Bit & Bridle

Equine Scours in Foals

Other Names

  • Foal heat diarrhoea
  • Diarrhoea in young foals
  • Neonatal diarrhoea
  • Foal scouring

What is Scours in Foals?

Scours — the colloquial term for diarrhoea in young foals — is one of the most common and potentially serious conditions affecting foals in their first weeks of life. It is characterised by loose, watery droppings, which can range from a minor, self-limiting episode to severe, life-threatening disease requiring emergency intensive care.

Diarrhoea in foals is most significant because of the speed at which it can lead to dehydration, electrolyte imbalance, and acidosis. Foals have a very limited reserve capacity — a foal in severe diarrhoea can become critically ill within hours. Prompt recognition and appropriate response are therefore essential for owners, stud managers, and handlers on any breeding property.

Two broad categories exist: infectious scours (caused by pathogens) and non-infectious scours (including the benign “foal heat diarrhoea”). These have different presentations, severities, and management approaches. For related gastrointestinal conditions, see our entry on Equine Glandular Gastric Disease.

Causes

Non-infectious causes:

  • Foal heat diarrhoea — occurs in foals aged five to twelve days, typically coinciding with the mare’s first post-partum oestrus (foal heat). Historically attributed to changes in the mare’s milk composition; current thinking suggests it is more likely related to colonisation of the foal’s gut with normal flora and dietary changes. Typically mild and self-limiting.
  • Dietary causes — lactose intolerance or ingestion of abnormally large quantities of milk if the foal has been separated and allowed to nurse excessively on return

Infectious causes (more serious):

  • Rotavirus — the most common infectious cause of diarrhoea in foals under three months of age; causes watery, profuse diarrhoea and can spread rapidly through a foal population
  • Escherichia coli — particularly enterotoxigenic strains, causing diarrhoea in very young foals (within the first few days of life); often associated with failure of passive transfer (inadequate colostrum intake)
  • Salmonella spp. — causes severe, haemorrhagic diarrhoea; can be life-threatening and is a significant biosecurity concern as it can spread to humans
  • Clostridium perfringens and C. difficile — clostridial enterotoxaemia can cause haemorrhagic, necrotising diarrhoea; often rapidly fatal without aggressive treatment
  • Cryptosporidium parvum — a protozoal parasite causing moderate to severe diarrhoea in immunocompromised foals; particularly significant in immunodeficient breeds such as Arabian foals with combined immunodeficiency
  • Coronavirus — emerging as a recognised cause of diarrhoea in foals, alongside respiratory signs

Symptoms and Signs

Clinical assessment should be prompt whenever any foal develops loose droppings. Signs indicating serious disease include:

  • Loose or watery droppings — note frequency, consistency, and whether blood is present
  • Perineal scalding — soiling and skin irritation around the tail and hindquarters
  • Depression and weakness — a foal that is not nursing enthusiastically or is lying down excessively is a concern
  • Reduced suckling activity
  • Sunken eyes and dry, tacky mucous membranes — signs of dehydration
  • Fever (rectal temperature above 38.5°C / 101.3°F) or subnormal temperature (hypothermia is a bad prognostic sign)
  • Abdominal distension or pain
  • Rapid heart rate or rapid breathing
  • Collapse or recumbency in severe cases

Foal heat diarrhoea is typically mild — the foal remains bright, nursing, and active, with loose but not profuse droppings. Any foal that appears dull, is not nursing, or has profuse or haemorrhagic diarrhoea needs veterinary attention urgently.

Diagnosis

Assessment combines clinical examination with laboratory diagnostics:

  • Physical examination — assessment of hydration status, mucous membrane colour and moisture, capillary refill time, heart rate, temperature, gut sounds, and degree of depression
  • Blood tests — packed cell volume (PCV) and total protein assess hydration; electrolytes (sodium, potassium, chloride, bicarbonate) quantify the degree of derangement; blood gas analysis confirms acidosis
  • Faecal testing — rotavirus ELISA or PCR; bacterial culture and sensitivity; Clostridium toxin assay; Cryptosporidium testing via modified Ziehl-Neelsen staining or PCR; Salmonella culture (multiple samples may be required)
  • IgG measurement — blood levels of immunoglobulin G confirm whether the foal received adequate passive transfer from colostrum. Failure of passive transfer (FPT) dramatically increases susceptibility to infectious disease.
  • Abdominal ultrasound — assesses gut wall thickness, fluid in the intestines, and identifies conditions such as intussusception

Treatment

Treatment is dictated by the severity of illness and the underlying cause:

