Ivermectin foal worm warning

Ivermectin should not be the drug of choice for controlling Parascaris equorum (large roundworm) in foals a recent study warns.

The National Veterinary Institute, Uppsala, Sweden, investigated the occurrence of Parascaris equorum infection on nine stud farms in Sweden and assessed the efficacy of three commonly used dewormers on fecal egg output.

The most striking result from this study was that "in five studs out of six, ivermectin failed to suppress the faecal output of P. equorum eggs" (Osterman-Lind and Cristensson Report).

"Ivermectin resistance is now a widespread problem in Swedish stud farms."

They advise that instead of ivermectin, fenbendazole or pyrantel are now the drugs of choice for use against P. equorum.

"It is important, however, that the anthelmintic efficacy is monitored routinely by a faecal egg count reduction test (FECRT)". "In the long-term it is also necessary to incorporate non-chemo-therapeutic methods to a greater extent to control parasite infections on stud farms."

Source:
Anthelmintic efficacy on Parascaris equorum in foals on Swedish studs.
Eva Osterman Lind, Dan Christensson
Acta Veterinaria Scandinavica (2009) 51, 45
doi: 10.1186/1751-0147-51-45

Written by Mark Andrews. Published online 28.01.10
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Equine Science Update
Reports from the world of equine research.