Comparison of adult somatic and cysteine proteinase antigens of Fasciola gigantica in enzyme linked immunosorbent assay for serodiagnosis of human fasciolosis.

Fasciolosis caused by Fasciola hepatica and Fasciola gigantica is one of the major public health problems in the world and in Iran. Considering that stool examination for Fasciola eggs is not a sensitive method and immunodiagnosis methods are more applicable for this purpose, so the present study was conducted to compare the somatic (S) and cysteine proteinase (CP) antigens of F. gigantica in IgG-ELISA to diagnose human fasciolosis. Serum samples obtained from 100 individuals collected during the fasciolosis outbreak in 1999 in the Gilan province of Northern Iran that were coprologically positive for fasciolosis were analyzed by IgG-ELISA. Sera from healthy control individuals, not infected with any parasitic diseases (n=50) and from others with different parasitic infections including hydatidosis (n=40), toxocariosis (n=20), amoebiosis (n=10), and malaria (n=5) were examined as well. The cut-off point for (S) and CP was 0.40 and 0.35, respectively. All 100 individuals that showed clinical manifestations of fasciolosis, were also seropositive using both antigens, whereas all 50 non-infected controls were seronegative, therefore the sensitivity of the test was 100% for both antigens. The specificity of (S) and CP antigens were calculated as 96.9 and 98.4%, respectively. The positive and negative predictive values of the test regarding (S) antigen were 96 and 100%, whereas these values as for CP antigen were 98 and 100% correspondingly. Two individuals with hydatidosis and two with toxocariasis had antibodies that were reactive against (S) antigen, whereas concerning CP antigen, one individual with hydatidosis and another with toxocariasis showed cross-reactivity against it. We have demonstrated that altogether CP antigen provides a more conclusive diagnosis as possessing lower cut-off and enabling better to discriminate between seronegative and seropositive subpopulations.