Immunohistochemical localization of Clostridium perfringens beta2-toxin in the gastrointestinal tract of horses.

Clostridia-associated intestinal disease in horses was generally reported to be due to infection with Clostridium perfringens type A, which harbors the cpa-encoded alpha-toxin. A recent study demonstrated a high incidence of beta2-toxigenic C. perfringens in horses suffering or dying from typhlocolitis, suggesting that this novel type of C. perfringens might play an important role in typhlocolitis and possibly other equine intestinal diseases. A retrospective study was conducted to assess the presence of the beta2-toxin in tissues of the equine gastrointestinal tract. Monospecific polyclonal antibodies against recombinant beta2-toxin were produced in rabbits and used to demonstrate the beta2-toxin in sections of the gastrointestinal tract by immunohistochemical methods. Sections from 69 horses were stained and beta2-toxin was observed immunohistochemically in 40 animals. Sections from the stomach, small intestine, and large intestine were positive. Immunopositivity for beta2-toxin was significantly associated with presence of beta2-toxigenic bacteria. This investigation demonstrates local production of beta2-toxin and suggests that immunohistochemistry using antitoxin antibodies represents a useful diagnostic method in those cases where isolation of bacteria and polymerase chain reaction typing is not feasible. Although the association between the presence of beta2-toxin and development of gastrointestinal disease in horses remains uncertain, the findings of this study indicate that the potential causal relationship warrants further investigation.