Echinococcus granulosus infection

Non-invasive methods for diagnosis of echinococcosis such as ultrasonography, computed tomography and chest radiographs have comparable sensitive. However, differential diagnosis from benign cyst and abscesses can be difficult. Ultrasonography seems to be an efficient mass-screening method in combination with serology.

A wide variety of immunological tests have been applied for detection of antibodies in patients where echinococcosis is suspected. These include complement-fixation, latex agglutination, indirect haemagglutination, immunodiffusion, immunoelectrophoresis, Casoni intradermal test, IFL, and ELISA. For the antigen crude cyst fluid appears to be the most suitable in terms of immunogenicity and availability, but the complex mixture of proteins produce varying degree of both positive and negative results (Thompson and Lymbery 1995). The use of more purified fractions of cyst fluid antigens may improve specificity. The cyst fluid contains two major lipoproteins referred to as Antigen 5 and Antigen B. Antibodies to Antigen B have been considered specific for Echinococcus granulosus, but it is now known that a certain proportion of cross-reactions occur with sera from persons infected with other species of Echinococcus (Ito et al. 1999).

ELISA provides a sensitive assay and IgG is the dominant class of specific antibody in E. granulosus infection and IgG4 seems to be of diagnostic value (Shambesh et al. 1997; Grimm et al. 1998; Sterla et al. 1999). Replacement of native antigens by recombinant antigen may provide a better standardised specific test (McVie et al. 1997). The diagnosis can also be improved by the application of at least two serological methods.

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