Wormer Classes for Cattle and Sheep - Understanding the Basics

Understanding the main wormer classes

There can be a lot of confusion around wormer classes...

"Should I use a blue wormer next?"

"Will that kill fluke too?"

Over the next couple of weeks, we'll look within each of the wormer classes in a bit more detail. Before we do that, it's important to note a couple of points on wormers.

• Every wormer belongs in a worm class - think of it as a family. Related wormers in the same class share similar modes of action and chemical structures.
• There are three wormer classes in cattle; Benzimidazoles (aka. white wormers), Levamisoles (aka. yellow wormers) and Macrocyclic Lactones (aka. clear wormers).
• In sheep, we have these three and a further two more: Amino-acetonitrile derivatives (orange wormers) and Spiroindoles (purple wormers).
• When we talk about wormers, we are referring to products that treat the main internal worms - stomach, gut and lungworm in cattle and the main gastrointestinal worms in sheep. All wormers in all classes should be effective against these. Yes, other internal worms will be killed - but for the most part, these are not of importance from production or welfare points of view.
• Some wormers also kill other parasites, e.g. Albendazole also kills adult liver fluke and the clear wormers have action against external parasites like lice and mites.
• Do not identify a wormer by the physical colour of the solution - e.g. "this drench is white so it must be a white wormer". Lots of mineral, fluke and coccidiosis drenches appear white, but will have no efficacy against worms.
• Look for the symbols/letters (e.g. 1-BZ) shown in the video above when identifying the class your product is in.

Product examples

White wormer

Yellow wormer

Clear wormer

Understanding the main wormer classes

There can be a lot of confusion around wormer classes...

"Should I use a blue wormer next?"

"Will that kill fluke too?"

Over the next couple of weeks, we'll look within each of the wormer classes in a bit more detail. Before we do that, it's important to note a couple of points on wormers.

• Every wormer belongs in a worm class - think of it as a family. Related wormers in the same class share similar modes of action and chemical structures.
• There are three wormer classes in cattle; Benzimidazoles (aka. white wormers), Levamisoles (aka. yellow wormers) and Macrocyclic Lactones (aka. clear wormers).
• In sheep, we have these three and a further two more: Amino-acetonitrile derivatives (orange wormers) and Spiroindoles (purple wormers).
• When we talk about wormers, we are referring to products that treat the main internal worms - stomach, gut and lungworm in cattle and the main gastrointestinal worms in sheep. All wormers in all classes should be effective against these. Yes, other internal worms will be killed - but for the most part, these are not of importance from production or welfare points of view.
• Some wormers also kill other parasites, e.g. Albendazole also kills adult liver fluke and the clear wormers have action against external parasites like lice and mites.
• Do not identify a wormer by the physical colour of the solution - e.g. "this drench is white so it must be a white wormer". Lots of mineral, fluke and coccidiosis drenches appear white, but will have no efficacy against worms.
• Look for the symbols/letters (e.g. 1-BZ) shown in the video above when identifying the class your product is in.