Coonhound paralysis (idiopathic polyradiculoneuritis) in dogs

Coonhound paralysis (also known as idiopathic polyradiculoneuritis) is similar to the disease in people known as Guillain-Barre. In these diseases the immune system starts to attack the nervous system, causing inflammation mainly in the nerves supplying the legs. In some dogs it has been associated with a reaction to Raccoon saliva (hence the name Coonhound paralysis (Coonhounds being a raccoon hunting breed)), but it can develop in dogs that have had no contact with raccoons. In people this nerve damage initially causes a sensation of tingling which then progresses, in both animals and people, to weakness and, in some cases, complete paralysis of all limbs.

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Polyradiculoneuritis is a condition that develops due to the animal’s own immune system attacking the nerve tissue. It is thought that this occurs when the immune system becomes activated against a foreign protein, such as that found in raccoon saliva or in some bacterial infections. The antibodies produced to remove this unexpected protein can also react with the body’s own tissue and cause accidental damage. In some cases in dogs there is strong association with contact with raccoon saliva (eg through a bite or scratch) but in other cases the disease is thought to have developed after eating raw chicken contaminated with Campylobacter, following respiratory infection or, in a few cases, after some vaccinations.

It is not possible to catch polyradiculoneuritis from anyone including your pet. The disease develops due to a reaction of your immune system to something you have come into contact with.

The first signs of disease will usually be noticed around 7-14 days after a raccoon bite or scratch (coonhound paralysis) or after vaccination or illness. The time lag between the contact with the cause and development of signs is why it can be so difficult to work out the underlying cause in individual cases. At first your pet may have an odd way of walking and may appear a bit ‘stiff’. Signs generally get worse over 4-5 days and animals may become weak on their legs and eventually be unable to stand. In very severe cases your pet may be unable to lift its head and may be unable to vocalize. Tail wagging is not affected, and bowel and bladder function is usually normal. The signs can persist for weeks or months depending on how severe the disease is at the start. The condition doesn’t cause your pet any obvious physical discomfort.

If you notice any signs of weakness or changes in movements in your pet you should always seek veterinary advice. Your pet may be unwilling to exercise, struggle to get up, walking in an unusual way or be dragging a leg.

The signs of such progressive and obvious weakness are unusual in pets and so your veterinarian may not have seen a condition like it. However, there are many conditions that can cause similar signs and further investigations will be needed to work out what is going on. Your pet may be referred to another hospital or to a veterinarian with additional training in neurological diseases. Here, the veterinarian will do a full examination of the nervous system and it is likely that the electrical conduction in the nerves would be measured to see how well they are working. A biopsy may be taken from one of the nerves to establish what kind of inflammation or damage was present. In some cases, a sample of fluid from around the spinal cord will be collected for analysis. A blood test may be able to be performed for anti-GM2 ganglioside antibodies which can be positive in about 6 out of 10 dogs. In many cases, the diagnosis is a process of elimination ruling out diseases such as botulism, myasthenia gravis, toxicity and in some countries, tick paralysis and snake bites.

There is no specific treatment for the condition, but good nursing care is essential to support your pet while they recover. If your pet is severely affected, they will need to be kept in the hospital for monitoring and treatment. This may last for weeks or even months. Good nursing is important to prevent sores and ulcers developing in pets unable to stand or move voluntarily. Dogs may need to be fed by hand if they are unable to reach a food bowl and they can be placed on a drip to keep them hydrated.

In a very small number of cases the muscles related to breathing can also be affected and your pet may need oxygen therapy to help them breathe.

As recovery begins your pet may be allowed home for continued nursing care. Regular monitoring will be needed as cases sometimes take a turn for the worse after initial improvement. Intensive physiotherapy or hydrotherapy can be helpful to build strength and prevent muscle loss in the limbs.

Most dogs begin to improve after 7-10 days and these will generally go on to recover normal function in their limbs. However, recovery may take weeks to months and longer-term physiotherapy is often needed. The outlook is much worse in severe cases where dogs are unable to stand for months, and in those cases where the muscles of breathing are also affected.