Heartworm disease, which affects dogs and cats differently, can be as complicated as the heartworm life cycle. Our Columbia Pike Animal Hospital team provides this story to  illustrate the heartworm’s path from its host—the mosquito—to its favorite hangout—your pet’s major blood vessels surrounding their heart and lungs. Follow along as we share highlights of Artie the heartworm’s adventure.

Meet Artie the heartworm

Hey, guys, I’m Artie the heartworm! Actually, I’m a microfilaria at this life stage. As an immature heartworm, I spend my days hanging out in my pal, the mosquito. A mosquito’s gastric juices are exactly what I need to spur myself to the next level—the L2 stage. 

During this life stage, I head over to the mosquito’s salivary glands, further evolving to the L3 stage. At this point, I am ready to branch out to a larger host—usually dogs, or any wild canines—but I’ll hitch a ride on any mammal. That’s right—humans can also contract heartworm disease, although their immune system typically fights me off before I grow and can cause harm.

Because my mosquito friend is hungry, and I need a new pal, we search for some fresh blood. Just our luck! We find a stray dog, and swoop in. As the mosquito feeds, I slip out through the saliva, and enter the dog’s skin at the bite wound.

Ah, there’s nothing better than new digs! I have a lot of room to grow in this dog’s body. But first, I have a long journey to my new permanent residence, because I have to travel through the dog’s subcutaneous tissues, abdomen, and diaphragm, and as I migrate, I mature along the way, becoming an L5 larva as I reach my final destination—near the lungs. 

I establish my home in the dog’s arteries surrounding their heart and lungs, where I mature to adulthood, and hope to find a mate, who is likely hanging out in the main pulmonary artery where all the action happens. Once our babies are born, they circulate through the dog’s blood, waiting to be picked up by their own mosquito pal, and continuing the circle of life. 

Fortunately, I made my home in a stray canine host who does not receive heartworm prevention medication, so I have a lifespan of five to seven years, which is much better than setting up home in an unprotected cat, who would be hospitable for about two to three years, if I’m lucky enough to reach adulthood. Oftentimes, a cat’s powerful immune system wipes out immature heartworms when we’re just tiny microfilaria.

I hope you have enjoyed following along on my adventure! A heartworm’s wild ride takes about five to seven months to complete, but the journey is necessary for my growth. Until next time, my friends!

Heartworm disease signs in pets

Although you may believe that a single heartworm, such as Artie, cannot do much damage to your dog’s health, one single parasite can be fatal to cats. And, multiple worms are typically passed during a mosquito bite, setting unprotected pets up for significant damage. Heartworm disease signs vary between cats and dogs, and some pets may be infected for years before signs appear. 

Dogs are heartworms’ preferred host. Canine heartworm disease signs include:

  • A soft, dry cough that progressively worsens
  • Inactivity or lethargy
  • Inappetence
  • Weight loss
  • Fluid-swollen abdomen attributable to heart failure

In cats, the first—and only—sign may be sudden collapse or death. However, cats can exhibit other heartworm disease signs such as:

  • Coughing
  • Asthma-like attacks
  • Vomiting
  • Inappetence
  • Weight loss
  • Difficulty walking
  • Fainting
  • Seizures

Preventing and treating heartworm disease in pets

Heartworm disease treatment, especially in the disease’s advanced stages, can be harrowing.  A heartworm-positive dog undergoes a series of immiticide (i.e., melarsomine dihydrochloride) injections, typically administered 24 hours and 30 days apart, and inserted deep in the lumbar muscles, which can cause discomfort, nausea, and a general malaise. In addition, during treatment, you must greatly limit your dog’s activity, because if your dog is too active after the injections, they can suffer potentially fatal adverse effects, such as embolism formed by the dying worms.

Unfortunately, no approved heartworm treatment is available for cats. Treatment focuses on managing an affected cat’s signs. 

While heartworm treatment can be challenging for dogs and nonexistent for cats, prevention is simple. A variety of heartworm preventive options are available to protect your pet from this serious disease, and many options also provide protection against intestinal parasites, mites, fleas, and ticks. 

To choose the best heartworm preventive medication for your pet, contact our Columbia Pike Animal Hospital team for advice.