Many pet owners wonder whether heartworm prevention is still necessary once winter arrives. With colder temperatures and fewer mosquitoes, it can feel reasonable to pause prevention. However, continuing heartworm prevention during the winter months plays an important role in protecting your dog’s long-term health.
Indian Peaks Veterinary Hospital recommends year-round heartworm prevention because relying on seasonal weather patterns alone does not provide reliable or consistent protection.
Why Heartworm Prevention Still Matters in Winter
Heartworm disease spreads through mosquito bites. While mosquito activity often decreases in colder months, it does not stop as predictably as many people expect—especially in Colorado.
Heartworm transmission does not reliably stop unless temperatures remain below approximately 57–60°F for at least 30 consecutive days. Short cold snaps do not eliminate risk. Even brief warm periods can allow mosquito populations to rebound and continue transmitting disease.
Because winter temperatures are increasingly unpredictable, seasonal prevention can leave gaps in protection.
Colorado’s Climate and Lifestyle Increase Risk
Colorado is a very dog-friendly state. Dogs frequently travel with their families, visit boarding facilities and dog parks, hike trails, and relocate here from other regions.
Many dogs living in Colorado come from higher heartworm-risk areas, including parts of the Midwest, South, and East Coast. This movement increases exposure risk, even for dogs that now live in a cooler climate.
According to data from the Companion Animal Parasite Council (CAPC), heartworm disease has been documented throughout Colorado, with risk varying by county. CAPC’s surveillance data also shows that heartworm prevalence can change over time based on climate patterns, pet travel, and relocation from higher-risk regions.
This data reinforces that heartworm risk is not limited to traditionally high-prevalence states and cannot be reliably predicted by weather alone.
Indoor Dogs Are Still at Risk
Living indoors does not eliminate heartworm risk. Mosquitoes can enter homes through doors, garages, and windows—particularly during warmer winter days.
Year-round prevention protects dogs regardless of lifestyle, housing, or time spent outdoors.
What Happens When Prevention Stops in Winter
Heartworm preventatives work by eliminating immature heartworms acquired in the previous month. When prevention stops or doses are delayed, gaps in protection can occur.
Restarting prevention after a lapse often requires additional testing and creates uncertainty. Maintaining prevention year-round avoids unnecessary risk and simplifies care.
Consistency Protects Your Dog—and Your Peace of Mind
Consistent heartworm prevention provides:
- Continuous protection despite unpredictable weather
- Fewer missed or delayed doses
- Simpler refill schedules
- Reduced risk of infection during warm spells
Prevention remains far safer, easier, and less stressful than heartworm treatment.
Year-Round Prevention Supports Manufacturer Guarantees
Heartworm prevention manufacturers require:
- Continuous dosing
- Annual heartworm testing
When these requirements are met and prevention is purchased through your veterinary hospital or approved online store, many manufacturers cover treatment costs if a dog tests positive.
Seasonal gaps in prevention can jeopardize this coverage and expose families to significant treatment expenses.
Winter Is the Ideal Time to Stay on Track
Rather than viewing heartworm prevention as seasonal, it works best as a routine part of preventive care—just like wellness exams and vaccinations.
Winter is an excellent time to:
- Maintain consistent prevention
- Schedule annual heartworm testing
- Refill medications ahead of spring and summer
Staying consistent now prevents complications later.
Heartworm disease remains preventable, and treatment is lengthy, costly, and physically demanding for dogs. Continuing heartworm prevention during the winter months provides reliable protection against an unpredictable disease.
Preventive care works best when it’s consistent—and your dog’s health deserves protection all year long.