What is Heartworm, Exactly?
- A parasitic worm (Dirofilaria immitis)
- Transmitted via mosquito bites
- Lives in the heart/lungs of dogs and sometimes cats
- Grows up to 12 inches long (yikes)
How It Spreads?
It all starts with a mosquito. When a mosquito bites an infected animal, it picks up microscopic baby worms (called microfilariae). After a short vacation inside the mosquito, those larvae become infectious. Then, the mosquito bites your pet- and the worms begin their journey through the body. It takes about six months for them to fully develop and reach the heart and lungs.
Why It’s a Bigger Deal for Dogs?
Dogs are the perfect hosts. Once infected, worms can mature, mate, and live in a dog’s system for 5 to 7 years. If left untreated, they can multiply into the hundreds and cause serious damage to the heart and lungs– eventually leading to heart failure.
Cats, on the other hand, are not ideal hosts. The worms don’t usually survive as long or multiply the same way, but even one or two worms can cause severe respiratory issues. And since there’s no approved treatment for heartworm in cats, prevention is really the only way to protect them.
What Should I Look Out For?
Here’s the tricky part: early-stage heartworm is sneaky. Many pets show no symptoms until the disease is advanced. But as it progresses, you might notice signs like a persistent cough, unusual tiredness, weight loss, vomiting, or a swollen belly due to fluid build-up. Cats may also experience sudden respiratory distress or even collapse.
Bottom line: if something feels off, don’t wait. Get it checked out.
Is it Contagious?
Nope. Heartworm doesn’t spread from pet to pet. It needs a mosquito to get from one animal to another- so technically, your biggest enemy here is winged and buzzing.
So How Do I Prevent It?
Thankfully, heartworm is preventable. Year-round prevention- whether it’s a chewable tablet, a topical medication, or a long-lasting injection- is your pet’s best defense. It’s safe, effective, and way more affordable than treatment.
We also recommend annual blood tests as part of a greater veterinary wellness and prevention plan to make sure the meds are working and your pet is staying protected.
Prevention is especially critical for cats, since there’s no post-infection treatment approved for them.
What If My Pet Tests Positive?
For dogs, treatment involves stabilizing your pet, strict rest, multiple vet visits, and medications designed to kill the worms safely. It’s not a quick fix- but with the right care and early detection, recovery is possible.
For cats, it’s more about managing symptoms. There’s no cure, but supportive care can improve their quality of life and reduce risk of complications.
One Complication You Don’t Want
If heartworm isn’t treated, it can lead to something called caval syndrome– a severe blockage caused by too many worms in the heart. It’s life-threatening and requires immediate intervention.
If your pet suddenly shows signs like pale gums, weakness, vomiting, or red urine, don’t wait- walk into our Midtown or Astoria clinic for emergency care.
Sources:
https://www.heartwormsociety.org/pet-owner-resources/heartworm-basics
https://www.avma.org/resources-tools/pet-owners/petcare/heartworm-disease
