© 2017 Chancellor Park Vet Surgery


Monday - Friday

8:30 AM - 5:30 PM


8:30 AM - 11:00 AM






        431 Tanawha Tourist Drive,

        Tanawha QLD 4556

        Tel:  0754 455 288

Heartworm Prevention

What Is Heartworm?

Heartworm (Dirofilaria immitis) is a parasitic roundworm that is transmitted from host to host by mosquito bites. Canines are considered the most common host for heartworm, but they have been seen to infect more than thirty animal species; cats and humans included.

The heartworm life-cycle involves a mosquito ingesting microfilaria from an infected dog’s blood. These mature in the mosquito, before being transmitted into another dog’s system as the mosquito sucks blood. The larvae will develop fully over time and migrate to the new host’s heart. After fertilisation, the male and female heartworms will release the microfilaria into the blood stream for the process to begin again.


What Are The Signs?

The infestation may go unnoticed with no outward signs during the early stages. Once this infestation has grown and replicated it will begin to stress the animal’s heart by restricting the blood flow. The heart may enlarge and become weakened due to this increased workload, and congestive heart failure may occur. Larvae circulating in the blood stream can often produce an immune response from the body which is likely to affect the body’s lungs, liver and kidneys.

The signs to look for are; weight loss, lethargy, excessive coughing, exercise intolerance, breathing difficulty, loss of appetite and anaemia.

The death of the adult worms causes them to detach from the artery of the heart, and their adrift body can block large blood vessels, which can inevitably cause organ failure or sudden death.


How Is My Dog Diagnosed With Heartworm?

If your dog is older than 6 months of age and has not be routinely been receiving heartworm prevention treatments, then it is advisable that it be tested through a simple, 10 minute blood test which is performed in clinic.

If the test result is negative, then prevention for heartworm disease is commenced. If the test shows a positive result, then a second blood test must be completed by a veterinary pathology laboratory to confirm this result.

Should they confirm our original diagnosis, then a series of tests are performed in order to determine how advanced the infection is and how much damage the heartworms have caused. These tests include further blood tests and radiographs.


How Is Heartworm Treated and Prevented?

Treatment of heartworm is determined by the degree of which the dog is infected. The drugs used to kill heartworm are dangerous in themselves and so great care is required. Dogs that are not exhibiting any signs generally have a better prognosis than those with signs.

As with most diseases and infections, prevention is the ideal option. Considering that there are a range of preventative treatments available, suited to all different life styles and budgets, all owners should be able to maintain prevention in their animal.

Heartworm prevention should begin at 6-8 weeks of age in the dog.There are a variety of monthly heartworm prevention doses such as standard tablets, flavoured or chewable tablets, or topical solutions that are applied to the skin on the back of the neck. There is also a yearly injection that we administer at 6 months of age (until this age the puppy will need to take monthly tablets). A lot of people prefer this option as they do not have to remember to give monthly doses.

Although heartworm infection in cats is less common than in dogs it does occur and can be fatal. It can be easily prevented by using topical or 'spot-on' products such as Revolution or Advocate.

Preventative medication is extremely effective when given according to the product instructions. Should you require any further knowledge or to discuss heartworming options for your pet, please contact us to speak to one of our veterinary nurses.