Neonatal Isoerythrolysis in the Foal

Call your veterinarian or contact the UF Large Animal Hospital at (352) 392-2229 if any of these diseases are present in your foal. If you have any questions do not hesitate to call us.

Information provided by Dr. Amanda House, Veterinarian of UF Large Animal Internal Medicine, Clinical Associate Professor, DACVIM, Equine Extension Specialist, and Course Director of the Practice-Based Equine Clerkship Program.

Neonatal Isoerythrolysis (NI)

NI is an acquired form of hemolytic anemia and the the most common alloimmune disease in foals. It occurs at 7 hours to 12 days of the foal’s life (average is 2.5 days). NI can be fatal in some severely affected foals. Call your veterinarian immediately if you suspect NI.

Clinical signs of NI may include:

  • Anemia
  • Dull and lethargic
  • Yellow mucous membranes
  • High heart rate
  • High respiratory rate
  • Cardiac murmur
  • Dark yellow urine
  • Hemoglobinuria in some (reddish-brown color)


Sepsis is defined as the presence of bacteria or bacterial toxins in the bloodstream, and it is the most common cause of death in newborn foals. Sepsis can manifest as pneumonia, diarrhea, meningitis (inflammation of the membranes of the brain and spinal cord), and joint and/or umbilical infections in the foal. Be sure to check the foal’s IgG in the first 24 hours of life. Adequate passive transfer helps to prevent sepsis.

Clinical signs of sepsis may include:

  • Pneumonia
  • Diarrhea
  • Joint infection
  • Umbilical infection
  • Weak, lethargic foal
  • Poor suckle
  • Fever or hypothermia

Neonatal Encephalopathy

Neonatal encephalopathy is also called HIE, Neonatal Maladjustment Syndrome (NMS), or “dummy foal.” Neonatal encephalopathy is the most common non-infectious medical condition in foals. These foals are typically recognized when they have a poor suckle reflex, do not nurse the mare, or display other neurologic signs (seizures may occur in severe cases). Contact your veterinarian if you observe any abnormal behavior in your foal.


If your foal is born prematurely, call your veterinarian or contact the UF Large Animal Hospital at (352) 392-2229.

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