Heartworm is a Serious Disease, and Difficult to Avoid — Here’s What Can Be Done

A warm, sunny summer day provides the perfect opportunity for you and your furry friend to make joyful memories. Any playful pup is grateful for all of that outdoor activity. But those halcyon days harbor a sinister secret.

Lingering in tepid ponds, around wooded areas, and even in your favorite picnic spots, are mosquitoes that carry the means of spreading the potentially fatal heartworm disease to pets.

More than 70 kinds of mosquitoes are known transmitters of Dirofilaria immitis, the microorganism responsible for heartworm infection in dogs, cats, and other mammals. The parasite feeds off nutrients in its host’s bloodstream, often finding refuge in the heart of the animal, lending to the nickname, “heartworm.”

This infection can span years, and severely inhibit a carrier’s pulmonary vascular system.

Once infected, parasitic worms can grow to as much as a foot long, traversing the host’s heart, lungs, and blood vessels. Dogs are natural hosts for the heartworm parasite, and if undiagnosed, may carry hundreds of the worms before heart or organ failure or severe lung disease eventually kills the animal. With prompt diagnosis and careful treatment, dogs can survive the ordeal.

Common mosquitoes are more than just annoying pests.
Common mosquitoes are more than just annoying pests.

Sandy’s Situation

For Sandy, a 2-year-old bulldog mix, a heartworm diagnosis is shortening her young life.

When Sandy arrived at the Animal House Shelter, along with testing positive for heartworm, she was suffering from a respiratory infection and a severe case of demodectic mange, and needed hip surgery. Yet her spirits were still as buoyant as her goofy grin.

“Sandy is the happiest, sweetest, most loving dog that you could ever hope to meet,” Animal House Shelter explains. “It is heartbreaking that such a wonderful girl is suffering from so many afflictions.”

Sandy has been a resident of the shelter for almost 2 months, and while her mange and respiratory infection have cleared up, heartworm treatment requires a much longer process.

Sandy needs your help!
Sandy needs your help!


Identifying the heartworm infection will often involve X-rays. As the “coin lesions” that develop in mature heartworm infections can resemble cancerous cells, invasive surgery may even be recommended as well.

Once heartworm has been confirmed, further blood tests should be performed to reveal liver or kidney problems that may interfere with drug therapies like melarsomine hydrochloride, as Pet MD reports. This drug involves several injections, requiring the animal to be hospitalized and monitored for shock or allergic reaction.

Even after treatment, it takes time for the animal’s system to work the dead heartworm parasites out. Booster shots in the following months may be recommended to keep new parasites from reproducing.

“During this time, your dog must be kept from running or playing, as this may cause a rapid movement of a large number of dying or dead worms to the lungs, where they can cause a blockage,” Jennifer Kvamme, DVM explains. “For this reason, the dog will need to be watched closely for signs of coughing, vomiting, depression, or diarrhea. Any abnormal signs should be checked by your veterinarian.”

Heartworm organisms can be found in wooded areas and in cities, as it is transmitted by a number of animals.
Heartworm organisms can be found in wooded areas and in cities, as it is transmitted by a number of animals.



While we know mosquitoes and infected animals can carry the disease, it’s virtually impossible to predict the vector of its annual spread. Weather events and unexpected migrations expose new animals to the disease every year.

In 2005, the devastation of Hurricane Katrina in the American Southeast left more than a quarter-million pets without homes, the American Heartworm Society (AHS) reports. Many of those animals had heartworm parasites and were transferred to homes and shelters throughout the rest of the country. The urgency of the situation coupled with some inadequate screening processes may have inadvertently increased the range of the disease.

Heartworm is known to be endemic year-round in southern states. It has been diagnosed in all 50 states, including desert regions like Arizona and even frigid Alaska. Its widespread ubiquity shouldn’t lessen the urgency a heartworm diagnosis signals.

“Heartworm disease causes lasting damage to the heart, lungs, and arteries, and can affect the dog’s health and quality of life long after the parasites are gone,” the AHS details. “Prevention is by far the best option, and treatment—when needed—should be administered as early in the course of the disease as possible.”


It’s recommended that animal owners have their pet tested every 12 months for heartworm, with heartworm preventive measures being taken each month as recommended by your vet.

Hope For Sandy

With generous assistance from donors, Sandy’s heartworm treatments will soon be complete. Then she will be ready to undergo the hip surgery she needs, which will enable her to walk and run without pain again. Given her resilience, the Animal House Shelter veterinarian is confident Sandy will make a full recovery from both.

The mission of Animal House Shelter is to rescue, rehabilitate, and re-home cats and dogs like Sandy regardless of age, health, or special needs. The shelter favors rehabilitation over euthanasia, meeting the physical and behavioral needs of each animal there, regardless of cost or time.

Once rehabilitated, Animal House Shelter animals are adopted out into forever homes, each individually vetted by a thorough screening process. Of course, none of this can be accomplished without your help, and the gracious assistance from programs like Zoetis for Shelters, which is matching donations up to $2,500 for Sandy and others like her in need of life-saving medicine. Click the button below to help Sandy and other animals in need!