Puppy taking heartworm medicine.

April is Heartworm Awareness Month. Maybe—hopefully—you already give your dog or cat their heartworm prevention medication regularly. But we believe it’s important to learn what heartworm disease is and why this preventive medicine is critical to your pet’s health. 

Heartworm disease is caused by the parasite Dirofilaria immitis. Adult female heartworms can grow up to 12 inches long and resemble cooked spaghetti noodles. Once a dog or cat gets infected with heartworms, the parasites will grow, settle down in your pet’s heart and pulmonary system, and reproduce. 

It’s as bad as it sounds. Heartworms can cause lung disease, heart failure, and lasting damage to your pet’s organs. Without treatment—and sometimes even with it—your pet can die. The good news is that heartworm prevention is a safe and easy way to help your pet avoid this devastating disease. 

How Do Dogs and Cats Get Heartworm Disease? 

One mosquito bite is all it takes for your dog or cat to be infected with heartworm. The parasite requires a definitive host for reproduction and an intermediate host to help it spread. All dogs and wild canids are definitive hosts. Here’s a quick breakdown of the life cycle of a heartworm: 

  1. A primary host—dog, wolf, fox, or coyote, for example—has heartworms. The male and female worms reproduce, releasing baby heartworms, called microfilariae, into the dog’s bloodstream. 
  2. One of roughly 30 mosquito species bites the infected dog and ingests microfilariae into its body. The mosquito is the intermediate host that helps heartworm parasites spread. 
  3. The microfilariae mature into larvae inside the mosquito’s gut, a process that takes between 10 and 30 days. 
  4. The larvae migrate to the mosquito’s proboscis. 
  5. The mosquito bites another dog or a cat, transferring heartworm larvae into the bite wound. 
  6. The larvae travel into the dog or cat’s bloodstream. This helps them reach the lungs and heart, where they’ll settle down and grow into sexually mature worms. 
  7. About 6-9 months after this, the worms will begin to reproduce, spreading microfilariae into the dog’s bloodstream. Many of these microfilariae mature into larvae and adult heartworms inside your pet. Others will get carried out of the dog’s body through a mosquito bite. 

A single adult heartworm can live for 2-4 years in cats or 5-7 years in dogs. Without treatment, the worms will reproduce, multiplying in your dog’s heart and lungs. Dogs can have anywhere from 15 to 250 heartworms inside them at one time. Heartworms have a harder time reproducing in cats, which means most cats only live with 1-6 heartworms. 

Spotting Signs of Heartworm 

The sooner your pet’s heartworm disease is caught and treated, the better your furry friend’s prognosis. Signs of heartworm in dogs include coughing, decreased appetite, weight loss, fatigue, and lethargy. Cats may experience these symptoms and also vomit food or blood. 

If you think your pet has heartworm disease, contact the MarketPlace Veterinary Hospital team at (916) 939-1705. We can perform the diagnostic tests your dog or cat needs and decide on a treatment plan. We’ll do everything we can to help your pet. But heartworm prevention is even better than early detection and treatment. And thankfully for you, it’s easy to do!

How to Prevent Heartworm 

The single best way to prevent heartworm disease is to give your pet preventive medication. From the age of about 6-8 weeks, dogs and cats can take heartworm medication as prescribed by a veterinarian. 

Some types of heartworm medication are given to your pet once a month, while others are administered once or twice a year. If it’s been a while since your pet had heartworm medication, bring them in for a heartworm test as soon as possible. We can prescribe preventive medication if the test is clear and start heartworm treatment if it isn’t. Schedule your pet’s appointment today!