Effect of parasite burden on the detection of Fasciola hepatica antigens in sera and feces of experimentally infected sheep

The effect of Fasciola hepatica parasite burden on the detection of excreto ry/secretory (E/S) antigens in sera and feces of experimentally infected sh eep was evaluated using a double antibody-based capture enzyme-linked immun osorbent assay (ELISA). Four groups of five sheep each were used. The first three groups were infected with 50, 100 and 200 metacercariae of F. hepati ca, and the fourth group remained as non-infected control. On the day of in fection and weekly thereafter, serum and fecal samples were taken. ELISA de tected F. hepatica E/S antigen levels in serum from the first week post-inf ection (wpi) and in fecal supernatant from the fourth wpi, which were signi ficantly (p < 0.05) higher than controls. F. hepatica eggs were not detecte d until after the eighth wpi, The correlation between absorbance of E/S ant igens in serum with the fluke burden was 0.77 (p < 0.0001) and in feces 0.7 6 (p < 0.0001) at 12th wpi. The sensitivity of the assay to detect E/S anti gens in serum was 86.6% and in feces 93.3%. It is concluded that the ELISA technique used in this study offers a diagnostic alternative for detecting early infections of F. hepatica in sheep. (C) 2001 Elsevier Science B.V. Al l rights reserved.