Until now, it has been common practice to routinely deworm horses with tapeworm dewormer, regardless of whether the horse has a tapeworm burden or not. In a routine deworming approach, horses are dewormed once or twice a year, traditionally during the spring and autumn. Deworming programmes such as these inevitably lead to worms building up resistance to dewormers. Resistance is essentially the ability of worms to survive the killing effects of deworming drugs. A build-up of widespread resistance would have devastating consequences, especially as there are only two drugs available for the control of tapeworm in horses. These drugs are praziquantel and pyrantel embonate (double dosed). See the table below for information on which dewormers control tapeworm.
Resistance to dewormers
Using routine deworming approaches, horse dewormers (anthelmintics) are often over-used in the equestrian community. It is thought that the majority of worms are present in just a small percentage of the horse and pony population, and the unnecessary, widespread dosage of dewormers in horses is now causing drug resistance.
With increasing reports of anthelmintic resistance in small redworms (cyathostomes), special attention should be paid to the management of tapeworm in horses, to ensure resistance does not build in tapeworm as well. Frequent use of dewormers puts tremendous selection pressure on the worms to adapt to survive this continuous onslaught and the result is a relentless, steady emergence of resistance. Additionally, under-dosing your horse also encourages resistance, as an insufficient dose which does not kill all of the worms, exposes surviving worms to the drug, giving them the opportunity to adapt and develop resistance.
Targeted deworming approach for tapeworm
Regular EquiSal Tapeworm testing now provides the means to adopt a targeted deworming approach for tapeworm. It is recommended that horses diagnosed as borderline or moderate/high are dewormed for tapeworm whilst those with a low diagnosis do not need deworming. Many horse-owners are already using a targeted deworming approach for redworms and roundworms, basing the use of dewormers on faecal egg counts which determine whether a horse has a worm burden that demands treatment.
Research has shown that a targeted worm control programme using the EquiSal Tapeworm saliva test controlled tapeworm infections and reduced the use of tapeworm dewormers at Bransby Horses. The published study reports the findings from 237 horses tested over the course of a year. Testing with EquiSal Tapeworm and only deworming horses with a diagnosed infection reduced the use of tapeworm dewormers by 86% compared to 6 monthly routine deworming strategies. Bransby’s vet consultant, Jeremy Kemp-Symonds, says “EquiSal has become integral to our targeted tapeworm control programme and has contributed to the very significant decline in tapeworm infection that we have achieved in recent years.” For more information click here.
The key message is to carry out routine testing and not routine deworming, reserving the use of dewormers for when they are recommended following diagnosis of a worm burden. It should be noted however that no diagnostic test is available for encysted redworm so all horses should be given an autumn/winter deworming dose with a product containing moxidectin.