Tag: Heartworm is a serious

If you’re a pet owner in Keysborough, there’s a good chance you’re already on top of flea treatments and intestinal worms. But here’s the thing: heartworm disease is a completely different beast, and many pet owners don’t even know their current flea and worm products don’t cover it.

Heartworm is a serious, potentially fatal condition that quietly damages your pet’s heart and lungs, sometimes for years, before any signs appear. The good news? It’s almost entirely preventable. The not-so-good news? If you’ve let prevention lapse, you can’t simply restart it without seeing a vet first.

This guide covers everything Keysborough pet owners need to know about heartworm disease, including how it spreads, what it does to your pet’s body, and what heartworm prevention actually looks like in Australia.

What Is Heartworm Disease and How Is It Different from Other Worms?

Heartworm disease is caused by Dirofilaria immitis, a parasitic worm that lives in the heart, lungs, and blood vessels of infected animals. Unlike intestinal worms, heartworm is not picked up from the environment or passed between pets directly. It spreads through mosquito bites, which makes it a very different kind of threat.

This distinction matters a lot for pet owners. Intestinal worms like roundworms, tapeworms, hookworms, and whipworms are covered by most standard worming products. Heartworm is not. Many heartworm preventatives also protect against intestinal worms, but the reverse is not true. If your dog or cat is only on a basic worming tablet, they are not protected from heartworm.

Here is a quick comparison to clear things up:

Is Heartworm a Risk in Keysborough and Victoria?

This is where a lot of Melbourne pet owners get it wrong. The general assumption is that heartworm is a “northern problem,” a concern for people in Queensland or the Northern Territory. And while it is true that the prevalence of heartworm disease is much higher in tropical and subtropical regions, that doesn’t mean Victorian pets are safe.

Research on foxes in the Melbourne surrounds found that around 7% carry heartworm, acting as a source of infection for city pets, suggesting that any pet not on heartworm prevention could have roughly a one-in-ten chance of being infected. 

Climate change is now increasing the risk of mosquito populations growing in Melbourne and across Victoria, with higher temperatures, higher humidity, and more extreme rain events contributing to the problem. Notably, the Australian backyard mosquito (Aedes notoscriptus) is the main vector for heartworms in dogs, and changing conditions are giving this species a leg up in southern regions. 

Dogs travelling interstate, particularly to Queensland or New South Wales, face a much higher risk. Studies of shelter dogs in Townsville found heartworm infection rates as high as 22%, compared to around 1.1% in Brisbane dogs tested by standard methods. If your dog accompanies you on interstate trips or holidays, this is a real consideration.

The bottom line for Keysborough: the risk in Victoria is lower than in the north, but it is not zero, and it is growing. And because heartworm is a slow-onset disease, the consequences of assuming you’re safe can show up years down the line.

How Heartworm Is Transmitted: The Mosquito Connection

Understanding how heartworm spreads helps explain why prevention is so important, and why it needs to be year-round.

Here is how the lifecycle works:

1. A mosquito bites an infected dog and picks up microscopic heartworm larvae (microfilariae) from the bloodstream.

2. Inside the mosquito, the larvae develop through a larval stage over approximately two weeks.

3. When that infected mosquito bites your pet, the heartworm larvae are deposited under the skin.

4. The larvae then migrate through the tissues and enter the bloodstream, eventually reaching the heart and the vessels going to the lungs.

5. Over the next six months, they mature into adult worms.

A few important things to note:

• Indoor pets are not fully protected. Mosquitoes enter homes, and it only takes one mosquito bite.
• There is a six-month gap between infection and detectability on a blood test, meaning heartworm can be silently developing without any clinical signs.
• Without effective heartworm prevention, heartworms may be silently and dangerously developing in your pet with no signs for up to five years.

This is what makes heartworm disease so insidious. By the time you notice something is wrong, significant damage may already have been done.

Clinical Signs of Heartworm: Often Absent Until Severe

One of the most concerning things about heartworm is that in the early stages, there are no obvious symptoms. Many dogs show nothing at all while the disease progresses internally.

As the worm burden grows and damage accumulates, clinical signs of heartworm disease begin to appear. Here is how it typically unfolds:

• Early to mid stages:
• Slight lethargy or a cough that doesn’t go away
• Reduced exercise tolerance (your dog tyres more easily than usual)
• Weight loss without an obvious reason
•  Late stages:
• Persistent coughing and laboured breathing
• A pot-bellied appearance due to fluid accumulation
• Signs of heart failure

Advanced or severe cases:

• Sudden collapse
• Caval syndrome (where the sheer number of worms blocks blood flow from the heart to the lungs)
• Death

The signs of heartworm disease in cats are different and often even more alarming. Cats with heartworm may show respiratory distress similar to asthma, or they may simply collapse and die without any prior warning. Sudden death is more common in cats than in dogs, and there is no approved treatment for cats once infection occurs.

The brutal truth: by the time most pet owners notice something is wrong, the damage is already significant. Early detection through routine veterinary checks is really the only safety net.

