The Heartworm Picture – Getting to the Heart of the Matter

Sometimes with the crazy weather lately, it’s hard to believe that spring is near. But blue skies and green grass are coming soon.  So are pesky insects that will hamper outdoor fun. Some of these insects are more than just annoying. They’re harmful. Case in point—the mosquito. Besides inflicting nasty bites that itch a lot, these flying mini-vampires transmit heartworms to dogs and cats.

The heartworm picture at right shows you what we mean.

Dog Heartworm Picture

This heartworm picture shows infection in a dog's heart

Heartworm is a blood borne parasite called Dirofilaria immitis. The adult is a whitish worm that grows up to 14 inches long and resembles angel hair pasta. Adult heartworms live in large blood vessels near the heart…hence the name. Female worms mate with smaller male worms to produce babies called microfilariae.

What do Mosquitoes Have to Do with Heartworms?

Heartworms are true parasites. They live off the efforts of others.  Heartworms need dogs, cats, and mosquitoes to survive. Dogs and cats provide a home and mosquitoes provide transportation between homes and serve as a temporary incubator.

Here’s How Dog and Cat Heartworm Infection Works.

Adult heartworms stay in the pulmonary artery, but their babies (microfilariae) venture into the circulatory system of their canine or feline host. While in the bloodstream, microfilariae are “picked up” by a mosquito. The hungry mosquito lands on a dog or cat, inserts it’s “siphon” (mouthpart) to take a blood meal and sucks up microfilariae in the process.

The microfilariae like their new home and mature inside the mosquito. They molt from L1 to L2 to L3 larval stages until they outgrow their mosquito incubator and seek better living quarters. Like many children, these larvae want a home like their childhood abode. But, how do they find an available dog or cat condo?

Serving as real estate agent, the hungry mosquito locates another dog or cat. While taking a blood meal, the mosquito deposits L3 larvae on the surface of the pet’s skin. These larvae crawl into the dog or cat’s body through the hole made by the mosquito bite. The L3 larvae migrate through the new pet’s body while further maturing. As grown up heartworms, they locate the pulmonary artery, set up residence, find a suitable mate and have babies of their own. The heartworm life cycle is complete.

Heartless Parasite – Heartworm Signs

Heartworms are heartless, harmful parasites. They not only affect the heart and major blood vessels, they also damage the lungs, liver and kidneys.

Infected dogs or cats may experience exercise intolerance, breathing difficulties, or loss of appetite. Heartworms can cause secondary fluid accumulation in the lungs or abdomen, clog large vessels like the vena cava making a dog gravely ill or cause sudden death in cats. In short, heartworms are not your pet’s friend.

Evicting Heartworms with Effective Dog Heartworm Treatment

To successfully clear a dog (and cat) of heartworms, both the babies and adults must be evicted. Heartworm treatment is a lengthy, expensive process that includes an injectable drug to kill adult worms plus oral medication to kill microfilariae. Prior to heartworm treatment, dogs undergo various tests including blood tests, urine analysis and chest radiographs. Unfortunately, there is no approved medication to treat feline heartworms.

Neighborhood Watch—Keeping Heartworms Out with Preventive Medication

Adult heartworms do not have to live in your pet. Heartworm disease can be prevented. Oral or topical monthly medications (for dogs AND cats) plus a six month injectable product (for dogs only) can stop heartworm development. The key is to start young pups and kittens on heartworm medication and continue consistent administration throughout their lives. The American Heartworm Society and the Companion Animal Parasite Council, two groups of veterinary thought leaders, advocate giving heartworm preventives all year round even in “cold” states. Every state in the continental US has heartworms.

Neighborhood Census—Finding Heartworms with a Heartworm Test

Heartworms can be detected with a simple blood test; however, due to the many stages in the life cycle, more than one test may be needed to confirm that a pet is free of heartworms. Follow your veterinarian’s advice on heartworm testing and prevention.

Mosquitoes are more than just annoying insects.  So, take precautions before going outside. Put on your insect repellent, then consider your pet.

Is your cat or dog on heartworm preventive? Please share your story. Thanks!


10 thoughts on “The Heartworm Picture – Getting to the Heart of the Matter

    • Barbara, please bring your pup to the veterinarian. Vomiting pups need to be checked for dehydration. Your pup will likely need to be dewormed as well.
      Dr. Lynn

    • Janet, thanks for visiting our blog site. We try to communicate helpful information in a manner that can be informative, fun, and easy to implement. Our goal is to help pets and the people that love them!
      Dr. Lynn

  1. Nice post about The Heartworm Picture – Getting to the Heart of the Matter | MyPetED Blog. I am very impressed with the time and effort you have put into writing this story. I will give you a link on my social media blog. All the best!

  2. I am impressed to read such a powerful story about The Heartworm Picture – Getting to the Heart of the Matter | MyPetED Blog. I will post a link on my coupon site to this blog post. I will be back to read more.

    • Glad you enjoyed the heartworm article. Getting the word out regarding this preventable, but deadly, disease will benefit many dogs and cats.
      Dr. Lynn

  3. Can we begin heartworm prevention immediately on a housedog that is symptom free? She goes to the vet regularly but hasn’t been tested for heartworm.

    • First of all, thanks for considering heartworm medication for your dog. All dogs in all parts of the country need consistent prevention from this parasite and the mosquitoes that carry it. Heartworm positive dogs can have adverse reactions to heartworm preventive drugs, so to start heartworm medication safely, have your dog tested now and repeat the test in 6 months. Sometimes the first test will be negative due to an immature infection. Re-testing in 6 months will give you more confidence that your dog is heartworm free. Call your veterinarian and start the process!
      Dr. Lynn

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