Prevalence of Clostridium perfringens in faeces and ileal contents from grass sickness affected horses

Bryony Waggett, EGSF Research Assistant, University of Edinburgh (2010)

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Clostridium perfringens colonies on tryptose sulphite cycloserine agar.

While previous studies have demonstrated an association between equine grass sickness (GS) and the presence of the bacteria Clostridium botulinum within small intestinal (ileum) contents and faeces, no such associations with other intestinal-derived anaerobic bacteria have been extensively investigated. The Waggett et al., (2010) study investigated the prevalence of a bacterium called Clostridium perfringens within small intestinal (ileum) contents and faeces of GS cases and control cases by using two techniques: selective culture and a commercially available enzyme linked immunosorbent assay (ELISA). The prevalence of Clostridium perfringens in faeces from GS horses and healthy grazing control horses was determined by both selective culture and ELISA to permit both validation of the ELISA and inter-group comparisons. Additionally, the prevalence of Clostridium perfringens (ELISA) in ileal contents from GS horses was compared with that for control horses with non-gastrointestinal disease. Finally, the prevalence of Clostridium perfringens (ELISA) in faeces from GS cases was compared with that from both horses with which they shared pasture at the time of disease onset and non-GS colic horses.

The prevalence of Clostridium perfringens in faeces as determined by both culture and ELISA was higher for GS horses (7/9 and 15/37, respectively) than for healthy grazing controls (0/60 and 1/74, respectively). The prevalence of Clostridium perfringens in ileal contents from GS horses (5/10) was non-significantly greater than that for horses with non-gastrointestinal disease (1/12). GS cases had a significantly greater prevalence of Clostridium perfringens in faeces (15/37) than co-grazing horses (1/18) and colic (1/16) horses.

The use of a commercial ELISA for the detection of Clostridium perfringens in equine faecal samples was comparable to, yet slightly less sensitive than, selective culture. The prevalence of Clostridium perfringens in faeces and ileal contents of both GS and control horses is comparable to that previously reported for Clostridium botulinum. The reason for the increase in prevalence in GS is unclear; however, it may reflect non-specific anaerobic bacterial overgrowth either in response to a nutritional trigger or within a dysmotile bowel and further work is warranted to determine whether anaerobic overgrowth precedes the development of GS or is a consequence of intestinal dysmotility. Finally, the use of a commercial ELISA to detect faecal Clostridium perfringens may be diagnostically beneficial when differentiating GS cases from colic cases, although further work is required to fully evaluate its potential.

Full reference: Bryony E. Waggett, B.C. McGorum, U. Wernery, D. J. Shaw and R.S. Pirie (2010). Prevalence of Clostridium perfringens in faeces and ileal contents from grass sickness affected horses: comparisons with 3 control populations. Equine Veterinary Journal (In press).