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.