Heartworm disease is common on the Atlantic and Gulf Coasts and the Ohio and Mississippi river basins.
Spread by the bite of an infected mosquito, heartworms can grow to lengths of 14 inches and live for up to five years within their canine hosts. Affected dogs are lethargic, intolerant of physical activity and can have a mild but persistent cough. If you suspect your dog has heartworms, your veterinarian should see him immediately.
Compared with the costs of treating heartworm disease, the preventative measures dog owners can take are relatively inexpensive, according to the American Heartworm Society. Administer prophylaxis tablets monthly for effective treatment, although other methods, including a monthly topical treatment and an injection effective for six months, also exist. All of these medications prevent heartworm larvae in different stages of their life cycle from reaching the lungs and causing disease. The pills do not kill adult heartworms, however, so veterinarians also provide a yearly blood test to check for their presence in dogs.
Infected dogs may exhibit a variety of symptoms, depending on the level of heartworm infestation within. Veterinarians define heartworm disease in three classes. Dogs with class I heartworm disease may show no symptoms at all, or only cough occasionally. When a dog reaches class II, he will have little tolerance for exercise and a pronounced cough. Dogs with a class III heartworm infestation may become anemic, lose weight, cough up blood, experience fainting spells and in extreme cases, heart failure.
To test for heartworms, the vet collects a blood sample to test for the presence of an antigen secreted by female heartworms, indicating an infestation. Complete blood count tests, blood chemistries and electrolyte tests test a dog's liver and kidney function health before starting treatment, according to the VCA Animal Hospital website. Veterinarians also use ultrasound and take x-ray images of the dog's heart and lungs, particularly if an infestation is suspected.
Treatment options for infected dogs depend on the level of his infestation. An injectable drug that kills adult heartworms treat dogs with a minor Class I infestation. Depending on the health of the dog, the veterinarian administer one injection or two, 30 days apart. Your vet might administer antibiotics to prevent an infection from the bacteria in the dying heartworms. The first week after treatment is a crucial time for canine patients to rest quietly, according to the VCA Animal Hospital, because the worms are dying. Your dog's body absorbs fragments of the dead heartworms over the course of several weeks or months. Some recovering patients still exhibit a noticeable cough, and require pain relief medications and drugs to improve their heart's function. Lifetime treatment for heart failure is sometimes necessary for dogs recovering from a serious infestation.
Animal Planet: What are the Symptoms of Heartworm in Dogs?
American Heartworm Society: What is Heartworm Disease?
Pet MD: How Do Heartworm Preventives Work in Dogs?