Abstract
Currently, the laboratory diagnosis of human fascioliasis is based on the parasitological examination of parasite eggs in stool specimens and serological detection of specific antibodies in serum samples, which are often unreliable diagnostic approaches. Ideally, a sensitive and specific diagnostic test for
Fasciola
infection should be based on the detection of circulating
Fasciola
antigen, which implies active infection. Here, a 27-kDa-molecular-mass antigen was identified in a
Fasciola gigantica
adult worm antigen preparation, excretory-secretory products, and sera from
F. gigantica
-infected individuals, and it was not detected in antigenic extracts of other parasites and sera from noninfected individuals. The target antigen was isolated and partially characterized as a protein. Immunoperoxidase staining located the target epitope within teguments and guts of
F. gigantica
adult worms. The performance characteristics of a newly developed enzyme-linked immunosorbent assay (ELISA) based on
F. gigantica
circulating antigen detection in serum (FgCA-27 ELISA) were investigated using sera of 120 parasitologically diagnosed
F. gigantica
-infected individuals and 80 noninfected individuals. The area under the receiving operating characteristic (ROC) curve (AUC) for ELISA was significantly high (AUC = 0.961,
P
< 0.0001) for discriminating
Fasciola
-infected and noninfected individuals. The developed assay showed high degrees of sensitivity, specificity, and efficiency (>93%), and a significant correlation (
r
= 0.715,
P
< 0.0001) between antigen level and parasite egg count was shown. In conclusion, a 27-kDa
Fasciola
antigen was identified in sera of
F. gigantica
-infected individuals. A highly sensitive and specific
Fasciola
antigen detection assay, FgCA-27 ELISA, was developed for laboratory diagnosis of human fascioliasis.