Evaluation of techniques for the enumeration of Dicrocoelium eggs in sheep faeces

To evaluate the accuracy of quantitative techniques for the enumeration of Dicrocoelium dendriticum eggs in faeces, eggs were added to fluke free sheep faeces to achieve densities of 25, 50, 100, 200, 400 or 800 eggs per gram (epg) (5 replicates per density). The faecal egg counts were determined by a modified McMaster method (WETZEL, 1951) utilizing solutions of ZnSO4 (sp. g. 1.3 and 1.45), K2CO3 (sp. g. 1.45) and HgI2/KI (sp. g. 1.44) for flotation or by a sedimentation technique (4 sedimentation processes of 45 min each). The influence of flotation time on egg counts was assessed by counting the eggs 3-5, 15-20, 30-35, 45-50 and 60-65 min after loading the McMaster chamber. The results were expressed as percentage rate of recovery. Significant best rate of recovery, 91.2 +/- 9.4%, was achieved using HgI2/KI solution for flotation and there was no significant influence of flotation time on the egg count. Utilizing ZnSO4 solutions and K2CO3 solution for flotation the rates of recovery for Dicrocoelium eggs were 9.0 +/- 7.1%, 26.7 +/- 24.9% and 13.0 +/- 11.6%, respectively, and a flotation time of more than 3-5 min did significantly increase the number of floated eggs. The rate of recovery for Dicrocoelium eggs using the sedimentation technique was 41.2 +/- 1.5%.