[Control of gastrointestinal helminthiasis in pasture-reared lambs]

Two sheep herds kept in different geographic conditions with spring lambing by the end of March and April (herd No. 1: 400 ewes, 600 metres above sea level; herd No. 2: 450 ewes, 300 metres above sea level) were examined. The dynamics of gastrointestinal nematode and Moniezia spp. cestode egg counts in samples taken regularly every 4 to 5 weeks was studied during the year 1995 with the intention to verify the system of effective control of these helminth infections under pasture conditions of lamb rearing. In ewes a significant rise in gastrointestinal nematode egg counts was proved during the lambing season, "spring rise phenomenon", and during the summer pasture until autumn months with maximum EPG values reaching 150 (Figs. 1 and 2). In lambs that started grazing at 1 to 4 weeks of age, the excretion steeply rose to maximum EPG values 350 and 290, respectively, after 4 to 5 weeks of grazing (Figs. 1 and 2). In order to control these rising infections, ewes were treated with antihelmintic albendazol by the end of February (herd No. 1) and in March (herd No. 2) and lambs during the first or third decade of July. This anthelmintic treatment significantly lowered egg excretion to EPG values lower than 30 in ewes and 50 or 60, respectively, in lambs. Later, during the summer and autumn months, a mild rise of egg counts was found in lambs. These maxima were liquidated anthelmintis treatment in both herds in late autumn months and it also lowered helminth infections to minimum during winter months (EPG values lower than 50). The excretion of Moniezia spp. eggs had the same dynamics as that gastrointestinal nematodes. Values of lamb infection prevalence reached 21% in herd No. 1 and 29% in herd No. 2. Anthelmintic treatment during July controlled cestode findings in lambs. Albendazol (Vermitan susp. 2.5%), dosed 5 mg/kg of body weight, proved highly effective in the control of gastrointestinal nematodes and Moniezia spp. cestodes.