Chagas disease, caused by the parasite Trypanosoma cruzi, affects more than 5 million people worldwide leading to serious heart and gastrointestinal disease in a proportion of chronically infected patients. Important modes of transmission include vector-borne, congenital, and via blood transfusion or organ transplant from an infected donor. Vector-borne transmission of Chagas disease occurs in the Americas, including the southern half of North America, where the specific vector insects (triatomines), T. cruzi, and infected reservoir mammalian hosts are found. In the United States, there are estimated to be at least 300,000 cases of chronic Chagas disease among people originally from countries of Latin America where Chagas disease is endemic. Fewer than 30 cases of locally acquired infection have been documented in the United States, although a sylvatic transmission cycle has been known to exist in this country for at least a century. Studies defining risks for locally acquired infection and effective prevention strategies are needed to help prevent domestic transmission of T. cruzi. To help address Chagas disease in the United States, improved health-care provider awareness and knowledge, better tools for screening and diagnosing patients, and wider availability of treatment drugs are needed.

Background

Chagas disease is caused by a protozoan parasite, Trypanosoma cruzi. Trypanosoma cruzi is transmitted by insect vectors called triatomines; vector-borne transmission occurs only in the Americas. The parasite is passed in the feces of infected triatomine bugs and enters the body when breaks in the skin or the conjunctiva are contaminated with infected bug fecal matter. Vector-borne transmission occurs primarily in parts of Mexico, Central, and South America, where triatomine species are adapted to domiciliary and peridomiciliary settings. In some parts of Latin America, transmission via contaminated food or beverages has been documented. Although vector-borne transmission of T. cruzi only occurs in the Americas, congenital transmission and transmission by blood transfusion or organ transplant from infected donors can occur wherever infected people are found. Infection with T. cruzi is characterized by an acute phase lasting several weeks to months, when parasitemia can be detected, and a chronic phase when the parasite is primarily present in various tissues and organs in the body. In the absence of treatment, infection persists for the lifetime of the individual and causes serious cardiac and/or gastrointestinal disease in about 30% of those chronically infected. Acute infection is rarely identified when it occurs; in vector-borne acute infection, symptoms are typically mild and often subclinical. In congenital acute infection, a small proportion of acutely infected babies can have serious disease at birth or shortly after. 1