Another Look at Inherited Disease

While researching our last column on health issues in the CKCS, I was drawn to the work of our Breeders, Researchers, the Animal Health Trust (UK) and the American Cavalier King Charles Spaniel Club Charitable Trust to eliminate those entities that may afflict our royal breed. One such success story involves two conditions which few but Cavalier lovers may have heard of. Episodic Falling Syndrome (EFS) and Curly Coat/Dry Eye Syndrome are two fairly rare but important conditions seen in our breed.

EFS is a neurologic condition with exercise-induced hypertonicity, meaning that there is increased muscle tone and the muscles are unable to relax. Episodes occur in response to excitement, exercise, or frustration, except in severe cases. Symptoms may be chronic or happen with no apparent cause. (1)

EFS displays itself as an array of symptoms so it is not easy to describe. Symptoms may include momentary freezing, stiffness, and loss of coordination, bunny-hopping gait, loss of rear leg control or collapsing. There is no clear pattern and affected dogs should be evaluated for conditions like Syringomyelia (SM), seizures, liver shunt and even cardiac disorders. A correct diagnosis is important to help alleviate symptoms if possible.

Dry Eye (Congenital Keratoconjunctivitis Sicca) is an inflammation of the cornea and the inability to produce tears. This lack of lubricating moisture in the eye causes an inability to eliminate foreign objects like hair and dust and can cause infections and painful ulcerations and most often blindness. This is a painful condition. Dry Eye is associated with Curly Coat (Ichthyosiform Dermatosis). This syndrome creates a condition where the coat is rough and often curls like lambs wool and has an oily texture. This coat texture can be seen at birth. The mouth and eyes do not seem to have moisture and the teeth and toenails can be deformed. Most puppies fail to thrive and will not grow at the same rate as their siblings.

These conditions, unique to the Cavalier are rare but can be devastating as many affected dogs are euthanized. I started this story using the word success since a tool has been found which can help eliminate these conditions from our Breed. Early in 2011 geneticists at the Animal Health Trust identified a recessive mutation associated with Dry Eye Curly Coat Syndrome. A DNA test was developed to provide a useful diagnostic tool to the veterinary profession and dog breeders and has been available from the Animal Health Trust since 18 April 2011. The DNA test is specific to the mutation causing Dry Eye and Curly Coat Syndrome. (2) Not to belabor the reader with basic genetics but this fairly inexpensive test allows breeders to place the perspective parents into one of three categories:

1. Clear: these dogs have two normal copies of DNA. Clear dogs will carry the affected mutation.
2. Carrier: these dogs have one copy of the mutation and one normal copy of DNA. These dogs will not develop the syndrome themselves but they will pass the mutation on to approximately 50% of their offspring.
3. Affected: these dogs have two copies of the mutation and will be clinically affected.

It must be noted that is it is possible for some Cavaliers to be affected by a non-congenital forms of ichthyosis or dry eye, which will not be detected by the DNA test.

It should be obvious to the reader at this point that two carriers should never be mated and I could make the case that any carrier should not be used as breeding stock for the future improvement of our breed and the eventual elimination of this congenital disease entirely. This also highlights the value and contribution of responsible breeders, research and purebred dogs despite the AR attacks on us. Research has demonstrated genetic links for conditions like Degenerative Myelopathy, Gout-Hyperuricemic Bladders Stones, and Progressive Retinal Atrophy (3) and the search is on for genetic markers for Mitral Valve Disease and Syringomyelia. This is all through the tireless efforts of breed organizations and the ACKCSC Charitable Trust in Cavaliers, which has financed a good deal of this research.

- John V. Ioia, MD, PhD This email address is being protected from spambots. You need JavaScript enabled to view it.
- American Cavalier King Charles Spaniel Club, ACKCSC.org

 

(1) http://www.episodicfalling.com/symptoms.html
(2) http://www.aht.org.uk/cms-display/genetics_curleycoat.html
(3) http://www.offa.org/

Reprinted from the AKC Gazette March 2016