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Trypanosoma cruzi

Disease. Chagas' disease, American trypanosomiasis

Geographic distribution. Endemic in 21 countries in the South and Central America.

Infection rate. 100 million people are at risk, which is about 25% of the population of Latin America. 16-18 million people are infected and 50,000 die annually.

Life cycle. When a kissing bug bites a person, it often leaves trypanosome-containing feces on the skin. Rubbing the bite site can pass the parasites into the skin, eyes, or mucus membranes, where the trypanosomes infect multiple cell types and reproduce. As the parasites increase in number, they rupture their host cells and spread through the blood to different tissues, with the muscles of the heart their primary target.

Transmission. 1) Through the bite of an infected triatomine insect (a blood-sucking, predatory bug of the Reduviidae family); 2) By transfusion of infected blood or organ transplants; 3) During pregnancy or at delivery, an infected mother can pass on the disease to her baby.

Morphology. The trypomastigote form is found in the circulating blood. This form is slender, about 20 ㎛ in length, and its posterior end is pointed. The body of stained specimens is U- or C-shaped. The nucleus is located near the middle of the body, and the kinetoplast is located near the posterior end. The undulating membrane is weakly developed, with two or three convolutions. The free flagellum extends to anterior portion. Intracellular amastigotes are oval-shaped and measure 1.5-4 ㎛ in diameter.

Pathology and clinical symptoms.
1) Acute stage: Acute symptoms occur mostly in children but rarely, lasting 4 to 8 weeks before disappearing even without treatment. Symptoms may include fever, fatigue, enlarged liver or spleen and swollen lymph glands. In some cases, eye swelling (Romana`s sign) may occur usually where a bite was received or where feces were rubbed into the eye. Infants in the acute stage of Chagas disease may experience brain swelling, which can lead to death.
2) Chronic stage: Chronic symptoms develop after a long symptom-free (or silent) period (10-20 years). Irreversible damage to the internal organs-the heart, esophagus, colon and to the peripheral nervous system-can occur. For individuals with compromised immune systems (such as those living with HIV/AIDS), the effects of Chagas disease can be severe.

Diagnosis. Blood test showing trypanosomes, or xenodiagnosis using cultured bugs.

Treatment. Treatment should begin as soon as possible following exposure as it is most effective during the acute stage of the infection. Once the chronic stage is reached, there is no effective treatment; only the related conditions, such as heart disease, can be treated or managed.

1) Avoid sleeping in mud, adobe or thatch houses; 2) Wear thick clothing that reduces the amount of exposed skin, such as heavy long-sleeved shirts, long pants, socks and shoes; 3) Sleep inside screened areas, under a bed net or in an air-conditioned room; 4) Avoid blood transfusions in countries where Chagas disease is endemic.

Min-Ho Choi

Trypanosoma cruzi amastigotes are seen in the section of cardiac muscle (H&E, 1000x).

DY Min/MH Ahn/JS Ryu

Epimastigote of Trypanosoma sp. showing a nucleus (Giemsa stain, 1000x).

DY Min/MH Ahn/JS Ryu