Field comment on anthelmintic resistance of sheep nematodes

Authors: Seifert DA, Hughes PL
Publication: New Zealand Veterinary Journal, Volume 31, Issue 10, pp 183-184, Oct 1983
Publisher: Taylor and Francis

Animal type: Livestock, Production animal, Ruminant, Sheep
Subject Terms: Abdomen, Alimentary system/gastroenterology, Animal remedies/veterinary medicines, Anthelmintics, Parasite control, Parasites - internal, Nematode, Treatment/therapy
Article class: Correspondence

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Abstract: Following a general trend in sheep practice we have been involved in a number of parasitological investigations in lambs over the last summer-autumn period. We would like to record the emergence of a resistance problem and comment on the use of total worm counts. This is the first season that worm resistance has been recorded in this country as a definite cause of clinical disease although its presence has previously been noted in survey work. The significance of this development was highlighted on one property in this practice. This property is involved with ram breeding and each year 600 ram lambs have been brought onto a separate 100 acre block and kept there from weaning until two tooth sale. Twenty heifers and, over tupping, 120 ewes are the only other stock farmed on this block. The lambs are drenched on the day of transfer but subsequent drenching is not accompanied by a change of pasture. On the initial visit (1st Feb. 1983), the lambs were found as a group to be in poor condition but approximately 25% showed severe ill thrift and were diarrhoeic. Blood samples (six) showed these animals to be severely anaemic with marginal Se levels. The lambs has been drenched with benzimidazoles at weaning and at intervals of 16, 11, 13 and 13 days afterwards; this frequency reflecting the poor responses being obtained…

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