Seasonal patterns of strongyle infections in grazing sheep under the traditional production system in the region of Trikala, Greece

Ten 4-month-old female sheep of the Karagouniko dairy breed were used to mo nitor the seasonal fluctuations of strongyle infections in sheep during the first year of grazing under the traditional production system in the regio n of Trikala, Greece, where control of nematodes is currently based exclusi vely on the frequent use of anthelmintics which might contribute to the app earance of anthelmintic resistance, The sheep grazed communal pasture plots and did not receive any anthelmintic treatment during the entire study per iod. Faecal egg counts (epg), plasma pepsinogen levels, blood values, and g enera of parasitic strongyles recovered from coprocultures were recorded mo nthly. Mean epg for strongyle-type eggs were significantly higher during su mmer. Mean plasma pepsinogen levels were significantly higher during spring and summer. The genera of parasitic strongyles recovered from the faecal c ultures were Haemonchus, Ostertagia, Trichostrongylus, Cooperia, Nematodiru s, Oesophagostomum, and Chabertia. The percentages of larvae for Haemonchus , Ostertagia, Cooperia, and Oesophagostomum were significantly higher durin g winter. The percentages of larvae for Trichostrongylus were significantly higher during summer. During summer, levels of RBC, HGB, and HCT were depr essed and levels of MCV, MCH, and MCHC were elevated. Mean epg for strongyl e-type eggs had a significant inverse correlation with RBC, HGB, HCT, and p ositive correlation with MCH, MCHC, and percentages of eosinophils in diffe rential leucocyte counts. The seasonal pattern of infection observed in the present study indicates that it is possible to decrease the number of trea tments to one per year, thus, reducing the possibility for the appearance o f anthelmintic resistance. (C) 2000 Elsevier Science B.V. All rig hts reser ved.