The traditional approach to deworming treatment varies little from the recommendations established 30 years ago – purge deworming through the administration of a paste dewormer every six to eight weeks, or, rotational deworming through the use of two or more different purge dewormers, at set intervals.
Continuous dewormers that are added to daily grain rations, like Strongid C, are also common. However, manufacturers of continuous dewormers now recommend supplementing their products with paste dewormers two to four times a year to effectively control small strongyles and tapeworms.
As with many medications, a rising concern with dewormers is drug resistance. Each year more and more farms are diagnosed with “super worms”, resistant to many of the standard deworming products. In addition, the recommendation of “routine” deworming unnecessarily exposes horses with low parasite burdens to harsh chemical treatments.
As implied by their name, purge dewormers use chemicals to kill off parasite populations. This means every six to eight weeks horses are exposed to low-grade poisons – whether they need it or not. It is not uncommon for horses to have small reactions to synthetic paste dewormers varying in severity from swollen glands and skin reactions to colic and laminitis.
Paste dewormers have their place and are still occasionally necessary to maintain a healthy horse. However, it is important to reevaluate their use and avoid scheduled administration without knowing a horse’s specific parasite burden.
The most important step owners can take in parasite management is a simple fecal egg count (FEC). Before paste dewormers became customary, parasite management always began with an FEC to determine if treatment was necessary. Reintroducing this small step can reduce drug resistance, increase effectiveness and minimize exposure to harmful chemicals by only treating horses with high parasite burdens. To learn how to do an FEC, please read our post on Fecal Egg Counts.