Comparative Neurology Program

Juvenile Laryngeal Paralysis & Polyneuropathy (JLPP) in Rottweilers

Also called: Neuronal Vacuolation and Spinocerebellar Ataxia (NVSA) or Polyneuropathy with Ocular Abnormalities and Neuronal Vacuolation (POANV)

 

What is Juvenile Laryngeal Paralysis & Polyneuropathy?

The brain controls muscles via signals that travel through nerves. A disease that affects the nerves is called a polyneuropathy: poly- (many), neuro- (nerves), -pathy (a disease). Due to a quirk in the way an embryo develops, one of the longest nerves in the body supplies the muscles of the voice box (larynx). The vocal folds vibrate as air moves over them allowing a dog to bark. When the dog breathes in, muscles in the larynx pull the vocal folds aside so that air can move easily into their lungs. These nerves also help to close the larynx when the dog swallows so they do not choke on their food.

If nerves are unable to convey messages properly, the muscles become weak or paralyzed. The longest nerves are often affected first; hence laryngeal paralysis is the first symptom. The vocal folds cannot be pulled out of the way as the dog breaths in. They vibrate noisily and can obstruct the flow of air into the lungs particularly when the dog is exercised or hot. The dog may also choke on their food or water or regurgitate, which can result in pneumonia.

The next longest nerves in the body go to the back legs, thus they are often affected next. The dogs have difficulty getting up and wobble as they walk. Eventually the front legs will also be affected. The symptoms do not occur until after weaning age, and thus the disease is called juvenile laryngeal paralysis/polyneuropathy or JLPP for short

Laryngeal Paralysis

If you look down the throat of a dog with laryngeal paralysis, the vocal folds (arrows) do not pull out of the way like they should as the dog inhales. The airway cannot then open up completely when the dog is breathing hard, and they have trouble getting enough air.

JLPP? NVSA? POANV? Why the alphabet soup of names?

The parable of the blind men and the elephants tells of blind men touching an elephant for the first time. Each comes away with a different impression of what an elephant is like (a wall, a tree, a brush) depending on which part they touched. When veterinary researchers first see a new disease, they describe what they observe but may be blind to other aspects of the disease that latter come to light.

In the late 1990s, veterinary neurologists in America and Europe recognized a new hereditary disease in Rottweilers. The affected pups showed coordination problems (spinocerebellar ataxia) and a very unusual form of degeneration in the brain at post-mortem with basically holes (vacuoles) developing within the brain cells (neurons). This syndrome was originally describes as “Neuronal Vacuolation and Spinocerebellar Ataxia” or NVSA for short. As more cases were studied, however, it was recognized that these pups can usually suffer from breathing difficulties due to paralysis of the muscles of the voice box (laryngeal paralysis) as well as weakness in the limbs. These symptoms were due to a degeneration of the nerves supplying these muscles (polyneuropathy). Laryngeal paralysis is common in old dogs, but since these dogs were affected at a young age, this portion of the syndrome was called Juvenile-onset Laryngeal Paralysis and Polyneuropathy (JLPP). Finally it was noticed that many of these pups also had cataracts along with other abnormalities within the eye (ocular abnormalities). Like laryngeal paralysis, cataracts are common in older dogs, but if they are found in a juvenile dog, that suggests a hereditary problem. Once it was clear that all these symptoms were part of a common disease, the broader term Polyneuropathy with Ocular Abnormalities and Neuronal Vacuolation (POANV) to encompass all aspects of the disease. For sake of simplicity, the term JLPP is still commonly used.

Vacuole

Two neurons from the brain of a dog with JLPP. One with a vacuole (arrow) is sitting above a normal neuron.

What does JLPP look like?

If your dog shows signs of JLPP, see your veterinarian. They will be able to utlize the results of the DNA test and their findings on examination to determine if your dog is suffering from JLPP and advise you appropriately.

