Detection of coproantigens by sandwich ELISA in sheep experimentally infected with Fasciola gigantica.

Two monoclonal antibodies to Fasciola gigantica excretory/secretory (ES) antigens were used in a sandwich ELISA for the detection of Fasciola antigens in faeces of 9 sheep experimentally infected with 300 metacercariae of F. gigantica. The detection of coproantigens was found in four of the seven sheep within 5 weeks of infection, and within 7 weeks of infection coproantigens were detected in all seven of the sheep. This technique was compared to an indirect ELISA for the detection of anti-Fasciola ES antigen specific antibodies in serum. The anti-F. gigantica antibodies were detected within 3 weeks of infection in all of the infected sheep, suggesting a greater sensitivity to detect early infections. However, following anthelmintic treatment and removal of parasites, the anti-Fasciola antibody levels still remained high for at least 6 weeks when the study was terminated. In contrast, the levels of coproantigens were no longer detected in the faeces within 2 weeks of anthelmintic treatment. This study demonstrates that our sandwich ELISA for the detection of Fasciola coproantigens is able to detect immature fluke infections and more importantly, was able to detect patent infection of fasciolosis.