| Summary: | Seasonal occurrence of gastrointestinal helminths was studied in ten replacement ewe lambs/young ewes in a flock of sheep in E Iceland from the round-up day 23 September 2002 until autumn of the next year, by performing faecal egg counts on 16 occasions. The lambs never received antiparasitic drugs. Five types of eggs were identified, corresponding to the four species Moniezia expansa, Trichuris ovis, Nematodirus filicollis and N. spathiger, as well as the group collectively known as “other strongyles”, which in sheep in this part of Iceland are comprised of the species Teladorsagia circumcincta, Trichostrongylus axei, T. capricola, T. vitrinus, Chabertia ovina and Oesophagostomum venulosum (Richter 2002). The seasonal occurrence of the helminths was markedly influenced by the farm managing practice characterized by a short (one to two weeks) grazing period stay of sheep on home pastures after parturition in late May and a long summer grazing period at low stocking rates on mountainous rangelands. After herding back to the lowlands in late September, sheep are grazed on home pastures until housing in late autumn with hay feeding for approximately six months. Usually, the lambs acquired the M. expansa, T. ovis, N. filicollis and N. spathiger infections after their return to home pastures in September; consequently these infections peaked during late autumn and early winter. “Other strongyle” infections confirmed in the four-month old lambs in September, upon their return from the summer rangelands, were either acquired on the farm in spring or in the sparsely grazed summer rangelands. According to Richter (2002) Teladorsagia and Trichostrongylus predominate in the group “other strongyles”. In general, worm egg counts in the present study revealed markedly lower values than reported in previous studies from Iceland. A distinct M. expansa egg excretion peak in late winter suggests that the cestode maintained its life cycle indoors on the farm. Fylgst var með árstíðabreytingum iðraorma í tíu ásetningsgimbrum á ...
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