02652naa a2200361 a 450000100080000000500110000800800410001902400380006010000210009824501320011926000090025152016140026065000200187465000170189465000310191165000140194265000150195665000130197165000170198465000170200165000160201865000190203465000180205365000250207165000100209665000180210665300170212465300180214165300150215970000210217470000160219577300790221115220562023-07-25       1976    bl uuuu     u00u1 u    #d7 a10.1016/0020-7519(76)90037-02DOI1 aLE JAMBRE, L. F.  aResistance of selected lines of Haemonchus contortus to thiabendazole, morantel tartrate and levamisole.h[electronic resource]  c1976  aAbstract: A field strain of Haemonchus contortus isolated from sheep at Armidale N.S.W., was found to be resistant to thiabendazole with approximately 20 per cent of the worms surviving a 50 mg/kg dose. The isolate was selected over six generations for resistance to 50 mg/kg thiabendazole. After this time, selection on one line was continued at 50 mg/kg thiabendazole and selection on a second line was extended to include 8·8 mg/kg morantel tartrate. A drug tolerance assay on the third generation of the thiabendazole-morantel tartrate selected line showed the ld5o to be 5·3 mg/kg and the ld95 to be 18 mg/kg morantel tartrate; the reported ld50 and ld95 for non-resistant strains of H. contortus to morantel tartrate are 2·5 mg/kg and 8 mg/kg respectively. In the fourth generation the thiabendazole and the thiabendazole-morantel tartrate selected lines together with a recently isolated field strain were assayed for resistance to thiabendazole, morantel tartrate and levamisole. The results indicated that the resistance to thiabendazole was probably due to a single gene. Both selected lines were more resistant to thiabendazole than the field strain. The thiabendazole-morantel tartrate selected line was more resistant to morantel tartrate than either of the other two. Resistance to morantel tartrate appeared to be polygenic in nature and due to increased vigour. The lowest dose of levamisole (1·6 mg/kg) killed more than 95 per cent of all strains of worms. There was no significant increase in effectiveness at higher dose rates indicating that surviving worms were resistant to the drug.  aDrug resistance  aDrug therapy  aGastrointestinal nematodes  aHelminths  aLevamisole  aMorantel  aParasitology  aPharmacology  aPyrimidines  aSheep diseases  aThiabendazole  aHaemonchus Contortus  aOvino  aParasitologia  aDrug effects  aHaemonchiasis  aNematodeos1 aSOUTHCOTT, W. H.1 aDASH, K. M.  tInternational Journal for Parasitologygv. 6, n. 3, p. 217-222, Jul. 1976.