Page 1361 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

1336 CHAPTER 14

VetBooks.ir 14.4 of alloantibodies in the dam’s blood or colostrum
directed against the foal’s red cells. Serum and red
cells from the mare and foal are required for this
test, which is offered by some commercial or spe-
cialist laboratories.

Management
Treatment is dependent on the severity of clinical
signs and the degree of anaemia. In mild cases the
foal should have minimal handling and box rest.
RBC parameters should be monitored twice daily
for the first few days. Management of these foals is
important, and care should be taken when handling
them not to excite or stress them. Exercise should be
limited to short periods of nursery paddock exercise.
Transfusion with donor red cells is usually consid-
ered appropriate when the PCV falls below 0.12 l/l
(12%) and RBCs below 3.5 × 10 /l (3.5 × 10 /µl). If
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there is early or rapid development of clinical signs
Fig. 14.4 Marked icterus of the oral mucous such as depression, loss of suck or signs of hypox-
membranes of a foal suffering from neonatal aemia then earlier transfusion should be considered.
isoerythrolysis. Slower falls in RBC numbers allow the foal to adapt,
leading to less obvious clinical signs and less need for
intensive treatment.
Differential diagnosis The volume of blood required can be calculated
Other causes of haemolytic anemia need to be con- as shown below (150 is considered the blood volume
sidered, including drug administration, haemopara- in ml/kg for a 2-day-old foal):
sites, toxin exposure and sepsis.
body weight (kg) × 150 ×
Diagnosis Volume(ml) = (PCV desiredPCV observed)
−
Diagnosis is based on clinical signs, history (mul- PCVof donor
tiparous mare, signs seen 12–72 hours after birth)
and laboratory results. Haematological examina- For a 50kg foal, it is usual to transfuse 2–4 l of
tion reveals a marked anaemia, an RBC count blood. The dam is usually considered the most suit-
<4 × 10 /l (<4 × 10 /µl), haemoglobin <70 g/l (<7 g/dl) able donor; however, her red cells must be washed
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and PCV <0.20 l/l (20%). Anaemia can be severe free of plasma containing antibody. This is achieved
(PCV <0.1 l/l [<10%]) and thrombocytopenia is by washing the cells three times in saline and then
present in some cases. Plasma protein concentration resuspending them in an isotonic solution of saline.
remains within the reference interval. Anisocytosis If it is not possible to wash the cells, or the dam is
and RBC ghosts may be seen on a blood smear, and not a suitable donor, then a cross-matched gelding
haemoglobinaemia and haemoglobinuria may be can be used as a source of whole blood. Electrolyte
present if sufficient intravascular haemolysis exists. solutions can be administered to provide diuresis
Unconjugated bilirubin concentration is increased. and prevent haemoglobin-associated renal failure.
A direct Coombs test (a non-specific test detecting Supportive therapy and nursing are an essential part
antibody or complement components on the red cell of treatment.
surface) will be positive, although false negatives do The foal should be restricted to the box while
occur. Definitive diagnosis requires demonstration showing clinical signs of disease. Once the clinical