Bay Street Animal Hospital

718-420-9100 | 999 Bay Street | Staten Island, NY 10305
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Heartworm Disease: Deadly Threat to Your Pet

Heartworm disease a serious, potentially fatal disease in house pets. The disease is caused by foot-long adult worms that live in the heart, lungs, and blood vessels of infected pets, causing severe lung disease, heart failure, and damage to other organs in your pet’s body. Heartworm is much more common and more severe among dogs than it is among cats.

Heartworm disease is transmitted by mosquitos who pick up microscopic baby worms when they feed on the blood of an infected dog, cat, ferret, or wild animals, such as foxes, wolves, and coyotes. The worms develop into infective larvae in the mosquito within 10 – 14 days. When an infected mosquito bites another dog, cat, or wild animal, the infective larvae are then transmitted through the bite wound to the blood of the newly-infected animal where they thrive and grow into huge adult worms.

Heartworms can live five to seven years in dogs and up to two or three years in cats. Because of the longevity of these worms, each mosquito season can lead to an increasing number of worms in an infected pet.

Though heartworm disease is linked to summer and mosquito season, it is found in every region and climate, and preventive treatment should be year around. According to the American Heartworm Society, heartworm disease has been diagnosed in all 50 states, and risk factors are impossible to predict.

Multiple variables, from climate variations to the presence of wildlife carriers, may cause rates of infections to vary dramatically from year to year — even within communities. And because infected mosquitoes can come inside, both outdoor and indoor pets are at risk. To date, no vaccine has been developed against heartworm disease.

The American Heartworm Society recommends that pet owners “think 12”: 1. Get your pet tested every 12 months for heartworm and 2. Give your pet heartworm preventive 12 months a year.

Prevention is Key in Dogs and Cats

Dogs — Treatment for dogs with heartworm disease is available, but it is costly, and the disease may cause lasting damage to heart, lungs, and arteries long after the parasites are gone. Heartworm prevention for dogs is by far the best option, and treatment—when needed—should be administered as early in the course of the disease as possible. Puppies under seven months of age can be started on heartworm prevention without a heartworm test, as it takes at least six months for a dog to test positive after it has been infected.

Cats — Unlike the dogs, cats are not ideal hosts for heartworms, and most worms in cats do not survive to the adult stage. Heartworm disease often goes undiagnosed in cats. But even immature worms cause serious damage in the form of a condition known as heartworm associated respiratory disease (HARD). The medication used to treat heartworm infections in dogs cannot be used in cats, so prevention is the only means of protecting cats from the effects of heartworm disease.

Heartworm is a progressive disease. The earlier it is detected, the better the chances the pet will recover. There are few, if any, early signs of disease when a dog or cat is infected with heartworms, so detecting their presence with a heartworm test administered by a veterinarian is critical. Results are obtained quickly. If your pet tests positive, further tests may be necessary.

For more information, go to To make an appointment for testing and treatment for heartworm and other pet parasites, call us at 718-420-9100.