01969naa a2200205 a 450000100080000000500110000800800410001910000250006024501620008526000090024752013070025665000210156365000160158465000150160065000230161570000150163870000200165370000180167377300720169120950772018-09-04       1993    bl uuuu     u00u1 u    #d1 aECHEVARRIA, F. A. M.  aSurvival and development of ivermectin-resistant or susceptible strains of Haemonchus contortus under field and laboratory conditions.h[electronic resource]  c1993  aThe free-living development of three strains of Haemonchus eontortus was studied in two experiments. Day 21 faecal samples were collected from lambs infected with either a susceptible strain, a laboratory-selected ivermectin (~M) resistant strain or a South African field strain showing multiple anthelmintic resistance, which included IVM. No eggs hatched in samples cultured at 4 or 10°C. At 22°C the laboratory-selected strain showed the highest rate of development while at 27°C the susceptible strain produced the highest yield of third stage larvae (L3): at both temperatures the field strain showed the lowest percentage development to L3. The second experiment was a field study carried out in southern Brazil. Faeces containing either an tOM-SUsceptible or an Iwa-resistant strain of H contortus were placed in two series of grass plots during each of three summer months. Soil subsequently yielded more larvae than did grass suggesting migration or mechanical transport into the soil. For plots contaminated during the first two months there was no significant difference in recovery rate between the two strains (P &gt 0-05). When contamination occurred during the third month, the IVM-resistant strain produced significantly higher recovery rates (P &lt 0"05) from both pasture and soil.  aAnti-Helmíntico  aMedicamento  aNematóide  aParasito de Animal1 aARMOUR, J.1 aBORBA, M. F. S.1 aDUNCAN, J. L.  tResearch in Veterinary Sciencegv. 54, n. 2, p. 133-139, Mar. 1993.