Demyelinating Polyneuropathy Health Testing

Demyelinating polyneuropathy is a serious and progressive health condition that is found in some breed lines of the miniature Schnauzer dog breed, which affects the peripheral nerves of the body and that worsens over time, to the point that it can have a significant impact on affected dogs.

The condition is hereditary, and is passed on from parent dogs to their litters, which enables the further spread of the disease down through the breed line. However, the gene mutation that causes demyelinating polyneuropathy in dogs has been identified, and a DNA test devised to recognise it in dogs that either have the condition or are carriers for it. This means that breeders can have their potential parent dogs tested prior to making a decision to breed, in order to ensure healthy litters.

In this article, we will look at demyelinating polyneuropathy in the miniature Schnauzer in more detail, including how the condition presents, how it is passed from dog to dog, and how breeders and potential puppy buyers can identify affected dogs. Read on to learn more.

More about demyelinating polyneuropathy

Demyelinating polyneuropathy is a nerve disorder, leading to the progressive destruction of the myelin sheaths that protect the body’s nerves from damage, which causes a wide range of problems that can affect the dog’s ability to move and even breathe normally and comfortably.

Polyneuropathy means a condition that affects lots of different nerve pathways and not just one or a small set of nerves, and usually affects both sides of the body at once. The polyneuropathy or nerve damage occurs due to the destruction of the protective myelin, which means that symptoms of the condition start off subtle and worsen over time, to the point that they have a significant impact on the dog’s general health and quality of life.

What sort of dogs are at risk of the condition?

Demyelinating polyneuropathy is a hereditary health condition, which means that it is restricted to dogs that inherit copies of the genetic mutation or fault that cause damage to the myelin sheaths. The condition has been identified as present within the miniature Schnauzer dog breed’s gene pool, although it is not highly prevalent within the breed as a whole.

Male and female dogs from affected breed lines are equally likely to be affected by the condition, and usually it will become apparent that something is wrong in affected dogs by the time that they reach around three months of age.

However, because this is around the age that puppies bred for sale will be going off to their new homes, miniature Schnauzer buyers may find themselves taking home a pup that appears healthy, only to see symptoms starting very soon afterwards.

What are the symptoms of demyelinating polyneuropathy in dogs?

The symptoms of demyelinating polyneuropathy usually begin to show up at around three months of age, or not long afterwards. This means that a breeder whose dogs are not tested prior to breeding may have an apparently healthy litter, which only begins to show signs of problems after they have been sold.

Some of the main symptoms of demyelinating polyneuropathy in dogs include:

• Whistling, laboured or noisy breath sounds on inhalation.
• Exercise intolerance or a lack of interest in exercising and playing, with the puppy becoming tired and unwilling to continue sooner than they should do.
• Regurgitation of food or water shortly after eating or drinking-it is important to note that regurgitation is not the same as vomiting, and involves food or water coming back up quickly, before it has begun the process of digestion in the stomach.
• Potentially, numbness, an unstable or staggering gait, and inability to walk or move around normally.

Because demyelinating polyneuropathy is a progressive condition, the symptoms will often be very subtle to begin with and only become more acute and noticeable as time goes on. This means that it is important to be vigilant for potential signs of symptoms in at-risk dogs, in order to spot the onset of the condition.

How is the condition passed from dog to dog?

Demyelinating polyneuropathy is an inherited health condition that is passed from dog to dog by means of autosomal recessive heredity. It cannot otherwise be caught or spread between dogs.

The status of any given dog for the condition is expressed in terms of either clear, carrier or affected-and carrier dogs will be healthy and not show any signs of the condition themselves, but they can still pass the disease on to their own offspring, either in the form of affected or carrier status.

To determine the chances of any given puppy having the condition, the status of both parent dogs comes into play. The heredity of the condition is outlined as follows:

• Two clear dogs will have clear puppies.
• Two affected dogs will have affected puppies.
• Two carrier dogs will have a mixture of 50% carriers, 25% clear and 25% affected.
• A clear dog and an affected dog will have puppies that are all carriers.
• A carrier and an affected dog will have 50% carriers and 50% affected.
• A clear dog and a carrier will have 50% carriers and 50% clear.

DNA testing for demyelinating polyneuropathy

Because carrier dogs will themselves be healthy and show no signs of problems, breeding carrier dogs can lead to the spread of the condition in either its affected form or in carrier status, depending on the status of the other dog in the mating match-as well as of course the added risk when breeding affected dogs.

In order to permit breeders to ensure that their litters are healthy, and do not pass the condition on, DNA testing can be performed on prospective breeding stock prior to mating, to allow breeders to make an informed choice. A cheek swab or blood sample is all that is required from each dog, and this is sent off to a laboratory for testing to return the result of the dog’s status.

Potential miniature Schnauzer puppy buyers should ask breeders about their health testing results, to ensure that they buy healthy puppies.