How it spreads
A mosquito bites an infected dog, then bites yours; larvae enter through the skin and about six months later grow into adult worms 15 to 30 cm long in the heart and pulmonary arteries. Dogs are the main host. Cats are infected less often and carry fewer worms, but a single worm can cause sudden breathing difficulty.
Signs
There are none at first. Over time:
- A mild, persistent cough
- Tiring easily after exercise, breathlessness
- Loss of appetite and weight
- Later, fluid in the abdomen, fainting and heart failure
In cats the signs look like asthma: intermittent coughing, vomiting and rapid breathing, and sometimes sudden death is the first sign.
Prevention
- A monthly preventive: chew, tablet or spot-on, some of which also cover intestinal worms and fleas.
- All year round. Hong Kong has mosquitoes in winter too; a gap of a few months is enough to become infected.
- Blood test first. Giving a preventive to an already infected dog can kill many larvae at once and cause shock. Dogs over six months need a heartworm test before the first dose and once a year afterwards (a few drops of blood, result in 10 minutes).
- Cats can take a monthly preventive too; feline heartworm disease has no safe treatment, so prevention is the only option.
Treatment
An infected dog is treated in stages: medication to kill larvae and settle the lungs, then injections to kill the adult worms, with strict exercise restriction for one to two months because dying worms can block lung vessels. It takes months and costs far more than a year of prevention.
How we can help
- Rapid heartworm test with same-day results
- Preventive products chosen for your pet's weight and lifestyle, available in our online shop
- X-ray, ultrasound and blood tests to assess the heart and lungs if infection is suspected