Heartworm Disease: The Silent Killer That's Completely Preventable
Heartworm disease is fatal if untreated but 100% preventable. Learn why prevention is essential for every dog and cat.
Heartworm disease is caused by parasitic worms (Dirofilaria immitis) that live in the heart and lungs. Transmitted by mosquitoes, it can be fatal if untreated. The worms grow up to 30cm long and cause severe heart and lung damage. The good news: monthly prevention is safe, affordable, and 100% effective.
Key Points
- Heartworm is transmitted by mosquitoes — any pet bitten is at risk
- Worms grow up to 30cm long and live in the heart and lungs
- Untreated heartworm is fatal in dogs
- There is no approved treatment for heartworm in cats
- Monthly prevention is safe and 100% effective
- Prevention costs a fraction of treatment
How Heartworm Spreads
When an infected mosquito bites your pet, it deposits microscopic larvae (microfilariae) into the skin. Over 6 months, these larvae migrate to the heart and pulmonary arteries, where they mature into adult worms. Adult worms can live 5-7 years in dogs and produce millions of microfilariae that circulate in the blood, ready to infect more mosquitoes.
Signs of Heartworm Disease
In dogs: early signs include a mild cough, exercise intolerance, and fatigue. As the disease progresses: weight loss, difficulty breathing, fluid accumulation in the abdomen, and heart failure. In cats: coughing, asthma-like breathing difficulty, vomiting, and sudden death. Cats can die from even a single worm.
Prevention Is Key
Monthly heartworm preventives (ivermectin, milbemycin, or moxidectin-based products) kill any larvae deposited by mosquitoes before they can develop into adults. Many products combine heartworm prevention with flea and intestinal parasite control. Prevention should be given year-round — even in cooler months, mosquitoes can still be active.
Testing and Treatment
Dogs should be tested for heartworm annually (a simple blood test) even if on prevention. Treatment for heartworm-positive dogs is expensive, risky, and requires strict rest for weeks. There is no approved treatment for heartworm in cats — only supportive care. Prevention is always better than treatment.
When to See a Vet Immediately
- Persistent cough in your dog
- Exercise intolerance or tiring easily
- Weight loss with no obvious cause
- Difficulty breathing
- You've missed heartworm prevention doses
- You want to start heartworm prevention
How RVC Can Help
RVC provides heartworm testing, prevention, and treatment. We recommend year-round prevention for all dogs and can recommend the best product for your pet. Call +853 6677 6611.
This article is for educational purposes only and does not replace professional veterinary advice. If your pet is showing any symptoms, please contact Royal Veterinary Center immediately at +853 6677 6611.