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Survey of anthelmintic resistance in Western Australian sheep flocks 1. Prevalence
Author(s) -
EDWARDS J R,
WROTH R.,
CHANEET G C,
BESIER R B,
KARLSSON J.,
MORCOMBE P W,
DALTONMORGAN G.,
ROBERTS D.
Publication year - 1986
Publication title -
australian veterinary journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.382
H-Index - 59
eISSN - 1751-0813
pISSN - 0005-0423
DOI - 10.1111/j.1751-0813.1986.tb02950.x
Subject(s) - levamisole , anthelmintic , flock , trichostrongylus , haemonchus contortus , veterinary medicine , nematodirus , biology , teladorsagia circumcincta , feces , helminths , zoology , medicine , ecology
SUMMARY Between July 1981 and December 1983, 116 randomly selected sheep farms in the south west of Western Australian were surveyed for resistance to anthelmintics. A faecal worm egg count reduction test was carried out on each farm. Anthelmintics tested were thiabendazole (44 mg/kg) and levamisole (7.5 mg/kg) given by intra‐ruminal injection and comparisons were made with an untreated group on each farm. Successful tests were carried out on 84 farms and 68% of these had resistant worms present. The prevalence of thiabendazole resistant populations was for H. contortus 18%; Teladorsagia , 41% and Trichostrongylus , 48% and for levamisole resistant populations H. contortus , 10%; Teladorsagia , 41%; Trichostrongylus 24% , and Nematodirus , 10%. Multiple resistant populations were found on 17% of farms. Although the distribution of nematode genera varied between the 400 to 750 mm and the greater than 750 mm rainfall zones there was no significant difference in the prevalence of resistance between zones. About one third of resistant populations were severely resistant (< 60% reduction). It is likely that resistant worms were present on many farms without causing clinical disease and continued anthelmintic selection pressure will result in further development of resistance.