Heartworm disease is often associated with dogs, but many cat owners don’t realize that their feline companions are also at risk. While heartworm in cats is less common than in dogs, it can be far more severe due to the limited approved treatment options. That’s why prevention is key.
In this article, we’ll walk you through everything you need to know about heartworm disease in cats, the risks, symptoms, and—most importantly—how to protect your cat with effective prevention strategies.
What is Heartworm Disease in Cats?
Heartworm disease is caused by a parasitic worm called Dirofilaria immitis, which is transmitted through the bites of infected mosquitoes. When a mosquito carrying heartworm larvae bites your cat, it injects the larvae into the cat's bloodstream. These larvae can travel to the lungs and heart, causing severe inflammation, respiratory issues, and even sudden death.
Unlike in dogs, where the worms mature and multiply, heartworms in cats often do not reach full maturity. However, the immature worms can still cause significant damage to the lungs and blood vessels. This condition is known as Heartworm-Associated Respiratory Disease (HARD).
Why Cats Are at Risk—even Indoor Cats
Many cat owners assume that their indoor cats are safe from heartworm. Unfortunately, that’s not true. Mosquitoes can easily find their way into your home through open doors, windows, or even hitch a ride on clothing or pets. Just one mosquito bite is enough to transmit the larvae.
Certain areas in the United States are particularly prone to heartworm due to their warm, humid climates. If you live in one of these states, the risk to your cat is even higher.
Symptoms of Heartworm Disease in Cats
Heartworm symptoms in cats can be sudden or subtle. In many cases, the first noticeable sign may be sudden collapse or death. Some common signs to look for include:
- Persistent coughing or wheezing
- Vomiting (unrelated to eating)
- Weight loss
- Lethargy
- Labored or rapid breathing
- Sudden collapse or death
Because these signs are often mistaken for other conditions like asthma or gastrointestinal problems, if your cat begins acting differently or displays any unusual signs, it's essential to seek guidance from your veterinarian promptly.
Diagnosis Can Be Challenging
Diagnosing heartworm in cats is tricky. Standard heartworm tests used for dogs are not always effective for cats, as cats typically carry only a few worms—or none at all—when infected. Your vet may need to use a combination of blood tests, X-rays, and ultrasounds to determine if your cat has heartworm.
Why Prevention is the Only Safe Option
Unlike dogs, there is no approved treatment to eliminate heartworms in cats. If your cat is infected, your vet can only manage the symptoms and try to reduce inflammation using steroids or supportive care. In some cases, the worm may die naturally, but the inflammation caused can still be life-threatening.
This makes prevention not just important, but essential.
Heartworm Prevention Options for Cats
Several safe and effective heartworm preventatives are available for cats. These usually come in the form of:
- Monthly topical treatments (applied to the skin)
- Monthly oral medications (though less common in cats)
Most of these preventatives also protect against fleas, ticks, and intestinal parasites, giving you comprehensive coverage.
Popular Heartworm Preventatives for Cats Include:
- Revolution (selamectin) – Offers protection against heartworms, fleas, ticks, ear mites, and roundworms.
- Advantage Multi for Cats (imidacloprid + moxidectin) – Covers heartworms, fleas, hookworms, and roundworms.
- Bravecto Plus – Provides extended protection against fleas, ticks, and heartworm disease with one dose lasting up to 2 months.
Be sure to consult with your veterinarian to select the appropriate heartworm prevention for your cat, taking into account their age, weight, and overall health. Your vet can recommend the safest and most effective option tailored to your cat’s specific needs.
When to Start Heartworm Prevention
It’s best to start your cat on heartworm prevention as early as possible, ideally by 8 weeks of age. These medications are usually given once a month, year-round—especially if you live in an area with a warm climate or a mosquito season that lasts several months.
Even if your cat has missed a dose or hasn't been on a preventative, it’s not too late to start. Consult with your veterinarian about testing and initiating a prevention plan as soon as possible.
Safety and Side Effects
When given as directed, heartworm prevention products for cats are typically very safe. Some cats may experience minor side effects, such as slight hair loss at the application site or mild stomach upset. Severe reactions are uncommon. Always use the correct feline dosage and never apply dog medications to cats.
Additional Prevention Tips
Aside from monthly preventatives, here are a few extra ways to reduce mosquito exposure:
- Install mosquito screens on windows and doors
- Use pet-safe mosquito repellents
- Try to keep your cat indoors during the early morning and evening hours, as mosquitoes are most active at these times.
- Also, remove any stagnant water near your home, such as in plant pots or buckets, to prevent mosquito breeding.
Final Thoughts: Keep Your Cat Safe with Year-Round Prevention
Heartworm disease in cats is a serious, challenging condition to diagnose, and it is incurable. The good news? It’s entirely preventable with consistent monthly care. Whether your cat loves outdoor adventures or prefers lounging indoors, working closely with your veterinarian and taking preventive measures can make all the difference in protecting their health and life.
Don’t wait for symptoms to appear. Consult with your veterinarian today and safeguard your cat year-round with a trusted heartworm prevention plan.
