Heartworm prevention is essential for greyhounds


Heartworm is prevalent in dogs throughout Queensland. Left untreated, heartworms will mature and cause severe disease.

To prevent heartworms infesting your dogs, they must be provided with up-to-date effective heartworm prevention as puppies and throughout their lives.

Once a dog has heartworm, it is at risk of severe and life-threatening disease, and requires extensive and costly treatment.

What is heartworm?

Heartworms (Dirofilaria immitis) are transmitted to dogs through mosquito bites. Both saltmarsh and freshwater mosquitoes carry and transmit heartworm. Wherever there are mosquitoes, there is potential for heartworm. While control of mosquitos can assist in prevention, effective control is only gained through administration of a preventative product beginning when pups are six to eight weeks of age and continuing throughout their lives.

Juvenile heartworms called microfilaria enter a dog’s bloodstream through the bite of an infected mosquito. The microfilaria matures in the organs of the dog, and then migrates to the heart and the blood vessels of the lungs. Adult worms in the heart and lungs of a dog cause coughing, exercise intolerance and breathing difficulties. Severe infestation causes damage to the lungs and eventual congestive heart failure.

Early in the infestation, signs can be mild or absent, and by the time the dog develops symptoms the heartworms are mature.


There are many heartworm preventatives currently on the market.

If your greyhound has not had heartworm medication for more than six months, a blood test is necessary before you can commence preventative treatment.

There are four kinds of heartworm preventatives. These are summarised below. Your vet is the best person to advise you on the most appropriate product for your greyhounds.

Yearly heartworm injection

Proheart SR12 is an annual injection that provides prevention against heartworm for 12 months. In puppies, boosters are required at 12 weeks and 6 months, and then again at around 12 months of age followed by an annual injection.

Oral monthly prevention

There are several very effective tablets or chews available. Many also treat some intestinal worms, fleas and ticks, but it is important to read the product label, as they all differ in their coverage of parasites. Ontime, monthly dosing is important to prevent gaps in protection and not all products are palatable, so it is important to ensure correct oral administration.

Topical monthly prevention

Topical spot-on treatments are applied directly to the skin where they are rapidly absorbed providing a convenient dosing method for fussy greyhounds. Some products cover a combination of internal and external parasites and require on time, monthly administration.

Daily prevention

Daily compliance is required and even two missed days can put your greyhound at risk of infection.


Testing for heartworm is simple, fast, and potentially lifesaving. A blood test can detect infestation of adult heartworms in your greyhound. An examination of blood under a microscope can identify juvenile heartworms. If a positive test is found your vet will complete a more thorough workup, including assessing clinical signs and lung x-rays, to determine the best course of treatment.


Treatment for heartworm disease can be risky and may be difficult, but if left untreated, it is usually fatal. Treatment improves clinical signs and eliminates all adult worms. However, careful veterinary treatment and monitoring is required as killing adult worms in large numbers can cause serious complications.

Careful treatment protocols are necessary, and dogs must be on strict exercise restriction and kept cool at all times during treatment to minimise problems. Treatment can take months to successfully clear all adult heartworms and resolve clinical disease.

Prevention of heartworm using an approved product from the time your dog is a puppy and throughout its life is essential to protect its health and performance.



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