Last Updated: 05/05/2025
Looking for the best wormer for your horse? See our vets recommendations depending on your horse's age weight and time of year.
Author: Dr Maree Monaghan BVSc (Hons)
Reading Time: 50 minutes - long read
With so many horse wormers to choose from with a myriad of different active ingredients, how do we know which one to give our horses? THPs, BZs, Mectins, Praziquantel - what do all these names mean? Our vets have written the following guide to help cut through the confusion and identify which horse wormer to use and when to use it.
Gone are the days of using one type of horse wormer for one year and then changing to a different type the next year. Research has shown that this approach has contributed to the development of resistance in worms to some classes of wormers. These days, we know that worming programmes for horses should be based on the lifecycle of the different types of worms, the risk of the horse being infected with a particular type of worm and any likely resistance of the worms to each class of wormer.
The key to a successful worm control program for horses lies in checking their manure for worm eggs with a test called a faecal egg count. Faecal egg counts can identify which horses are shedding the most worm eggs on to the pasture and, if used after worming, can be used to determine if the wormer you are using is effective. Speak to your veterinarian about how to do a faecal egg count for your horse.
Using the correct wormer at the right time is only a small part of a successful worm control program. Pasture management is the most critical factor in controlling worms on horse properties. This involves removing manure from paddocks on a regular basis, avoiding overstocking, resting paddocks to reduce contamination with worm eggs, quarantining and worming all new horses that arrive on the property and cross grazing horse paddocks with sheep and/or cattle.
Four factors to consider when choosing a wormer for your horse:
The age of the horse: Foals are at significant risk of disease due to roundworm infections and they should receive their first worming treatment at around 8 weeks of age. All horses less than 5 years old are more likely to have significant worm burdens than horses between 5 and 15 years of age as horses develop immunity to worms over time. Horses over 15 years of age become increasingly more susceptible as their immunity wanes.
The weight of horse/s to be treated:
The most common mistake horse owners make when treating their horses for worms is under or overestimating their horse's bodyweight. It isn't easy to access a set of scales that are capable of weighing your horse, however, with the aid of a tape measure and some mathematical calculations, it is easy to get a fairly accurate idea of your horse's weight. Measure your horse in centimetres around their "heart girth" and their length from the point of the shoulder to the point of their buttock. Multiply heart girth by heart girth by length and divide by 11877 to get your horse's weight in kilograms.
The time of year: Unfortunately, in most parts of Australia, seasonal conditions are ideal for the development of parasites for most of the year, however, Spring and Autumn are always critical times to treat horses for worms. The different life cycles of worms means that they will be most active in the horse at different times of year e.g. bots and strongyles ( redworms) in the cooler months. It is critical to ensure that the active ingredient you use will kill the species of worms that are likely to be infecting your horse at each particular time of year.
The active ingredients in the product: Horse wormers contain either a single active ingredient or a combination of ingredients from four different chemical classes.
Tetrahydropyrimidines or THPs (Pyrantel and Morantel): This class of chemicals treats a variety of worms including some tapeworms but does not treat bots. Horses under 2 years of age should be treated with a wormer containing Pyrantel or Morantel because they are reliably effective against roundworm.
Benzimidazoles or BZs (Oxfendazole, Oxibendazole and Fenbendazole): This group treats the majority of worms in horses except bots and tapeworms. There is resistance to this class of chemical in small strongyles when used on their own, however they are useful for the treatment of mectin resistant worms when used in combination with other classes of wormers.
Macrocyclic Lactones or Mectins (Abamectin, Ivermectin and Moxidectin) treat a wide range of parasites, however, they do not treat tapeworm and roundworm are commonly resistant to this class of chemical.
Isoquinolines (Praziquantel) This ingredient is used in combination with other classes of chemicals in horse wormers because it is very effective against tapeworms.
Results:
Our Pet Circle Vet Squad comprises 30 vets with over 120 years of collective, independent veterinary expertise. Our Vet team use their health and husbandry knowledge, along with their own personal and clinical experiences to evaluate each product and provide detailed, informative reviews, free of any commercial bias. We then collate this information into our 'best of' recommendations.
Ammo Rotational Wormer is a palatable, broad spectrum wormer that is safe and easy to use in foals. It has a wide safety margin and is also suitable for yearlings, stallions and pregnant mares. Ammo Rotational Wormer is perfect to use for treatment of mectin resistant worms as it contains a benzimidazole (Oxfendazole) as the only active ingredient. Contamination of pastures with worm eggs is a serious concern on properties that breed and run youngstock, so Ammo Rotational Wormer's ability to sterilise worm eggs within 24 hours of dosing is ideal in these situations.
What our customers say: "Great price compared to other horse stores. Great when you have to buy for several horses."
