Page 1357 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

1332 CHAPTER 14

VetBooks.ir poor-quality colostrum or those with premature colostrum substitute may be used. Routine blood
samples taken at 12–36 hours can be used to identify
lactation who have lost all their colostrum. A read-
ing of >25% indicates excellent quality colostrum
passive immunity. A profile including haematology,
and <15% indicates very poor quality. High-quality early signs of disease and the efficacy of transfer of
donor colostrum can be administered to high-risk proteins, immunoglobulins and inflammatory pro-
foals, by bottle or stomach tube, as soon after birth teins will provide this information.
as possible in order to ensure adequate transfer of Care of the umbilicus is important. It should be
passive immunity. Foals that fail to suck within kept clean and dry. A 0.5% solution of chlorhexidine
3 hours should receive good-quality colostrum can be used for topical application. This should be
(a minimum of 500 ml for a 50 kg foal) by naso- applied directly after birth and then 2–3 times over
gastric tube. If no donor colostrum is available, a the first 24 hours.

IMMUNODEFICIENCY DISORDERS

FAILURE OF TRANSFER OF compromise of the non-specific immune system,
PASSIVE IMMUNITY rendering the immunologically naïve foal suscep-
tible to infection.
Definition/overview FTPI can occur because of mare and/or foal
The most common immunodeficiency in the new- factors. Premature lactation is a common cause. If
born foal is failure of transfer of passive immunity the mare drips milk in the days preceding parturi-
(FTPI). The foal is agammaglobulinaemic at birth tion, colostrum can be rapidly lost. Poor-quality
and is dependent on ingestion and absorption of colostrum may also result in FTPI. Some mares
adequate quantities of good-quality colostrum in naturally produce poor-quality colostrum, and this
the immediate post- partum period for the transfer tends to be repeated in subsequent pregnancies. The
of antibody. Failure of this process increases suscep- specific gravity (SG) of colostrum should be 1.080 or
tibility to infection in the neonatal and paediatric higher. On a sugar refractometer the reading should
periods. The incidence of FTPI in foals is estimated be greater than 22%.
to be between 2.9 and 25%. Failure to absorb IgG from ingested colostrum
is uncommon but may occur. This may be caused
Aetiology/pathophysiology by a primary problem with intestinal absorption or,
The epitheliochorial structure of the equine pla- more commonly, by ingestion of colostrum after
centa prevents the transfer of maternally derived 12–24 hours of age, when immunoglobulins are no
antibodies to the foal in utero. Passive immunity is longer absorbed. Failure to ingest adequate quan-
dependent on ingestion and the transfer of colostral tities of colostrum is a major cause of FTPI, and a
immunoglobulins. Antibodies and other important variety of problems can prevent the foal from stand-
factors are selectively secreted into the udder in ing, reaching the mare and/or successfully nursing.
the last few weeks of gestation. Short-lived special-
ised cells in the foal’s small intestine pinocytose Clinical presentation
large molecules (e.g. immunoglobulin [Ig]G and, FTPI may be detected on routine screening blood
to a lesser extent, IgA and IgM), which pass into samples taken at 12–36 hours or when investigating
the lymphatics and then into the circulation. It is newborn foals for infectious disease. It should also
thought that other factors, including complement, be suspected in foals presenting with signs of sepsis
lysozyme, lactoferrin and B lymphocytes, may be or infectious disease.
transferred via the same mechanism and enhance
the foal’s naïve immune system. Failure of this pro- Differential diagnosis
cess results in low levels of specific antibody and Congenital immunodeficiences.