Chagas’ disease is caused by which organism?

Chagas' disease is caused by the protozoan parasite Trypanosoma cruzi. This organism is transmitted primarily through the bite of triatomine bugs, commonly referred to as "kissing bugs." These insects are prevalent in certain areas of Central and South America, where Chagas’ disease is endemic.

Once inside the human host, Trypanosoma cruzi can lead to a chronic infection that principally affects the heart and gastrointestinal system, potentially resulting in severe complications such as cardiomyopathy, arrhythmias, and megaesophagus or megacolon over time. The life cycle of T. cruzi involves both the insect vector and mammalian hosts, highlighting the importance of vector control in preventing the disease.

Other choices provided are related to different diseases: Trypanosoma gambiense and Trypanosoma brucei are responsible for African sleeping sickness, while Leishmania donovani is the causative agent of visceral leishmaniasis. Each of these parasites has distinct transmission routes and clinical manifestations, which further differentiates them from Trypanosoma cruzi. Therefore, identifying the specific causative agent is crucial for proper diagnosis and treatment of the conditions associated with each of these parasites.