Equine Neonatal Isoerythrolysis

Question 1

What are the most common erythrocyte antigens implicated in equine neonatal isoerythrolysis?

Answer 1

Aa and Qa

Question 2

What type of reaction is equine neonatal isoerytholysis?

Answer 2

immunologic type II hypersensitivity reaction between RBC antigens on the neonatal foal’s RBCs and antigen-specific antibodies produced by the mare and ingested by the foal when consuming colostrum

• foal inherits foreign RBC antigens from the sire not possessed by the mare (stallion +, mare -)

Question 3

When do mares begin producing antibodies associated with equine neonatal isoerythrolysis?

Answer 3

after prior exposure, either from prior blood transfusions or exposure to fetal blood from placental abnormalities or parturition

• more common in foals from multiparous mares

Question 4

How do donkeys compare to horses with equine neonatal isoerythrolysis?

Answer 4

unique “donkey factor” RBC antigen causes donkeys to have higher incidences of NI

Question 5

What 3 things must be present for a foal to develop neonatal isoerythrolysis?

Answer 5

1. neonatal RBC antigen inherited from sire that the mare does not express
2. mare does not express neonatal RBC antigen, but has developed maternal antibodies to that specific neonatal RBC antigen
3. neonatal ingestion of colostrum

Question 6

When are clinical signs of equine neonatal isoerythrolysis most commonly seen? What signs are most common?

Answer 6

<7 days of age

reflects poor oxygen content of the blood + severity depends on amount of antibodies absorbed:

• tachycardia
• tachypnea, dyspnea
• lethargy
• icterus

Question 7

What are 2 supportive clinicopathologic results in possible cases of equine neonatal isoerythrolysis? How is it confirmed?

Answer 7

hyperbilirubinemia + anemia

cross-match of foal’s RBCs and the mare’s serum –> jaundice foal agglutination test

Question 8

What treatment is recommended if equine neonatal isoerythrolysis is recognized if the foal is less than 24 hours old?

Answer 8

withhold dam’s colostrum (muzzle foal) and provide an alternate source of milk and passive transfer

Question 9

What treatment is recommended if equine neonatal isoerythrolysis is recognized if the foal is greater than 24 hours old?

Answer 9

monitor the foal’s PCV and the rate of decline

• if PCV falls below 12%, a blood transfusion is indicated
• if the PCV is low (18%), but stable, conservative monitoring is recommended –> no further decline over 24 hours = transfusion not necessary

(+ stress and exercise restriction)

Question 10

How is equine neonatal isoerythrolysis prevented?

Answer 10

client education of mare and sire blood types and future pregnancies