Infectious foal diarrhoea: Pathophysiology, prevalence and diagnosis

Rotavirus, Salmonella and large numbers of Cryptosporidium oocysts or helminthic parasites are long established causes of foal diarrhoea. They can be easily and fairly reliably diagnosed using commercially available assays, consecutive faecal cultures, acid fast faecal staining or faecal egg counts, respectively. Controversy exists regarding how to accurately diagnose clostridial diarrhoea, as Clostridium difficile and perfringens, as well as their toxins, can be identified in asymptomatic foals. Further investigations are required to clearly document their role in foal diarrhoea. Cyathostomiasis and Lawsonia intracellularis are more recently recognised pathogens causing weight loss, diarrhoea and severe hypoproteinaemia in foals two months of age and older. The diagnosis of cyathostomiasis is difficult to establish intra vitam. Serological evaluation and faecal PCR can aid in identifying proliferative enteritis caused by L. intracellularis in affected foals. There is minimal information about infection by this organism in foals in recent peer-reviewed literature. However, due to the worldwide distribution of the organism and increasing recognition of infection in foals, we included the organism in this discussion to hasten the awareness of the disease amongst practitioners and provide currently available information about clinical signs and diagnosis.