Diagnosis of human fasciolosis in the Gilan province of Northern Iran: Application of cathepsin L-ELISA

Fasciolosis, or liver fluke disease, caused by parasites of the genus Fasciola is emerging as an important disease in man, particularly in countries such as Bolivia, Peru and Egypt. Several outbreaks of this disease recently occurred in the Gilan province of Northern Iran and in 1999 alone over 10,000 individuals were infected. Our laboratory recently developed an enzyme linked immunosorbant assay (ELISA) test for diagnosing human fasciolosis in an endemic area of northern Bolivia. The assay was based on the detection of serum antibodies reactive with antigens secreted by the parasite. In the present report we examined the sensitivity and specificity of this ELISA to diagnose 176 patients residing in the Gilan province of Northern Iran. These individuals presented at health clinics with clinical symptoms of fasciolosis and were subsequently positively diagnosed by fecal analysis. The ELISA employed total molecules secreted by the parasites (excretory/secretory, ES, products) and a protease, termed cathepsin L1 (CL1), which was purified from this preparation, as antigen. In addition, the specificity of the assay was investigated using serum from Iranian individuals that were infected with hydatidosis, toxocariasis, amoebiasis, malaria and kalaazar. Using this assay, both CL1 and ES exhibited a sensitivity of 100% (all 176 patients tested positive) and a specificity of 100% and 98.9%, respectively. In conclusion, our standardized diagnostic ELISA for human fasciolosis based on the detection of IgG responses to parasite ES and CL1 would be a valuable tool to diagnosis human fasciolosis in Iran and could be employed in a large survey to determine the prevalence of the disease throughout this region.