The aim of this work was to verify the possible activity of copper oxide wire particles against reinfection by gastrintestinal nematodes in sheep under extensive grazing. Thirty-two sheep, all wethers, aged 18 months and kept on native pastures naturally contaminated by trichostrongylides were used. The animals were weighed and treated with anthelmintics and then allocated to four experimental groups: T I (treated with copper and necropsied on Day 28), T II (untreated control and necropsied on Day 28), T III (treated with copper and necropsied on Day 56), T IV (untreated control and necropsied on Day 56). Groups T I e T III received, per os, a 4g bolus containing 3.4g of copper oxide wire particles. The animals were monitored, at weekly intervals, for faecal egg counts (EPG), packed cell volume (PCV), aspartate aminotransferase (AST) and plasma copper concentration. At necropsy, worm burdens, liver copper concentration and liver weights were determined. There were no differences in plasma copper levels between treatments (P>0.05). As for copper in the livers, all treated groups had higher levels than the untreated animals (P<0.05). Plasma AST activity was slightly higher during the experimental period in the treated groups. However, significant difference was only detected between treatments T I e T II (P<0.05). There were no significant differences in EPG counts between treated and control groups (P>0.05). Worm counting at necropsy revealed that copper was effective only against Haemonchus contortus and only in the animals slaughtered on Day 28º where the reduction was 60% in comparison to the untreated group (P<0.05). It is believed that in this experiment copper did not reach toxic levels as there were no significant differences in PCV, plasma copper concentrations, liver weights and body weights (P>0.05). It is concluded that 3.4g of copper oxide wire particles can have a significant action in reducing reinfections by H. contortus during four weeks without toxicity to animals under conditions of extensive grazing.
copper; nematode; Haemonchus; sheep; control