  • Oral electrolyte supplementation — appropriate for mild to moderate dehydration in foals that are still nursing. Commercial equine oral rehydration solutions provide electrolytes and glucose to support intestinal absorption. Do not replace milk entirely with electrolytes — foals need the energy from milk.
  • Intravenous fluid therapy — essential for foals that are severely dehydrated, depressed, or unable to nurse. Isotonic crystalloids (e.g., Hartmann’s solution) are used to restore circulating volume, correct electrolyte abnormalities, and treat acidosis. This requires hospitalisation and close monitoring.
  • Broad-spectrum antibiotics — indicated when bacterial infection is suspected or confirmed, particularly in foals showing systemic signs of infection (fever, depression, high white cell count). Combination therapy covering both gram-positive and gram-negative organisms is standard.
  • Plasma transfusion — for foals with failure of passive transfer, plasma from a vaccinated donor horse provides IgG to support immune function until the foal can produce its own antibodies.
  • Clostridial antitoxin — for severe clostridial enterotoxaemia; must be used promptly
  • Nutritional support — foals that cannot nurse may require nasogastric tube feeding
  • Perineal skin protection — applying petroleum jelly or zinc oxide cream around the perineum and hindlegs prevents acid scalding from prolonged diarrhoea

Prevention

Preventing infectious diarrhoea in foals requires a combination of management, vaccination, and biosecurity:

  • Ensure adequate colostrum intake — this is the single most important preventive measure. The foal should receive at least 200–250 ml of good-quality colostrum within the first two to four hours of life, and at least 1 litre in the first 12 hours. Test colostrum quality with a Brix refractometer (aim for >22% Brix).
  • Test IgG levels at 18–24 hours — test the foal’s blood to confirm successful passive transfer. If IgG is less than 4 g/L, plasma transfusion should be considered.
  • Mare vaccination — vaccinating mares four to six weeks before foaling against rotavirus and Clostridium increases antibody concentration in colostrum
  • Foaling environment hygiene — clean, disinfect, and rest foaling boxes between uses; pathogens such as rotavirus and Salmonella persist in the environment
  • Biosecurity — new foals arriving at a facility should be managed with care. Any sick foal should be isolated immediately to prevent spread of infectious agents, particularly rotavirus and Salmonella.
  • Staff hygiene — handwashing between handling foals is essential; Salmonella and Cryptosporidium are zoonotic (can infect humans)

Prognosis

The prognosis for foal heat diarrhoea is excellent — almost all cases resolve within a few days without treatment. The prognosis for infectious diarrhoea depends on the causative agent, the severity of dehydration and systemic illness, and how quickly treatment is initiated. Rotaviral diarrhoea carries a good prognosis with appropriate supportive care. Clostridial enterotoxaemia and severe Salmonella infection carry a guarded to poor prognosis and can be rapidly fatal. Early, aggressive treatment significantly improves outcomes.

When to Call the Vet

  • Any foal less than one week old showing loose droppings — the youngest foals carry the most risk
  • A foal of any age with profuse, watery, or haemorrhagic diarrhoea
  • A foal showing signs of depression, weakness, or reduced nursing regardless of how mild the diarrhoea appears
  • Foal heat diarrhoea that is not resolving within three to four days
  • Multiple foals on a stud developing diarrhoea simultaneously — this indicates an infectious outbreak requiring urgent investigation and biosecurity measures

Frequently Asked Questions

Is foal heat diarrhoea always mild?

Foal heat diarrhoea is typically mild and self-limiting, but it is important not to assume all early foal diarrhoea is just “foal heat.” Concurrent infectious causes — particularly rotavirus — can develop at the same age and produce much more severe disease. If a foal with early diarrhoea appears dull, is not nursing, or has very watery droppings, a vet should assess them rather than waiting for natural resolution.

Can rotavirus in foals spread to other horses or to humans?

Equine rotavirus is highly contagious between foals but does not appear to readily infect adult horses or cause significant disease in them. It is not considered a significant zoonotic risk to healthy adults, though people with compromised immune systems should exercise caution. Strict hygiene and isolation of affected foals is essential to prevent spread within a foal population.

How do I know if my foal received enough colostrum?

You can test the foal’s blood for IgG levels at 18–24 hours of age — this is the most reliable method. A level below 4 g/L indicates failure of passive transfer. Alternatively, test the mare’s colostrum quality with a Brix refractometer or colostrometer before the foal suckles, allowing you to supplement with stored or donor colostrum if quality is poor.

What should I put on a foal’s skin to protect it from scald?

Apply a thick layer of petroleum jelly (Vaseline) or a zinc oxide–based barrier cream to the perineum, inner thighs, and tail base as soon as diarrhoea begins. This creates a physical barrier against the acid in the loose droppings. Reapply after each cleansing. Keeping the area clean with warm water and avoiding harsh detergents helps prevent skin breakdown. See our foal care terminology for more neonatal health guidance.