The phrase "to affect the breed" means to make changes or have an impact on a particular group of animals or species, typically with the intention of improving their characteristics or qualities. Full definition
This is especially important if the dog you are considering belongs to one of the commonly affected breeds, and even more so if you are thinking about breeding the animal in the future. (petwave.com)
While these fungi can affect any breed of dog, male dogs are often at greater risk of fungal pneumonia than females. (dogcare.dailypuppy.com)
This is because it is a voluntary scheme and only a small proportion of dogs / puppies in affected breeds are scored. (dogbreedhealth.com)