T. cruzi trypomastigotes seen in a blood smear The presence of T. cruzi in the blood is diagnostic of<unk> . During the acute phase of infection, 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. Blood smear examination detects parasites in 34–85% of cases. The sensitivity increases if techniques such as microhematocrit centrifugation are used to concentrate the blood. On microscopic examination of stained blood smears, trypomastigotes appear as S or U-shaped organisms with a flagellum connected to the body by an undulating membrane. A nucleus and a smaller structure called a kinetoplast are visible inside the parasite's body; the kinetoplast of is relatively large, which helps to distinguish it from other species of trypanosomes that infect humans. Alternatively, T. cruzi DNA can be detected by polymerase chain reaction (PCR). In acute and congenital<unk> , PCR is more sensitive than microscopy, and it is more reliable than antibody-based tests for the diagnosis of congenital<unk>  because it is not affected by transfer of antibodies against from a mother to her baby (passive immunity). PCR is also used to monitor levels in organ transplant recipients and immunosuppressed people, which allows infection or reactivation to be detected at an early stage. In chronic<unk> , the concentration of parasites in the blood is too low to be reliably detected by microscopy or PCR, so the diagnosis is usually made using serological tests, which detect immunoglobulin G antibodies against in the blood. Two positive serology results, using different test methods, are required to confirm the diagnosis. If the test results are inconclusive, additional testing methods such as Western blot can be used. Various rapid diagnostic tests for<unk>  are available. These tests are easily transported and can be performed by people without special training. They are useful for screening large numbers of people and testing people who cannot access healthcare facilities, but their sensitivity is relatively low, and it is recommended that a second method is used to confirm a positive result. T. cruzi parasites can be grown from blood samples by blood culture, xenodiagnosis, or by inoculating animals with the person's blood. In the blood culture method, the person's red blood cells are separated from the plasma and added to a specialized growth medium to encourage multiplication of the parasite. It can take up to six months to obtain the result. Xenodiagnosis involves feeding the blood to triatomine insects, then examining their feces for the parasite 30 to 60 days later. These methods are not routinely used, as they are slow and have low sensitivity.
Chagas disease
Loa loa filariasis
Cyclosporiasis
Tylosis
Isosporiasis
Cryptosporidiosis
Paragonimiasis
Strongyloidiasis