What our vets say: "Ammo Rotational Wormer is ideal for treating foals as it is effective against ascarids (roundworm) which are a significant cause of disease in foals." - Dr. Josepha
Equimax is Australia's most trusted broad spectrum wormer for horses. It contains a combination of abamectin and praziquantel which makes it ideal for targeting bots, skin parasites and tapeworm during the cooler months. Equimax is formulated in a palatable oatmeal paste and one syringe treats up to 700 kg.
What our vets say: "Equimax Wormer Paste is a safe and easy-to-dose macrocyclic lactone class of wormer. It covers a broad spectrum of intestinal parasites, and can be safely used in different age groups for foals, pregnant mares and breeding stallions." - Dr. Nicole
Strategy T is the ideal wormer to use in rotation with a mectin wormer as it combines a benzimidazole (Oxfendazole) and a THP (Pyrantel). These two classes of chemicals have a synergistic effect which means that the combination of the two is more effective than treatment with both these chemicals separately. Strategy T is recommended for use in Spring because it targets the parasites that are more active as the weather warms up.
What our customers say: "Best rotational wormer, easily taken by my horses it isn't runny so no mess. Really improves the condition of horses with a worm burden. Gentle on tummies so no scours after treatment"
Equimax Elevation is a broad spectrum, easy to use worm paste that controls all equine worms, bots, lungworms, intestinal threadworms, tapeworms and skin parasites (summer sores and neck threadworms). It is recommended for treating horses under 2 years of age in autumn and winter to guard against mectin resistance in parasites.
What our customers say: "Highly recommend this product to kill parasites. Certainly will be repurchasing this product. Thank you"
Equimec Plus Tape Wormer Gel is a broad spectrum wormer that contains Praziquantel - the only type of worming chemical that kills tapeworm. There are several species of tapeworm that affect horses in Australia and are spread by pasture mites. These mites ingest tapeworm eggs from horse manure which develop into larvae and horses become infected by eating pasture mites in pasture, hay or straw. Adult tapeworms attach to the junction of the small and large intestine (ileocaecal valve) where they cause inflammation of the gut wall and physical obstruction of the gut resulting in colic.
What our customers say: "Handle on the tube makes it really easy to administer, horse seemed to love the taste too, low volume so not heaps for the horse to swallow!"
Equimec Paste is a broad spectrum low dose volume worm paste with a wide safety margin. It is ideal to use in the cooler months to target bots along with the parasites, Habronema, Draschia spp, and Onchocerca spp. which cause skin lesions. Bots aren't actually worms but rather the larvae of Gasterophilus spp flies - those annoying bee like flies that lay yellow eggs on horses' which are very difficult to remove. Bot fly larvae attach to the wall of the horse's stomach where they cause ulcers. It is recommended to treat for bots at the end of Autumn after a frost that has killed the adult flies.
What our customers say: "Excellent price for a great product"
The larvae of small strongyles (redworms) can "hibernate" by forming cysts in the lining of a horse's intestine. They do this when environmental conditions are not favourable for them to reproduce by developing into adults and laying eggs that are passed out on to pasture. These larvae can stay encysted for up to 2 years and be protected from worm treatments. The most serious consequence of this behaviour is the emergence of large numbers of larvae from their cysts in late Winter and Early Spring. The damage that these emerging larvae cause to the intestinal mucosa leads to chronic diarrhoea, colic, anorexia and weight loss. Horses of any age are susceptible to infection with strongyles at any time of year, so treatment of these worms is very important.
What our vets say: "Small strongyles are a very common parasite in horses. Unfortunately, these are very hardy parasites that can stay encysted (hibernate) for up to 2 years in a horse's gut and when they emerge, can cause serious illness in some cases. Because of this, it's important to not just target adult strongyles but the encysted stage as well and Equest Plus Tape Wormer Gel is a wormer that is effective as a single dose against this. It's a broad-spectrum wormer that also targets the other major intestinal parasites, making it a fantastic choice as part of an effective rotational worming strategy for your horses" - Dr. Tony
Razor is safe to use in all horses, including foals, pregnant mares and breeding stallions. It is ideal for treating very large horses like Clydesdales and Warmbloods as well as being a convenient and economical way to treat groups of horses. The combination of Ivermectin and Praziquantel provides effective coverage of the major internal parasites that affect horses in Australia.
Different types of worms require particular active ingredients for their control. When choosing a horse wormer, firstly identify the worms that are most likely to be infecting your horse and purchase a wormer that contains active ingredients that will kill these worms.
Wormers come in a variety of sizes and dose rates, so it is important to make sure that the wormer you purchase will be enough to cover the bodyweight of the horse.
As we all know, there are some horses that absolutely hate being treated with a wormer. To make life a little easier for you and your horse, choose a low volume paste or gel.
Want to know more? Check out our Discover Page for more tips from our expert vets on keeping your horse happy and healthy.
