Comparative analysis of the viability of Fasciola hepatica eggs collected from fecal and gallbladder samples in experimentally infected sheep

Abstract

The objective of this study was to determine and compare the viability of Fasciola hepatica eggs collected from fecal and gallbladder samples through the egg hatching test of experimentally infected sheep. The biological samples used come from a previously reported sheep vaccination trial. Twenty-five sheep free of fasciolosis and housed in pens with cement floors were used. The sheep were grouped into five groups (G1–5, n = 5 sheep per group). Groups G1(100 ug), G2 (200 ug), G3 (400 ug) were immunized with the chimeric protein (rFhLAP-CL1) and, groups G4 and G5 were the adjuvant and infection controls, respectively. All sheep were orally infected with 200 metacercariae. The experimental period was 24 weeks. Fasciola hepatica eggs were collected every 15 days from fecal samples from weeks 14–24 of the experiment, and from the gallbladder after euthanized. The viability of F. hepatica eggs was determined through an egg hatching assay (EHA). Eggs that had developed miracidium and hatched were considered viable eggs. The viability range of F. hepatica eggs from gallbladder was 22–59.6 % and of fecal samples was 67–88 %. The viability of F. hepatica eggs from fecal samples was higher (>90 %) than that of eggs from the gallbladder (<60 %). In the vaccination trial, the viability of F. hepatica eggs in the G3 group was significantly different compared to the control group, in fecal samples (p < 0.001) and in the gallbladder (p < 0.05). Higher viability of F. hepatica eggs was observed in fecal samples than in gallbladder samples. Fecal samples are suggested for determining the viability of trematode eggs in vaccination trials or evaluation of fasciolicides.