Heartworms are deadly to animals. However, pet owners have the potential to prevent them. It's important to know what they are and what to look for if you're not giving your canine any preventative medicines for them.

Definition of Heartworms

Heartworms are a type of worm, commonly known as a foot-long worm, that lives inside the heart, lungs and blood vessels in close proximity to these organs. Dogs are natural hosts for heartworms. The heartworms inside the pet grow into adult worms, and once they mate and reproduce, your pooch may be infected with several hundred. Cats, on the other hand, aren't natural carriers, meaning it's rare for a cat to have adult worms. They tend to have far fewer worms, sometimes just one or two. Cats who have heartworms still have serious complications as a result of the immature parasites. For instance, they can develop heartworm-associated respiratory disease, referred to by the acronym, HARD.


Mosquitos spread heartworms from pet to pet. They bite a pet who has the heartworms, and when they do, they ingest microfilaria, better known as baby worms. The baby worms are then carried inside the mosquito anywhere from 10 to 14 days. During this time, the next victim the mosquito bites will be infected.

Prevention & Treatment

Prevention in dogs is the most successful method to protect against heartworms. However, it's the only way to protect cats against heartworm damage. A vet will prescribe a medication that's best suited for cases where there are no or mild signs of heartworms. Severe cases can be treated, but complications are more likely in these instances. Keep in mind. even dogs with numerous worms may have no or mild symptoms. Cats can't take treatment for heartworms, so they must be kept stabilized. In some instances, it's possible to operate to remove the parasites in cats and dogs, but more so in canines.

Signs of the Condition

Signs of the disease include the following:

  • Mild, persistent cough
  • Reluctance to exercise
  • Weight loss
  • Decrease in appetite
  • Exercise-related fatigue

More advanced cases may have the following symptoms: 

  • Fluid retention in the abdomen
  • Heart failure
  • Pale gums
  • Cardiovascular collapse
  • Dark, bloody, coffee-colored urine
  • Labored breathing

Symptoms exclusive to cats:

  • Difficulty walking
  • Fainting
  • Seizures
  • Asthma-like attacks
  • Periodic vomiting 


Prevention is the most successful way to prevent damage from heartworms since even small worms can have a negative impact that's permanent. If you don't give your pet a preventative treatment, make sure you watch for the symptoms because early detection means a better prognosis.