Heartworm Disease

Here comes spring! It brings warm weather, green grass, and longer days. For many areas, it also brings the beginning of mosquito season. That means increased risk for Heartworm. That’s why March is Heartworm Month at Sandia Animal Clinic. It’s the perfect time to learn about this serious, potentially fatal condition.

What It Is and Does

Heartworms are thin, parasitic worms. They live inside the heart, lungs, and blood vessels surrounding these organs. An infestation of a few worms can turn into hundreds of worms. They can cause heart, kidney, and liver failure.

As the heart pumps blood through the body, worms agitate inside the pulmonary arteries. This causes arterial inflammation, thickens the arterial lining, and creates lesions. Masses of tangled worms, and dead worms floating through arteries, obstruct blood flow.

Even after diagnosis and treatment, damage from heartworms is often irreversible. The longer an animal lives with these parasites, the more likely it is they’ll suffer lasting damage. Heartworms have lifespans of five to seven years in dogs and two to three years in cats. That’s a lot of potential damage.

How It’s Contracted

Cats, dogs, and ferrets all fall victim to this disease via the same method. The cyclical process begins when a mosquito draws blood from an infected animal. Inside this blood are tiny larvae, called microfilariae. The hungry mosquito then transfers the microfilariae to other animals while it’s feeding. These larvae grow into damaging heartworms. The cycle continues.

Symptoms and Diagnosis

Unfortunately, symptoms of heartworm infestations don’t appear until the damage has begun. These symptoms include coughing, loss of appetite and weight loss, fatigue, and a distended belly. It takes six months before the blood of an infected animal will read positive for heartworms. This is why yearly testing is important.

Diagnosis begins with blood antibody and antigen tests. When positive, further diagnosis may be necessary. It can include additional bloodwork, physical examination, ultrasound, and radiographs.


The American Heartworm Association recommends giving pets heartworm prevention medication 12 months out of the year and testing once every year. There’s good reason that. Heartworm damage is severe, debilitating, and sometimes fatal. Prevention is the best way to battle it. The range of products available today makes prevention easy.

Some owners wonder why yearly testing is necessary when their pet is already on prevention medicine. Humans aren’t perfect. Any lapse in administration leaves pets vulnerable. That means being a week off from last month or even skipping a monthly dose. Pets could also spit out their pills when their human isn’t looking. It happens.

With heartworm, time matters. Larvae evolve quickly into stages unaffected by prevention medication. That’s why owners should always pair testing with medication. While prevention is the best weapon, diagnosing as early as possible is next best.

At the very least, heartworm reduces an animal’s quality of life. Too often, it’s fatal. Now is the time to make sure your pet is protected.

Call us at Sandia Animal Clinic for an appointment to get your pet tested and receive your prevention medicine.

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