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

What is heartworm?

The dirofilaria immitis is a roundworm parasite that travels from host to host through the blood, transferred by mosquitoes biting multiple victims. The worm itself is a filament-like, slim worm that completes its life cycle in mammals.

Heartworm in dogs:

In dogs, the adult heartworm takes up residence, sometimes for many years, in the right ventricle of the heart.

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 symptoms can include cough, exhaustion after light exercise, and cough during exercise. Severe signs include weight loss, fainting or coughing up blood and extend to congestive heart failure. Occasionally, but rarely, heartworms may migrate internally and end up causing seizures in the brain, blindness, or lameness.

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 prevention is assisted, but not guaranteed, by removing all damp or standing water areas around the property where mosquitoes can lay eggs. Naturally, if all animals in the area have been vaccinated against heartworm, the possibility to get heartworm is reduced. Your vet may prescribe various types of heartworm medication: ivermectin (Heartguard), milbednycin (Interceptor and Sentinel), or moxidectin (ProHeart 6, pro Heart 12) or may prescribe topical treatments that include imidacloprid & moxidectin (Advantage-Multi) or delamectin (Revolution). You may have to use heartworm medicine for 12 months out of the year if your temperatures never falls below 14C (57F).

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 heartworm treatment. Following evaluation, commonly, melaresomine dihydrochloride (Immiticide) 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.

Heartworm in cats:

Cats are far less likely than dogs to develop heartworm. Typically they get fewer worms and the period of infection is shorter than in dogs. But cats are more lik...