Coonhound paralysis, technically called idiopathic acute polyradiculoneuritis, is an acute and rapidly progressive inflammation of spinal nerves and nerve roots. It normally causes complete paralysis of all four of a dog's legs, but after a period of time goes away. It is among the most common peripheral nerve disorders in North American dogs, but it still is an uncommon ailment. The popular name "Coonhound paralysis" persists, because early cases of the condition in were thought to be caused by contact between hunting dogs and raccoons. However, many cases of acute polyradiculoneuritis occur spontaneously in dogs with no exposure to raccoons or raccoon saliva.
Causes & Prevention
Causes of Coonhound Paralysis
Coonhound paralysis is thought to involve an immune-mediated attack of antibodies directed against a dog's own peripheral nerves. It may be precipitated by contact with the saliva of a raccoon following a bite incident, although there is no known scientific reason for this connection. There may be a viral or bacterial agent involved that has not yet been identified. The actual cause of this condition is not well-understood.
Prevention of Coonhound Paralysis
Dogs who suffer a bout of idiopathic acute polyradiculoneuritis do not develop immunity to the condition. They remain at risk of subsequent episodes if they come into contact with the causative agent at some later date. Until the cause of this condition is identified, prevention is not possible.
The time from onset of clinical signs to complete paralysis can be as short as 12 hours or as long as 10 days. Owners who notice early symptoms often are not overly concerned, because their dogs are alert and continue to eat and drink normally. As the disease progresses and the dog deteriorates, it becomes increasingly obvious that something is seriously wrong. Until the affected dog recovers motor function in its legs, it will need supportive nursing care around the clock, because it will not be able to rise, stand or walk without assistance. Soft bedding and daily physical therapy are important to a full recovery. As long as supportive therapies are continued, the prognosis for this condition is very good.
Symptoms & Signs
Coonhound paralysis, actually called idiopathic acute polyradiculoneuritis, is an acute inflammatory condition of nerves and nerve roots. The popular name persists because early cases of the condition were thought to be caused by contact with raccoon saliva. Hunting dogs occasionally developed this disorder roughly one week after being bitten by a raccoon. However, many cases of Coonhound paralysis occur spontaneously in dogs with no exposure to raccoons. Whatever the underlying cause, Coonhound paralysis is thought to involve an immune-mediated attack on peripheral nerves and nerve roots located near the base of the spinal cord, causing paralysis that can range from mild to very severe. Clinical signs of this disorder develop rapidly and often start with hind end weakness of unknown origin.
Symptoms of Coonhound Paralysis
Coonhound paralysis can occur in dogs of any breed, age or gender, but it seems to show up more frequently in outdoor dogs and hunting dogs after contact with a raccoon. Symptoms develop quickly and typically include many or most of the following:
Progressive hind end weakness of unknown origin that worsens over 5 to 10 days
Changes in vocalization (bark becomes raspy and hoarse due to vocal cord damage)
Stiff, stilted gait; progresses to affect all limbs
Loss of leg reflexes
Loss of muscle tone
Severe muscle wasting (atrophy)
Rapid progression to complete flaccid paralysis in all four legs
Hypersensitivity to touch (hyperesthesia); vigorous objection even to very light contact or mild stimulation
Sensory function remains intact in almost all dogs, including the sensation of pain
One of the most confusing aspects of this condition for owners is that most affected dogs continue to urinate and defecate normally and can still wag their tails. Most also can chew and swallow normally and do not have pupillary or other eye abnormalities. In a very few cases, the facial nerves become damaged, although appetite and thirst almost always are unaffected. The paralysis generally worsens for several days once clinical signs appear, and then stabilizes. Most dogs will develop relatively few symptoms other than limb paralysis and will eventually recover spontaneously, without treatment and without permanent neurological damage. Unfortunately, respiratory paralysis occasionally occurs, and some dogs become severely debilitated. In those cases, hospitalization with mechanical respiratory support may be essential to the dog's survival.
Dogs at Increased Risk
"Coonhound" is a term loosely applied to a number of different hunting dogs, most of which live in the southern United States. Few of these are recognized as specific breeds by any official canine organization. Outdoor dogs allowed to roam freely and hunting dogs in areas frequented by raccoons are at an increased risk of developing Coonhound paralysis, although it can occur in other dogs as well, for no apparent or identifiable reason.
Diagnosis & Tests
Coonhound paralysis refers to an acute-onset of progressively worsening paralysis that can affect dogs within 1 to 2 weeks of coming into contact with raccoon saliva. It also can be seen in dogs with no history of access to raccoons. It can be very difficult to diagnose, because the signs of the disorder mimic those of several other diseases.
