Ivermectin Could be Ineffective Against Some Pinworms
Targeted deworming practices should continue to be the treatment of choice in managing equine intestinal parasites.| iStock
As reports of intestinal parasite resistance to drugs increases, owners and veterinarians are heading toward more targeted approaches for managing worms. But French researchers suggest that targeted treatment with ivermectin might be overlooking a nuisance worm: the pinworm.

Ivermectin is a currently used treatment against cyathostomins (small strongyles) and other life-threatening parasites. But it was ineffective in treating a herd of Welsh ponies against Oxyuris equi (pinworms) at a French research center over the course of three years.

Fenbendazole, however, eliminated the worms, which can cause anal itching and tail-rubbing, said Guillaume Sallé, DVM, PhD, of the French National Agricultural Institute (INRA), in Nouzilly, France.

“The targeted treatment strategy that’s generally recommended (with ivermectin) aims to control strongyles, against which the drug fenbendazole is no longer effective,” said Sallé. “However, fenbendazole is still every effective against ascarids (roundworms) and Oxyures (pinworms). It’s possible that by reducing the treatment load, we’re favoring a greater prevalence of Oxyures

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