Field evaluation of anticoccidial efficacy: A novel approach demonstrates reduced efficacy of toltrazuril against ovine Eimeria spp. in Norway

Publication date: August 2018Source: International Journal for Parasitology: Drugs and Drug Resistance, Volume 8, Issue 2Author(s): Ane Odden, Matthew J. Denwood, Snorre Stuen, Lucy J. Robertson, Antonio Ruiz, Inger Sofie Hamnes, Lisbeth Hektoen, Heidi L. EnemarkAbstractOvine Eimeria spp. infections cause reduced welfare, increased mortality, and substantial economic losses, and anticoccidials are crucial for their control. Recent reports of toltrazuril resistance in pigs, and anecdotal reports of reduced anticoccidial efficacy in lambs, necessitate evaluation of anticoccidial efficacy. Due to the substantial lifecycle differences between nematodes and coccidia, current WAAVP methods for assessing anthelmintic efficacy are not suitable for such evaluations. Faecal samples were collected from 8 pairs of twin lambs from 36 Norwegian sheep farms 6–8 days after turnout. One twin of each pair was then treated with 20 mg/kg toltrazuril and a second faecal sample from all lambs was collected 7–11 days later. Oocyst excretion rate in all samples was determined using McMasters. Suitability of treatment timing was investigated by evaluating the increase in mean log oocyst excretion in untreated lambs. Based on comparisons between groups, a threshold of ≥0.75 (13 farms) was used to identify farms where drug efficacy could be assessed with confidence, drug efficacy on farms with increases of ≥0.5 but <0.75 (7 farms) were evaluated with caution, and drug efficacy on farms wi...
Source: International Journal for Parasitology: Drugs and Drug Resistance - Category: Parasitology Source Type: research