Exercise-Induced Collapse is an inherited condition that affects Labrador Retrievers and related breeds. Affected dogs can endure mild to moderate exercise but after 5 to 20 minutes of heavy exercise with extreme excitement, the dog shows weakness and then collapse. Severely affected dogs may collapse whenever they are exercised to this extend – other dogs only exhibit collapse episodes sporadically.
Signs of EIC are not typically seen until the dog begins intense training. First symptoms are usually noted between 5 months and 3 years of age. However, it is confirmed that some affected dogs did not have collapse episodes until as late as age 10.
The first symptom noted during an episode is usually a rocking or forced gait. The rear limbs then become weak and unable to support the weight. Many affected dogs will continue to run while dragging their back legs. Some dogs appear uncoordinated, especially in the rear limbs, with a wide-based, long, loose stride rather than the sort stiff strides typically associated with muscle weakness.
In some dogs, the rear limb collapse progresses to forelimb weakness and occasionally to a total inability to move. Some dogs appear to have a loss of balance and may fall over, particularly as they recover from complete collapse. Most collapsed dogs are conscious and alert, still trying to run and retrieve, but as many as 25% of affected dogs will appear stunned or disoriented during the episode.
- Genotype: N / N [Homozygous normal]
- The dog is noncarrier of the mutant gene
- The dog will never develop Exercise Induced Collapse ( EIC ) and therefore it can be bred to any other dog
- Genotype: N / EIC [Heterozygous]
- The dog carries one copy of the mutant gene and one copy of the normal gene
- The dog will never develop Exercise Induced Collapse ( EIC ) but since it carries the mutant gene, it can pass it on to its offspring with the probability of 50%
Carriers should only be bred to clear dogs – avoid breeding carrier to carrier because 25% of their offspring is expected to be affected (see table above)
- Genotype: EIC / EIC [Homozygous mutant]
- The dog carries two copies of the mutant gene and therefore it will pass the mutant gene to its entire offspring
- The dog will develop Exercise Induced Collapse ( EIC ) and will pass the mutant gene to its entire offspring