Heartworm Prevention for Dogs and Cats: Options and How They Work

The good news is that heartworm prevention is highly effective, widely available, and far less complex than treatment. The Australian Heartworm Advisory Panel recommends that all dogs be on year-round heartworm prevention, regardless of where they live in Australia.

Here are the main options available:

Monthly Oral Tablet
How It Works: Eliminates heartworm larvae before they develop into adults
Frequency: Every 30 days

Monthly Topical Spot-On
How It Works: Applied to the skin and absorbed into the bloodstream for protection
Frequency: Every 30 days

Annual Heartworm Injection (ProHeart SR-12)
How It Works: Slow-release moxidectin provides continuous protection against heartworm
Frequency: Once yearly

In Australia, prevention can involve monthly topical or oral preventatives, or annual injections of extended-release moxidectin (ProHeart SR-12), and poor compliance with any of these products can leave dogs susceptible to infection.

The annual injection is particularly popular in Australia because it removes the risk of forgetting a monthly dose. It ties in neatly with your dog’s yearly wellness visit, meaning one appointment covers heartworm prevention for the entire year.

A critical point: if prevention has lapsed, do not simply restart it without seeing a vet first.

If there has been a gap in your pet’s heartworm prevention, a blood test is needed before restarting any preventative product. Giving heartworm prevention to a dog that already has an active infection can trigger a dangerous reaction as the larvae die rapidly in the bloodstream. Your veterinarian needs to confirm your pet is clear before recommending the next steps.

Puppies should start heartworm prevention from around six to eight weeks of age, though the specific product and timing will depend on your vet’s recommendation. Adult dogs that have never been on prevention, or that have had a gap, need to be tested first.

The team at Keysvet in Keysborough can advise you on the right product and schedule at a wellness visit, including whether your current flea and worm product also protects against heartworm. Many heartworm preventatives also protect against intestinal worms, so it is worth reviewing what your pet is currently on.

Heartworm Treatment: Why Prevention Is the Best Option

If prevention is the easy path, treatment is the hard one. And it really is the best course of action to avoid it altogether.

Treating heartworm disease in dogs is a long, difficult, and risky process. Here is what it typically involves:

• A course of antibiotics (doxycycline) to weaken the worms
• A series of arsenic-based injections (melarsomine) is administered into the muscle over several months to kill the adult worms
• Strict rest and exercise restriction for weeks, because activity during treatment causes dead worms to fragment and lodge in the lung blood vessels, which can be fatal
• Multiple follow-up blood tests and veterinary visits to monitor recovery

The heartworm treatment is demanding on your dog’s body, and while most dogs do survive with proper veterinary care, complications can and do occur. The enforced rest period alone is extremely difficult for active dogs and their owners.

As for cats, the situation is even more serious. There is no approved treatment for heartworm in cats. Management is palliative, meaning the goal is to keep the cat as comfortable as possible while the infection runs its course.

Prevention is the best option always.

Should You Ask Your Vet About Heartworm? Yes, Especially If You’re Unsure

Here is a checklist that might help you work out where you stand:

• Do you know whether your current flea and worm product covers heartworm? (Many don’t, so check the label or ask your vet.)
• Has your dog or cat had a gap in their prevention in the last six to twelve months?
• Have you recently adopted a pet with an unknown medical history?
• Does your dog travel interstate, particularly to Queensland or northern New South Wales?
• Has your pet never been on heartworm prevention?

If you answered yes to any of these, it is worth having a conversation with your veterinarian. A simple blood test can confirm whether your pet has been exposed, and from there, your vet can recommend the right path forward, whether that’s a preventative product, a heartworm injection, or further investigation.

Diagnosing heartworm can be challenging in the early stages because the disease takes months to show up on standard tests. This is another reason why prevention is so much better than waiting to find a problem.

To book a wellness visit at Keysvet in Keysborough, call (03) 9798 7274. The team can review your pet’s current parasite prevention, check whether heartworm is covered, and make sure your dog or cat is protected year-round.

Learn more about our Flea & Worm services and Vaccination & Wellness visits to see how we can keep your pet healthy from the inside out.

Frequently Asked Questions About Heartworm in Dogs and Cats

Is heartworm common in Victoria? 

It is less common than in northern Australia, but the risk is real. Research on foxes in the Melbourne surrounds found heartworm in around 7% of animals, and climate change is extending the mosquito season in Victoria each year.

Does my dog’s monthly worming tablet cover heartworm? 

Most standard worming tablets do not cover heartworm. Check your product label or ask your vet, as some combination products do include heartworm protection.

Can cats get heartworm? 

Yes. Heartworms in cats behave differently from dogs, but even one or two adult worms can cause serious illness. Sudden death is more common in cats, and there is no approved treatment, so prevention is essential.

What happens if I miss a month of heartworm prevention? 

A short gap may not lead to infection, but it increases the risk. If the gap has been longer than a month or two, see your vet before restarting prevention, as a blood test may be needed first.

How does the annual heartworm injection work? 

The ProHeart SR-12 injection uses slow-release microspheres that gradually release a protective compound over 12 months. It is not a vaccine but a long-acting preventative, and it is administered by your vet once a year, making it very convenient for busy pet owners.