(shag′ăs)

[Carlos Ribeiro Justiniano Chagas, Brazilian physician, 1879-1934]
Chronic infection with the protozoan parasite Trypanosoma cruzi.

CAUSES
Chagas disease is primarily transmitted to people by fecal contamination of the bite of an insect of the genus Triatoma that harbors T. cruzi in its gut. The parasite may also be passed from person-to-person by needlestick injury, transfusion, organ donation, or during childbirth.

INCIDENCE
Triatoma species live in South and Central America, where more than 8,000,000 people are thought to be infected. Approximately 300,000 people who have emigrated to the U.S. are believed to carry the infection.

SYMPTOMS AND SIGNS
Acute infection causes a febrile illness that lasts about 1 or 2 months. A classical finding in those infected via the conjunctiva is swelling of the eyelid (Romana sign). Occasionally, during acute infection, the parasite replicates in the heart, causing myocarditis, or within the brain, where it causes meningoencephalitis. Most patients survive the acute phase of infection and are parasitized for life. Over years or decades, the infection may result in cardiac complications such as heart block or heart failure, which can prove fatal, or, less often, in gastrointestinal nerve damage, which results in megaesophagus or megacolon.

DIAGNOSIS
Acute infection can sometimes be identified when the parasite is seen on blood smears. Chronic infection is diagnosed when at least two different confirmatory blood tests identify antibodies to T. cruzi.

PREVENTION
Avoiding contact with the insect vector helps prevent trypanosomiasis and Chagas disease. The insect lives in mud huts and bedding and tends to feed on human hosts at night.

TREATMENT
Benznidazole and nifurtimox are two antiparasitic drugs used to treat trypanosomiasis. Chronic infection requires several months of therapy.

IMPACT ON HEALTH
Decades after initial infection, some patients develop heart disease, esp. cardiomyopathy. About 45,000 Americans are suspected of having Chagas-induced heart failure.

PATIENT CARE
Patients with Chagas disease should not donate blood. Most blood banks screen donations for the presence of T. cruzi. Infected mothers may transmit the disease to their children. Chronically infected patients should have intermittent cardiovascular screening examinations to see, for example, if they are developing early signs of heart disease such as heart block. Patients treated with antiparasitic regimens should be educated about the many side effects of their medications (rashes, anorexia, weight loss, and nerve damage) and the need to complete the full course of treatment to eradicate infection.

SYN: SEE: American trypanosomiasis; SEE: South American trypanosomiasis
SEE: Trypanosoma cruzi