Heartworm Symptoms in Dogs

Heartworms are parasites that cause infection of the cardiovascular system, especially in small animals. Although small, heartworms can cause severe internal damage to organs and should be treated immediately. As the weather warms up, heartworm infections are more common, as the parasites are spread by mosquitos. Learn how to recognize heartworm symptoms in dogs – it could save your pet’s life.


What causes heartworms?

Heartworms are most prevalent in the Southeast United States, especially in humid climates where mosquitos thrive. (American Heartworm Society)

The bite of an infected mosquito transmits the parasite, a roundworm called Dilofilaria immitis. Heartworms cannot be passed between pets or to humans! After a pet is bitten by an infected mosquito, the roundworm’s larvae enter the skin through the bite wound and emerge into the bloodstream.

Heartworms reproduce quickly and become adults within 6 months, reaching up to a foot in length. Mature heartworms may live 5 to 7 years inside an untreated dog; up to 250 heartworms can live in a single pet. The parasites live in the internal organs, namely the heart and lungs, and blood vessels.


What are the symptoms of heartworms in dogs?

This anatomical model shows where heartworms infections are most commonly located. (Flickr.com/23748404@N00)

During the early states of infection, pets may be asymptomatic, showing no signs of heartworms. As the disease progresses, the following symptoms may appear:

Symptoms of more severe heartworm infections include heart failure and abdominal swelling as the parasite continues to reproduce.

How are heartworms treated?

A veterinarian will first perform a battery of tests to diagnose a potential heartworm infection, including blood work, a stool sample, and an X-ray. After a diagnosis of heartworms has been reached, Inmiticide is a anti-parasite drug that will slowly work to kill all heartworms present in the pet.

While your dog is undergoing heartworm treatment, it’s essential to limit physical activity; as the medication kills the heartworms, they break up into tiny pieces, which can become lodged in the blood vessels and lead to congestive heart failure.

The cost of heartworm treatment and medication can run several hundred to a thousand dollars, depending on the severity of infection, the size of the dog, and the city.


Are heartworms preventable?

If you live in an area where heartworms are present, puppies should start preventative medications as young as 8 weeks. (Flickr.com/hand-nor-glove)

Yes, there are many preventative medications available in a wide range of options, including injections, topical lotions and pills. Preventative heartworm medications are very affordable, ranging from $30 to $80 yearly, depending on your dog’s weight. You must get a prescription for these drugs, which target and kill the heartworm larvae, preventing the adult roundworms from developing.

If you live in an area where heartworms are rampant, it’s highly recommended to start prevention in puppies as young as 8 weeks old. Be aware, as your pet grows, the dose of medication must also be increased, as it is based on weight. These treatments must be administered exactly as directed, on schedule, or heartworm larvae could hatch and lead to infection.

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