How do we prevent heartworm disease in dogs?

Heartworm disease sounds scary, and for good reason—those tiny parasites can grow into foot-long worms in a dog’s heart, lungs, and blood vessels, causing lasting damage or even death. The worst part? It’s totally preventable, but too many owners skip the simple steps that keep their pups safe. Unlike some illnesses, there’s no quick fix once a dog is infected; treatment is expensive, painful, and not always successful. That’s why focusing on prevention from day one is non-negotiable.​

The cornerstone of prevention is consistent medication. Most vets recommend year-round heartworm preventatives, even in cooler climates—mosquitoes, which spread the disease, can sneak in during warm spells or hang around indoor spaces. These meds come in chewables, topicals, or injections, and they work by killing the baby heartworms before they mature. The key is sticking to the schedule: missing a dose, even for a few weeks, leaves a window where a mosquito bite could lead to infection. Talk to your vet about which option fits your dog’s lifestyle—some chewables taste like treats, making them easy to give, while topicals are great for pups who spit out pills.​

Cutting down on mosquito bites helps, too. Heartworms spread when an infected mosquito bites your dog, so reducing their exposure lowers risk. Keep stagnant water out of your yard—birdbaths, clogged gutters, and old buckets are breeding grounds. At dusk and dawn, when mosquitoes are most active, keep your dog indoors or use a pet-safe mosquito repellent (ask your vet for recommendations—some human products are toxic to dogs). Screened porches or dog runs can let them enjoy fresh air without the swarms, especially during humid summer months.​

Regular testing is another layer of protection. Even with consistent meds, it’s smart to get your dog tested once a year. The test checks for early signs of infection, catching any parasites that might have slipped through before they cause harm. Puppies can start prevention as early as 6 to 8 weeks old, but they’ll need their first test around 6 months—before that, their tiny bodies might not show signs of infection. For adult dogs, annual tests are a must, even if they’ve been on preventatives religiously. It’s a simple blood draw, and catching an issue early could save their life.​

Skipping prevention because “my dog stays indoors” is a risky myth. Mosquitoes sneak through open doors or windows, and even a single bite from an infected one is enough. Small dogs and seniors are especially vulnerable, but no breed or size is immune. And remember, prevention is far cheaper than treatment—fighting an active infection can cost thousands in vet bills, not to mention the stress of watching your pup suffer through injections and rest periods.​

At its core, preventing heartworm disease is about consistency: giving the meds on time, keeping an eye on mosquito hotspots, and never skipping that annual test. Your dog can’t tell you when something feels off, so it’s up to you to stay one step ahead. Those small, regular efforts add up to years of healthy runs in the park, cozy naps by the fire, and tail wags that never slow down. That’s a gift worth giving.