Heartworm is a parasitic disease that can affect any dog regardless of age, sex or habitat. It is found in many parts of Australia. Heartworm is spread by mosquitoes, and tends to have a higher incidence in areas heavily populated by mosquitoes. Dogs are considered the most common host for heartworms, however heartworms may also infect more than thirty animal species (including foxes, domestic cats, ferrets) and, rarely, even humans.

What are heartwoms?

Heartworms are parasites that live in the blood of a dog’s heart and adjacent blood vessels. They can grow from ten to thirty centimetres in length, reach maturation 6 to 7 months after infection and live for approximately five to seven years. Adult heartworms living in the heart produce offspring, known as microfilariae, which circulate in the animal’s blood. When a female mosquito bites an infected animal, it sucks out the blood containing the microfilariae. When the mosquito bites another pet, the infectious larvae are transmitted. In many cases the infected dog will not show symptoms in the early stages.

Heartworm is the most serious common parasite in dogs because it stresses the dog’s heart by restricting blood flow and also damages other internal organs. The heart may enlarge and become weakened due to an increased workload, and congestive heart failure may occur. Left untreated, the disease can be fatal to dogs. Blood screening tests can verify the presence of heartworms. Ultrasound and x-rays are used to detect the disease in its later stages. 


Canine heartworm symptoms include:

  • Difficulty breathing

  • Coughing

  • Fatigue, a dog that tires easily

  • Listlessness

  • Weight loss

  • Rough hair coat


Heartworm treatment and prevention

The good news is that most dogs with heartworm can be successfully treated, usually with drugs (adulticide, microfilaricide) that kill adult heartworms and their offspring. Prevention is the best solution – it’s safer, less expensive, and better for your pet!

There are a variety of options for preventing heartworm infection, including a yearly injectable, monthly topicals and monthly chewable or flavoured tablets. Preventative medications are extremely effective and when given properly, on a regular basis, can prevent your pet from contracting heartworm. Remember, year-round heartworm protection relies on remembering to give your pet the prescribed medication, as directed by our Vets. Depending on where you live, our Vet may also recommend a repellant to help avoid mosquito bites.

Can humans catch heartworm and other parasites from their pets?

Humans are unnatural hosts for heartworm – therefore cases of infection are rare. Many heartworm preventative medicines for pets also control other parasites such as hookworms, roundworms, tapeworms and whipworms. Parasitic infections that can be transmitted from animals to humans and are known as parasitic zoonoses.


Ask our Vets at Caloundra Vet Surgery

Our Veterinarian’s are your best reference, with expert knowledge of the heartworm cycle and transmission patterns in your region, along with the individual health and activity profile of your dog. The Sunshine Coast Council’s has fact sheets for each area on the Sunshine Coast together with Council’s management plan.

Before starting a preventive program, all dogs that could possibly be affected with mature Heartworms should be tested, as preventive medicines may cause severe reactions in dogs that are already hosts to adult heartworms. A dog that is NOT on preventive heartworm regime should be tested for heartworm by their Veterinarian, before purchasing any over the counter medication - especially when a dose has been missed or forgotten.  


We are here to help so give Caloundra Vet Surgery a call on (07) 5492 7997 and our knowledgeable team can help.


Click here for a downloadable PDF version of this information sheet.

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Caloundra 4551

QLD, Australia

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