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WINTER 2014 ISSUE
EQUINE MATTERS
6
GENETIC DISEASES
This recently recognised syndrome was
previously known as 'Fell Pony Syndrome',
because it was first recognised in this
breed in the 1990s. It has since been
recognised in Fells, Dales and Cobs
worldwide and causes anaemia and
suppressed immunity making them prone
to infection.
Affected foals are born apparently normal
then at two to six weeks of age, develop
signs such as diarrhoea, pale gums,
inappetance, nasal discharge, poor growth
and become increasingly lethargic.
Treatment involves antibiotics to prevent
infection developing when the immune
system is weak, rehydration, pain relief,
vitamin and mineral supplementation
and blood transfusion. Unfortunately
despite treatment there are no reports
of foals with Foal Immunodeficiency
Syndrome surviving.
Foal Immunodeficiency
Syndrome
Quarterhorses and Painthorses are typically
affected. This is a fatal condition in which
the foal is unable to store enough energy
for organ function. Foals might be aborted
before term or stillborn. If born alive, foals
are weak, struggle to stand, may seizure
and are unlikely to survive beyond eight
weeks of age. Many are euthanased as
there is unfortunately no treatment for
this condition.
Genetic Muscle Disease
Examples of Genetic Disease
This disorder affects pure and part-bred
Arabian horses, especially Egyptian lines.
Foals are typically born weak, invariably
unable to stand or position themselves
when lying down. They may be found
lying with an arched back, seizuring
and paddling their legs. The disease is
associated with 'coat dilution' meaning
affected foals have a light coat varying
from silver to dull lavender to pale
chestnut. Unfortunately there is no cure
for this disease and affected foals
are euthanased.
Lavender Foal Syndrome
This genetic disorder occurs most frequently
in American Painthorses. Foals are born
after term apparently normal but with white
coat and blue eyes, akin to the Cremello
colouring, and with a non-functioning
intestinal colon. Foals typically fail to pass
the 'meconium' (the first faeces), and within
24 hours of birth display signs of colic
due to intestinal obstruction. Obstruction
develops because the colon of the affected
foal develops without nerves to stimulate
intestinal motility and this becomes blocked
with static faecal material. Unfortunately
there is no treatment for this condition
and affected foals must be euthanased.
Overo Lethal White
Syndrome
Glycogen Branching Enzyme Deficiency
American Quarterhorse, American
Painthorse and Appaloosa breeds are
typically affected. In this condition there is
a disturbance in how the muscle cells work,
resulting in generalised muscle weakness or
uncontrolled muscle trembling. Other signs
might include a change in the horse's
whinny because the muscles around the
voicebox are affected. In very severe cases
the horse might die because of paralysis
of the diaphragm leaving the horse unable
to breathe. This condition can be managed
with high carbohydrate diets and various
sugar and electrolyte therapies are
available for veterinary treatment of
severe attacks.
Hyperkalaemic Periodic Paralysis
Clydesdales, Shires, Belgian Drafts, Suffolk
Punches and Percherons are typically
affected. In this condition there is a failure
to digest grain correctly which results in
muscle damage. Affected horses may not
show clinical signs, however sometimes
a change in diet or work might trigger
disease. Symptoms include muscle
wastage, muscle weakness, 'tying up',
lameness or abnormal gait, poor
performance or a failure to rise after
anaesthesia. Diagnosis is made by
collecting a muscle sample and analysing
the muscle architecture under microscopy
for characteristic changes. This condition
can be managed and reversed with
dietary management to replace starch
and sugars with fats.
Polysaccharide Storage Myopathy
Implications for
breeding
When considering breeding from your mare
it is important to carefully consider that she
is not suffering from or carrying a genetic
disease which might be apparent if her
ancestry is known. Genetic tests are available
to establish the risk status for some of the more
common genetic diseases, which should be
especially considered when breeding from
Arabians, Quarter Horses, Drafts and
American Saddlebreds. These tests are
non-invasive and simply require collection
of a blood sample or hair pluck depending
upon the test.
We recommend veterinary checks for
newborn foals to identify the presence of
genetic or congenital disease. Some diseases
may not manifest until later in life but early
detection of disease which might not be
readily apparent to the owner might influence
treatment and management.
There are no reports of foals surviving ‘Foal
Immunodeficiency Syndrome’
Foal immunodeficiency syndrome was first
reported in Fell ponies