BENZIMIDAZOLE RESISTANCE IN SMALL STRONGYLES OF HORSES - OCCURRENCE IN GERMANY AND STRATEGIES FOR AVOIDING RESISTANCE

DRUDGE and LYONS described for the first time the occurrence of benzim idazole (BZM)-resistant strains of small strongyles (Cyathostomidae) i n the U.S.A. in 1965. In the meantime, in Germany as well as in other European countries anthelmintic control of strongyles has become incre asingly difficult because of side-resistance within the BZM group. Tri als which were carried out in Germany during the 1992 pasture period p roved that BZM resistant small strongyles are regionally distributed a nd, once they have occurred, persist for years in the respective horse stables. In order to avoid development of resistance, rotating anthel mintic products has been recommended. However, new research questions the reliability of this strategy where equine small strongyles are con cerned.