Detection and significance of inapparent infection in Chagas disease in western Venezuela

Inapparent infections of Trypanosoma cruzi were detected in symptomless ser opositive people living in close proximity, and under the same conditions o f risk, to patients with acute Chagas disease. Similar infections were also detected in sera samples of people from 25 villages of western Venezuela w here Chagas disease is endemic. Seropositivity in all the 1,251 studied sam ples was established by use of 3 serological methods (direct agglutination test, indirect immunofluorescence antibody test, and enzyme-linked immunoso rbent assay). Each seropositive sample was tested for detection of anti-T. cruzi-specific immunoglobulin (Ig) M and IgG levels and specific T. cruzi i nfection by molecular methodology (polymerase chain reaction assay). The co mbined analysis of the serologic (IgM and IgG levels), molecular (specific T. cruzi DNA), and statistical findings demonstrated the existence of a dif ferent stage of T. cruzi infection in asymptomatic patients, which is sugge sted to be recognized as inapparent infection. Its definition, significance , and comparison with typical Chagas disease phases are presented, and its potential epidemiological importance is discussed.