Methicillin-resistant Staphylococcus aureus in horses at a veterinary teaching hospital: frequency, characterization, and association with clinical disease

Methicillin-resistant Staphylococcus aureus (MRSA) is an emerging equine pathogen. To attempt to control nosocomial and zoonotic transmission, an MRSA screening program was established for all horses admitted to the Ontario Veterinary College Veterinary Teaching Hospital, whereby nasal screening swabs were collected at admission, weekly during hospitalization, and at discharge. MRSA was isolated from 120 (5.3%) of 2,283 horses: 61 (50.8%) at the time of admission, 53 (44.2%) during hospitalization, and 6 from which the origin was unclear because an admission swab had not been collected. Clinical infections attributable to MRSA were present or developed in 14 (11.7%) of 120 horses. The overall rate of community-associated colonization was 27 per 1,000 admissions. Horses colonized at admission were more likely to develop clinical MRSA infection than those not colonized at admission (OR 38.9, 95% CI 9.49 160, P < 0.0001). The overall nosocomial MRSA colonization incidence rate was 23 per 1,000 admissions. The incidence rate of nosocomial MRSA infection was at the rate of 1.8 per 1,000 admissions, with an incidence density of 0.88 per 1,000 patient days. Administration of ceftiofur or aminoglycosides during hospitalization was the only risk factor associated with nosocomial MRSA colonization. MRSA screening of horses admitted to a veterinary hospital was useful for identification of community-associated and nosocomial colonization and infection, and for monitoring of infection control practices.     

Brittle tail syndrome is an emerging infection in horses caused by a keratinolytic fungus Equicapillimyces hongkongensis gen. nov., sp. nov

The newly described brittle tail syndrome causes weakening and breakage of the tail hair of horses. Extensive mycological and molecular studies showed that a novel fungus Equicapillimyces hongkongensis gen. nov., sp. nov. is the most likely cause of this syndrome. It is a septate branching hyaline mould which grows optimally at 30°C, requires nicotinic acid but is inhibited by cycloheximide, and specifically infects horse hair. Hyphae fill the core of infected hair shafts with short-necked structures resembling ascomata containing banana-shaped septate ascospore-like structures perforating the hair cortex from within. Compared to asymptomatic horses (n=31), horses with clinical signs of the syndrome (n=22) are significantly more likely to have positive E. hongkongensis gen. nov., sp. nov. smear (6.5% vs. 100%), culture (6.5% vs. 72.7%), and PCR (32.3% vs. 100%, P<0.001 for all). No other potential pathogens were found on bacteriological and mycological culture or PCR (for Trichophyton, Microsporum and Epidermophyton). Genotyping of pure E. hongkongensis gen. nov., sp. nov. isolates and their corresponding direct specimens by PCR and sequencing of the 18S rRNA, ITS1-5.8S-ITS2, 28S rRNA, beta-actin, beta-tubulin, and elongation factor 1 alpha showed that they are all identical but unique, and related distantly to fungi mostly in the class Sordariomycetes and the family Ophiostomataceae. Its geographical distribution, environmental or animal reservoirs are still unknown. Besides the ugly appearance of infected horse tails, this fungus may emerge as another equine pathogen if it affects the skin and hoof of horses.