Comparison of Adult Somatic and Cysteine Proteinas Antigens of Fasciola gigantica in Enzyme Linked Immunosorbent Assay for Serodiagnosis of Human Fasciolosis

Fasciolosis caused by Fasciola hepatica and F.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 only 25% of infected patients pass the eggs in the faeces, and immunodiagnosis methods are more applicable for this purpose, 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. This has been the first report on this case so far in Iran. Serum samples obtained from 178 individuals collected during the fasciolosis outbreak in 1999 in the Gilan province, northern Iran, that were coprologically positive for fasciolosis, were analyzed by IgG-ELISA for total antibody responses against (S) and CP antigens from Fasciola gigantica. The cut-off points for (S) and CP were 0.38 and 0.33, respectively. All cases that showed clinical manifestations of fasciolosis, were also seropositive using both (S) and CP antigens whereas all 25 non-infected controls were seronegative. Therefore, the sensitivity of the test was 100% for both antigens. On the other hand the specificity of (S) and CP antigens were calculated as 96.4% and 98.1%, respectively. The positive and negative predictive values of the test regarding (S) antigen were 97.8% and 100%, whereas these values as for CP antigen were 98.9% and 100% correspondingly. Two individuals with hydatidosis and two with toxocariasis had antibodies 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 provide a more conclusive diagnosis as possessing lower cut-off and enabling better to discriminate between seronegative and seropositive subpopulations.This study may be useful to implement a reliable test to diagnose human fasciolosis and for seroepidmiological objectives.