The short answer
Yes. Cats get heartworm from mosquito bites, same as dogs. The critical difference: there is no approved treatment for heartworm in cats. If your cat gets infected, you’re limited to managing symptoms and hoping the cat outlives the worms. Prevention is the only real protection.
How it’s different in cats
Cats are not the natural host for Dirofilaria immitis. Dogs are. So heartworm behaves differently in cats:
Fewer worms survive. A typical infected cat has only 1 to 3 adult worms, compared to dozens or even hundreds in an untreated dog. But even 1 or 2 worms in an animal that small can cause serious problems.
The immune response is intense. When immature heartworms arrive in a cat’s lungs, the inflammatory reaction can be severe enough on its own to cause a condition called heartworm-associated respiratory disease (HARD). This gets misdiagnosed as asthma regularly.
Diagnosis is harder. The standard heartworm blood tests designed for dogs are less reliable in cats because cats carry so few worms. False negatives are common.
Indoor cats are not safe
About one-third of cats diagnosed with heartworm live exclusively indoors. Mosquitoes enter through doors, windows, and any small opening. The same logic that applies to indoor dogs applies here, arguably more so because cats have no treatment option if infected.
Symptoms in cats
Some infected cats show no symptoms at all. Others show vomiting, coughing, difficulty breathing, weight loss, or lethargy. In some cases, the first and only sign is sudden death from a blood clot or respiratory failure.
Because symptoms overlap with feline asthma and other respiratory conditions, heartworm in cats often goes undiagnosed.
Prevention for cats
Monthly heartworm preventives for cats are available as topical spot-on treatments or oral tablets. They’re effective and straightforward.
If your dog is on heartworm prevention during Ontario’s heartworm season, your cat should be too. Talk to your vet about the right product for your cat.
Key takeaways
- Cats can get heartworm from mosquito bites. There is no approved treatment for infected cats.
- Even 1 or 2 worms can cause serious disease in a cat.
- One-third of heartworm-positive cats are indoor-only. Mosquitoes get inside.
- Symptoms often mimic asthma, leading to misdiagnosis.
- Monthly preventive medication is the only reliable protection for cats.
References
- American Heartworm Society. “Heartworms in Cats.” heartwormsociety.org
- Cornell University College of Veterinary Medicine. “Heartworm in Cats.” vet.cornell.edu
- VCA Animal Hospitals. “Heartworm Disease in Cats.” vcahospitals.com
- PetMD. “Heartworm Disease in Cats: Symptoms, Treatment, and Prevention.” petmd.com