In general, there is resistance to all the currently available equine dewormers, which is why parasite egg counts are important for horses, says parasitologist Martin Nielsen.
“There are no safe choices out there — we’ve got to get on to the testing. That is the only way forward.
“How else would you know if what you’re actually doing is working? If you use a wide range of dewormer products, you’re very likely to have resistance to at least one of them.
“And it could be more than just one.”
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