Neonatal Isoerythrolysis
Description
Neonatal isoerythrolysis is a disease of humans and domestic animals and has been observed in newborn cats, horses, pigs, cows and rarely in dogs. It is characterised by immune-mediated haemolytic anaemia due to ingestion of maternal colostral antibody directed against surface antigens on neonatal red blood cells. The maternal antibodies develop in response to specific foreign blood group antigens during previous pregnancies, unmatched transfusions, and from Babesia and Anaplasma vaccinations in cattle.
Pathogenesis
Feline neonatal isoerythrolysis
Although feline neonatal isoerythrolysis (FNA) is rare, the mortality associated with it is high. FNI develops when type B blood mothers mate with type A tomcats. Type B cats have naturally occurring anti-A antibodies without prior exposure. FNI affects the A, or AB blood type kitten, born from a B blood type mother by receiving anti-A antibodies when it ingests maternal colostrum.
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. Previous 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.
Clinical signs
Horses
Affected foals appear clinically normal at birth, and clinical signs develop from several hours up to a week after ingestion of colostrum. Foals with NI usually become progressively weak, lethargic and depressed develop icterus, tachycardia and tachypnoea. Although the signs are not pathognomonic for NI, a foal displaying haemoglobinuria and icterus born to a multiparous mare should be strongly suspected to have the disease. If the foal becomes severely hypoxic, seizures may occur. Death usually occurs if NI is not diagnosed and treated promptly.
Cats
In a similar way to affected foals, kittens are born and nurse normally and clinical signs develop within a few hours or days. Clinical signs may include dark red/brown urine, icterus, weakness, anaemia.
Diagnosis
To definitively diagnose the condition in horses, a minor cross-match is performed using the foal's red blood cells and the mare's serum. A positive agglutination indicates a diagnosis of NI.
Treatment
Treatment in foals depends on rapid identification of sick foals and prevention of suckling the dam for 48-72 hours. If foals are less than 24 hours old at the time of diagnosis, it should be muzzled and fed supplemental milk. As the foal's intestine becomes impermeable to absorption of colostral antibodies by 24 hours of age, prevention of nursing until the foal is 30 hours of age should be sufficient.
Prevention
The disease in horses is prevented by ensuring that mares are blood-typed before being mated. Mares who are negative for the blood antigens known for causing disease (primarily Aa, Qa, Qc and Ua) can be matched to stallions who are also negative.