24/05/2026
Why Parasitologists Get Nervous About Routine Moxidectin Use?
Moxidectin is one of the most valuable worming ingredients we have in horses — and that’s exactly why parasitologists are so cautious about overusing it.
It’s incredibly effective, including against encysted small redworm larvae (cyathostomes) — parasite stages that don’t show up on a standard faecal egg count but can cause serious disease when they emerge.
But there’s a catch.
The more often worms are exposed to any wormer, the more pressure we place on them to develop resistance.
Long-acting products can increase that selection pressure because worms are exposed to low levels of drug over extended periods. That means the worms most able to survive the treatment are the ones left behind to reproduce.
And once resistance develops, we can’t undo it.
Resistance to moxidectin has already been identified internationally and in Australia, which is why preserving its effectiveness matters so much.
That’s why many parasitologists get nervous about routine or unnecessary moxidectin use — especially when it’s being used simply because:
* it’s convenient,
* long acting,
* “stronger,”
* or on special.
A product being long acting or heavily discounted doesn’t automatically make it the best choice for every horse or every property.
But Here’s The Important Part…
This does not mean moxidectin is “bad.”
In fact, moxidectin is one of our BEST wormers.
That’s exactly WHY we want to protect it.
So When Is Moxidectin Appropriate?
Moxidectin absolutely has an important place in modern parasite control.
Situations where it may be appropriate include:
* Annual autumn treatment targeting encysted small redworm larvae
* Horses at higher risk of encysted cyathostominosis
* Younger horses or consistently high shedders
* Properties with significant pasture contamination pressure
* Cases where season, history, testing, or clinical signs suggest larvicidal treatment may be beneficial
* Situations where your vet or parasite management plan specifically recommends it
In many adult horses with low-to-moderate FECs, ivermectin or abamectin may adequately target the adult worm burden without unnecessarily using one of our most valuable larvicidal actives.
What About Environmental Impact?
Environmental impact matters too, and some studies suggest differences between worming actives and their effects on dung fauna such as dung beetles.
That’s an important conversation to have — but resistance preservation and strategic use are still critical parts of sustainable long-term parasite control.
The Goal
The goal isn’t to avoid moxidectin forever.
The goal is to:
✔ use it when it offers a genuine benefit
✔ avoid unnecessary exposure
✔ preserve its effectiveness for the future
✔ make treatment decisions based on testing, risk, season, and the individual horse
Because smart parasite control isn’t about using the strongest product all the time.
It’s about using the right product, at the right time, for the right reason.
🧪 Smart. Strategic. Science Based.