Faecal Microbiology

A number of bacterial pathogens are frequently implicated as causes of diarrhoea in horses including,

  • Salmonella sp.
  • Clostridium perfringens
  • Clostridium difficile
  • Lawsonia intracellularis

Infection with Salmonella can result from consumption of contaminated feed or water or contact with carrier animals which shed the bacterium in their faeces. Horses of any age may be affected. Signs of Salmonella infection in horses can range from inapparent infection to severe septic shock and sudden death. Most horses will present with an increased body temperature and diarrhoea. Salmonella from any animal, including horses, can infect humans, so good hygiene practices should be observed when handling any horse with diarrhoea.

Clostridium perfringens and Clostridium difficile are anaerobic bacteria which may be found in the environment, particularly soil, and in the intestinal tract of healthy horses and other animals. In some horses, for reasons that are not entirely clear, these bacteria may cause a severe, and sometimes fatal, diarrhoea. As these bacteria can be found in the faeces of healthy horses, bacterial culture alone is not diagnostic and detection of the toxins associated with the disease is required.
Lawsonia intracellularis is the bacterium responsible for the condition known as Equine Proliferative Enteropathy (EPE) which affects weanlings and yearlings primarily. As the name suggests, this disease causes a thickening of the intestine resulting in protein loss through the gut. Affected animals may show signs of dullness, colic, diarrhoea, weight loss and filling of the lower legs. This bacterium cannot be cultured in the laboratory as it only grows inside living cells, therefore, PCR testing is required to detect the DNA of the organism in faeces.

Other bacterial species which are less frequently identified in cases of diarrhoea include, Campylobacter sp., Aeromonas sp. and Enterococcus durans.

Unlike many other labs, the IEC routinely carries out full faecal culture on samples of diarrhoea to identify all potential pathogens which may be present, including these less frequently identified pathogens and others. This allows us to monitor for and identify any novel causes of diarrhoea which might emerge.