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The aim of this study was to develop an immunological method for the identification of sheep infected with Echinococcus granulosus which would allow the monitoring of animals imported into countries free from hydatidosis and as an aid to countries where control schemes for the disease are in operation. Three enzyme-linked immunosorbent assays (ELISAs) were developed and validated, using as antigen either a purified 8 kDa hydatid cyst fluid protein (8kDaELISA), a recombinant EG95 oncosphere protein (OncELISA) or a crude protoscolex preparation (ProtELISA). Sera used for the assay validations were obtained from 249 sheep infected either naturally or experimentally with E. granulosus and from 1012 non-infected sheep. The highest diagnostic sensitivity was obtained using the ProtELISA at 62.7 and 51.4%, depending on the cut-off. Assay sensitivities were lower for the 8kDaELISA and the OncELISA. Diagnostic specificities were high, ranging from 95.8 to 99.5%, depending on the ELISA type and cut-off level chosen. A few sera from 39 sheep infected with T. hydatigena and from 19 sheep infected with T. ovis were recorded as positive. Western immunoblot analysis revealed that the dominant antigenic components in the crude protoscolex antigen preparation were macromolecules of about 70-150 kDa, most likely representing polysaccharides. This study demonstrated that the ProtELISA was the most effective immunological method of those assessed for detection of infection with E. granulosus in sheep. Because of its limited diagnostic sensitivity of about 50-60%, it should be useful for the detection of the presence of infected sheep on a flock basis and cannot be used for reliable identification of individual animals infected with E. granulosus., (Copyright 2002 Elsevier Science B.V.)

Hydatid cyst fluid from sheep and camels infected with Echinococcus granulosus, together with partially purified preparations of hydatid fluid antigen B and a recombinant antigen B product, were tested in an ELISA for their ability to detect IgG antibodies against E granulosus in the serum of naturally infected sheep. The antibody activity in sera from sheep naturally infected with Taenia hydatigena cysticercosis or Fasciola hepatica was also tested. All the antigen preparations from native hydatid cyst fluid were able to detect antibodies in the sera from a significant proportion of sheep with natural hydatid cyst infection, as identified by inspection at slaughter, although the seroreactivity was variable. The native antigen B preparation from camel hydatid cyst fluid gave the highest sensitivity in the ELISA (total 90 per cent), with 99 per cent specificity. In all cases, the recombinant antigen B was the least sensitive antigen (25 per cent) although it was highly specific (99 per cent).