Evaluation of two Fasciola hepatica faecal egg counting protocols in sheep and cattle

Fascioliasis causes significant economic losses and is a constant challenge to livestock farmers globally. Fluke faecal egg counts (flukeFECs) are a simple, non-invasive method used to detect the presence of patent liver fluke infection. Many flukeFEC techniques exist but they vary in complexity, precision and accuracy. The objective of this study was to evaluate the egg recovery capabilities of two simple flukeFEC methods at different egg concentrations in two ruminant species, using artificially spiked faecal samples. We added Fasciola hepatica eggs to sheep and cattle faeces at 2, 5 10 and 20 epg and utilised the Flukefinder® (FF) and a simple sedimentation method (referred to as the Becker method) to investigate the effects of methods, species and egg density on egg recovery. We calculated the proportion of fluke eggs recovered using each technique, and determined the lowest reliable egg detection threshold of each flukeFEC method. The performance of the flukeFEC methods were also compared using faecal samples collected from naturally infected animals. The egg-spiking study revealed that both FF and the Becker sedimentation method are significantly more likely to recover eggs from cattle faeces than sheep (P < 0.001). Overall, FF recovered more eggs than the Becker method (P < 0.001), and importantly has a reliable low egg detection threshold of 5 epg in sheep and cattle. The kappa coefficient indicated a substantial agreement between FF and the Becker method in naturally infected faecal samples collected from cattle (0.62, P < 0.05) and a moderate agreement in sheep (0.41, P < 0.05). This study demonstrated that FF has a low egg detection threshold and therefore has promising potential for the future of on-farm liver fluke diagnostics.