 The presence of T. cruzi is diagnostic of Chagas disease . It can be detected by microscopic examination of fresh anticoagulated blood , or its buffy coat , for motile parasites ; or by preparation of thin and thick blood smears stained with Giemsa , for direct visualization of parasites . Microscopically , T. cruzi can be confused with Trypanosoma rangeli , which is not known to be pathogenic in humans . Isolation of T. cruzi can occur by inoculation into mice , by culture in specialized media ( for example , NNN , LIT ) ; and by xenodiagnosis , where uninfected Reduviidae bugs are fed on the patient 's blood , and their gut contents examined for parasites . 
