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The ultrastructure of the hydatid cyst germinal membrane was studied. It was divided into 3 regions, the tegument, the tegumental cell region, and the innermost area bordering the cyst cavity. The morphology of tegumental, muscular, flame, duct, and glycogen-containing cells and cells containing lysosomal-like bodies is described. The significance of these findings is discussed in terms of the possible function of these structures and present knowledge on the penetration of macromolecules into hydatid cysts.

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The immunodiagnosis of human hydatidosis caused by Echinococcus granulosus is based on the detection of antibodies against arc 5 antigens by the double diffusion (DD5) or counterimmunoelectrophoresis (CIE5) tests. However, neither of those tests is practical for seroepidemiological surveys in which a great number of samples have to be processed. The present study was carried out to evaluate if a solid phase enzyme immunoassay (EIA) standardized to detect total antibodies against E. granulosus cyst fluid antigens would permit the selection of sera with antibody activity against arc 5 antigens detectable by DD5. Groups of sera representing 5 possible results with DD5 were studied by the EIA proposed as a screening test. Using the EIA all the sera with antibody activity against arc 5 antigens were differentiated from all those which did not produce any precipitation band in DD5. It was also possible to differentiate those with no antibodies from all those with antibodies against 3 non-arc 5 antigens, most with antibodies against 2 non-arc 5 antigens and about a fifth with antibodies against 1 non-arc 5 antigen. It is concluded that the EIA, standardized as described, is capable of detecting with a high degree of efficiency all the sera that should be tested by DD5 and excludes most of those in which results with DD5 have no diagnostic significance.

This report deals with an evaluation of a double diffusion (DD5) test which employs a control antiserum against Echinococcus granulosus arc 5 antigens to recognize arc 5-positive sera by a reaction of identity. The DD5 test was more sensitive than the immuno-electrophoresis (IEP5) test based on the same positivity criterion and was equally specific for the immunodiagnosis of human hydatidosis. Its greater simplicity suggest its application as a substitute for the IEP5 test in diagnosis, particularly areas. The application of both DD5 and latex agglutination tests is recommended for hydatid immunodiagnosis on the basis of the present findings.