A strategic dosing scheme for the control of fasciolosis in cattle and sheep in Ireland

This study examined the effectiveness of a strategic dosing scheme in lower ing the incidence of fasciolosis on a mixed dry-stock farm and in maintaini ng the reduced incidence following a reduction in dosing intensity. Two nei ghbouring farms with a history of chronic fluke disease were selected, the strategic dosing scheme being implemented on one:(the trial farm) while the other (the control farm) continued to treat according to its normal practi ce. The strategic dosing scheme was designed to suppress the faecal egg out put of Fasciola hepatica at critical times of the year in order to limit in fection of the intermediate host snail population and thus reduce the subse quent contamination of the pasture with metacercariae. On the trial farm ca ttle and sheep were treated three times per year for the first 2 years at a pproximately 8 week intervals, starting in March of each year. A fourth tre atment was given when the cattle were housed and out-wintered sheep receive d an additional treatment in January. In Years 3 and 4 the dosing intensity was reduced. By the end of Year 2, data from faecal egg counts, tracer-she ep fluke burdens and snail infection levels indicated that the treatment st rategy had succeeded in suppressing the fluke population and eliminating th e occurrence of clinical fasciolosis. The decrease in dosing intensity in:Y ears 3 and 4 maintained both stock and snail infections at low levels and t here was no re-emergence of the disease. (C) 2000 Elsevier Science B.V. All rights reserved.