According to findings from the 2016 National Equine Health Survey, almost a third of owners are using the wrong wormer, or one to which there is widespread resistance when they treat their horses for encysted small redworm.
Experts from animal health company Zoetis
confirmed the accuracy of these findings, stating that misunderstandings about
worming remain commonplace.
Severe infestations of encysted small redworm larvae can lead to fatal disease. Treatment should be regardless of the results of faecal worm egg counts as these tests do not show the presence of encysted small redworm.2
More than 77% of respondents to the 2016 NEHS intended to treat their horse for encysted small redworm. But of the 89% of respondents who could remember what they used, only 68% of these actually used an effective product.
The remaining 32% used a product not indicated to treat for the encysted larval stages of these parasites or used a product for which there is widespread evidence of resistance.
The survey also showed that 68.4% of those who specified how they treated for encysted small redworm had correctly used moxidectin either as solo therapy or in combination with praziquantel.
Just over 5% had used a five-day course of Fenbendazole, a product which is licensed but for which resistance has been widely documented.2
However, of the remainder, 19% had used ivermectin and 7.5% had used other products, none of which are licensed or effective against encysted small redworm.
Encysted small redworm kills horses every year, particularly young animals or those with an incorrect worming regime,” said Wendy Talbot, vet at Zoetis.
She recommended owners needing more information should speak to their vet or SQP (suitably qualified person).
References: 1NEHS The National Equine Health Survey, conducted by the Blue Cross and supported by Zoetis, was completed by 5635 horse owners and keepers in May 2016, with records returned for 16,751 horses. The survey contained questions on general horse health, care and management and was validated by Professor Josh Slater of the Royal Veterinary College. 2Matthews (2008) Equine Veterinary Education, p 552-560.