Heartworm in dogs is caused by an infestation of the organism Dirofilaria immitis, a parasitic nematode (roundworm) commonly referred to as the heartworm. The severity of this disease is directly dependent upon the number of worms present in the body, the duration of the infestation, and the response of the host (the infested dog is the host).
In regions where Dirofilaria immitis is endemic, dogs without proper heartworm protection are almost 100 percent likely to suffer from heartworm infestation. The heartworm is mainly endemic in geographic areas with tropical and subtropical climates, and is also commonly found along the Atlantic and Gulf Coasts, and the Ohio and Mississippi river basins. The presence of Dirofilaria immitis is not limited to these areas, however, it is found worldwide. Dogs have been diagnosed with heartworm disease in all 50 U.S. states.
Heartworm disease is preventable with the administration of a heartworm prophylaxis (preventative) medication, as recommended by a veterinarian. For those dogs that do contract heartworm disease, the prognosis is good for mild to moderate cases, and such conditions can be relatively uneventful. Dogs with more severe cases may suffer from lung complications resulting from extreme medication given to kill serious infestations.
Symptoms Of Heartworms
Initially there are no symptoms of heartworms in dogs, making it difficult to spot the illness early. As the disease reaches an advanced stage however, complications begin to arise and may begin to multiply as time goes by.
- Coughing
- Lethargy
- Labored breathing
- Fainting spells
- Rasping sounds coming from the lungs
- Congestive heart failure
- Fluid retention (chest area)
- Tachycardia (rapid pulse)
- Dry coat
- Rapid weight loss
- Vomiting and diarrhea
A vet can diagnose heartworms by using one of several different methods including the modified Knott test or an antigen test. Dogs should be routinely screened for heartworms, especially between the ages of four and eight.
Diagnosing Heartworms
If heartworm disease is suspected, an electrocardiograph (which monitors changes in the heart) may reveal heart rhythm disturbances and/or enlargement of the right ventricle of the heart (hypertrophy).
Additional tests may include a urine analysis, serologic tests that can identify the female heartworm antigen, and X-rays, which may reveal enlargement in key arteries associated with heartworm disease.
Treatment for Heartworms
In initial treatment, most patients are hospitalized as they receive administration of an adulticide designed to kill the adult heartworms. The microfilariae in the body can be eliminated with a monthly prophylaxis, which can be administered at home. For more severe cases, such as dogs experiencing thromboembolic complications (in which a blood clot that has formed breaks loose and travels through the blood stream to clot another vessel), hospitalization may be necessary for a longer period of time.
In some cases, a surgical procedure may be necessary to remove adult worms from the right heart and pulmonary artery by way of the jugular vein. This procedure is recommended if the infestation consists of a high number of adult worms.
Prevention
Routine heartworm prophylaxis (preventative) should be given to any at-risk dogs, for example those living in endemic regions, as directed by your veterinarian. This is essential to preventing heartworm infestation. There are a number of medical preventatives that are highly effective and commonly used. It is possible for reinfestation to occur if a prophylaxis is not regularly administered.
