Episodic Falling (EF) is a paroxysmal exertion-induced dyskinesia. It is usually exercise, excitement or stress-induced and episodes begin between three to seven months of age. EF is a disorder of the muscles that causes increased muscle tone and muscle spasticity (especially those of the limbs) resulting in limbs that appear “locked” in an extended position and dogs are unable to relax their muscles. This muscle spasticity results in a characteristic “praying” position and/or collapse. Episodes can last from a few seconds to a few minutes, and dogs appear fully conscious throughout.
The single nucleotide substitution in the gene called BCAN that causes episodic falling (EF) in many breeds is recessive. This means that dogs that carry two copies of the mutation (homozygotes) will almost certainly develop EF during their lives. Dogs that carry a single copy of the mutation (also known as carriers or heterozygotes) will not develop EF as a result of the BCAN mutation, but they will pass the mutation onto about half of any offspring they have. Breeding dogs that will not develop EF should be the breeder’s priority, with a reduction in mutation frequency within the whole breed being the secondary, longer-term target.
Carriers can be bred from safely, provided they are mated to a dog that has also been tested and is clear of the BCAN mutation (i.e. carry no copies of the mutation). If a carrier is mated to a clear dog approximately half of the resulting puppies will also be carriers, so should be tested themselves prior to breeding. Breeding carriers to tested, clear dogs is safe, in terms of avoiding dogs affected with EF, and will help to maintain the genetic diversity of a breed. It is therefore encouraged, particularly in the first few generations following the availability of a new genetic test, so that other desirable characteristics and traits can be preserved before the frequency of the disease mutation within the breed is gradually reduced.