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Heartworm in dogs & cats

Published on 28 Apr 2021

Sick Sshepherd dog losing appetite and not eating a bowl of dry food.

Year-round heartworm prevention is an important part of routine care for most Australian dogs and cats. 

Heartworm is transmitted by mosquitos and can be a serious and even deadly disease. 

How is heartworm transmitted?

Mosquitoes transmit heartworm. When a mosquito bites an infected dog, the immature stages of the heartworm called microfilariae, are transmitted to the mosquito. These microfilariae develop in the mosquito and can be transmitted to other dog and cats when the mosquito bites them. Once infected, the heartworms continue to develop within the host and infect the heart, lungs and associated blood vessels. 

It is important to note that heartworm disease in cats is very different to heartworm disease in dogs. The cat is not the typical host for heartworm and on many occasions the worms do not survive to the adult stage. 

Although adult worms are concerning, even the immature worms can cause severe clinical disease, in cats this is referred to as heartworm associated respiratory disease. 

Who is affected?

Any dog or cat can be infected with heartworm disease. 

What are the signs of heartworm disease?

The signs of heartworm disease vary between dogs and cats. Heartworm is considered a disease with a slow onset and it may take many months (and in some cases years!) for clinical signs to be present. 

Species Symptoms
Feline Vomiting, weight loss, coughing and/or asthma like attacks, decreased appetite, collapse, death
Canine Exercise intolerance, coughing, lethargy, decreased appetite, weight loss, distended abdomen. Dogs with large numbers of worms can develop blockages of blood flow in the heart leading to collapse 

Management of heartworm 

Preventing heartworm in pets is the best option to ensure your pet protected against them.

This means regular worming with a reputable brand of heartworm preventative medications according to the schedule that your vet recommends. 

For adult pets, this generally means administering monthly heartworm prevention. An annual heartworm preventative injection for dogs is also available from your vet. If in doubt, speak to your vet who will be able to recommend an appropriate worming product for your pet. Prevention is safe, effective and more affordable than cure.

Even when a pet is on regular heartworm prevention, annual testing for heartworm is recommended 

In cases where a pet is sick due to heartworm, management relies on administering an appropriate anthelmintic (antiparasitic medications), as well as supportive care to manage the symptoms. Your veterinarian will be able to discuss the best treatment plan for your pet with you. 

How much does it cost to treat?

According to PetSure claims data in 2020, the average single treatment cost relating to Heartworm was $258 with the highest single treatment cost being $884.  

Disclaimer: Reimbursement for these claims would be subject to limits, such as annual benefit limits or sub-limits, benefit percentage, applicable waiting periods and any applicable excess. Cover is subject to the policy terms and conditions. You should consider the relevant Product Disclosure Statement or policy wording available from the relevant provider.


  1. American Heartworm Society, “Heartworm Basics”, accessed on 27/11/20
  2. NexGard, “What is Heartworm Disease”, accessed on 27/11/20
  3. Greencross, “Heartworm Signs, Treatment and Prevention”, accessed on 27/11/20

Terms, conditions, waiting periods, limits and exclusions apply. is issued by The Hollard Insurance Company Pty Ltd ABN 78 090 584 473, AFSL 241436, is arranged and administered by PetSure (Australia) Pty Ltd ABN 95 075 949 923, AFSL 420183 (PetSure) and is promoted and distributed by PetSure’s Authorised Representatives (AR) Pet Insurance Pty Ltd ABN 38 607 160 930, AR 1234944 and Pet Culture Pty Ltd ABN 69 644 613 098, AR 001284860. Any advice provided is general only and does not take into account your individual objectives, financial situation or needs. Please consider the Product Disclosure Statement (PDS) to ensure this product meets your needs before purchasing. PDS and Target Market Determination available at .

Cat Flea, Tick & Worming

Kylie Mitchell

Kylie Mitchell


Kylie Mitchell is a veterinarian with over 17 years experience in animal health and welfare, including in the veterinary and pet insurance industries

She has three rescue cats (Noah, Bei Bei and Meeka), four very old cockatiels and a pond-full of fish.

Kylie Mitchell's Pets

  • MeekaMeeka
  • Bei BeiBei Bei
  • NoahNoah

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