Recently researchers Dr Angelika Schoster, University of Zurich; Dr Scott Weese OVC; Miranda Abrahams, and Mohammad Jalali studied the organisms potentially causing diarrhea in foals in a longitudinal study.

Foals and mares

Results of the research are significant because they highlight the continued importance of multiple pathogens in causing foal diarrhea.

According to the researchers, most foals experience an episode of diarrhea before 6 months of age. In this study, we collected fecal samples biweekly from normal foals, foals with diarrhea, and their dams (604 samples total) over their first four months of life.

Samples were cultured for Clostridium difficile, a common bacterial pathogen isolated from foals with diarrhea. Samples that were cultured positive for C. difficile were also tested for the presence of toxins, which are thought to be required for the bacteria to cause diarrhea.

Additionally ribotype strains were determined for all culture positive samples to determine genetic relationship to previously identified strains.

Mares, healthy foals, and diarrheic foals all shed C. difficile at different time points throughout the study. Foals under one month of age were significantly more likely to shed C. difficile than older foals, but foals with diarrhea did not shed more C. difficile than foals without diarrhea.

All of the culture positive samples contained toxins, and 21 different ribotype strains were identified. Four of these strains have been previously identified in human C. difficile infections.

These results are significant because they highlight the continued importance of multiple pathogens in causing foal diarrhea; the fact that shedding of C. difficile was not significantly correlated with diarrhea in these foals suggests that a multitude of other pathogens may have been responsible for the diarrhea observed in these foals.

Younger foals were more likely shed C. difficile, which is consistent with previous reports. Additionally, the identification of strains which cause disease in humans amongst our study population raises concerns for biosecurity and public health on equine breeding farms.

Further analyses in the laboratory are currently under way to identify additional organisms present potentially causing diarrhea in foals.

Dr. Henry Staempfli, Department of Clinical Studies