A Note About The Series

This series covers the various health screening tests that are available to breeders to assist them in making breeding decisions. When you purchase a purebred puppy you should expect that a reputable breeder has done health screenings on the parents of that dog. In fact, you should expect that health screenings have been done on several generations of the dogs in your puppy’s pedigree.  See other posts in the series here.

Keep in mind that while a particular health screening test may be recommended for a certain breed, if there is a low occurrence of that disease in a particular breed or in the lineage of particular dogs, the breeder may elect not to do it.  A prospective breeding dog is more than any particular health screening. A better approach is to consider the entire dog, including health, proper temperament, conformation and important breed characteristics.

This post is about Exercise-Induced Collapse (EIC).

What Is EIC?

EIC is a syndrome that occurs predominately in  Labrador Retrievers although it also occurs in Chesapeake Bay Retrievers and Curly Coated Retrievers and some other breeds, but with a much lower frequency.  Dogs affected with EIC show muscle weakness, lack of coordination, and collapse.  These dogs can tolerate mild to moderate activity, but may show symptoms or collapse after as little as 5 to 20 minutes of strenuous activity or intense excitement.  Strenuous activity is not recommended for these dogs, but they can live normal lives as house pets.

From the AKC Canine Health Foundation:

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.)

Note: This syndrome has been identified in all Labrador lines tested: field trial, hunt test, conformation, pet and service.

Also from AKC Canine Health Foundation, 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

Factors That May Trigger A Collapse

For years many dogs experiencing a collapse were thought to be suffering from heat exhaustion, low blood sugar, cardiac or other medical issues.  Symptoms of EIC usually become apparent in young dogs between the ages of 7 months and 2 years.  Through research, it has been determined that these factors can trigger a collapse:

• Temperature–Dogs seem more likely to collapse while working in high temperatures or humidity, although they have also been known to experience a collapse while working in freezing temperatures.
• Excitement–Dogs are more likely to experience a collapse doing something they find exciting, although for severely affected dogs, it may not take a lot of excitement for them to collapse.
• Type Of Exercise–Continuous activity that the dog finds exciting such as pheasant or grouse hunting, or repetitive retrieving appear more likely to trigger a collapse.

How Is EIC Inherited?

EIC is an autosomal recessive syndrome so a dog must inherit a defective gene from both parents in order to be affected.

How Do Breeders Screen For EIC?

Researchers at the University of Minnesota (in part through a grant from the AKC Canine Health Foundation), identified a mutation in the DNM1 gene which they believe is associated with a defect in the nerve communication during strenuous activity or intense excitement.  Although nothing in genetic science is ever 100 percent sure, the researchers are confident that this gene mutation causes EIC.  Once this gene was identified, a DNA screening test was developed.  The DNA test can be done on blood, cheek swabs, dew claws and semen.

The recessive gene is most commonly seen in Labrador Retrievers but it is present in other breeds.  The University of Minnesota has screened various breeds and recorded the results.  This PDF is a log of testing results.  If you review this PDF, you will note that some breeds have tested 100 percent clear for the dogs tested.

How Should Puppy Buyers Use This Information?

The EIC mutation is fairly prevalent in Labrador Retrievers and in some of the most successful field trail lines.  Breeders could simply stop breeding dogs from those lines.  But does that benefit the breed?  Does it benefit the breed to remove all the other qualities that make the dog successful at field trials or as a hunting partner such as the ability to mark, a good memory,  trainability, strong drive?

Whenever a genetic issue is identified, people proclaim that breeders should just eliminate the dog from the gene pool.  In my opinion that view is extremely short-sighted.  Genes do not act in a vacuum.  By eliminating dogs which carry this one gene (in Labs it may be as much as 30 percent of their gene pool), you are eliminating all of their good qualities too and all of the “good” genes they could pass on to offspring.  Perhaps these dogs also carry genes which prevent them from developing cancer?  Or epilepsy?  When you breed dogs, even with all the health screenings, there are no guarantees.  You do the best you can and hope for healthy pups.

It is important that if you are thinking of purchasing a breed where the mutation that causes EIC is prevalent, Labs in particular, you verify that the breeder has done the screening test on the prospective parents and verify the results, keeping in mind that this screening test is relatively new and may not have been done on dogs further back in a pedigree.

Remember that if Normal/Clear dogs are bred to other Normal/Clear dogs, they will only produce Normal/Clear puppies, (none of the pups will inherit the gene which causes EIC).  Carrier and Affected dogs must only be bred to Normal/Clears.  At worst, this mating will produce puppies that are Carriers.  Again, while Carriers carry the mutated gene, it is believed that they will not develop EIC.  Carrier and Affected dogs should not be bred together because they will produce some Affected dogs.

The University of Minnesota has a good explanation of possible breeding choices with graphs to help explain them here (PDF).

Sources:

• University of Minnesota-EIC
• Implications of the EIC Mutation for Breeding
• Frequency Of Affected, Clear, Carriers