Hoof Wall Separation Disease or HWSD is a condition that has been identified in Connemara ponies and horses that have been crossed with Connemara ponies. HWSD is an autosomal recessive disorder that causes the hoof wall to easily break and crack. Autosomal recessive disorders are disorders that require two copies of the disease in order to present symptoms. If two copies are received, all four feet will be affected by the disease. Damage can be seen in affected ponies as young 2-3 weeks of age.
In rare cases, some affected ponies develop a less severe form of the disease. This is due to the fact that the mutation is not fully penetrant. In very few cases, the disease can be managed. However, for most other case the ponies must be euthanized. Studies estimate that the general population of horses carrying HWSD is around 15%. These carriers do not present symptoms, which makes DNA testing an extremely valuable tool while breeding.
Unfortunately, there is no cure of HWSD. As the condition worsens, the foal will begin to develop severe infections, as well as suffer from increasing pain and discomfort.
HWSD is an autosomal recessive trait, meaning a foal can only be affected if the foal inherits the disease from both parents. Carriers have only one copy of the disease and do not present symptoms. If two carriers of the disease are bred together, there is a 25% chance per foal born that they will develop symptoms of HWSD. There is a 50% chance per foal born that they will also become carriers of the disease. This makes testing important so as to avoid accidentally breeding a horse with a higher propensity of developing HWSD.
|Affected: Horse carries two copies of the HWSD gene mutation and will exhibit signs of the disorder. Horse will pass on a copy to all offspring.
|Carrier: Horse has one copy of the HWSD gene mutation. Horse has a chance to pass this gene on to any offspring.
|Clear: Horse is negative for HWSD.