This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.Page 1 interactions that depend on animal and parasite species, (ii) their feasibility under field 28 conditions, (iii) appropriateness of study design, and (iv) the low analytic sensitivity of the 29 recommended faecal egg count (FEC) method. Therefore, the objective of the present study 30 was to empirically assess the impact of the level of excretion and aggregation of FEC, sample 31 size and detection limit of the FEC method on the sensitivity and specificity of the FECRT to 32 detect reduced efficacy (<90% or <95%) and to develop recommendations for surveys on 33 anthelmintic resistance. A simulation study was performed in which the FECRT (based on the 34 arithmetic mean of grouped FEC of the same animals before and after drug administration) 35 was conducted under varying conditions of mean FEC, aggregation of FEC (inversely 36 correlated with k), sample size, detection limit and "true" drug efficacies. Classification trees 37 were built to explore the impact of the above factors on the sensitivity and specificity of 38 detecting a truly reduced efficacy. For a reduced-efficacy threshold of 90%, most 39 combinations resulted in a reliable detection of reduced and normal efficacy. For the reduced-40 efficacy threshold of 95% however, unreliable FECRT results were found when sample sizes 41 <15 were combined with highly aggregated FEC (k = 0.25) and detection limits ≥5 EPG or 42 when combined with detection limits ≥15 EPG. Overall, an increase in sample size and mean 43 preDA FEC, and a decrease in detection limit improved the diagnostic accuracy. FECRT 44 remained inconclusive under any evaluated condition for drug efficacies ranging from 87.5% 45 to 92.5% for a reduced-efficacy-threshold of 90% and from 92.5% to 97.5% for a threshold of 46Page 3 of 19 A c c e p t e d M a n u s c r i p t 3 95%. The results highlight that (i) the interpretation of this FECRT is affected by a complex 47 interplay of factors, including the level of excretion and aggregation of FEC and (ii) the 48 diagnostic value of FECRT to detect small reductions in efficacy is limited. This study, 49 therefore, provides a framework allowing researchers to adapt their study design according to 50 a wide range of field conditions, while ensuring a good diagnostic performance of the 51 FECRT. 52

No abstract

No abstract

No abstract

No abstract