Monitoring drug efficacy against gastrointestinal nematodes when faecal egg counts are low: do the analytic sensitivity and the formula matter?
- First Online:
- 235 Downloads
The faecal egg count reduction test (FECR) is the recommended technique to monitor anthelmintic drug efficacy in livestock. However, results are often inconclusive due to the low analytic sensitivity of the diagnostic technique or the conflict in results from FECR formulae. A novel experimental set-up was, therefore, used to compare the impact of analytic sensitivity and formulae on FECR results. Four McMaster techniques (analytic sensitivities 50, 33.3, 15 and 10) and a FLOTAC technique (analytic sensitivity ~ 1) were used on faecal samples of 30 calves with a FEC of less than 200 eggs per gram. True drug efficacies of 70%, 80% and 90% were experimentally mimicked by comparing FEC before and after dilution (3:10, 2:10 and 1:10, respectively). The FECR was summarized using group (FECR(1)) and individual (FECR(2)) based formulae. There was a significant increase in precision of FECR when the analytic sensitivity increased (p < 0.0001). The precision also depended on the formula used, FECR(1) (p < 0.05) resulting in more precise FECR compared to FECR(2). The accuracy of the FECR differed marginally between the two formulae (p = 0.06), FECR(1) being more accurate. In conclusion, the present study describes a novel methodology to compare techniques for the precision and the accuracy of their FECR results. The results underscored that techniques with high analytic sensitivity will improve the interpretation of FECR in animal populations where baseline FEC are low. They also point out that the precision of individual-based formulae is affected by the analytic sensitivity.
- Coles GC, Bauer C, Borgsteede FH, Geerts S, Klei TR, Taylor MA, Waller PJ (1992) World Association for the Advancement of Veterinary Parasitology (W.A.A.V.P.) methods for the detection of anthelmintic resistance in nematodes of veterinary importance. Vet Parasitol 44:35–44PubMedCrossRefGoogle Scholar
- El-Abdellati A, Charlier J, Geldhof P, Levecke B, Demeler J, von Samson-Himmelstjerna G, Claerebout E, Vercruysse J (2010) The use of a simplified faecal egg count reduction test for assessing anthelmintic efficacy on Belgian and German cattle farms. Vet Parasitol 169:352–357PubMedCrossRefGoogle Scholar
- Ministry of Agriculture, Fisheries and Food (1986) Manual of veterinary parasitological laboratory techniques (reference book; 418), 3rd ed. Her Majesty’s Stationery Office (HMSO), London 160 ppGoogle Scholar
- Vercruysse J, Behnke JM, Albonico M, Ame SM, Angebault C, Bethony JM, Engels D, Guillard B, Hoa NTV, Kang G, Kattula D, Kotze AC, McCarthy JS, Mekonnen Z, Montresor A, Periago MV, Sumo L, Tchuem Tchuenté L.-A, Thach DTC, Zeynudin A, Levecke B (2011) A multinational trial of the efficacy of albendazole against soil-transmitted helminth infections in children. PloS Negl Trop Dis 5(3):e948PubMedCrossRefGoogle Scholar