Van Schalkwyk, P.C.Visser, Evelyn L.Alves, Regina M.R.Gerber, H.M.Verwoerd, Daniel Wynand2014-10-022014-10-0220141989Van Wyk, JA, Van Schalkwyk, PC, Gerber, HM, Visser, EL, Alves, RMR & Van Schalkwyk, L 1989, 'South African field strains of Haemonchus contortus resistant to the levamisole/morantel group of anthelmintics', Onderstepoort Journal of Veterinary Research, vol. 56, no. 4, pp. 257-262.0330-2465http://hdl.handle.net/2263/42219The articles have been scanned in colour with a HP Scanjet 5590; 600dpi. Adobe Acrobat XI Pro was used to OCR the text and also for the merging and conversion to the final presentation PDF-format.A strain of Haemonchus contortus from the Pietermaritzburg district of Natal was found to be resistant to levamisole (geometric mean efficacy 76,5 %), morantel (41,9 %), the benzimidazoles (oxfendazole: 33,7 %) and rafoxanide (82,0% ), but apparently fully susceptible to closantel and disophenol. In the case of ivermectin, a mean of 5.2 % of the H. contortus was not removed at a dosage of 200 µg kgˉ¹ live mass. A second strain of H. contortus, from Amsterdam in the south-eastern Transvaal, showed reduced susceptibility to levamisole (80,8%) and morantel (46,2% ), the only 2 drugs tested. This is apparently the first report of resistance to the levamisole/morantel group of anthelmintics in sheep in South Africa.en©ARC - Onderstepoort and Faculty of Veterinary Science, University of Pretoria (original). ©University of Pretoria. Dept. of Library Services (digital).Veterinary medicineVeterinary medicine -- South AfricaArticle