Heartworm is a parasite worm that is transmitted by mosquitos that infects both dogs and cats. An infected mosquito bites the pet and injects a larval stage of the worm under the skin. Once this larval stage has matured it affects the pet’s organs. After 5-6 months the adult worm makes its way into the organs such as the heart and the lungs, which as you would expect have significant effects on the animals health and well being. These adult worms then breed and produce small heart worm so they cycle begins again.

As you would be aware mosquitoes make their way into our homes, which does means that even indoor pets are at risk of infection from heartworm.ent is definitely prevention.

What are the signs of heartworm?


Initially few signs of infection may be seen. Heartworm is usually a slow onset disease. Months or years may pass before signs are seen. When symptoms do appear, they are usually signs of heart failure. The worms interfere with the working mechanisms of the heart & blood flow through to the lungs. The heart is a pump – when it is under duress such as this it has to work much harder. This generally leads to the heart becoming enlarged. Your dogs earliest signs are shortness of breath, and a nagging hacking dry cough. As the disease progresses, breathing is more difficult and the dog becomes lethargic, loses weight, and can stop eating. If left untreated, heartworm is almost always fatal!


Cats are infected with heartworm at about 10% as often as dogs are. Usually, there are few clinical signs in the cat. Heartworm may be associated with heart failure, a cough, and a degree of lethargy. Often it is the sudden death, after the cat coughs up blood.

How do I know if my pet has heartworm?

A blood test is performed. In the case of dogs, the test is very accurate, with results available before you leave the clinic.

For cats, testing is less accurate because of the lower number of worms involved.

How common is heartworm?

Heartworm is very common. Studies have shown that over 50% of dogs who are not given preventative treatment will become infected with heartworm! Infection rates in cats are uncertain.

Can heartworm be treated?


Yes. However, treatment is not without its potential problems. The immiticide used can cause allergic reactions in some dogs, requires a long treatment course and ongoing follow-up medications to prevent potential side effects. It is important to understand that for heartworm prevention is a much better option for your pet than treatment.


Treatment is difficult and is usually very complex surgical extraction. There are no drugs approved for treatment of heartworm in cats, so again prevention is far better.

How do I prevent my pet getting heartworm?


If your dog is over 6 months old, a blood test is necessary before you commence prevention. This is to make sure that your dog doesn’t already have heart worm. It is advised that prevention commences at 8 to 12 weeks of age, and is available in several different forms. The most convenient heart worm prevention is a yearly injection “Proheart SR-12” administered by your veterinarian.


Monthly tablets or top-spots are available for cats to prevent heartworm infection. These products also control gastrointestinal worms and some products also control fleas.

Remember if you are being bitten by mosquitoes, there is a risk that your pet could also e infected with heartworm through a mosquito bite. The best treatment is definitely prevention.