Does inbreeding have any relationship to autoimmune disease?
It might in some cases. The more common ancestors appear on both sides of a dog’s pedigree, the more frequently they appear, and the closer they are to the dog ancestrally, the greater the chance that the dog will have inherited two like or very similar copies of the major histocompatibility complex (MHC) which governs the immune system. It is called a “complex” because the genes are strung together on a chromosome rather than being spread around the genome. Having two like copies of MHC genes can limit the immune system’s ability to function properly; the more that are duplicated the more limited its tool kit.
Should autoimmune diseases be addressed individually by breeders?
No. They should be considered as a class. Frequently, multiple autoimmune diseases will occur in the same family, probably because vulnerable individuals happened to encounter different triggers that started the disease process. The presence of any autoimmune disease in a dog or its relatives should be considered a sign that other autoimmune diseases might also occur in that same family.
Given the complex inheritance and the many different autoimmune diseases isn’t the situation too complicated for breeders to do anything about?
Absolutely not. With some homework, good record-keeping, and determination breeders can reduce the frequency of autoimmune diseases. Whenever possible, a cooperative effort amongst concerned breeders will be most effective. For example, ASHGI’s IDASH Open Health Database could be used to record cases of autoimmune disease for reference by current and future breeders.
If dog is diagnosed with autoimmune disease, how should breeders handle it?
Breeders should follow these steps:
- Any dog that is sick with any kind of chronic autoimmune disease should not be bred.
- If the coefficient of inbreeding (COI) on the affected dog is very high (20% or greater,) inbreeding may have contributed. Try to lower the COIs in future offspring of near relatives.
- If the parents are healthy, you can continue breeding them, but:
a. Do not repeat the cross or breed either parent to relatives on either side of the cross that produced autoimmune disease.
b. Do not breed close relatives of the affected dog to mates who are their own close relatives or to dogs with a family history of any kind of autoimmune disease.
c. If a dog has a near relative with autoimmune disease hold off breeding until I is 3-4 years of age to be reasonably sure they will not develop autoimmune disease.
Should breeders do screening tests for autoimmune diseases?
Where they are available, yes. But for many autoimmune diseases there are no tests. Two exceptions are the thyroid panel used to screen dogs for autoimmune thyroiditis and the DNA test that indicates risk for degenerative myelopathy. Whether or not a particular test should be considered necessary for all breeding dogs depends on how common the particular disease is in the breed. Autoimmune thyroiditis is very common in aussies, so every breeding Aussie should be screened. However, degenerative myelopathy is rare so it is only necessary to test near relatives of an affected dog or one that is known to have at least one copy of the genetic mutation. There are numerous diagnostic tests for autoimmune diseases but these are designed to aid vets in diagnosis and are unsuitable as screening tools.