Chagas disease

By Peter Galvin, MD

Chagas disease is a parasitic infection that can cause heart and/or gastrointestinal problems. The parasite that causes it, Trypanosoma cruzi, is transmitted to humans by contact with the infected feces of triatomine insects, found throughout Latin and South America and the southern U.S. There are other routes of transmission including blood transfusion, organ transplant, mother-to-child transmission during pregnancy, and contaminated food and drinks. Chagas affects about six million people worldwide, including 300,000 in the U.S. Most infected individuals in the U.S. are immigrants from Latin America, but locally acquired infections have been reported in Texas, California, Tennessee, and other southern states.

The acute phase of infection can last two to three months and may cause mild, non-specific symptoms such as fever and fatigue, which usually resolve without treatment. Most infected individuals who do not receive treatment develop a lifelong, chronic infection, which is typically asymptomatic. However, about 20% to 30% develop heart damage years to decades after initial infection, which may lead to heart rhythm abnormalities, heart failure, or, rarely, sudden cardiac death. Less commonly, people with chronic Chagas disease may develop gastrointestinal complications like difficulty swallowing or constipation.

During the acute phase, Chagas disease may be diagnosed by using a microscope to see parasites in a blood smear or a blood test to detect parasite DNA in the blood. Chronic Chagas is diagnosed by two separate tests which detect antibodies to the parasite in the blood. Benznidazole and nifurtimox are medications that can be used to treat Chagas. Benznidazole is preferred as it has fewer side effects and is more effective than nifurtimox. Treatment usually lasts for at least 60 days and frequent monitoring during treatment is recommended.

Testing for Chagas should be offered to those with the following risk factors:

• Lived at least 6 months in Mexico, Central or South America
• Mother lived 6 months or longer in Mexico or Central or South America
• Family member with Chagas disease
• Known contact with triatomine insects in the US or Latin America

Women of reproductive age with any of these risk factors who are considering pregnancy should benefit from screening because treatment before conception can decrease transmission during pregnancy by more than 95%. Immunocompromised individuals (HIV or organ transplant) who have risk factors should be prioritized for screening because they are at serious risk for Chagas complications. Treatment of asymptomatic patients is important as it reduces the risk of complications from Chagas. Once heart complications develop, there is no benefit from treatment. For more information go to the website of the American Society for Microbiology at www.asm.org

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