Protecting Pets from Heartworm

April is National Heartworm Awareness Month. What is heartworm disease you may ask? It is a serious, and potentially fatal, disease in pets across the U.S. and many other parts of the world.

Heartworm disease affects dogs and cats, but heartworms also live in other mammal species and — in rare instances — humans. It is caused by foot-long worms (heartworms) that live in the heart, lungs and associated blood vessels of affected pets. These parasites cause severe lung disease, heart failure and damage to other organs in the body.

Heartworm-1-188x300How Does the Heartworm Parasite Work?

The heartworm parasite begins its cycle inside an infected pet. When an infected pet is bitten by a mosquito, the microfilariae (the young of the adult female heartworm) infect the mosquito. Then, after about two weeks, the microfilariae reach the infective larval stage inside the mosquito. The infected mosquito bites a pet not infected with heartworm and then passes the infective larva into the dog. After the larva reach adulthood, they travel to the pulmonary vessels, reproduce, and repeat the life cycle.

Heartworm and Dogs

Dogs are natural hosts for heartworms, meaning that heartworms living inside a dog mature into adults, then mate and produce offspring. If untreated, their numbers can increase and dogs have been known to harbor several hundred worms in their bodies. 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. For this reason, prevention is by far the best option, and treatment — when needed — should be administered as early in the course of the disease as possible.

Heartworm and Cats

Heartworm disease in cats is very different from heartworm disease in dogs. Cats are atypical hosts for heartworms, and most worms in cats do not survive to the adult stage. Cats with adult heartworms typically have just one to three worms, and many cats affected by heartworms have no adult worms. While this means heartworm disease often goes undiagnosed in cats, it’s important to understand that even immature worms cause real damage in the form of a condition known as heartworm associated respiratory disease. In addition, 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.


There are successful treatments for the heartworm parasite, but sometimes the treatment can be just as dangerous, if not more dangerous, than the parasite itself. If the infection is severe or a dog overexerts himself during treatment, the dead worms can clog vessels or go to the lungs and cause respiratory failure. That is why it is best to prevent heartworms from ever occurring, rather than to treat the infection when it becomes apparent.


While treating heartworms can be an intensive, exhaustive process on both pet and owner, the heartworm parasite is easy to prevent. A single pill once a month for cats, or PetTrust Plus for dogs, can prevent heartworm from ever infecting your dog. While mosquitoes are not a year-round concern in many parts of the U.S., most heartworm preventatives also provide protection against intestinal parasites, which can be prevalent even during the winter months.

Remember: the best heartworm treatment is prevention! Don’t leave you pet vulnerable to this nasty disease!




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