Intact (unneutered) male dogs are susceptible to several common health issues. Some diseases have the potential to leave the dog permanently sterile, while others are life-threatening. Most of these conditions are treated by surgical castration.
Brucellosis is a sexually transmitted disease that is passed between dogs. Males have reduced sperm motility and abnormal sperm development. The testes may atrophy in severe cases and the dogs sometimes become infertile, according to Iowa State University. Some animals are successfully treated with antibiotics, but others relapse.
Three types of testicular tumors are common in older intact dogs, according to Pet Education. The symptoms of a sertoli cell tumor or a seminoma are swelling in the scrotum and testes, as well as estrogen production resulting in swollen mammary glands and nipples. An interstitial cell tumor does not show noticeable symptoms.
Intact dogs suffer from a variety of prostate-related issues. For example, Pet MD explains that a condition called benign prostatic hyperplasia, or BPH, causes swelling in the prostate gland as the dog ages. The prostate pushes against the rectum and makes defecation difficult. The disorder is caused by an increase of estrogen in the prostate gland.