How Coonhound Paralysis is Diagnosed
Routine blood and urine tests are typically inconclusive in cases of Coonhound paralysis, although they can reveal infectious causes of similar symptoms. More advanced testing can include assessment of serum immunoglobulins and of serum reaction to raccoon saliva, although these are also usually inconclusive as to the exact cause of the dog's condition. Sampling and analysis of cerebrospinal fluid will often disclose an abnormally elevated protein level in dogs with Coonhound paralysis. Diagnostic tests of muscle electroconductivity and sensory nerve function are also available. However, most affected dogs never are diagnosed with certainty. Thankfully, most also recover spontaneously without major medical therapy or intervention. Your veterinarian can discuss these diagnostic procedures with you in greater detail if you suspect that your dog may be suffering from this condition.
Sensory function remains intact in almost all dogs with this disease, including the sensation of pain. Some dogs even become hypersensitive to touch (called "hyperesthesia") and object vigorously to even the mildest of stimulation. This reaction is one of the few signs that helps veterinarians distinguish Coonhound paralysis from tick paralysis and botulism – the two other canine disorders that cause extremely similar clinical presentations. Usually, however, motor/muscle dysfunction predominates over sensory dysfunction in dogs with Coonhound paralysis, while dogs with either of the other two disorders tend to have more pronounced sensory disabilities in combination with their muscle paralysis.
Coonhound paralysis can take weeks to months to resolve. While there is no specific treatment for this disorder, both inpatient and outpatient supportive therapy have proven extremely helpful. Fortunately, the prognosis for full or nearly full recovery is very good.
Dogs suffering from severe signs of rapidly progressive paralysis should be hospitalized until the progressive stage of the disease is stabilized. Usually, this takes at least 4 days, and it can take longer. During inpatient treatment, veterinary professionals will monitor the patient closely and provide intensive supportive care, particularly for dogs with respiratory distress. Mechanical ventilation may be used if the dog's breathing is severely compromised or if it is otherwise necessary to provide oxygen support. Most affected animals retain their desire and ability to take in and swallow food and water, as long as they can get to it with their limited and worsening physical mobility. Fluids can be administered through an intravenous catheter if the dog is dehydrated from being unable to reach or drink water. Other inpatient therapies may include manual expression of the bowels and bladder (normally unnecessary) and administration of intravenous antibiotics if infection occurs (uncommon with this disease).
Once a dog is stabilized, owners usually can continue providing supportive care at home. As mentioned above, most affected dogs can eat and drink if they can reach their food and water bowls. They often must be hand fed and have their water bowls brought to them because of muscle weakness and paralysis. Their appetite and degree of thirst should be normal, and they should not need any particular dietary restrictions or changes in most cases.
At home, the dog will need to be turned frequently to prevent pressure sores and possible lung collapse (called "atelectasis"). It will need extremely good padding, such as an air mattress, waterbed, lounge chair pad, regular bed mattress, fleeces, sleeping bags, blankets, straw or other lofty and soft forms of bedding to lie on. The outer layers of bedding will need to be changed and laundered often, and the dog will need to be cleaned frequently, until muscle function returns to normal. This is critical to prevent or reverse muscle atrophy and to prevent urine scalding, which can be severe and lead to secondary infections. Affected animals normally will not require their owner's assistance to urinate or defecate, but their limb paralysis will prevent them from moving voluntarily to an appropriate place to accomplish these bodily functions. They will have to eliminate wherever they are bedded down. In-home care can be difficult and impractical for many owners, and it may be too much for one person to manage alone. Professional pet sitters, friends, partners, spouses and other family members can be recruited to help to with the necessary tasks to ensure that the dog gets the care that it needs to recover successfully.
Physical therapy is critical to the dog's recovery as well. The attending veterinarian is in the best position to discuss the types of therapeutic exercises that are best for a dog recovering from Coonhound paralysis. It seems to be more important that physical exercises be performed correctly than that they be performed frequently (but incorrectly). Generally, owners should encourage as much managed activity as possible, despite the fact that most dogs are temporarily paralyzed in all four legs (tetraplegic). Each of the legs should be passively stretched and flexed by hand – called "range of motion" or "ROM" exercises – in a manner described by a veterinarian or veterinary physical therapist. When the dog begins to recover limb function, its owner will need to help it stand, put its limbs in the right place, shift weight, retain balance, turn, walk, exercise and otherwise regain muscle strength, stamina and control. Therapeutic massage and swimming exercises have been found to be quite helpful to dogs recovering from this disease, as well.
Most dogs begin to improve after the first week of supportive care, but actual recovery can take months. Some dogs recover spontaneously. Some dogs never recover completely, but this too is uncommon. Normally, the prognosis for full recovery is good. Owners should know that their dogs' chances of developing this disease do not decrease after they have had it once. In other words, affected dogs that have recovered fully are just as likely to get Coonhound paralysis again - especially if they are outdoor dogs repeatedly exposed to wild raccoons.