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FAQ About Heartworms and Heartworm Disease

Find answers to FAQs about heartworms in dogs and cats.

Heartworms and Heartworm Disease

Diagnosed in all 50 states, heartworm disease is a critical illness affecting dogs and cats year-round. Find answers to FAQs about heartworms and heartworm disease in dogs and cats within the information outlined below.

What is heartworm disease?

Heartworm disease is a serious and potentially fatal disease affecting a number of mammals, including cats and dogs. It is caused by foot-long worms (heartworms) that live in the heart, lungs and associated blood vessels of affected pets. Their lasting impact causes severe lung disease, heart failure and damage to other organs in the body. A pet’s very life is a stake, even if their heart just contains one heartworm. Through prevention, including monthly heartworm pills for dogs or for cats, a pet’s life can be saved.

How can dogs catch heartworms?

Mosquitoes transmit heartworm disease. When adult female heartworms reside in an infected animal, they produce microscopic baby worms (microfilaria) that circulate in the infected animal’s bloodstream. As a mosquito feeds on a heartworm-positive animal, it picks up these baby worms and deposits the larvae onto the surface of the next animal it feeds on, allowing the host entrance through the mosquito’s bite wound.

How do cats get heartworm disease?

Cats become infected with heartworms in the same way that dogs catch heartworms through the bite of a heartworm-infected mosquito. It only takes the larvae six months to develop into a mature heartworm after entering the new host.

Can dogs catch heartworms from other dogs?

A common misconception is that dogs catch heartworms from other dogs, as well as if a dog is in his own yard, away from contact with others, he is at no risk for heartworms. Heartworms are spread by mosquitoes and in just one heartworm-positive pet’s kennel, seven of 10 mosquitoes within it are carrying heartworm.

Can heartworms be transmitted year-round?

While you might hear a mosquito’s annoying buzz and feel their bites more during summertime, heartworm risk remains throughout the year. Mosquitoes will shelter from the colder months indoors or other protected areas, so pets are still at risk for heartworms no matter the season.

How long can heartworms live?

Once mature, heartworms can live up to seven years in dogs and three years in cats.

What are the first signs of heartworm disease in dogs?

Within the earliest stages, most pets will not demonstrate any heartworm symptoms. As heartworm disease progresses over time, affected dogs may develop a persistent cough, fatigue, decreased appetite and weight loss. Dogs with increased numbers of heartworms are at risk for cardiovascular collapse, as the worms suddenly block blood flow within the heart.

What are the symptoms of heartworm disease in cats?

Heartworm disease symptoms in cats can be more difficult to define. Keep a watchful eye for symptoms such as asthma-like attacks, decreased appetite, vomiting and weight loss. Cats also may experience fainting episodes and difficulty walking. Sadly, the first sign in many cases of heartworm disease in cats consists of sudden collapse or death.

Can a cat survive heartworms?

As their heart cavity is much smaller than that of the canine family, a single worm can potentially end their life.

Do heartworms decrease a pet’s lifespan?

Unfortunately, with both dogs and cats, should they become infected with heartworms and survive, their lifespan can be shortened.

How do veterinarians test for heartworms?

Your veterinarian can take a small blood sample during your pet’s regular exam appointment. Once the blood sample is tested at the lab, which is usually a quick process, your pet will be determined positive or negative for heartworms. If the results are heartworm positive, your veterinarian will share with you next steps for heartworm treatment.

Do dogs need to be tested for heartworm every year?

Yes, even if a dog is on a preventive heartworm medication, he or she should be tested for heartworms every year. The earlier heartworm disease is detected, the better the chances for your pet’s survival, should he test positive for heartworms. Ensure heartworm testing is always included in your pet’s annual exam with your veterinarian.

Can heartworm be prevented?

Yes! Monthly heartworm preventives offer nearly 100% protection. After your pet is tested for heartworms, you can obtain a prescription from your veterinarian to order your pet’s heartworm preventives. Remember the rule of 12. Every 12 months, ensure your pet is tested for heartworms, and remember to administer your pet one heartworm preventive for dogs or for cats every month.

How much does heartworm prevention cost?

Heartworm preventives can cost an average of $10 per month, compared to heartworm treatment, which can cost more than $1,000 or the priceless cost of your pet’s life. 

What is the best heartworm medicine for dogs?

There are a number of prescription heartworm pills for dogs that you can easily give to your pet at home. Protect dogs against heartworms with trusted heartworm preventives like: Trifexis, Interceptor Plus, Heartgard or Heartgard Plus, Advantage Multi for dogs, and Tri Heart Plus.

What is recommended for heartworm prevention for cats?

There are several trusted options to also protect cats from heartworms, including Revolution for Cats, Advantage Multi for Cats and Revolution Plus for Cats.

Do indoor cats really need heartworm prevention?

Yes, even indoor cats require heartworm prevention. Of cats diagnosed with heartworm disease, 25% are indoor-only cats.

You can trust the Valley Vet Supply Pharmacy will handle your pet’s prescription accurately and fast, as if it is a medication for our own family member. Continue learning; read up on the top misconceptions about heartworm disease, and learn three steps on how you can prevent heartworms in dogs and cats.

Statistics/data included above provided by American Heartworm Society. Visit for more information about heartworms and heartworm prevention.

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