The Cavalier King Charles Spaniel
According to the Kennel Club’s Annual Registration figures, the Cavalier King Charles Spaniel (CKCS) is the sixth most numerous pedigree breed of dog in the United Kingdom with more than 11,000 puppies being registered annually.
In this article we will consider two disease conditions which are perceived to be particular problems affecting the breed.
Mitral Valve Disease
Mitral valve disease (MVD) is the most common cardiac disorder in the dog. It is most commonly found in small to medium sized dogs and the prevalence in the CKCS is especially high. If mitral regurgitation occurs, the most prominent clinical finding is a systolic heart murmur.
Some studies have shown that approximately 50% of dogs of this breed have developed a murmur by 5-6 years of age, and by the age of 10 years most dogs are affected. MVD in other dog breeds also becomes increasingly prevalent as dogs get older, but it occurs in the CKCS at a much younger age. One study found approximately 19% of CKCS under 1 year of age had a heart murmur, and the incidence of MVD in males is significantly higher than that in females.
The results of the Purebred Dog Health Survey for Cavalier King Charles Spaniels indicated that cardiac disease was by far the most frequently reported cause of death in the breed, accounting for nearly 43% of all deaths. Taking into account non-fatal disease conditions, cardiac disease accounted for nearly 25% of all illness in the CKCS.
One heartening piece of information to come out of this survey is that, despite the very high incidence of cardiac disease in the CKCS, the average life span of dogs of the breed is slightly higher than the average for all breeds, coming in at 11 years and 5 months. This suggests that, although there is a high burden of illness associated with cardiac disease in the breed (with the average age at diagnosis being around 7 years), medical treatment is very effective and affected dogs can still have a good life expectancy.
It has been postulated that there is a genetic predisposition to mitral valve disease in the CKCS, and a polygenic mode of inheritance has been suggested.
There have been efforts to screen individuals of the breed for MVD with the aim of reducing the incidence of the disease in the CKCS or increasing the average age at onset of the MVD. Initially the method for these programs was cardiac auscultation, but more recently echocardiography has superseded this as a more sensitive and accurate tool.
Sadly, efforts to reduce the incidence of MVD in the CKCS may have inadvertently brought another condition to the fore – syringomyelia.
Syringomyelia is characterized by the development of fluid-filled cavities within the spinal cord. In the CKCS it occurs because of a developmental abnormality of the skull, which leads to an obstruction of the flow of cerebrospinal fluid (CSF) in and out of the cranium. This leads to fluid coalescing in cavities within the spinal cord.
The degree of syringomyelia in affected individuals is very variable. Some dogs only have a small, subclinical, syringomyelia which is only detectable by MRI scan or at post mortem examination. More severe cases develop considerable spinal cord damage and are significantly disabled by 1 year of age.
The classical clinical signs of the condition are scratching at the neck and/or shoulders when walking (often without contacting the skin) and pain. Sometimes there is also cervical scoliosis (where the neck deviates to one side), limb weakness and in coordination. These clinical signs can be partially alleviated medically and in more severe cases surgery is sometimes indicated.
Syringomyelia in the CKCS is most common in Blenheims and Rubies – these coat colours are recessive and must therefore be bred from a more restricted gene pool than the other colours.
The Purebred Dog Health Survey for Cavalier King Charles Spaniels showed that neurological conditions including syringomyelia were the cause of death in just 2.8% of CKCS – this is substantially less than was the case for cardiac conditions. Neurological conditions accounted for 7.9% of all illness in the CKCS.
Research into the condition is ongoing at both the Royal Veterinary College in North Mymms and the Stone Lion Veterinary Centre in Wimbledon with the latter also focusing heavily on its inheritance.
A restricted breeding programme, such as was used to try to reduce the incidence of MVD, would lead to further narrowing of the gene pool of the CKCS and may possibly result in other diseases increasing in frequency.
Development of a DNA test for syringomyelia would allow detection of carriers or affected dogs not showing clinical signs. Carrier dogs could still be used, with guidance, which would enable preservation of the gene pool.
In summary, although a lot of attention is currently being focused on syringomyelia, the results of our survey indicate that mitral valve disease is still by far the most significant disease affecting the CKCS. It is important that this is borne in mind, and efforts should continue to try to reduce its incidence.
This articled was published in the Kennel Gazette and is reproduced by kind permission of the author Katy Evans BVSc CertVA MRCVS, Animal Health Trust
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Material Copyright © 2011 The Cavalier King Charles Spaniel Club