Publication history: Accepted - 3 July 2021; Published online - 6 July 2021.Fasciolosis, a global parasitic disease of agricultural livestock, is caused by the liver fluke Fasciola hepatica.
Management and strategic control of fasciolosis on farms depends on early assessment of the extent of disease so
that control measures can be implemented quickly. Traditionally, this has relied on the detection of eggs in the
faeces of animals, a laborious method that lacks sensitivity, especially for sub-clinical infections, and identifies
chronic infections only. Enzyme linked immunosorbent assays (ELISA) offer a quicker and more sensitive
serological means of diagnosis that could detect early acute infection before significant liver damage occurs. The
performance of three functionally-active recombinant forms of the major F. hepatica secreted cathepsins L,
rFhCL1, rFhCL2, rFhCL3, and a cathepsin B, rFhCB3, were evaluated as antigens in an indirect ELISA to serologically
diagnose liver fluke infection in experimentally and naturally infected sheep. rFhCL1 and rFhCL3 were
the most effective of the four antigens detecting fasciolosis in sheep as early as three weeks after experimental
infection, at least five weeks earlier than both coproantigen and faecal egg tests. In addition, the rFhCL1 and
rFhCL3 ELISAs had a very low detection limit for liver fluke in lambs exposed to natural infection on pastures and
thus could play a major role in the surveillance of farms and a ‘test and treat’ approach to disease management.
Finally, antibodies to all three cathepsin L proteases remain high throughout chronic infection but decline
rapidly after drug treatment with the flukicide, triclabendazole, implying that the test may be adapted to trace
the effectiveness of drug treatment.This work was supported by a European Research Council Advanced
Grant (HELIVAC, 322725) and Science Foundation Ireland (SFI) Professorship grant (17/RP/5368) awarded to J.P. Dalton