Improved isolation of Clostridium perfringens from foal faeces

Enteritis and colitis in horses

Enteritis and colitis remain challenging and life-threatening diseases despite many recent advances. Successful treatment is largely dependent on early recognition and directed therapy, which is facilitated by obtaining a complete history and physical examination. A number of new therapies and methods of monitoring critically ill patients have become integral components of treatment success. The critical monitoring of equine foals and adults continues to be an exciting and emerging field.

Population-based study of fecal shedding of Clostridium perfringens in broodmares and foals

OBJECTIVE

To determine the percentage of broodmares and foals that shed Clostridium perfringens in their feces and classify the genotypes of those isolates.

DESIGN

Prospective cross-sectional study.

ANIMALS

128 broodmares and their foals on 6 equine premises.

PROCEDURES

Anaerobic and aerobic bacteriologic cultures were performed on feces collected 3 times from broodmares and foals. All isolates of C. perfringens were genotyped.

RESULTS

Clostridium perfringens was isolated from the feces of 90% of 3-day-old foals and 64% of foals at 8 to 12 hours of age. A lower percentage of broodmares and 1- to 2-month-old foals shed C. perfringens in their feces, compared with neonatal foals. Among samples with positive results, C. perfringens type A was the most common genotype identified (85%); C. perfringens type A with the beta2 toxin gene was identified in 12% of samples, C. perfringens type A with the enterotoxin gene was identified in 2.1% of samples, and C. perfringens type C was identified in < 1% of samples.

CONCLUSIONS AND CLINICAL RELEVANCE

Clostridium perfringens was identified from the feces of all but 6 foals by 3 days of age and is likely part of the normal microflora of neonatal foals. Most isolates from broodmares and foals are C. perfringens type A; thus, the clinical relevance of culture results alone is questionable. Clostridium perfringens type C, which has been associated with neonatal enterocolitis, is rarely found in the feces of horses.

Clostridial enterocolitis

Equine clostridial enterocolitis is being recognized with increasing frequency. It has been identified in foals with diarrhea, antibiotic-associated enterocolitis, or nosocomial enterocolitis. The sporadic occurrence of clostridial enterocolitis, the variety of types of clostridia involved, and the difficulty of experimentally reproducing the disease suggest that it is a poorly defined multifactorial syndrome. The risk factors associated with susceptibility to colonization and progressive infection are largely based on anecdotal observations and extrapolation from human studies. Quantitative studies are needed to decipher the complex interactions between host and indigenous microflora that provide for and maintain a healthy colonization resistance environment. It seems that such studies might be more beneficial in furthering our understanding of the pathogenesis of clostridial enterocolitis than attempting to implicate another agent or toxin as the sole cause of the disease in equids. Treatment protocols that interrupt the pathogenesis of the disease need to be devised and critically evaluated to complement the present protocols emphasizing supportive care. Perhaps it is time to consider clostridial enterocolitis as yet another consequence of the use of antimicrobials analogous to the selective pressures that result in the emergence of multiple drug-resistant pathogens.

Molecular analysis of the virulence determinants of Clostridium perfringens associated with foal diarrhoea

During an epidemiological study of foal diarrhoea, over half of the cases yielded Clostridium perfringens which was significantly associated with disease (Netherwood et al., 1996b). However, the association could not be accounted for by enterotoxigenic isolates which had a low prevalence (Netherwood et al., 1997). Nonetheless, we have hypothesized that the association may be caused by a pathogenic sub-population which would be significantly more common amongst C. perfringens-positive cases compared with C. perfringens-positive healthy controls if it acted as a pathogen when present. Conversely, if foal diarrhoea caused by C. perfringens was dependent on a predisposing factor, then such an association might not be evident. As a first step to determine if a molecular marker was more frequently to be found in C. perfringens-positive cases than controls, we have genotyped the study isolates (up to five per foal) by polymerase chain reaction (PCR) based on the published gene sequences for the major lethal toxins alpha, beta, epsilon and iota as well as for theta toxin, large and small sialidases, hyaluronidase and virulence regulation. Isolates of major toxin types B, C, D and E, or isolates which were untypeable, were isolated from less than 15% of C. perfringens-positive foals and these were not associated with diarrhoea nor were they more commonly found in C. perfringens-positive cases. Isolates of type A were found in more than 90% of all C. perfringens-positive foals. A number of different genotypes were identified by their different patterns of gene possession but types without any of the genes for theta toxin, large and small sialidases, hyaluronidase and virulence regulation were found in only 10% of positive foals. Only type A isolates with all of these genes were associated with diarrhoea overall but they were not more commonly isolated from C. perfringens-positive cases than controls. In conclusion, genotyping by the sequenced virulence genes did not identify a marker for a sub-population of C. perfringens which may be acting more frequently as a pathogen when present.