Neonatal isoerythrolysis

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Neonatal Isoerythrolysis

Hemolytic Icterus

Neonatal isoerythrolysis (NI) is a highly fatal haemolytic disease of newborn horse and mule foals. When the blood types of the mare and stallion are different, if the foal inherits the sensitizing red blood cell type from the stallion, they are at risk of NI from nursing from the mare. This is because sometimes the mare produces antibodies against the foal's red blood cells, and transfers these antibodies to the foal when nursing.

Development of liver failure, kernicterus, and complications related to bacterial sepsis are the most common causes of death in foals with NI. Foals administered a large volume of blood products are at greater risk for developing liver failure.


Failure to nurse
Increased respiratory rate
Elevated pulse


  • History
  • Clinical signs
  • Physical exam
  • Lab Test
  • Demonstrating anti-red cell antibodies in the colostrum or serum of the mare



If the foal is less than 24 hours old at time of diagnosis it should be restricted from nursing the mare until it is between 24-48 hours old.
Blood transfusion


  • Testing the mare's serum for antierythrocyte antibodies 1 to 2 weeks prior to giving birth to the foal
  • Blood typing of the mare and potential stallion


Success depends on rapid identification of sick foals and seperating it from the dam to prevent suckling for 48-72 hours, until the mare no longer produces colostrum and the foal's GI tract is closed.

Scientific Research

General Overviews

Age Range

NI is seen in newborn foals.

Also Consider