The dog cancer is most commonly affecting disease. The dog cancer is similar to that of any type of tumor and it mainly affects the healthy tissues of the human. The dog cancer can lead to the death in dog. The cancer in dog is a highly variable disease. The dog cancer does not have any specific source and it can spread quickly. The proper and possible sources of cancer are genetics, diet, environment and exposure to harmful chemicals. The older dogs should be checked properly and regularly. We should take the dogs to the veterinarian when it is affected by fever, weight loss, lethargy and loss of appetite. The heart problems and the blood vessel problem will arise due to the heart worm parasite in dog. This heart worm parasite will live in the heart and blood vessels and it causes the heart to weaken. The heart worm will be transmitted from dog to dog and it is spread through the mosquitoes. Once this worm is affected, the dog will begin to experience reduced blood flow to its major organs. Prevention is the best approach to control the disease. The dogs should be given a heart worm pill each month and it should have regular treatment and visits with doctor.