A DOG WITH active heartworm disease has thousands of microfilariae (the immature form of heartworm) circulating in his body along with many adult worms. All heartworm infections do not necessarily include circulation of adult and juvenile heartworms. These are called occult infections. Occult infections are very difficult to diagnose. Both types of heartworm disease are dangerous to your dog's health.
Diagnosis of heartworm disease is determined by blood tests. The most common blood test detects certain proteins (antigens) on the adult female worm. Another blood test detects antibodies the pet's body has made in an attempt to kill the heartworms. If a blood test is positive, other confirmatory tests are performed, including x-rays, ultrasound, and additional laboratory tests.
Many factors influence the severity of a dog's heartworm infection, including:
Number of heartworms circulating in the body
Number of heartworms in the dogs' heart and/or lungs
Length of time the dog has had the infection
Age of dog
Size of dog
Health status of dog
Activity level of dog
Once heartworms become numerous, they move into the heart. Adult heartworms live in the right-side chambers of the heart and the vessels leading from the heart to the lungs. Initially, the inflammatory processes of the dog are responsible for a soft cough, some exercise intolerance, and abnormal lung sounds. As the disease becomes more serious, the heart may enlarge and become weak since it must work harder. Additionally, a number of conditions may occur, including congestive heart failure and liver disease. Any of these scenarios can lead to sudden collapse and death.
Heartworm disease, as you can see, is devastating. The good news is that this disease is preventable. To ensure that your dog does not get this disease, we recommend regular testing and heartworm preventives given year 'round.