Levamisole- and tetramisole-resistant gastrointestinal nematodes in sheep
Praslicka, J.; Pilko, P.; Várady, M.; Corba, J.
Veterinarni Medicina 40(2): 45-48
1995
ISSN/ISBN: 0375-8427 PMID: 7740715 Document Number: 454875
Two experiments were carried out with sheep naturally infected with gastrointestinal nematodes to evaluate efficacy of anthelmintics using in vivo faecal egg count reduction (FECR) test. In experiment 1 with 28 ewes, the following efficacy of anthelmintics given at recommended dose rates was observed: albendazole 99.4%, ivermectin 99.3% and levamisole 81.8%. In experiment 2 with 18 ewes, tetramisole exhibited 71.3% efficacy. Suspected resistance to imidothiazole anthelmintics was confirmed by in vitro larval development test (LDT)--minimal inhibition concentration (MIC) values were estimated at 2.0 micrograms/ml. Infective larvae L3 cultivated from eggs produced by the population of resistant helminths were identified as Ostertagia and Trichostrongylus spp.