Juvenile Myoclonic Epilepsy (JME) Testing in Dogs

Juvenile myoclonic epilepsy is just one of the various types of epilepsy that can affect dogs – but unlike most other types of epilepsy, JME usually presents for the first time in younger dogs, as opposed to during middle age, which is more common for other variants of the condition.

JME is a hereditary health condition that is contracted when a dog inherits a specific pair of faulty genes from their parents – and dogs of the Rhodesian ridgeback breed have been found to be particularly at risk of inheriting juvenile myoclonic epilepsy, making it largely a breed-specific health issue.

Juvenile myoclonic epilepsy in the Rhodesian ridgeback cannot be reversed or cured in affected dogs, and the condition can be very hard to manage on an ongoing basis, having a potentially large negative impact on the quality of life of affected dogs.

The only way to prevent any given dog from inheriting the condition is to perform pre-breeding health screening on the two parent dogs, so that if either dog carries the gene mutation that causes the condition, the breeder in question can make an informed decision about mating matches and how to proceed.

If you are considering adopting or buying a Rhodesian ridgeback, are in the market for a ridgeback puppy or are considering breeding from your own dog, understanding the risks of JME and how to breed or buy healthy puppies is important.

In this article we will look at juvenile myoclonic epilepsy in the Rhodesian ridgeback in more detail, covering how the condition presents, how it is inherited, and how to get your dog health tested to find out their status. Read on to learn more.

What is juvenile myoclonic epilepsy?

Juvenile myoclonic epilepsy is a type of epilepsy that leads to sudden-onset seizures in the form of muscle spasms and jerky, uncontrolled movements that can occur at any time without warning.

JME seizures are most common when the dog in question is asleep or resting quietly, but certain triggers such as bright light can also initiate seizures too. Dogs affected with JME tend to suffer very acutely from regular seizures, unlike some other forms of epilepsy that often have gaps of weeks or even months between fits.

In dogs affected with juvenile myoclonic epilepsy, daily seizures are common, and whilst the seizures are generally short in duration, some affected dogs may undergo over 100 seizure cycles every day.

This means that affected dogs require virtually constant supervision or provision made for their safety and security during attacks, and the frequency of the seizures in some dogs can make enabling a normal lifestyle whilst keeping them safe very challenging.

What sort of dogs are at risk of the condition?

Juvenile myoclonic epilepsy is considered to be a risk to dogs of the Rhodesian ridgeback breed, and data collected by the Center for Animal Genetics in Germany indicates that as many as 15% of dogs of the breed may be carriers for the gene mutation that causes the condition.

The average age at which dogs are diagnosed with JME or begin to show symptoms for the first time is about six months of age, although in some cases, seizures can begin as early as a few weeks old, or as late as 18 months. However, JME is a type of epilepsy that universally presents for the first time in young dogs, and so Rhodesian ridgebacks over the age of two with no symptoms are highly unlikely to be affected later on – although they could still be carriers for the condition.

How do dogs get JME?

JME in dogs is a hereditary condition, which occurs when parent dogs that carry the gene fault that causes JME are bred and produce a litter, who may in their turn be affected depending on the status of their parents.

JME is passed from dog to dog by means of autosomal recessive heredity, which means that a dog needs to inherit two copies of the faulty gene, one from each parent, in order to be affected. If a dog inherits just one copy of the gene, they will not be epileptic themselves, but can still pass the gene on to their own young.

Dogs can be either clear, carriers or affected, and knowing the status of the two parent dogs allows you to determine the subsequent status of any offspring that they might have according to the following model:

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

Health testing for JME in dogs

In order to find out the JME status of any given dog, a simple DNA test can be performed in a laboratory. To do this, you just need to ask your vet to take a blood sample or buccal swab from your dog and send it off to the appropriate laboratory, which will return the result of your dog’s status.

Breeding and buying healthy Rhodesian ridgebacks

Breeding from affected dogs serves to spread the gene mutation that causes JME, leading to the growth and spread of the condition and further risk for the breed as a whole as well as individual affected dogs.

However, breeding a carrier with a clear dog will result in pups that are not affected, but that may be carriers themselves – breeding a carrier with a clear dog is currently accepted in order to preserve the genetic diversity of the ridgeback breed, and avoid reducing it by potentially 15% by removing known carriers from the gene pool.

Puppies that have one carrier parent must themselves be tested if they might make for future breeding stock, to once more assure a healthy mating match.

Potential Rhodesian ridgeback puppy buyers are urged to choose pups from breeders who health test their parent dogs first, and provide copies of the test results for future puppy buyers.