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1992-94 first cases of ivermectin
resistance to Cooperia in cattle
reported
1996 - 16 identified cases of BZ
resistance in cattle, mostly Cooperia
1996-97 - sheep -BZ resistance 68%,
LEV 42% and combination
BZ+LEV 39% of farms
1999 - first 2 cases of ivermectin
resistance in sheep confirmed
(Ostertagia)
1999 - first case of ivermectin (+BZ
and ?+ LEV) resistance in
Trichostrongylus colubriformis
confirmed in goats and sheep