EquiDiary
Guide · Australia

Horse worming schedule (Australia): egg counts, resistance, and a climate that never resets

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Last reviewed 12 October 2026

Most Australian horses are still wormed the way they were twenty years ago: a tube every six to twelve weeks, a different brand each time. In a 2020 survey of 102 properties, 85 percent dosed at intervals of twelve weeks or less, and fewer than three percent used an egg count to decide. Australia now has its own worming guidelines, and they ask for something quite different.

This is a summary of published guidance, not veterinary advice. The 2025 guidelines are written for vets, and a worming program is something to set with yours. Products and labels change; read the current label before you dose.

In the UK or the US? Read the UK worming guide or the US deworming guide instead. Their seasons run the other way and their wormers are supplied differently.

Australia has its own guidelines now

In 2025 the Australian Equine Parasitology Advisory Panel published the Australian guidelines for equine internal parasite management in the Australian Veterinary Journal. The Australian Veterinary Association's own policy says the same thing more bluntly: routine interval or rotational worming is outdated, and treatment should follow faecal egg counts, timed to the spring and autumn peaks in transmission.

The guidelines sort adult horses by the strongyle eggs they shed, counted as eggs per gram (EPG) of manure:

Egg countShedding bandAdult treatments a year
under 200 EPGlowa foundation treatment, usually one or two a year in spring and autumn, with a tapeworm drug in one of them
200 to 500 EPGmoderatetwo to four, guided by follow-up counts
over 500 EPGhightwo to four, guided by follow-up counts

Two things make this workable rather than expensive. The bands describe how many eggs a horse puts on the pasture, not how many worms it carries, and most adult horses are consistent: three or four well-timed counts across a year establish where a horse sits, and testing can ease off after that. And the distribution is lopsided. Usually only 10 to 30 percent of adult horses are high shedders, which means most of a typical paddock's horses have been wormed far more often than they needed.

Why: the drugs are failing here too

The guidelines exist because the old approach wore out the drugs. A national study published at the end of 2023 ran 86 faecal egg count reduction tests on 22 Thoroughbred farms. Against small strongyles, ivermectin cut egg counts by only 82 to 92 percent, abamectin by 73 to 92, moxidectin by 89 to 91, oxfendazole by 0 to 56, and oxfendazole with pyrantel by 0 to 82. In 31 tests where a drug still looked effective at two weeks, eggs were back within four to six weeks, sooner than those drugs normally allow.

Two years earlier the same group reported the first evidence of moxidectin-resistant and multi-drug-resistant small strongyles in Australia, on Thoroughbred farms in Victoria. The Australian Veterinary Association now states that resistance to all three major drug classes has been reported in this country.

How you would know on your own property. A faecal egg count reduction test: count eggs before treatment and again 14 days after. The guidelines set it out for vets in detail, with horses shedding at least 200 EPG and a lab method sensitive enough to count them. A wormer that does not cut the count is not working, whatever the drum says.

Foals are a separate problem

Young horses carry roundworm (Parascaris), and it has gone furthest. In the national study, ivermectin cut roundworm egg counts by 10 to 43 percent, and abamectin and moxidectin did nothing measurable. Earlier work found ivermectin failing on three of five farms in southern New South Wales, and only 65 percent effective in weanlings in south-east Queensland.

The plan for foals is therefore not the adult plan. The Australian Veterinary Association, citing the guidelines, advises not treating before two months of age unless threadworm is a concern, treating at two and five months with a combination of a pyrantel-class drug and a benzimidazole, and deciding after that on whether roundworm eggs are present. Horses aged one to three may need three or four strongyle treatments a year; mature horses often only one or two. Because roundworm has no low-shedder strategy to fall back on, some interval dosing in young stock is likely to remain.

A climate that never resets

British and American advice leans on winter: cold kills larvae on pasture and gives the year a clean start. Much of Australia never gets one. The guidelines note that many regions allow worm larvae to survive on pasture all year. Warm, moist weather speeds their development and mild weather keeps them alive longer, which makes south-east Queensland, with summer rain and warm springs and autumns, highly favourable to them. The hot, dry summers of south-west Western Australia are the opposite, and hard on them.

Two practical consequences. The peaks fall in spring and autumn, so a northern-hemisphere guide's months are six months out. And pasture hygiene does a lot of the work: the guidelines suggest picking up manure two to three times a week in the warmer months.

Tapeworm is rarer than the drench label suggests

Combination wormers that include praziquantel are everywhere, but the guidelines put tapeworm prevalence in Australian horses below five percent. One study found eggs in 0.5 percent of horses, and tapeworm DNA on 3.9 percent of farms. No praziquantel resistance has been reported here. That is why the guidelines fold a tapeworm drug into one foundation treatment a year rather than every dose.

Over the counter, with a warning on the label

Unlike the UK, where wormers are supplied by vets, pharmacists or qualified retailers, Australian horse wormers are bought off the shelf at produce and saddlery stores as easily as from a vet. What comes with them is the label: the APVMA's labelling code requires every registered horse wormer to carry a resistance warning, advice to consult a vet, and a recommendation to test for resistance before treating. Dosing is to weight, and a 2026 survey of Pony Club families found that 42 of 98 had guessed their horse's weight. An underestimated horse is an underdosed horse, and underdosing is how resistance is bred.

Why the plan drifts

A count-based program is a list of dates and numbers: when each horse was last counted, what it shed, what it was given, and whether the count fell afterwards. Kept in someone's head or on the feed-room whiteboard, it collapses back into "every eight weeks or so", which is exactly the habit the guidelines are trying to replace. The count from last spring is only useful if it is still there this spring.

Keep the counts where the horse is

EquiDiary keeps each horse's egg counts, treatments and products in one history. Log the faecal egg count with its result, log the wormer with the product and the date, and the record does the remembering. Put each horse's foundation treatment on a rhythm in the care schedule and a morning email says when it is due. Your vet, your agistment manager and you all see the same page.

Start free for 3 months

Sources

Guidance is revised periodically; check the current edition before relying on it, and confirm the program with your vet.

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