Prevalence of netF-positive Clostridium perfringens in foals in southwestern Ontario.

NetF-producing Clostridium perfringens have recently been identified as a cause of necrotizing enteritis in neonatal foals, but little is known about its prevalence in clinically normal foals. Foals (n = 88) ranging in age from < 1 wk to 2 to 4 mo (median age 2 to 4 wk) on 8 horse-breeding farms in Ontario were examined on 1 or 2 occasions for the presence of C. perfringens. Of the foals that tested positive, 5 isolates (n = 675) were examined for the netF and enterotoxin (cpe) genes. Colonization by C. perfringens was most marked in foals < 1 wk of age [4.85 ± 2.70 log10 colony-forming units (CFU)] and declined markedly over time (1.23 ± 1.06 log10 CFU at 1 to 2 mo of age). Only 2 isolates possessed the cpe gene and none possessed netF. We concluded that netF-positive C. perfringens does not colonize young foals with any detectable frequency in Ontario and this organism is not likely to be adapted to the intestine of the horse.