Heartworm Symptoms in Dogs

Heartworm disease in dogs is variously treatable. While both cats and dogs are subject to heartworm, the illnesses and treatments are different for each. It is important to know the symptoms, causes and areas at risk and to be prudent in heartworm treatment. Although this disease was once confined largely to warm and wet areas, it has now spread globally.

What is Heartworm?

The dirofilaria immitis is a roundworm that travels from host to host through the blood, transferred by mosquitoes biting multiple victims. The worm itself is a filament-like, slim creature that completes its life cycle in mammals. In dogs, the adult heartworm takes up residence, sometimes for many years, in the right ventricle of the heart.

Symptoms of Heartworm in Dogs:

Heartworm is a stealthy invader. Worms tend to accumulate gradually in the body, and clinical signs or other obvious symptoms may not appear for months after initial infection. Common signs of heartworm infection in dogs include the following:

  • lethargy
  • anorexia
  • coughing (especially during physical exertion/exercise)
  • reluctance to exercise/play
  • rapid breathing
  • weight loss.

Heartworm symptoms may be undetectable after infection and through the early adulthood of the parasite, especially for sedentary dogs, or dogs whose sedentary habits suggest age or fatigue. For active dogs, or dogs with a high rate of infestation, the most visible symptoms include cough, exhaustion after light exercise, and cough during exercise. Occasionally, but rarely, heartworms may migrate internally and end up causing seizures in the brain, blindness, or lameness.

Signs of heartworm infection in cats often mirror other more common respiratory ailments in cats and heartworm infected cats may exhibit many of the same symptoms that infected dogs display, along with allergy-like symptoms.

Heartworm Diagnosis

Your pet should be tested at least once, possibly twice annually for heartworm infection through a simple and inexpensive blood test. The earlier heartworm is detected the better the prognosis for treatment. Canine heartworm sufferers are staged in levels I through IV based on the severity of the infection - it is much easier to treat a stage I infection than an advanced stage IV infection.

Heartworm diagnosis is carried out through a blood test for antigens secreted by female worms. For the blood test, a false negative can result if the worm population is low or if all the worms are males. Dogs who test positive for heartworm should have a heart x-ray to see the extent of the worm population in the heart itself.

Heartworm treatment is a prolonged process because adult heart worms take months to die. Dogs diagnosed with heartworm must be evaluated to make sure they are strong enough to withstand the treatment. Following evaluation, commonly, melaresomine dihydrochloride is used.

Dogs must rest for several months after treatment to prevent dead worms from entering the lungs. Surgery to remove the worms is possible, but is considered somewhat dangerous.