Warmblood Fragile Foal Syndrome (WFFS)
What is WFFS?
WFFS is an inherited fatal disease. The disease caused by a genetic mutation, means the embryo does not produce collagen. Some embryos/foals will be aborted during pregnancy. If the foal is born the foal will have friable skin that will tear and ulcerate, its joints will be lax and unable to bear weight. The diseased foal will have to be euthanised within days of birth.
How does it occur?
WFFS is caused by a genetic mutation. The gene is recessive meaning affected horses can unknowingly be carriers of the mutation without any effect or loss of performance. The disease only occurs when two carriers are mated. If two carriers are mated there is a 25% (one in four) chance of an affected foal, a 50% chance of passing on the mutation, that is two in four foals will be carriers and a 25% chance of a foal being negative. Mating a carrier to a non-carrier means there is a 50% chance of passing on the mutation – that is two in four foals might be carriers.
What do we know?
It is now known that the disease is older and more widespread than previously thought. It has previously gone undetected due to lack of knowledge and awareness – mares can abort for a variety of reasons, foals that have been born with the disease may have been labelled dummy foals. It is recognised that removing all carrier stallions at this stage will remove many good stallions from the international and national herds as well as reducing the gene pool. It is advised however that future offspring, sired by a carrier stallion or out of a carrier mare are tested before being earmarked as potential stallions or broodmares and these ones are not bred from in the future.
What are stud books doing?
SHB(GB) has requested that all owners of warmblood or mixed breed stallions have them tested for WFFS before the start of the stud season. In line with other international studbooks it will publish the results on the website at the top of the page of each stallion either as; carrier, negative or ‘not tested’.
The KWPN (Royal Dutch Warmblood Association) has decreed that all breeding stallions must undergo genetic testing for Warmblood Fragile Foal Syndrome.
Warmblood Studbook of Ireland has been offering testing services to ISH breeders for mares, stallions, and foals.
The Dutch Riding Horse and Pony studbook (NRPS) has immediately made the WFFS test mandatory for licensed stallions.
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