Trypanasoma cruzi is a single-celled parasite and, together with Leishmania, belongs to the Trypanosomatidae family. It is considered the causative agent of the so-called Chagas disease and is found mainly in Latin America.
What is Trypanasoma cruzi?
Trypanosoma cruzi, along with Trypanosoma brucei, belongs to the genus Trypanosoma. These belong to the protozoan family, a group of various unicellular eukaryotic organisms. Protozoa are subdivided according to their locomotor organs. Trypanosomes belong to the flagellates, which move with the help of a flagellum. While Trypanosoma brucei, which occurs mainly in Africa, is responsible for sleeping sickness transmitted by the tsetse fly, Trypanosoma cruzi is responsible for Chagas disease, which is spread by predatory bugs. Trypanosoma cruzi is a parasite, i.e. it attacks a host and benefits from its damage. Humans are only an intermediate host. The parasite was first described in 1909 by Carlos Chagas, a Brazilian physician, after whom the disease it causes was also named. The protozoan was also named after a physician – Oswaldo Cruz. Based on the different molecular characteristics, two subtypes of Trypanosoma cruzi are distinguished.
Occurrence, distribution, and characteristics
Trypanosoma cruzi is found primarily in Central and South America. The parasite undergoes a unique life cycle as it spreads. Its final host in this process is the predatory bug, which lives primarily as vermin in slums. Intermediate hosts are humans, but also domestic animals such as dogs and cats, as well as some rodents. Just before the parasite is ingested by the predatory bug, it is in the trypomastigote stage. This stage is characterized by a sinuous, elongated shape with a long flagellum whose base is close to the nucleus. The trypomastigote also has a pointed posterior end and is approximately 20 µm in size. When the trypomastigote is ingested by the predatory bug, it transforms into an epimastigote. This form is very similar to that of a trypomastigote, except that the base of the flagellum is in a different location. In addition, the epimastigote can divide in the bug’s intestine. If the epimastigote now enters the rectum, it transforms back into the stage of a trypomastigote. If the predatory bug sucks the blood from a host, the bugs expose the trypanosomes with their fecal droplet immediately after the blood meal. Since the bite wound is itchy, the affected person scratches and in the process contaminates the wound with the trypomastigote-containing feces and becomes infected. The trypomastigotes thus enter the blood of the affected person and spread. If they get inside body cells, the trypomastigote transforms into the amastigote stage. In this process, they primarily affect macrophages and smooth muscle. The amastigote is much smaller than the trypomastigote (about 4 µm) and its flagella is virtually invisible. In addition, the amastigotes can in turn divide in the cell and thus multiply. After enough amastigotes have formed, they transform back into trypomastigotes, destroying the cell, and then re-enter the bloodstream. There they can infect further cells of the host or the trypomastigotes are again ingested by bloodsucking predatory bugs, in which they can then reproduce again. Another way to become infected is through infusion of infected blood or transplants. Transmission via breast milk or through the placenta from mother to child is also conceivable. Trypanosoma cruzi belongs to the flagellates, which means they move around with a flagellum that can take on a different shape at different stages.
Diseases and symptoms
Trypanosoma cruzi is primarily responsible for Chagas disease, which is prevalent in Central and South America. Initial infection carries no symptoms in approximately 60-70 percent of cases. Among the first clinical signs of infection is the so-called Romana sign, which is eyelid edema due to transmission through the conjunctiva of the eye. This is because the predatory bug sucks blood in the area of the head, especially at night, as this is usually not noticed and the head is not protected by a blanket. If the swelling is in a place other than the eyelid, this is called a chagoma.After several weeks, the acute stage begins, which is characterized by high recurrent fever. In addition, there is swelling of the lymph nodes, enlargement of the liver and spleen, and anemia. Abdominal pain, diarrhea and vomiting may also occur. Already at this stage, tachycardia, i.e. an increased pulse, may occur, due to which myocarditis may develop. This is often the result of an autoimmune reaction. The parasite induces the formation of autoantibodies directed against the heart muscle tissue. Patients usually recover within 1 to 2 months, but the pathogen may continue to persist asymptomatically for 10 to 20 years (latent phase) and may erupt again at any time. Typical of Trypanosoma cruzi infection is the chronic phase. It is manifested by enlargement of internal organs (enteromegaly), as well as involvement of the central nervous system.
