Even though this disorder is aimed at Labrador Retrievers, it can affect all herding dogs. This is an inherited defect of the dynamin-1 (DNM1) gene and more than 80% of Labradors have experienced at least one collapse episode by the age of four years. This is usually noticed between six and nine months of age, most often during a field trial competition, which is what triggers the episodes. Affected dogs will suffer from hyperventilation and a serious drop of carbon dioxide in their blood, causing dizziness and confusion in some dogs as well.

Collapse during exercise (exercise induced collapse) in Labrador Retrievers is a mild disorder that causes your dog to lose the use of their hind legs during brisk exercise. This disorder has also been known to affect several other breeds, including spaniels, sheepdogs, collies, and other herding dogs and it is the most common reason for exercise induced collapse of Labrador Retrievers. In fact, as much as 40% of Labradors tested are carriers of this disorder and 14% of all dogs are susceptible to collapse.

The symptoms of collapse during exercise can vary depending on your dog’s age and health. Some dogs have severe side effects that may be life-threatening, but most are only affected by the inability to move the hind legs for approximately 10 to 20 minutes during strenuous exercise. The most often reported signs of this disorder are:

 Types

Although this disorder affects Labrador Retrievers most often, the following breeds have also been affected:

The reason for collapse during exercise in dogs is a genetic mutation in the dynamin-1 (DNM1) gene which causes a decrease in the DNM1 protein. This protein is needed for transmission of the nerves from the brain and spinal cord during exercise.

Diagnosing your dog with collapse during exercise is difficult because there are no clinical symptoms to look for. The veterinarian will usually go by your description of what happened and your dog’s previous medical history if it is available. A physical examination will be performed by the veterinarian to check body temperature, reflexes, pulse, blood oxygen level, and respirations, which are all abnormal during an episode. 

Your dog’s weight, blood pressure, and breath sounds will all be normal, even during an episode of collapse. There are no electrolyte disturbances, heartbeat irregularities, respiratory difficulty, or decreased blood glucose that may explain the collapse. Your dog will show an increase in blood pH and decrease in carbon dioxide. Arterial blood gas and lactate pyruvate (LP) ratio will also show signs of abnormalities. The only reliable test for diagnosing collapse during exercise is a genetic (DNA) test, but since it is rather expensive and has to be sent to a special laboratory, many veterinarians only use this as a backup to verify their diagnosis. This test will show a mutation in the dynamin-1 (DNM1) gene that decreases the function or amount of DNM1 protein in dogs affected with this disorder. In addition, your veterinarian may want to produce an episode in a controlled environment your dog to see the severity of the disorder.

The only treatment is to avoid brisk exercise so it will not happen again. It is not a progressive disorder, so it will not get any worse than what it is at the time of diagnosis. However, some dogs have died after collapse so it is essential that you keep your dog from getting too worked up. If you have a dog that is used to being outside, they need to become an indoor dog. You can take your pet outside, but you will need to supervise and do not let your dog exercise until collapse. If you notice your dog getting weak or uncoordinated, cease the exercise immediately to prevent an episode.

Your dog will have recovered within 10-30 minutes of the collapse and should have no lasting complications. Management includes reducing your dog’s exercise levels to an accepted intensity to eliminate the chance of a collapse. In some cases, the veterinarian may suggest treatment with phenobarbital so your dog can still perform in competitions, but this is not a reliable or proven treatment so it is not recommended. You will still be able to give your dog daily exercise with mild activities such as walking on a leash or a short game of fetch. You just have to watch for signs of a collapse episode and call your veterinarian if there are any questions.