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Types of Horse Wormers

2nd October 2017

When it comes to protecting your horses and ponies, you want the best possible treatments and products available.

But, with so many distinct brands and makes of horse wormers out there, how do you know which is best for you?

We’ll guide you through the types of horse wormers on the market so you can pick the best choice for you and your animals.

Types of Horse Wormers

There are four main groups of horse wormers, based on the ingredients they use:

Macrocyclic Lactones (includes Ivermectin and Moxidectin)

Ivermectin is a great all-purpose horse wormer as it treats more types of parasites than any other kind of wormer, including lungworm.

Moxidectin is a medication designed to target encysted small strongyle and is the only one of its type. The downside is it is easy to overdose small or weakened horses using this wormer.

Benzimidazoles (includes Fenbendazole, Mebendazole and Oxibendazole)

Some worms have developed partial resistance to these horse wormers but this can be partly offset by using higher dosages or repeat treatments.

In more recent times, this type of treatment has declined in use in favour of other types of wormers.


An effective treatment against tapeworms, although you may need to use a double dosage to get a high kill percentage.


This is one of the two medications available that is effective against tapeworms.

Within each of these groups, there are six common chemicals that are used to treat worms in horses.

Each chemical combination will treat a different type of worm.


Ivermectin Fenbendazole Pyrantel Oxibendazole Praziquantel Moxidectin
Bot Larvae        
Large Roundworms          
Large Strongyles  
Small Strongyles  
Large-mouthed Stomach Worms          
Stomach Hair Worms        


While this table will help you to narrow down your choice of horse wormer, it is not definitive.

There are some additional things you will need to consider:

1) Both Ivermectin and Moxidectin can be used to treat parasitic bot fly larvae. However, Moxidectin is effective only effective on larvae in the second stage.

2) Invermectin is effective against all three stages of parasitic bot fly larvae, all forms of large strongyles, and against adult and larvae stages, with the exception of encysted larvae.

3) Praziquantel is effective against all three species of tapeworm

4) Fenbendazole and Pyrantel are not effective against all three species of tapeworm

5) Moxidectin is the only medication effective against all stages of small strongyles and is effective against all forms of large strongyles except the adult form (strongylus equinus)

6) Fenbendazole, Pyrantel, and Oxibendazole will only treat the adult version of large strongyles

As you can see, there is no one-size-fits-all solution when it comes to horse worms.

To offer complete protection for your horses and ponies, you will need to combine medications, as well as monitor the peak times of year for treatment and prevention.

Combining Medication

Some wormers will use a combination of ingredients to tackle a variety of worms. However, do not use multiple types of wormer products at the same time. Doing so could run the risk of overdosing your animal.


Rotating your medications is a better option of you are concerned about overdosing. This allows you to switch up the different types of horse wormers you use to offer better protection all year round.

For further information, please download a copy of our Horse Worming Calendar.

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