Low risk of invasive amebiasis in cyst carriers. A longitudinal molecular seroepidemiological study.

seroepldemloiogicai study of a household cohort, using both clinical observational and molecular criteria was conducted in a periurban area endemic for E. histolytiea infection. This longitudinal study was undertaken to determine the risk of asymptomatk cyst carriers to de- velop invosive illness. Zymodeme patterns ofstralns iso- lated from these patlents were correlated both with the cllnlcal presentadon of disease and with the serological response ogalnst the M-17 ameba antigen and further compared with that found in 16 proven cases of amebic Uver abscess. Fmm a total of163 housewivesscreened.39. (24 %)were asymptomatic cyst carriers; 31 ofthem (Index crrses) and 114 members of their househol& remained h the study over an 8 month follow-up perlud to detect ameba infection and Illness. Ofthe household members at risk, 46 (40%) became infected within 6 weeks. None 01 the index or secondary cases developed ameba-related symptoms and cyst excretion followed a chronic persis-