There's no doubt rates of heartworm infection in Australia have dropped in the past 10 years. However, once confined to tropical regions, heartworm has now spread to southern regions of Australia and, as a disease that can be fatal to our four-legged friends, there is a growing need to raise awareness in pet owners, and reinforce the fact that prevention is key.

Prevention is Easy

According to a 2015 survey of 1600 Australian dog owners, as many as 64% of pet owners admitted to administering monthly heartworm prevention medication after it was due - leaving their dogs at risk of contracting heartworm. More alarmingly, while 99% of surveyed pet owners admitted knowing heartworm can be fatal to their pets, 8% did not use any prevention at all and 48% missed doses all together.

The good news is, prevention for both dogs (and cats) is easy. But before we get into that, let's take a look in more detail at heartworm.

What is heartworm?

Heartworm - or Dirofilariaimmitis - is carried and spread amongst certain species by mosquitos, in much the same way Malaria is spread by mosquitos in humans. Mosquitos bite an infected animal, ingesting microscopic heartworm larvae which are circulating in the blood of the infected animal. They develop further within the mosquito before being passed on to another host when the mosquito next bites an animal, which may be your beloved dog.

Once in its host, the heartworm matures, moving through the tissues, into the bloodstream and finally into the heart, by which time they are around 20-30cm in length. This can take around six months. At this stage, the adults will mate, producing millions of microscopic larvae, which again beging circulating the host's bloodstream.

Heartworm becomes fatal in host species (e.g. dogs, foxes), when hundreds of heartworms clog up the heart chamber and artery leading into the lungs - something that can take up to three years after initial infection.



How do I know if my dog has heartworm?

Because of the lifecycle of heartworms, it can take many years before the first symptoms appear. According to Vet Supply, heartworm is most commonly diagnosed in dogs aged between three and eight.

When they do start to show symptoms, tiredness and intolerance to exercise is often the first sign. During later stages, coughing, collapse, weight loss, bleeding from the nose and fluid retention can be symptoms.

It's worth noting that, while cats can be infected with heartworm, they are not a typical host as heartworm larvae don't survive to the adult stage. Sadly, this doesn't mean that heartworm isn't a significant problem for cats as infection can result in coughing, wheezing, difficulty breathing, lethargy and weight loss.


How can I prevent heartworm in my pet

If you have not been administering heartworm prevention medication to your dog, it's important to get him tested. Even if your dog is infected, your vet will be able to start treatment with chaces of survival extremely good in a dog showing little to no clinical sign of the infection.

You can choose from monthly chewable treats or spot on preparations to give to your dog, but if remembering to administer heartworm medication on a monthly basis is too much, you can now take advantage of an annual heartworm prevention injection, which can be administered alongside your pet's regular annual vaccinations. If you have just brought home a new puppy, the annual vaccination can be administered in those as young as three months, but will need to be administered again at six and 12 months of age.

Do I need to administer medication when I don't live in the tropics?

Put simply, yes. While heartworm is more prevalent in regions of North East Queensland, it has been detected in 9% of foxes in Sydney surrounds and 7% of foxes in Melbourne surrounds. This means there is a clear source of infection for city pets, and if your pet is not protected, it risks infection. Furthermore, heartworm affects up to 80% of totally unprotected dogs and 30% of dogs who have not received regular heartworm prevention.

We hope this month you will remember the impact heartworm can have on our beloved community of domestic pets, and take steps to test and prevent heartworm in your four-legged family.