Many dog diseases have a genetic component, meaning that to at least some degree, the genes carried within a dog’s DNA determine whether or not the individual develops a particular disease.
Sometimes the inheritance of these genes follows the simple dominant/recessive pattern that you may or may not remember from high school biology. In other cases, multiple genes are involved and interact with environmental factors to create a much more complicated picture.
Depending on a disease’s inheritance pattern, responsible breeders can use information gathered from either phenotypic testing (i.e., examination of a dog’s body or biochemistry) or from genetic testing (i.e., DNA tests) to determine which individuals should be used in a breeding program and which should be spayed or neutered and become solely pets--a noble calling, to be sure.
Negligent breeders may choose to skip this step and focus only on producing “pretty” animals, but they do their customers and dogs a great disservice.
If you are interested in purchasing a purebred dog, make sure you support breeders who are working to improve canine health and well-being.
When the genetics behind a disease are complicated, DNA testing is often not available and we have to fall back on phenotypic testing. This is a less than ideal situation because, in many cases, the symptoms of the disease in question do not appear until after a dog is old enough to be bred. These types of tests also do not identify individuals that can pass on a disease to their offspring but do not display symptoms themselves.
Hip dysplasia is good example. Multiple genes, husbandry and environmental factors all work together to determine if and how severely a dog will be affected.
Because of this, genetic testing is impractical. To lower the incidence of hip dysplasia in at risk breeds, responsible breeders will screen their dogs’ hips with either PennHIP or OFA x-rays before including them in their breeding population. Over time, the use of these specialized x-rays has helped lower the incidence of hip dysplasia in several breeds.
Other examples of phenotypic tests include Canine Eye Registration Foundation (CERF) testing for diseases that affect eyesight, brainstem auditory evoked response (BAER) testing for deafness and thyroid hormone evaluations.
When available, genetic testing is the best way to screen animals prior to breeding. These tests can be performed very early in a dog’s life, well before breeding decisions need to be made.
Genetic testing can also be very important when it comes to maintaining the health of a particular individual.
For example, Collies and related breeds have a higher than normal incidence of the MDR1 (multiple drug resistance) gene. These dogs are at risk for having severe, potentially life threatening side effects from several commonly prescribed drugs. Knowing that your dog carries this gene will help you and your veterinarian make both wise treatment and breeding choices.
Sources of Information
For a list of commonly available canine DNA tests and which breeds should be considered for testing, see the Orthopedic Foundation for Animals website. This organization is also an excellent source of information on phenotypic testing for a variety of orthopedic diseases, heart problems, thyroid disease and more.
Another good source of information is the Canine Health Information Center (CHIC). Their website includes a list of breeds enrolled in the CHIC program and associated with each breed is a list of recommended phenotypic and genetic tests. Both the OFA and CHIC websites also include searchable databases containing information on dogs that have undergone testing.
Jennifer Coates, DVM graduated with honors from the Virginia-Maryland Regional College of Veterinary Medicine in 1999. In the years since, she has practiced veterinary medicine in Virginia, Wyoming, and Colorado. She is the author of several books about veterinary medicine and animal care, including the Dictionary of Veterinary Terms: Vet-speak Deciphered for the Non-veterinarian.
Jennifer also writes short stories that focus on the strength and importance of the human-animal bond and freelance articles relating to a variety of animal care and veterinary topics. Dr. Coates lives in Fort Collins, Colorado with her husband, daughter, and pets.