Arc-C-5 in Countercurrent electrophoresis of Serum is diagnostic of -

Cystic echinococcal disease (Echinococcus granulosus). Indirect hemagglutination (IHA), indirect fluorescent antibody (IFA) tests, and enzyme immunoassays (EIA) are sensitive tests for detecting antibodies in serum of patients with cystic disease; sensitivity rates vary from 60% to 90%, depending on the characteristics of the cases. Crude hydatid cyst fluid is generally employed as antigen. At present, the best available serologic diagnosis is obtained by using combinations of tests. EIA or IHA is used to screen all specimens; a positive reaction is confirmed by immunoblot assay or any gel diffusion assay that demonstrates the echinococcal "Arc 5." REF;