Experimental Clostridium difficile Enterocolitis in Foals

Abstract

Despite empirical clinical association of infection withClostridium difficilewith colitis in horses, a causal link has not been confirmed. The objective of this study was to develop a model ofC difficile–associated diarrhea in foals with normal transfer of passive immunity. Nine 1‐day‐old pony foals were inoculated intragastrically with spores or vegetative cells ofC difficile.Five foals were challenged with spores, with 2 receiving 105colony‐forming units (CFUs) and concurrently 3 receiving 107CFUs once daily for 3 days. Clindamycin was administered orally to disrupt gastrointestinal flora. A further 4 foals were challenged by orogastric administration of 1010CFUs of vegetative cells once daily for 3 days or until diarrhea developed. This group did not receive clindamycin. Spore and vegetative cell preparations were negative for toxins ofC difficileand common enteropathogens. Clinical signs varied from mild abdominal discomfort and pasty feces to colic and watery diarrhea in 8 of 9 foals. Four of 5 foals challenged with spores developed mild diarrhea, whereas all foals challenged with vegetative cells developed moderate to severe diarrhea.C difficilewas isolated from feces of all foals between 24 and 72 hours after inoculation and toxins A or B or both were detected in the feces of all foals by an enzyme‐linked immunosorbent assay. We concluded that spores and vegetative cells ofC difficileare capable of colonizing the gastrointestinal tract, producing toxins, and inducing clinical signs similar to those encountered in naturally occurring cases. This study fulfilled Koch's postulates forC difficile–associated diarrhea in foals and provides a model for consistent reproduction of the disease for future studies.