Evaluation of a recombinant cathepsin L1 ELISA and comparison with the Pourquier and ES ELISA for the detection of antibodies against Fasciola hepatica

Abstract

The liver fluke Fasciola hepatica is one of the most important parasites in cattle farming worldwide and responsible for serious economic losses. In this study, three ELISAs for the detection of antibodies against F. hepatica were compared by analysis of serum antibody levels of 20 calves infected with different doses (50-1000 metacercariae) of F. hepatica metacercariae. The commercially available Pourquier ELISA was tested against an in-house ELISA based on excretory-secretory (ES) products as well as an ELISA based on recombinant cathepsin L1 (rCL1). During the period 4-21 weeks post infection (pi) the Pourquier ELISA showed 100% sensitivity (Se) and 100% specificity (Sp). ROC-analyses revealed a cut-off value of 0.090 ODR for the ES and 0.096 ODR for the rCL1 ELISA. Se of the ES ELISA was 90% and 95% in weeks 4 and 5 pi, respectively, and reached 100% during the period 6-12 weeks pi. Between weeks 13-21 pi Se varied from 90 to 100%. Sp of the ES ELISA was 99.3%. By comparison, calculated rCL1 ELISA Se values were rather low during prepatency (20-85% during weeks 4-7 pi), but increased with early beginning of patency and reached 100% during weeks 10-15 pi. Afterwards, Se ranged between 90% and 100%. With regards to different doses of F. hepatica metacercariae, Spearman rank correlation showed a significant relationship between the infection dose and measured antibody levels for the Pourquier ELISA but not the ES and rCL1 ELISA. Overall, the present study revealed the Pourquier ELISA as the superior test followed by the ES ELISA. Nonetheless, even if rCL1 ELISA was obviously inferior during prepatency, its test parameters associated with patent infections make it a convincing ELISA to diagnose patent fluke infections in cattle.