Figure 1
Detecting Trypanosoma cruzi in field-caught vectors. The figure illustrates our strategy of repeatedly checking for infection using (i) optical microscopy (OM) including slides read in routine surveillance (fresh, FS; Giemsa-stained, SS) or at the University of Brasília (fresh, FU; Giemsa-stained, SU), (ii) a conventional PCR (cPCR), and (ii) a replicate quantitative PCR (qPCR R1 and R2). Blank ‘slides’ represent OM slides that were not prepared for a given bug (coded ‘−’); in grey, tests that were scored as negative with ambiguity (possible false negatives, coded ‘0’); in light blue, dark blue, orange, light green, and dark green, tests scored as positive with ambiguity (possible false positives, coded ‘1’); and, in dark red with a parasite, a slide scored as positive without ambiguity (only when a professional parasitologists of the University of Brasília unmistakably identified T. cruzi trypomastigotes in a Giemsa-stained slide, coded ‘2’). The last column shows, for each bug, the “detection history” we used to construct our database, using the codes (‘−’, ‘0’, ‘1’, and ‘2’) defined above. Of the four bugs in this example, only the first one was scored as positive without ambiguity (hence its darker colour); the three light-coloured bugs might or might not have been infected: for the third and fourth, there were some ambiguous detections; for the last one, the six non-detections could have arisen either because the bug was not infected or because the tests failed to detect the parasite.
