Heartworm in Dogs and How to Prevent It
Heartworm spreads through mosquito bites, not directly from dog to dog. Once adult worms are established in the heart, treatment is far more complicated than prevention. Here is how the infection cycle works and what you can do at home.
Short answer: Heartworm in dogs is transmitted by mosquito bites. It can be prevented by giving heartworm preventive medication consistently, following your veterinarian's schedule, together with reducing mosquito breeding sites around the home. Left unprotected, a dog can suffer serious long term damage to the heart and lungs.
Heartworm is a parasite that affects the heart and lungs of dogs. It is transmitted when a dog is bitten by a mosquito carrying the parasite.
The infection cycle
When a mosquito carrying larvae bites a dog, the larvae enter the bloodstream and, over time, develop into adult worms in the heart and pulmonary blood vessels. This can take many months before clear signs appear.
Why prevention matters
Once heartworms have matured inside the heart, treatment becomes more complex and carries more risk than preventing the infection in the first place. This is why veterinary medicine places the emphasis firmly on prevention.
How to prevent it
Giving heartworm preventive medication consistently, on the schedule your veterinarian sets, is the main effective method. Alongside it, reduce standing water around the house where mosquitoes breed.
I recommend a blood screening test for heartworm before starting or continuing preventive medication. At Hug & Heal we offer screening and a prevention plan matched to each dog's lifestyle.
Frequently asked questions
Q: Can heartworm pass directly from dog to dog?
A: No. It cannot spread directly. A mosquito must act as the carrier in between.
Q: Is a dog that stays indoors still at risk of heartworm?
A: There is still a risk if mosquitoes can reach the dog, so consistent prevention is still recommended.