ANTHELMINTIC RESISTANCE - CURRENT STATUS IN FRANCE

In France, anthelmintic resistances have been identified only in sheep and goat parasites. Dairy ewes and lactating ewes with lambs fattened indoors are not exposed to resistance because few treatments are give n each year, lambs never go to pasture and do not recycle larvae. Lact ating ewes living in the open-air (or << semi-open-air >>) are quite e xposed to resistance because the lambs are not immunized and therefore recycle parasites. This requises the farmer to use anthelmintics very often during the year. Then in areas where this production exists, so me cases have been identified : 2 000 000 of the french ewes (40 % of the population) and their lambs are exposed to anthelmintic resistant worms. Benzimidazoles and Pro-benzimidazoles are involved. Thirty-seve n << resistant >> strains isolated from fecal egg count reduction test (F.E.C.R.T.) have been checked by in vitro egg hatch test. This demon strated that 56,5 % were resistant (Resistance Ratio > 5), 41 % showed low level resistance (RR < 5) and 2,5 % sensitive (RR less-than-or-eq ual-to 1). In goat farming, risks are widespread. There is no recyclin g of parasite by kids but the number of treatments per year is often v ery high and the ovine dose which is licenced is badly adjusted to goa ts' metabolism. Resistance has been demonstrated in some areas. Ten << resistant >> strains isolated from F.E.C.R.T. have been checked by in vitro egg-hatch-test: 60 % were resistant, 20 % showed low level resi stance and 20 % were sensitive. Prevention of resistance is briefly ov erviewed.