Heartworm Signs, Treatment and Prevention

What is heartworm?

Heartworm is a parasitic worm that can infect your pet through a mosquito bite. An infected mosquito injects a larval stage of the worm under your pet’s skin. These larvae mature in the pet’s organs for five to six months, traveling through the organs to the heart and blood vessels of the lungs. These adult worms then breed to produce microfilaria (baby heartworm) in the bloodstream which is drawn up by a mosquito when it feeds on the pet, continuing the cycle once again.

Mosquitos are hard to keep out of both the yard and house, so even your indoor-only pals are at risk.

What are the signs of heartworm?


Initially, it’s tough to tell that anything is wrong with your pet at all. Heartworm is a slow onset disease, so months or even years may pass before the signs become obvious. When symptoms do appear, your pet could be at the stage of heart failure. Worms interfere with the movement of the heart valves, creating turbulence in the blood, and causing the blood vessels that lead to the lungs to roughen. This puts the heart under immense strain, where it can become enlarged and exhausted.

Early signs could be shortness of breath, loss of stamina, or a nagging, dry cough. As the disease progresses, breathing becomes more difficult, the abdomen may swell with fluid and your dog could become lethargic and lose weight and their appetite. These symptoms are often subtle and hard to detect, so prevention is the best option. If left untreated, heartworm is nearly always fatal.


Usually, there are few clinical signs of heartworm in cats. Your cat could develop slight lethargy or a cough, but heart failure and sudden death are more common if your cat’s heartworm has gone undetected and untreated. It only takes one to two heartworms infecting your feline pet for the disease to become fatal.

How do I diagnose heartworm in my pet?

Get your pet tested at the vet. A simple blood test will reveal whether or not your pet is infected. Unfortunately, diagnosis is more difficult in feline pets, so prevention in all cases is always the best option. Keeping your pet up-to-date with an all-round worming treatment paired with regular vet check-ups is the best way to ensure their health.

How common is heartworm?

The prevalence of heartworm in Australia remains poorly understood. There are ongoing studies to help experts find out more about heartworm infection in pets, which will assist in the treatment and prevention of the disease. With the information currently available, it has been concluded that prevention is the best form of heartworm control.

Can heartworm be treated?


Yes. However, prevention is far better than treatment. Because diagnosing heartworm can be so tough, your pet’s illness may be too far along to treat. Allergic reactions to heartworm treatments have been identified, so stay on the safe side and keep your pet up-to-date with their heartworm prevention.


Treatment in cats involves a complex surgical extraction. There are no drugs approved for the treatment of heartworm in cats, so prevention is almost the only option.

How do I prevent my pet from getting heartworm?


If your dog is over six months old, a blood test is necessary before you can commence preventative treatment, just to make sure they don’t already have heartworm. Prevention should begin at six to eight weeks of age. Monthly medication comes in either tablet or top-spot application, and many brands help protect your pet against intestinal worms and other parasites like fleas. However, the most convenient and effective heartworm prevention is a yearly injection administered by your veterinarian.


Monthly tablets or top-spot applications are the best retail products available to prevent infection in cats. You can purchase high-quality all-wormers, with some also controlling fleas. We know your cat can be difficult to medicate, so regular visits to the vet where a professional can administer them for you is a good idea.

Remember that prevention is always the best medicine. Keep your pet happy and healthy all year round by sticking to a good preventative treatment plan. They’ll thank you for it.

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