The last 50 years or so have seen tremendous advances in the types of veterinary products that have been developed to treat canine illnesses. As a result, many of the diseases that posed serious problems decades ago, like bacterial and viral infections, have been controlled. This has caused a significant shift in the types of diseases that cause problems today, and most modern day vets will see far more dogs that are suffering from a condition that is either inherited or in which inheritance seems to play a major role.
Approximately 400 inherited diseases have now been identified in the dog and of these the majority have a simple recessive mode of inheritance. Conditions like progressive retinal atrophy (PRA) in the Labrador, the Golden Retriever and the Lhasa Apso, and Canine Leucocyte Adhesion Deficiency (CLAD) in the Irish Setter and Irish Red & White Setter.
Some of the inherited conditions that most worry present day dog breeders are more complex, being caused by problems in more than one different gene, so called polygenic diseases. Conditions like hip dysplasia, which affects a number of the physically larger breeds, like the German Shepherd, heart disease and epilepsy are polygenic. In addition, some of these polygenic conditions are also influenced by environmental factors. Hip dysplasia, for example, can be affected by both exercising and feeding.