Page 80 - The Veterinary Care of the Horse

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ANTHELMINTIC RESISTANCE
In the UK, there is widely recognized resistance of small strongyles to fenbendazole and

increasing resistance to pyrantel. Reduced egg reappearance times have been reported
following treatment with ivermectin or moxidectin, which can be a sign of emerging

resistance. Ascarid worms are also showing resistance to ivermectin, moxidectin and pyrantel
with a reduced time before egg reappearance after treatment. The more frequently the various

wormers are used, the greater the likelihood of the worms becoming resistant to them. It is
therefore important to use the drugs as sparingly as possible.

WORMING INTERVAL

There are two recognized ways of using worming preparations:

1 Strategic treatment
2 Targeted treatment

Strategic treatment