguishable SCCmec type IV gene cluster as the CMRSA-5 strains.
CONCLUSIONS: Based on timing of isolation, sub-typing and evaluation of animal and human contact, combinations of human-to-horse, horse-to-human, and horse-to-horse transmission were all suspected. Equine MRSA infection may be emerging as an important zoonotic and veterinary nosocomial disease.
