Immunoassay Developed to Diagnose Human Fascioliasis

An immunoassay has been evaluated for its diagnostic ability to detect human immunoglobulin G (IgG) antibodies against Fasciola hepatica, a common liver fluke.

The indirect enzyme-linked immunosorbent assay (ELISA) that detects antibodies against F. hepatica saposin-like protein-2, was compared with another indirect ELISA that detects excretory–secretory products (FhES) from adult F. hepatica.

Scientists at the University of Puerto Rico (San Juan), analyzed the sera of 37 patients infected with F. hepatica, 40 patients with other parasitic infections, and 50 healthy controls. A recombinant F. hepatica saposin-like protein-2 product was prepared and compared with the FhES products obtained from adult flukes collected from cattle's bile ducts obtained from a slaughterhouse.

The sensitivity of both ELISA assays was 100%. However, the FhSAP2-based ELISA had a specificity of 95.6%, while that of the FhES-ELISA was 91.9%. The results indicate that FhSAP2 is more specific than FhES products as target antigen for ELISA-based serodiagnosis of human fascioliasis since the best results for specificity and accuracy were achieved with the recombinant protein. The investigators noted that the mean value for negative controls and for other groups of samples is higher for the FhSAP2-ELISA than for the FhES-ELISA assay, which leads to a higher cut-off value, and that the mean value for the positive control samples in the FhSAP2-ELISA is slightly lower than the mean value obtained for these samples in the FhES-ELISA.

The authors concluded that their results demonstrated that FhSAP2 could be used in the serodiagnosis of chronic human fascioliasis with the additional advantage of being relatively cheap and easy to produce. Studies are in progress to evaluate this FhSAP2-ELISA assay in a large-scale prevalence surveys in endemic areas. It is estimated that worldwide 180 million humans are at risk from this zoonotic disease. Typical early symptoms include fever, abdominal pain, gastrointestinal disturbances and urticaria and hepatomegaly, anemia and jaundice may also be present The article was published in July 2011, in Diagnostic Microbiology and Infectious Disease.

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