The typical affected pup begins showing symptoms at around 3 months of age. The initial symptoms can be breathing difficulties, especially with exercise or excitement, or they can begin with weakness and incoordination of the legs. Cataracts or other changes may be visible on careful examination of the eyes. The breathing problems from the laryngeal paralysis can be improved with surgery, but the disease is progressive. The weakness and coordination problems become more severe and the dogs can develop problems swallowing. All affected dogs had to be euthanized before a year of age to prevent suffering.

For more information on this disease, please see our publication in the

Journal of Veterinary Internal Medicine

.

Cataract

Cataracts are common in older dogs, but when they appear in young dogs it can be a symptom of a hereditary disease.

What else can look like JLPP?

There are other, much more common diseases that can affect a pup’s ability to breath.  The windpipe (trachea) is stiff to keep it open when the dog is breathing hard.  In some dogs, particularly toy breeds, the trachea does not have the proper stiffness and it can collapse as the dog breathes producing a honking cough.  This condition is called collapsing trachea.  An infection of the trachea such as kennel cough can cause irritation to the trachea and a similar sounding cough.  The major difference is that dogs with tracheal disease cough when breathing out, while laryngeal paralysis produces noise when the dog breathes in. Infections can cause swelling of the tonsils & lymph nodes around the throat in a young pup (strangles) shich can make it difficutl for the pup to breathe.  Finally, other diseases of the nervous system, such as distemper infections, can affect nerves producing signs of weakness, sometimes with pneumonia.  Laryngeal paralysis also occurs in older dogs, but JLPP is different because they develop paralysis at such a young age. 

DNA test for JLPP is now available!

Researchers at the University of Missouri, College of Veterinary Medicine have found the mutation associated with JLPP in Rottweilers. A DNA test is now available to determine if a dog is a carrier of the mutation or at risk for JLPP, also referred to as Polyneuropathy with Ocular Abnormalities and Neuronal Vacuolation (POANV).

If you suspect your dog has JLPP, see your veterinarian. As discussed above, there are many conditions besides JLPP that can cause these symptoms. Your veterinarian will be able to examine your dog to determine if one of these more common, potentially treatable diseases is causing your pet's difficulties. If necessary, they can refer you to a Veterinary Neurologist board certified by the ACVIM. who can help them make the diagnosis. The DNA test can be ordered through the Orthopedic Foundation for Animals website (www.ofa.org). To order a test, CLICK HERE, then click on "Order OFA DNA Test Kit" and scroll down to "Juvenile Laryngeal Paralysis and Polyneuropathy".

What if my dog is a carrier?

JLPP is inherited as a recessive trait. In a recessive disease, both parents of an affected pup are carriers but do not show any symptoms of the disease. All animals have two copies of each gene, one that is inherited from the mother and one inherited from the father. A dog that has one normal gene and one gene that causes the disease is a carrier of the trait. They show no symptoms because the one good gene is enough for their brain to develop normally, but they will pass that bad gene on to about half of their offspring. If a carrier dog is bred to another carrier, then some of the pups (25% on average) will get a bad gene from each parent. Without one good gene to carry the day, the brains cannot function normally and the unlucky pup has JLPP.

The DNA test can identify carriers of the mutation so that breeders can make wise breeding decisions. While the initial response is often to want to eliminate all carriers of a mutation from the breeding pool, this is not the recommended approach. Eliminating all the carriers will narrow the gene pool and limit the breeding choices available. This reduces desirable genetic diversity in the breed and may inadvertently increase the incidence of other hereditary problems that may be lurking the lines that are free of the JLPP mutation. There are often highly desirable traits in the lines with a mutation that made them popular to begin with. Eliminating those lines can eliminate those desirable traits, throwing out the baby with the bathwater. The best approach is to test breeding stock and ensure that two carriers are never bred together so that no affected pups are produced. A carrier that has desirable traits can be bred to a dog who is tested clear of the mutation since no affected pups can result from such a breeding. When selecting future breeding stock, the gene status can be considered in deciding which pups to keep but does not have to be the sole factor. Over time, the prevalence of the mutation in the breed will decline while a genetic bottle-neck is avoided. The key is to ensure that carriers are never bred to each other so that no affected pups are produced.

Thanks!

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