top of page


Heartworm disease is a silent killer of dogs and cats. It gradually affects your pet, and often by the time you notice the signs of the disease, the damage that has been caused is serious. This is one disease where prevention is definitely the best option!


What causes heartworm disease?

Heartworm is spread by mosquitoes. After injection by a mosquito, adult worms start to grow inside a pet's heart and lungs, causing serious damage. As they grow, they become a barrier to the passage of blood from the heart to the lungs. The infection progresses, the heart dilates and becomes weak and in the lungs, the worms cause scarring and pneumonia.

What effect does heartworm disease have on a pet?

In a dog, the disease initially causes a cough which becomes worse as time passes. The dog becomes inactive and lethargic due to the weakening of its heart. Exercise often causes coughing and in severe cases, fluid leaks out of the blood vessels and accumulates in the lungs and the lower part of the abdomen. Sometimes, the dog will suddenly collapse, which often occurs with no warning.

In cats, serious heartworm disease can be caused with just one or two worms. Tragically, the most common sign of the disease in cats is sudden death, but if your cat is breathless or develops a cough, you should be concerned and have your cat vet checked as soon as symptoms start.


How can heartworm disease be prevented?

Thankfully, preventing heartworm disease is easy and all dogs and cats should be on some form of preventive medication. There are several choices. Daily tablets are still used but the most common forms of prevention are monthly medications or yearly injections. Some monthly preparations are available in a chewable treat form, while 'spot-on's are also an easy option. In addition, many of the monthly preparations also help to control intestinal worms.

The yearly injection is useful to save time and remembering the regular doses. The ideal time for your dog to receive the injection is at the time of its annual vaccination. If your dog is currently on a monthly or daily heartworm preventive, it can be easily switched onto the yearly injection. Unfortunately the yearly injection is not currently suitable for cats.

It is very important that you know with certainty that your pet is free from heartworm disease before starting on any heartworm preventive medication, including yearly heartworm prevention injections. Therefore, unless your veterinarian knows that your pet is free from heartworm disease, they may advise that your pet is tested for heartworm infection before commencing any preventive medication.


For more advice on heartworm prevention, please contact us to arrange a consultation.

bottom of page