Disease of the equine neonate pt 3 Flashcards
Neonatal Isoerythrolysis
- how many erythrocyte groups in horses:
- Seven erythrocyte groups in horses:
A C D K P Q U
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The blood group genes produce surface molecules that contain antigenic sites known as factors. Over 30 different factors have been identified.
Alloantibodies definition
immune antibodies that are only produced following exposure to foreign red blood cell antigens
> Produced by exposure to foreign red cell antigens which are non-self antigens but are of the same species. They react only with allogenic cells. Exposure occurs through pregnancy or transfusion.
all standardbreds are which blood type?
All Standardbreds are Qa negative
what is neonatal isoerythrolysis? how does it occur?
- Destruction of foal erythrocytes by alloantibodies from the dam absorbed by ingestion of colostrum
- Alloantibodies only develop after exposure of dam to foreign erythrocyte antigens
Prerequisites for NI
- Dam must be negative for the offending antigen
- Dam must be exposed to the offending antigen
- The sire must carry the offending antigen
how does mare sensitization occur for NI?
- Previous blood transfusion
- Exposure to foal blood in a previous gestation (*parturition)
- Exposure to foal blood across abnormal placenta
prevalence of NI;
- in throroughbreds, standardbreds, mules
- Thoroughbreds: = 1%
- Standardbreds: = 2%
- Mules: = 10%
NI clinical signs
- Normal at birth
- Progressive depression, weakness and failure to nurse by 24 – 36 hours old
- Pale or icteric mucous membranes
- Tachypnea
- Tachycardia
- Seizures
- Death
Neonatal isoerythrolysis Dx
- Anemia:
> Packed cell volume
> Red cell count - Hemoglobinemia
- Hemoglobinuria
- Bilirubinemia
- Acute renal failure
NI
* Foal erythrocytes bound by alloantibodies are removed by:
- reticuloendothelial system
- intravascular Compliment-mediated lysis
Treatment of NI foals
Clinically affected:
* Withholding colostrum
* Rest (confinement)
* Diuresis > pigments toxic to kidneys
* Whole blood transfusion (PCV<15%)…
what can we do if we give a transfusion for NI foal to make sure it will work
- Crossmatch against mare’s serum
- Washed mare rbc’s (must remove plasma)
- Donor rbc’s (Aa and Qa -): Stb gelding preferred
- Not the sire
Detection of erythrocyte antigens for NI
- Agglutination
- Complement-mediated lysis by specific
alloantibodies - Foal rbc’s + mare serum
- Foal rbc’s + mare colostrum
incidence of neonatal isoerythrolysis?
- are most groups strongly antigenic?
- which are particularly antigenicc?
- Most blood groups are not strongly antigenic
- Incidence is low (1% TB, 2% STB, 10 % Mules)
- Factors Aa and Qa of A and Q systems are particularly antigenic
- Mule “donkey factor”
- Qa not present in STB population.
NI: Treatment
- is transfusion permanent
- how much
- what to do with mare
- Transfusion is temporary
- 1 – 4 liters
- Avoid volume overload
- Also, milk out the mare regularly
