Diagnosis of Fasciola hepatica infections in sheep by an enzyme-linked immunosorbent assay.

An enzyme-linked immunosorbent assay (ELISA) was evaluated for diagnosis of Fasciola hepatica infections in sheep maintained under isolation and drylot conditions. Sheep were exposed to various numbers (100 to 500) of metacercariae, and blood was collected for assay at regular intervals thereafter. The ELISA values of controls were low and varied little. Although the ELISA detected antibodies to the flukes as early as postinoculation week (PIW) 2, ELISA values suggested as diagnostic (1.75 times control values) did not occur until PIW 6 to 8. Positive diagnosis of the infections by fecal examination for fluke eggs was not established until after PIW 10. Results also indicated that ELISA values were generally not correlated with magnitude of infection, concurrent nematode infections, or husbandry practices.