Canine Multiple System Degeneration (CMSD) Health Testing

Canine multiple system degeneration or CMSD is a hereditary health condition that is found in some populations of dogs of the Chinese crested and Kerry blue terrier dog breeds. The condition has long been recognised as a hereditary problem within the Kerry blue terrier breed, with the first recorded cases of the condition occurring in the 1940’s.

CMSD in dogs is also sometimes called progressive neuronal abiotrophy or PNA, which was the original term used for the condition – but both PNA and CMSD refer to the same condition.

Because CMSD is hereditary, it spreads throughout the wider gene pool of the affected dog breeds when affected dogs and/or carriers of the condition are bred, and cannot be reversed or cured. However, a health testing scheme is now in place to find out the status of any given dog prior to breeding, which enables breeders to make an informed choice about potential mating matches which over time, should ensure the spread of the condition is limited and ultimately, bred out of the gene pool.

In this article, we will look at canine multiple system degeneration in dogs in more detail, including how it affects dogs, how the disease is transmitted, and how to get your dog health tested for the condition. Read on to learn more.

More about canine multiple system degeneration

Canine multiple system degeneration is a degenerative condition that tends to affect dogs while they are still young, and is a type of neurological disorder. Puppies born with the condition appear to be normal and healthy during their first few months of life, but by the time the dog reaches 3-6 months old, they begin to develop cerebellar ataxia, or loss of coordination and muscle control.

This leads to the progressive onset of movement disorders that begin with the head, causing shaking and nodding movements that the dog cannot control. As the disease worsens, it affects the legs and spine, leading to poor balance, lack of coordination and problems walking, which lead to the dog falling over a lot and generally being unable to move and function normally.

Left to progress naturally, CMSD affects the whole body, but affected dogs are usually euthanised before their second birthdays, due to their poor quality of life.

What causes the condition?

Canine multiple system degeneration is hereditary, which means that dogs can only develop the disorder by inheriting the right combination of faulty genes that cause the condition from their parents.

In order to pass the condition on, a parent dogs has to be either affected by or a carrier of the condition, and mated with another dog with carrier or affected status to pass on two copies of the gene fault.

Breeding carriers to clear dogs does not cause puppies to be born with the affected form of the condition itself, but can lead to carrier status being passed on to the pups.

What sort of dogs are at risk of CMSD?

CMSD is found in populations of the Kerry blue terrier and Chinese crested dog breeds, and not in general canine populations of other dog breeds. It affects males and females equally, and presents for the first time in young dogs.

Any dog of potentially at-risk breeds that have reached the age of two in good health cannot be affected with the condition themselves, as symptoms first present in puppies a few months old – but they may still be carriers.

How is the condition passed from dog to dog?

CMSD is passed from dog to dog by means of autosomal recessive heredity, which means that for a dog to be affected by the condition, they need to inherit the faulty genes that cause the condition from both of their parents, not just one. Dogs are classed as either clear, carriers, or affected.

Knowing the status of the two parent dogs allows breeders to accurately predict the status of the litter, following this model:

• Two clear dogs will have a clear litter.
• Two affected dogs will have an affected litter.
• Two carriers will produce a litter of 50% carriers, 25% clear and 25% affected.
• A clear dog and a carrier will produce 50% clear and 50% carriers.
• A clear dog and an affected dog will produce a litter of carriers.
• A carrier and an affected dog will produce 50% carriers and 50% affected.

Health testing for canine multiple system degeneration

The only way to find out the status of any given dog prior to breeding is to have a DNA test performed, to identify the presence or absence of the gene mutation that causes the condition.

In order to have your dog tested, you just need to ask your vet to take a DNA sample from your dog in the form of a blood sample or cheek swab, which is then sent off for laboratory testing to return a result of clear, carrier or affected.

Breeding and buying healthy puppies

Breeders of Kerry blue terriers or Chinese crested dogs should have both their dams and sires DNA tested before they are bred for the first time, and remove affected dogs from the breeding stock pool.

Breeding a carrier with a clear dog won’t cause affected puppies, but it will pass on carrier status for some of the litter, which means further implications for breeding from the subsequent stock.

Potential puppy buyers for the two at-risk breeds are urged to buy from breeders who health test their dogs, and make the test results available to potential buyers.