Late in the disease, parasites are rarely detected in the heart, and may be present at only very low levels.In the heart, colon, and esophagus, chronic disease leads to a massive loss of nerve endings. In the heart, this may contribute to arrythmias and other cardiac dysfunction. In the colon and esophagus, loss of nervous system control is the major driver of organ dysfunction. Loss of nerves impairs the movement of food through the digestive tract, which can lead to blockage of the esophagus or colon and restriction of their blood supply. Diagnosis
The presence of T. cruzi in the blood is diagnostic of Chagas disease. 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, T. cruzi 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 parasites body; the kinetoplast of T. cruzi 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).
Regional bodies dedicated to controlling Chagas disease arose through support of the Pan American Health Organization, with the Initiative of the Southern Cone for the Elimination of Chagas Diseases launching in 1991, followed by the Initiative of the Andean countries (1997), Initiative of the Central American countries (1997), and the Initiative of the Amazon countries (2004). Research
Treatments
Fexinidazole, an antiparasitic drug approved for treating African trypanosomiasis, has shown activity against Chagas disease in animal models. As of 2019, it is undergoing phase II clinical trials for chronic Chagas disease in Spain. Other drug candidates include GNF6702, a proteasome inhibitor that is effective against Chagas disease in mice and is undergoing preliminary toxicity studies, and AN4169, which has had promising results in animal models.A number of experimental vaccines have been tested in animals. In addition to subunit vaccines, some approaches have involved vaccination with attenuated T. cruzi parasites or organisms that express some of the same antigens as T. cruzi but do not cause human disease, such as Trypanosoma rangeli or Phytomonas serpens. DNA vaccination has also been explored. As of 2019, vaccine research has mainly been limited to small animal models. Diagnostic tests
As of 2018, standard diagnostic tests for Chagas disease were limited in their ability to measure the effectiveness of antiparasitic treatment, as serological tests may remain positive for years after T. cruzi is eliminated from the body, and PCR may give false-negative results when the parasite concentration in the blood is low.