To discover the status of your dog regarding a particular disease you have to use a DNA test
What is a DNA test?
When a mutation is known, the diagnosis is easy and accurate. DNA samples from dogs can be obtained from any cells. They are easily obtained by taking a small blood sample or by scrapping a few cells from the inner cheek. The portion of DNA surrounding a mutation can be synthesized readily in the laboratory by a process called PCR (polymerase chain reaction). This method allows specific regions of the genome to be amplified from a small sample, and the DNA can be analyzed quickly to check if the mutation is present or not!
The second way to identify mutations is known as linkage. A linked marker is a DNA region close to the genetic defect that segregates together with the deficient gene. In this case the exact mutation responsible for the disease is not yet clearly identified but the DNA segment surrounding the mutation is known. The closer the marker is, the more accurate is the test.
How can I use the results of a DNA test?
If the test concerns a dominant mutation a dog will be affected with only one copy of mutated DNA. All the animals positive for that test (with only one DNA copy mutated) must not be used for breeding.
If the mutation is recessive, the test can be positive although the dog appears healthy but in fact he carries one copy of the mutation, he is a CARRIER. This dog should be taken away from breeding schemes or only bred with completely healthy dogs (with no mutation at all for that precise gene). This presumes that all dogs from that breed are tested for the concerned mutation. Once you breed a carrier with a completely free dog, all puppies will be healthy but half of them will still carry the mutation! The attitude to take for the different genetic tests available is advised by each kennel club.
What are the tests currently available on the market?
Depending of companies you can have access to different canine genetic tests. The most frequent tests concern vision disorders for example in Briard, Corgi, Collie and Setter or locomotor disorders in Golden and Labrador Retrievers or Schnauzer, several metabolic disorders in Cocker, Springer Spaniel or Basenji but also immunological disorders in Cairn, Collie, Setter, Westies, etc. This list is far of being exhaustive. Each country has one or several laboratories specialised in dog genetic testing, you may ask more information to your veterinarian.