Neonatal Isoerythrolysis

Neonatal Isoerythrolysis


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Definition


Hemolytic anemia of newborn foals caused by alloantibodies directed against the foal’s red blood cells (RBCs).



Synonym(s)




• Jaundiced foal syndrome


• Isoimmune hemolytic anemia


• Alloimmune hemolytic anemia



Epidemiology



Species, Age, Sex


Newborn foals are affected, with clinical signs appearing at 1 to 8 days.



Genetics and Breed Predisposition


Any breed may be affected, but Thoroughbreds, Standardbreds, and American Paint Horses are overrepresented. There is a higher incidence in mule foals than in horse foals because of a unique blood group antigen called “donkey factor.”



Risk Factors




• Dams previously administered blood transfusions or other equine biologic agents


• Mares are exposed to fetal RBCs with each pregnancy; thus multiparous mares produce foals at higher risk than primiparous mares.



Clinical Presentation



Disease Forms/Subtypes




• Subclinical


• Peracute



History, Chief Complaint




• Foal normal at birth, stood and nursed, acute or insidious onset of weakness, tachypnea, icterus. Presentation of clinical signs typically occurs 2 to 5 days after birth.


• Peracute cases may collapse 8 to 36 hours after nursing.



Physical Exam Findings




• Weakness, lethargy, tachypnea, tachycardia, pale or icteric mucous membranes, pigmenturia, cardiovascular collapse.


• Fever is variable.


• Death may occur before icterus develops in peracute cases.


• Mild cases result in subclinical disease.



Etiology and Pathophysiology




• NI occurs when a fetus inherits the RBC antigens of the stallion and the mare is negative for these RBC antigens. She develops alloantibodies to the offending RBC antigen of the foal through exposure by prior pregnancy, blood transfusion, or transplacental contamination with fetal blood earlier in the current pregnancy. At birth, the foal ingests colostrum containing the alloantibodies. The alloantibodies then bind to the RBCs of the foal, resulting in agglutination, lysis, or both.


• The most common factors (antigens) involved in neonatal isoerythrolysis (NI) are Qa and Aa; mares without Qa and Aa factors are at an increased risk of producing NI-causing antibodies.

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Jul 24, 2016 | Posted by in SMALL ANIMAL | Comments Off on Neonatal Isoerythrolysis

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