The domestic dog (Canis familiaris) has been bred for different purposes and characteristics for thousands of years. The creation of modern dog breeds started around 200 years ago and was based on a few founders and breeding strategies such as strong selection for certain traits, popular sires and inbreeding/ backcrossing. This has led to the enrichment of disease mutations in different breeds. Dog owners should be aware of the fact that puppies are usually born with some immunity, which soon wanes. This is why vaccinations are necessary. Some diseases are hereditary and cannot be detected until a dog becomes at least 18 months of age.