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Understanding Heartworm Disease in Pets: What Every Pet Parent Should Know

Updated: Apr 10

Everything You Need to Know to Keep Your Dogs and Cats Safe from Heartworm Disease!

Keep reading to...

  • Find out what Heartworm Disease is and how it's spread

  • Learn the signs and symptoms of Heartworm Disease

  • Discover the best ways to protect your pets from Heartworm Disease

What is Heartworm Disease?

Heartworm Disease is a potentially deadly disease caused by the Dirofilaria immitis, or heartworm parasite - a worm that invades and infects the heart of its host. These worms reproduce at a fast rate and can grow up to 14" long, causing serious disruption to the internal body system of their hosts.

How is Heartworm Disease Transmitted?

Heartworm Disease is transmitted (passed) through the bite of an infected mosquito. When a mosquito carrying heartworm larvae (microfilariae) bites a pet, the larvae is then passed to that pet. The larvae migrate through the bloodstream to the pet's heart where they are mature into adulthood and begin to reproduce - heartworm positive pets can have hundreds of adult heartworms in their heart at any given time! Until treated, this infected pet is now a 'heartworm host', passing heartworm on to any mosquitos that bite them, perpetuating the transmission cycle.

Can My Heartworm Positive Pet Give It to My Other Pets?

No, not directly. The heartworm parasite requires the mosquito as an intermediate host in order to complete its life cycle, and therefore cannot be passed directly from one companion animal to another. Transmission between the pets within your household would require a mosquito to bite your heartworm positive pet before biting your heartworm negative pet.

To reduce the likelihood of third party transmission, ensure all of your pets are on consistent heartworm prevention, especially if one of the animals in your home is positive.

Who Is at Risk for Heartworm Disease?

Both dogs and cats are able to contract Heartworm Disease, however cats are not a natural host for the heartworm parasite, which puts felines at a slightly lower risk of contracting the disease than dogs. It's important to note though that there is currently no approved treatment option for Heartworm Disease in cats, so consistent prevention is of utmost importance despite their decreased risk of transmission.

Can My Indoor Only Cat Get Heartworm Disease?

Yes, even indoor only cats are at risk to contract Heartworm Disease. Mosquitos can enter your home through open doors and windows, making even indoor only cats vulnerable to a bite from an infected mosquito.

How is Heartworm Disease Diagnosed?

In dogs, Heartworm Disease is most commonly diagnosed through routine blood testing. Due to the life cycle of the heartworm parasite, it is recommended that dogs be routinely screened for Heartworm Disease every single year. It can take up to six or seven months for heartworm larvae to grow big enough to be detected in the blood, so ongoing testing is imperative to catch previous exposure. Following a diagnosis of Heartworm Disease, further diagnostics of the lungs and heart may be recommended to assess the progression of the disease. These diagnostics could include radiographs (x-rays) and an echocardiogram (imaging of the heart).

Currently there is no routine screening option that is recommended for cats. Diligent heartworm prevention is the priority

for felines.

What are the Symptoms of Heartworm Disease?

Patients infected with heartworms typically appear asymptomatic (symptom free) for many, many months (sometimes even years). By the time symptoms of heartworm disease become noticeable, the disease is well advanced. For this reason, routine screening is especially vital in catching heartworm disease in its early stages.

Common symptoms of Heartworm Disease include:

- persistent, dry cough

- shortness of breath

- decreased stamina during exercise

- fatigue

How is Heartworm Disease Treated?

In dogs, the treatment of Heartworm Disease is a multi-step process involving veterinary-lead administration of different medications over several weeks. Pets should be closely monitored while these medications are given, so typically patients will be admitted for day stays at their veterinary hospital. Throughout this time the patient must be kept on strict cage rest (restricted from physical activity), due to the risk that the heartworms pose if they become dislodged within the body during treatment.

Unfortunately there is currently no approved treatment for heartworm disease in cats. Prevention is the best treatment for felines.

How Do I Protect My Pet From Heartworm Disease?

The single best way to protect your dogs and cats from contracting Heartworm Disease is to give them heartworm prevention prescribed by your veterinarian. We do not recommend giving your pet over the counter products marketed to prevent heartworms, as these medications are ineffective.

There are many different prescription heartworm preventions available, including injectable, topical and oral variations. Each product has its own specifications in regards to dosing frequency, and it's vital that you keep your pet up to date. A lapse in prevention, even just by a couple weeks, leaves your pet vulnerable to the heartworm parasite.

If you are an existing client of Fire Mountain Veterinary Hospital, visit our online pharmacy to order more of your pet's parasite prevention.


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