Exercise Induced Collapse in Chesapeake Bay Retrievers
by Dr. Mario Beauregard
It started two years ago. I had an 8 months old bitch from a nice trial breeding . It was November, and I had to take all the leaves out of the pool to close it for the winter. My four dogs were in the yard with me, playing around, and Saga was very intense, almost in frenzy, chasing the leaves that I was throwing out of the pool. I didn’t pay attention to her, but when I checked , she was dragging her hind legs, not in pain, still wanting to chase the leaves. I figured she has hurt her back, so I carried her in her kennel, and I got ready to take her to my clinic, but she was fine after 20 minutes. She never had another episode, although I trained her that winter and spring. She ran with a lot of style and marked well, so I decided to send her to a pro for the summer.
While she was at the pro, I had a call from the owner of one of her littermates who showed similar signs every time she was exercised hard. I began suspecting EIC, though it was only reported in Labradors. I called the pro to let him know that I wanted him to check for any signs in Saga, and there were none. Then I got in touch with Dr. Susan Taylor, of the University of Saskatoon, we sent her a video of the affected bitch, and she confirmed that it looked very similar to EIC in Labradors. She then referred me to Katie Minor, of the University of Minnesota, who works with Dr.Jim Mickelson on identifying the EIC gene in Labradors. Katie told me that they would like to have blood samples from affected Chessies and their relatives, to see if the Labrador EIC gene could be present in our breed. Through various contacts, I found two other Chesapeake families, in addition to my dog’s, with suspicion of EIC. The owners and breeders of one of these families were willing to cooperate. So there were 8 blood samples from their family and my dog’s sent in for analysis.
Six months later, in early August, the results finally came in. Katie Minor told me that they believed they had found the mutation for EIC susceptibility in Labradors and that they found the same mutation in some of the Chesapeake samples we sent her. As she told me “The mutation, at this point, is used as likelihood for status, and not an actual confirmation, because we have not done a functional study to verify the effect of the mutation. So please note this is not 100% accurate, though there is a very high degree of association between the mutation and disease status. This appears to be a recessive disease, so two copies are needed to be affected.
One of the families (Affected dog, sire, dam, and a healthy littermate) was clear, so the affected dog probably has another disease with similar symptoms, and even though he has been through a bunch of tests, we still don’t know what it is.
Out of the other family (Affected dog, healthy littermate, dam, and sire’s littermate) the affected dog was homozygous (Had 2 copies) for the EIC gene, the dam and the littermate were heterozygous carriers (Had one copy), and the aunt was clear.
So now we know:
- That the same EIC mutation that is present in the Labradors also exists in Chesapeakes
- That EIC seems to be caused by a recessive gene, like PRA
- That the severity of clinical signs seems to be variable
- That some similar clinical signs might be due to something else than EIC
- That there will probably be a test to detect it in the future, just like for PRA
- The test can now be done using a cheek swab ( Available from medical supplies catalog, OmniSwab, by Whatman) instead of a blood test
- Dr. Mickelson and his team would like two things from our Chesapeake group:
One, test any dog with some clinical/physical signs of EIC that would indicate that there is a significant prevalence in the breed.
Two, a random sample of up to 200 (or more) dogs to see what the allele frequency and potential magnitude of any EIC affect on the breed really is, whether it is recognized at this time or not.
I would like to thank all the people who sent blood samples for the study, they did this unselfishly, at their own expenses, only for the good of the breed. Their contribution is much appreciated. I also want to thank Katie Minor for all her help and support.