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==Description==

==Description==

Neonatal isoerythrolysis is a disease of humans and domestic animals and has been most commonly observed in newborn cats and horses. Rarely it has also been described in other species following blood transfusions, vaccination or previous pregnancy. The disease is characterised by immune-mediated haemolytic anaemia due to ingestion of maternal colostral antibody directed against surface antigens on neonatal red blood cells. This leads to extravascular and intravascular haemolysis during the first few days of life.  

Neonatal isoerythrolysis is a disease of humans and domestic animals and has been most commonly observed in newborn cats and horses. Rarely it has also been described in other species following blood transfusions, vaccination or previous pregnancy. The disease is characterised by immune-mediated haemolytic anaemia due to ingestion of maternal colostral antibody directed against surface antigens on neonatal red blood cells. This leads to a Type II hypersensitivity reaction causing extravascular and intravascular haemolysis during the first few days of life.  

==Pathogenesis==

==Pathogenesis==

===Equine neonatal isoerythrolysis===

===Equine neonatal isoerythrolysis===

In foals, the condition results when a foal inherits red blood cell antigens (which the dam does not have) from its sire. Exposure of the mare to these antigens during a previous pregnancy or whole blood transfusion leads to the mare producing alloantibodies to the foal's red blood cells. At birth the foal ingests large numbers of antibodies in the colostrum, leading to severe haemolytic disease. During pregnancy however, the foal is unaffected because blood and antibodies are unable to cross the placenta.  

In foals, the condition results when a foal inherits red blood cell antigens (which the dam does not have) from its sire. The Aa and Qa antigens are  Exposure of the mare to these antigens during a previous pregnancy or whole blood transfusion leads to the mare producing alloantibodies to the foal's red blood cells. At birth the foal ingests large numbers of red blood cell antibodies in the colostrum, leading to severe haemolytic disease. During pregnancy however, the foal is unaffected because blood and antibodies are unable to cross the placenta. First foals are rarely affected, as a sensitization reaction (during an earlier pregnancy) is usually required.

==Clinical signs==

==Clinical signs==