How Often Should My Pet Be Tested for Heartworm?

Do I Really Need Heartworm Tests for My Dog or Cat?

If you’ve ever owned a pet before, or even known anyone who has, you’re probably already somewhat familiar with the concept of heartworm disease and prevention.

But even if you’re not, don’t worry. In this piece, we’ll walk you through the basics of heartworms and discuss prevention and treatment so you can ensure your dog or cat is as healthy and happy as possible.

What is Heartworm Disease?

Heartworm disease is a serious and potentially fatal disease caused by heartworms (Dirofilaria immitis), which can grow up to a foot long and live in the heart, lungs and blood vessels of dogs and cats, as well as many other mammals, including in rare cases, humans.

This can cause organ damage, lung problems and even heart failure.

How is Heartworm Spread?

Heartworm infection is caused by female mosquitoes that feed on infected dogs, cats, foxes, coyotes and ingest microfilaria. Inside the mosquito, the microfilaria mature into heartworm larva, which are then spread to new mammal hosts as the mosquito feeds.

After the larva enters an animal’s body, they migrate through the tissue and eventually travel to the bloodstream, from which they enter the heart and lungs. Male heartworms can reach six inches in length, with females doubling that size.

Heartworms in Dogs vs Cats

Dogs are natural hosts for heartworms and, in extreme cases, have been known to harbor hundreds of the parasites.

Cats, while not immune to heartworms, are an atypical host. Most worms in cats don’t survive to the adult stage, and felines typically only harbor between one and three of the worms. Unfortunately, this means heartworms often go undiagnosed in cats.

What is a Heartworm Test?

Heartworm testing is quick and relatively stress-free for pets. Your vet or a veterinary assistant will collect a small blood sample and analyze it for proteins from adult female worms. These are often available in a few minutes.

Why is a Heartworm Test Important?

Most pets infected with heartworms show no outward signs, which is why testing is crucial to prevent long-term damage and death.

How Often Should My Pet Be Tested for Heartworms?

Dogs and cats should both have an annual heartworm test. This is important because heartworm prevention isn’t retroactive and only kills larvae acquired in the past month. Additionally, no product is 100% guaranteed, so adding a yearly test adds an important safety net.

What if My Pet Tests Positive for Heartworms?

If your dog or cat tests positive for heartworms, your veterinarian will perform additional tests to determine how advanced the infection is, check if the heart and lungs are already affected, and determine a course of treatment.

The good news is that most infected animals can be successfully treated.