Heartworm Disease in Dogs

5 min read



Dogs with heartworm disease will initially receive any treatments needed to stabilize their condition. They will then be given medication to kill circulating microfilariae, and most will undergo a series of three injections over a month’s time to kill adult worms in the heart and lungs. Hospitalization when these injections are given, and possibly at other times, is necessary so that your veterinarian can watch closely for side effects. Prednisone and doxycycline are also typically prescribed to reduce the chances that the dog will react badly to the death of the worms. Other treatments may be needed based on an individual dog’s condition.  


If a dog has caval syndrome, a surgical procedure will be necessary to remove adult worms from the right heart and pulmonary artery by way of the jugular vein. Most dogs with caval syndrome die regardless of treatment.


Living and Management


Exercise restriction before, during, and after treatment for heartworm disease is absolutely vital to its success. Severely affected dogs may need to be kept in a cage to limit activity. For dogs recovering from congestive heart failure, a moderately restricted sodium diet may be recommended.


A  test for the presence of adult heartworms should be done approximately six months after treatment is complete to check for continued presence of Dirofilaria immitis. If the test is positive, the treatment can be repeated.




Heartworm prevention medications should be given to all at-risk dogs, for example those living in or traveling to endemic regions, as directed by your veterinarian. There are a number of preventatives that are safe, highly effective, and commonly used. Dogs who have been treated for heartworm disease also need to receive preventive medications since they can be reinfested. Heartworm preventatives are not 100 percent effective, particularly if they are not used per label instructions or doses are missed. Therefore, routine heartworm screening is recommended so that the disease can be caught early, when treatment is safest and most effective.