Rotation Of Wormers / Drenches

Horses

There is some controversy regarding the value of anthelmintic rotations, however, parasitologists generally recommend annual rotation of anthelmintic drug classes. The rationale is that an effective wormer from a different class may kill worms that were resistant to the anthelmintic class used at the previous treatment. It is important that all the classes of drugs used in a rotational program retain their effectiveness on the individual property.

Sheep and Goats

It is generally recommended to rotate among effective drench classes either annually or each time a mob is drenched. Drench rotation is particularly recommended if anthelmintic combinations are not routinely used. When combination drenches are used, the current drench would ideally not contain any drug from a drench class that was used in the last drench, but given the limited number of drench classes, the best that you might achieve is for the current drench to contain at least one drug from an effective drench class that was not used in the last drench. It you are drenching with a flukicide, it is also recommended to rotate from one flukicide to another at each drenching time. Overall, however, the most critical factor is that the drenches that you use have been shown to be effective on your property (FECR test).

Horses, Sheep and Goats

When you rotate, ensure that you are changing the anthelmintic drug class and not just the product,and use the FECR test to make sure that the new drug class is effective in killing the worms on your property.