Fell ponies are not the only breed to be affected with a syndrome involving immunodeficiency and anaemia syndrome, according to researchers. A similar condition has been reported in a Dales pony.
Fell Pony Syndrome is a fatal condition that affects the immune system of young foals.
Affected animals are unable to respond adequately to infection.
Signs usually appear first when the foal is a few weeks old. They include loss of condition, diarrhoea, coughing and weight loss.
As the condition progresses, the foal develops anaemia, immune dysfunction, and wasting. Foals die, usually before they reach three months of age, from infectious diseases that they cannot overcome.
The condition is not only found in the Britain. Affected Fell pony foals have been reported in the Netherlands and the United States. Until recently, the syndrome had not been identified in other pony breeds.
A report in the Veterinary Record describes a case in a Dales pony that showed characteristic signs of Fell pony syndrome.
The authors, based at the Animal Health Trust in Newmarket and the Liverpool Veterinary School, described a female Dales pony foal with marked anaemia, diarrhoea and pneumonia, that failed to respond to treatment.
The foal was euthanized at just under six weeks of age. Post mortem signs were typical of Fell pony syndrome.
In Fell ponies, analysis of the pedigrees of affected foals strongly suggests that the condition is caused by a single autosomal recessive genetic defect. This means that foals are only affected if they inherit a defective gene from both parents.
It is not known how many animals are carriers. Research funded by The Horse Trust aims to develop a test to identify carrier animals. Until that is available, an estimate based on the number of affected foals suggests that probably between 60-90 per cent of the breed carry the defective gene.
Although the Dales and Fell ponies are closely related, the report's authors suggest that it is unlikely that the disease has been present in the Dales pony going back many years.
No cases have been identified previously in the breed, despite close monitoring by the breed society.
They explain that all cases in the Fell pony can be traced back to a common ancestor in the 1950s. It is more likely that the defective gene passed to the Dales pony by cross-breeding with the Fell pony after that date.
The scientists, who are already studying Fell Pony Syndrome, are now widening their scope to pay close attention to the Dales pony as well.
They suggest that, although there are other causes of anaemia in foals, the anaemia/immunodeficiency syndrome should be considered in any young foal with marked anaemia and relevant clinical signs.
They urge owners, breeders and veterinarians dealing with Dales ponies to be aware of the disease, and ask that any suspect cases be referred to the research team at the Animal Health Trust or the Liverpool University Veterinary School.
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