What You Should Know About Heartworms and Heartworm Disease

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Testing for Heartworms

Year after year, you take your pet to his yearly check-up with your regular veterinarian.

Every year, your veterinarian recommends a blood test to check for heartworms. He also recommends that you buy heartworm preventative.

But my dog seems fine! Why should I test for/prevent something I can’t even see?

What are Heartworms?

Heartworms are parasitic worms that can grow up to a foot long. They set up residence in the heart, lungs and blood vessels of some species of mammals, including dogs and cats. As the heartworms mature into adults, they mate and produce microfilaria (baby heartworms). As long as the parasites are living and thriving off their host, they damage the heart, lungs and other viable organs found in the host’s body.

How Did My Pet Get Heartworms?

As if mosquitoes don’t cause enough problems in the human world, they are also the vector for heartworm disease in our pets. As you may know, when a mosquito bites, it sucks blood. When a mosquito bites an animal whose blood is infected with heartworms and then bites your pet, the microfilaria are then transmitted to your pet.

Why Don’t We Test Cats for Heartworms?

Dogs are considered “natural hosts” which means the worms can live happily, grow and reproduce inside a dog’s body. Cats, on the other hand, are considered “atypical hosts”. Most heartworms do not mature to the adult stage; thus, they do not reproduce. If a heartworm does make it to the adult stage in a feline host, there are typically only 1 to 3 adult heartworms that will survive. Dogs can host hundreds.

The blood sample used to test for heartworms only detects adults; so, heartworm disease often goes undiagnosed in cats. Additionally, the drug used to treat heartworm disease is not safe and is not approved for use in cats.

Even though heartworms rarely mature into adults in cats, the baby heartworms can do considerable damage with a condition known as heartworm associated respiratory disease (HARD). Keeping your cat on heartworm prevention is the only way to keep them fully protected.

How Do I Know If My Dog Has Heartworms?

The only way to know for sure is to do a blood test. As with every disease, symptoms vary from patient to patient. Your pet may display some or none of the signs at first. However, as the disease progresses, so do the symptoms.

Signs of heartworm disease in a dog include:

  • Mild, persistent cough
  • Inappetence
  • Fatigue following moderate activity
  • Reluctance to exercise
  • Weight loss
  • Congestive heart failure
  • Death.

Signs of heartworm disease in a cat include:

  • Coughing
  • Asthma-like attacks
  • Periodic vomiting
  • Inappetence
  • Weight loss
  • Difficulty walking
  • Fainting/seizures
  • Fluid accumulation in belly
  • Death.

Frequently Asked Questions about Heartworms

I just brought my puppy in for her first set of shots. Why didn’t they test her then?

It takes baby heartworms 7 months to mature into adults. The blood sample used to test for heartworms only detects adult heartworms.

My pet rarely goes outside. Does he really need to take a heartworm preventative?

Yes, in order to keep him fully protected. It only takes one bite from an infected mosquito. Most preventatives also have other dewormers included to prevent roundworms, hookworms and sometimes whipworms, which is a definite plus!

My pet takes a heartworm preventative every month -why do I have to test him every year?

Heartworm preventatives are labeled by the FDA as a prescription, meaning they must only be used or used under the direction of a licensed veterinarian.

Most veterinarians require yearly testing to assure no adult heartworms are present.

While heartworm preventatives are HIGHLY effective, no product is 100% effective.

Giving your pet heartworm prevention without knowing if heartworms are present could result in a severe reaction and/or death.

My Pet Tested Positive for Heartworms

What happens now?

To start, a second test is always recommended to rule-out a false positive result. If a second test confirms a positive diagnosis, treatment may begin.

You will be asked to keep your pet’s activity very restricted throughout the entire process.

Your veterinarian will perform a preliminary exam after confirmation of heartworm disease.

Further testing, such as radiographs and an ultrasound, may be necessary to determine what stage of the disease your pet is in.

Before the actual treatment, your veterinarian may want to treat your pet for other medical conditions. Sometimes this is necessary in order for the animal to safely undergo treatment for the heartworms.

Once your pet is stabilized, treatment may begin. Depending on the severity of the disease, one or two treatments may be required. After treatment, your pet’s activity level must still be kept to a minimum.

After treatment, it is highly recommended that you put your pet on a preventive and keep them on it for life.

Approximately six months after the treatment, your veterinarian will want to test your pet again to ensure the treatment was effective.

Unfortunately, there is no approved treatment for heartworm disease in cats at this time. However, with some additional testing, your veterinarian can develop a plan to treat the symptoms and keep the disease maintained.

For additional information on heartworm disease, please visit https://www.heartwormsociety.org.

Heartworm prevention is the only way to keep your pet safe from heartworm disease!

Chelsea Davis

Chelsea Davis

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