Field evaluation of an enzyme immunoassay for detection of asymptomatic patients in a hydatid control program

In South America programs to control hydatidosis caused by Echinococcus granulosus include the active search for asymptomatic patients through population surveys for the detection of antibodies against arc 5 antigens using the double diffusion arc 5 test (DD5). Though simple to perform and highly specific, DD5 is not practical for population studies due to the time lapse between testing and receiving results. This work evaluates the application of an enzyme immunoassay to screen sera for subsequent processing using DD5. The efficiency of an enzyme immunoassay screening/DD5 confirmation scheme vs. DD5 alone was compared within the framework of a control program. A total of 5,839 sera from residents of endemic areas was processed and 47 hydatid patients were detected by both schemes. The proposed enzyme immunoassay identified all sera having antibody activity against arc 5 antigens detectable by DD5 and ruled out 95.3% of sera which tested by DD5 would have produced negative results.