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Exercised Induced Collapse

Exercise Induced Collapse: An Overview

Exercised Induced Collapse (EIC) is a genetic syndrome, predominately occurring in Labrador Retrievers. Affected dogs show signs of muscle weakness, lack of coordination, and life-threatening collapse when participating in strenuous exercise or activity. Dogs that have EIC are prone to mild-to-severe collapse that can range from dragging of the hind legs to complete collapse. Most affected dogs have been from field-trial breedings. Black, yellow and chocolate Labradors of both sexes are affected, with the distribution of colors and sexes closely reflecting the typical distribution in field trials (black males are most common.) Affected dogs can tolerate mild to moderate exercise, but just 5 to 20 minutes of strenuous activity or even extreme excitement can induce weakness or collapse. EIC is also seen in Chesapeake Bay Retrievers and Curly Coated Retrievers. Dogs Affected with EIC usually cannot tolerate intense retriever training, but can live normal lives as house pets.

Causes of Exercise Induced Collapse

For years veterinarians evaluated affected dogs for episodes of collapse, and speculated that their episodes were due to heat intolerance, low blood sugar, cardiac arrhythmias or possibly metabolic myopathies. Now, EIC has been established as an autosomal recessive syndrome caused by a mutation in the DNM1 gene, which causes a defect in nerve communication during intense exercise. To be effected a dog must receive a defective gene from both parents.

In dogs with EIC, certain factors can cause collapse:

Temperature: Actual ambient temperature is not a critical factor contributing to collapse, but if the temperature is much warmer or the humidity is much higher than what the dog is used to, collapse may be more likely. Affected dogs are less likely to collapse while swimming than when being exercised on land. There are dogs, however, who have exhibited collapse while breaking ice retrieving waterfowl in frigid temperatures and there are dogs that have drowned when experiencing EIC-related collapse in the water.
Excitement: A dog's level of excitement plays a role in inducing the collapse. There are some severely affected dogs that, if very excited, do not require much exercise to induce the collapse. Dogs with EIC are most likely to collapse when engaging in activities that they find very exciting or stressful. This can include retrieving birds, participating in field trials, training drills with electric collar pressure, and quartering for upland game.
Type of Exercise: Routine exercise such as jogging, hiking, swimming, waterfowl hunting and even agility training are not very likely to induce an episode in dogs with EIC. Activities with continuous intense exercise, particularly if accompanied by a high level of excitement or anxiety most commonly cause collapse. Activities commonly implicated include grouse or pheasant hunting, repetitive "happy retrieves", retrieving drills or repetition of difficult marks or blinds where the dog is being repeatedly corrected or is anticipating collar correction, and running alongside an ATV.

Preventing Exercise Induced Collapse

Responsible breeding is the key to preventing EIC. The EIC mutation is fairly prevalent (25%) in Labrador Retrievers and is seen in some of the most successful field trial lines, thus it unreasonable to suggest breeding only dogs that are "clear" of this mutation. However, "affected" dogs should not be bred, and "carrier" dogs should only be bread to "clear" dogs. Whenever a dam or sire of a litter is a known carrier of EIC, puppies should be tested before 7 weeks of age.

Symptoms of Exercise Induced Collapse

Signs to look for include:

Weakness after 5-15 minutes of strenuous exercise
Lack of coordination
Dragging of rear legs
Dazed, confused appearance
Collapse
Staggering, falling to one side, or difficulty maintaining balance is common during recovery

Diagnosing Exercise Induced Collapse

There is a specific DNA test for EIC. The University of Minnesota Veterinary Diagnostic Laboratory offers testing of blood, semen, dew claw or cheek swab and provides three levels of results: Clear, Carrier, or Affected. A Clear result means that the dog has two copies of the normal EIC gene. A Carrier result means that the dog has one copy of a normal EIC gene and one mutated copy of the gene. Carrier dogs do not show signs of EIC. Carrier dogs, pass on the mutated gene, on average, to half of their offspring. An affected result means that a dog that has two copies of the mutated EIC gene. These dogs are susceptible to collapse episodes under their trigger conditions. An affected dog will pass on the mutated EIC gene to all of its offspring. By mating an affected dog to a clear dog, a litter that is made up of 100 percent carrier offspring will be produced no clears, but also no affecteds.

Signs become apparent in young dogs as they enter heavy training - usually between 7 months and 2 years of age. Dogs with EIC are always normal at rest and are usually described as being extremely fit and athletic.

Treating Exercise Induced Collapse

Treatment for EIC consists of avoiding intensive exercise in conjunction with extreme excitement, and ending exercise at the first sign of weakness. However, numerous anecdotal reports show that dogs may be able to resume trigger activities (i.e. competition, retrieving) when they are treated with the anti-seizure medication, Phenobarbital. Phenobarbital and other sedative drugs may simply decrease the dog's level of excitement or anxiety, thereby decreasing the likelihood of collapse. In some dogs; however, Phenobarbital administration will cause noticeably impaired judgment, interfering with training or trialing. Phenobarbital also has potential side effects, so it should only be administered under the direction and monitoring of a veterinarian.

Care for Dogs with Exercise Induced Collapse

Dogs symptomatic for EIC must be retired from the activities that cause them to collapse. When trigger activities are limited, dogs with EIC can live normal lives. Many affected field trial dogs have been adopted out as pets, and if intense exercise, excitement and training stressors are avoided, dogs with EIC typically never experience another episode of collapse.

The AKC Canine Health Foundation and Exercise Induced Collapse

CHF has funded the research that determined the genetic cause of EIC in the Labrador Retriever. Subsequent grants have been approved to investigate the genetic cause of EIC in other sporting breeds.

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