Dog Heartworm Prevention: Protecting Canine Health Year-Round

Heartworm disease is a serious, potentially fatal condition in dogs caused by parasitic worms spread by mosquitoes. Prevention is far safer and more effective than treatment.

Key Facts

Heartworm (Dirofilaria immitis) is transmitted by over 70 mosquito species across many climates
Adult worms can grow up to 30 cm and live for 5-7 years in a dog's heart and lungs
Dogs may show no symptoms until the disease is advanced, making prevention critical
Monthly preventatives (oral, topical, or injectable) are nearly 100% effective when given correctly
Treatment of established heartworm disease is expensive, painful, and requires weeks of strict rest

Welfare Considerations

Heartworm disease causes significant suffering: infected dogs experience exercise intolerance, respiratory distress, and heart failure as worm burdens grow. Treatment involves arsenic-based injections and strict confinement that is itself stressful for active dogs. Yet prevention is simple, affordable, and virtually eliminates risk. Many dogs are lost to heartworm simply because owners in cooler regions assume they are safe, or because preventatives are skipped. Year-round prevention is now recommended in most regions due to climate shifts extending mosquito seasons. Veterinary guidance on the right product for each dog's size and health status is essential.

What You Can Do

Talk to your veterinarian about year-round heartworm preventative for your dog
Never skip monthly doses — even one missed dose can allow infection
Test annually for heartworm even when on prevention, as recommended
Support low-income pet owner programs that provide free or subsidized preventatives