Keeping up with heartworm prevention all year round is one of the simplest things you can do to protect your dog from a potentially fatal disease. In Australia's warm, humid climate — where mosquitoes thrive well beyond summer — even a single missed dose of heartworm medication for dogs can leave a dangerous gap in protection. Here's why consistency matters and how to stay on track every month of the year.
How Heartworm Spreads in Australian Conditions
Heartworm disease is caused by the parasite Dirofilaria immitis, which is transmitted through the bite of an infected mosquito. When a mosquito feeds on an infected animal, it picks up microscopic larvae. Those larvae are then deposited into your dog's skin the next time that mosquito bites.
Once inside, the larvae migrate through your dog's body over several months, eventually maturing into adult worms that lodge in the heart and pulmonary arteries. Left untreated, heartworm can cause severe heart failure, lung damage, and organ compromise.
In Australia, mosquitoes are active across a much longer season than many pet owners realise. Northern regions like Queensland and the Top End see mosquito activity virtually year-round, while even southern states like Victoria and Tasmania experience unpredictable warm spells during autumn and winter that keep mosquitoes biting.
What Actually Happens When You Skip a Month
Monthly heartworm preventatives work retroactively — they eliminate larvae that entered your dog's body during the previous 30 days. They don't create a protective barrier going forward. This is a critical distinction most owners miss.
When you skip a dose, any larvae deposited by mosquitoes during that unprotected window get a free pass to keep developing. After roughly 51 days, larvae mature to a stage that most monthly preventatives can no longer kill. By the time you resume dosing, it may be too late to stop those worms from reaching adulthood.
The scary part? There are no visible symptoms in the early stages. A dog can harbour developing heartworm for months before showing signs like coughing, lethargy, or exercise intolerance. By then, significant damage may already be done.
Why a Year-Round Approach Beats Seasonal Dosing
Some owners in cooler parts of Australia assume they can pause heartworm medication for dogs during winter. The logic seems sound — fewer mosquitoes, less risk. But the reality is more complicated.
Australia's climate is increasingly unpredictable. A run of warm days in July is all it takes for dormant mosquito populations to surge. Urban environments with standing water, garden ponds, and poor drainage provide breeding grounds regardless of the calendar.
Maintaining heartworm prevention year round eliminates the guesswork entirely. You don't need to monitor mosquito forecasts or gamble on the weather. Consistent monthly dosing ensures that any larvae picked up at any time of year are dealt with before they can do harm.
Quick tip: Set a recurring monthly reminder on your phone for the same date each month. Pairing the dose with another routine — like the first of the month or rent day — makes it almost impossible to forget.
There's also a financial argument. Preventing heartworm costs a fraction of what treatment for an established infection involves. Prevention is measured in dollars per month; treatment can run into thousands and carries real risks to your dog's health during the process.
Choosing the Right Heartworm Medication for Your Dog
There are several effective options for keeping your dog protected. Monthly chewables are among the most popular — they're palatable, easy to administer, and many also cover intestinal worms. Brands like Heartgard have been trusted by Australian dog owners for years and offer reliable, broad-spectrum protection in a tasty chew.
When browsing flea, tick, and worm products for dogs, look for options that combine heartworm prevention with protection against other common parasites. Many modern treatments cover heartworm, roundworm, hookworm, and whipworm in a single monthly dose, simplifying your dog's parasite control routine.
Consider your dog's size, age, and temperament when choosing a format. Some dogs take chewables like treats. Others may do better with spot-on topical treatments. The best product is the one you can administer consistently — because consistency is everything with heartworm prevention.
Tips for Staying on Schedule
Life gets busy, and it's easy to let a dose slip by a few days — or worse, a few weeks. Here are practical strategies to keep your dog's heartworm protection airtight:
- Buy in bulk: Purchase a 6- or 12-month supply so you're never caught short. Having the next dose already in the cupboard removes a common excuse for delays.
- Use a calendar or app: Mark dosing dates clearly. Many pet health apps send automatic reminders.
- Store products visibly: Keep the box near your dog's food or treats so it stays top of mind.
- Dose on the same date monthly: Pick a date and stick with it. If you're a day or two late occasionally, administer the dose as soon as you remember and continue on your regular schedule.
If you realise you've missed a dose by more than two weeks, give the next dose immediately and then continue monthly from that new date. For extended gaps of two months or more, have a conversation with your vet about whether testing is needed before resuming.
Frequently Asked Questions
Can dogs in southern Australia skip heartworm prevention in winter?
It's not recommended. While mosquito activity drops in cooler months, warm spells can trigger unexpected mosquito breeding even in Melbourne, Hobart, or Adelaide. Maintaining protection year round is the safest strategy, and it avoids the risk of forgetting to restart when the weather warms up.
How quickly can heartworm develop if I miss a dose?
Larvae deposited by a mosquito bite can mature beyond the reach of monthly preventatives in as little as 51 days. That means missing just one dose gives larvae enough time to advance to a stage where standard monthly products may not eliminate them. Early-stage heartworm infection shows no outward symptoms.
Do heartworm chewables also protect against fleas and ticks?
It depends on the product. Some heartworm chewables focus solely on heartworm and intestinal worms, while others offer broader coverage. Check the product label or browse our dog flea, tick, and worm range to compare what each product covers so you can build a complete parasite protection plan.
Protecting your dog from heartworm doesn't have to be complicated — it just has to be consistent. If you're unsure which product suits your dog best, have a quick chat with your vet, then stock up on trusted heartworm prevention from our Heartgard range so you're covered every single month.