Neonatal Isoerythrolysis aka Hemolytic Disease of the Newborn

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Neonatal Isoerythrolysis akaHemolytic Disease of
the Newborn

• Linda Veinot, BSc, DVM
• Intern, Large Animal Medicine Surgery
• University of Minnesota Veterinary Medical Center

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Definition

• immune-mediated
• hemolytic disease
• maternal antibodies
• against the foals RBCs
• ingested
• destroy the RBCs

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Equine Blood Groups

• Seven groups A,C,D,K,P,Q,U
• All have proteins that stimulate an immune
  response in an animal that does not have that
  blood group
• A and Q are the most common

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Blood Groups (contd)

• If a sire has a blood type
• ..the foal may inherit that type
• If the mare doesnt have that type
• ..she sees those RBCs as foreign
• and produces antibodies against them

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What are antigens antibodies? They are both
proteins

• ANTIBODIES
• are made by lymphocytes
• are raised by our bodies
• help defend us against anything foreign

• ANTIGENS
• any substance seen as foreign
• AND can produce an immune response

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So for NI to occur

• Blood type from sire that mare doesnt have
• Foal inherits that blood type with its antigen
• Mare has been previously sensitized to the
  antigen has produced antibodies
• Foal must ingest colostrum carrying the
  antibodies to its RBCs

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Soas an example
1.Aa negative mare 2.that has antibodies to
Aa 3.Aa positive foal 4.foal ingests antibodies
via colostrum 5.abs enter foals blood and
cause RBC destruction
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But how does the mare see the antigen?Prior to
this pregnancy

• 1. Blood gets exchanged between foal and mare
  during delivery.
• 2. Transplacental hemorrhage may occur in late
  gestation.
• 3. A blood transfusion
• In any of these cases, if the blood is of a
  type not carried by the mare, she makes
  antibodies.

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So how does that result in a sick foal?

• These antibodies dont cross the placenta
• BUT..
• They DO cross into the colostrum

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Dont go near the colostrum!!

• If the foal suckles colostrum..

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.the foal will ingest the antibodies from the
mare they will coat the foals RBCs and
destroy them AND the foal has hemolytic anemia!
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Clinical Signs

• Healthy at birth
• Sickens several hours after suckling
• Weakness lethargy
• Pale (even white!) mucous membranes
• Progresses to yellow (icteric)

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Icterus
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More Clinical Signs

• Rapid, shallow breathing
• May progress to labored breathing
• Tachycardia
• Red urine (hemoglobinuria)
• Red plasma (hemoglobinemia)
• Convulsions/coma when terminal

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Laboratory Findings

• Progressive hemolytic anemia
• Low packed cell volume (PCV)
• Neutrophilic leukocytosis
• (hypoglycemia/acidemia)

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Tests for NI

• Jaundice Foal Agglutination Test (JFA)
• Can be done stall side

• Direct Coombs Test
• done in the laboratory

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Treatment

• Dont allow foal to suckle for 24-48 hr
• Milk out the mare
• Administer a source of antibodies to the foal
• Measure blood glucose
• Treat with dextrose if needed
• Minimize exercise stress

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Supportive Care
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Supportive Care

• Fluids intravenously
• Flush kidneys of hemoglobin
• Correct electrolyte imbalances
• DONT over hydrate!!!
• Oxygen may be needed
• Prophylactic antibiotics

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Prevention

• ID mares at risk
• Qa/Aa negative
• Multiparous
• Test for abs late in gestation
• Test stallion for compatibility
• Test colostrum

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If any of these factors exist. just prevent
the foal from suckling for the first
24-48 hours
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The Prognosis depends on

• Quantity of mares antibody ingested
• Time from onset of clinical signs

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Prognosis is usually GOOD in uncomplicated
cases
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Questions????