Pocket VetHeartworm disease in dogs
Heartworm is a mosquito-transmitted parasite that grows into foot-long worms in the heart and lungs. Treatment is long, risky, and expensive; prevention is a monthly chew.
What it is
A mosquito bite deposits larvae that mature over months into adult worms living in the heart and pulmonary arteries, causing progressive damage. By the time signs show, disease is established. Cats can get it too, with fewer treatment options.
Symptoms
- ●A soft, persistent cough
- ●Tiring easily on exercise
- ●Weight loss, reduced appetite
- ●A swollen belly in advanced disease
🔴 When to act now
- ●Sudden collapse, laboured breathing, or dark urine — possible caval syndrome, a true emergency
Treatment & management
Annual testing plus year-round monthly preventives (or long-acting injections) keep dogs safe. Treatment of established infection requires months of strict rest and a series of injections — far harder than prevention. Talk to your vet about regional risk.
Seeing these signs in your dog?
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Check my dog nowFrequently asked
Does my dog need heartworm prevention in winter?
Vets generally recommend year-round prevention — mosquito seasons are unpredictable, missed doses create gaps, and many preventives also cover intestinal parasites.
Can heartworm be cured?
In dogs yes, but treatment takes months, requires strict exercise restriction, and carries risk. That's why testing and cheap monthly prevention matter so much.
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Pocket Vet editorial team
Written and maintained by the Pocket Vet editorial team using authoritative veterinary sources. Reviewed June 9, 2026. This guide is informational only and not a substitute for professional veterinary care — see our editorial & safety policy. When in doubt, contact your vet; in a true emergency, go to an emergency clinic immediately.
Sources