Paul J. Edelson, MD
For nearly a century, since its recognition in 1909, Chagas’ disease, or American trypanosomiasis, was strictly a disease of the Latin America rural poor. The organism, Trypanosoma cruzi, which causes Chagas’ disease, is transmitted by triatomine bugs that pass the parasite in their feces; the bug feces can contaminate a skin puncture, allowing a transmission of the parasite. Untreated Chagas’ disease leads to life-long infection with a prolonged asymptomatic period which may progress, in approximately 20-30 percent of cases, to serious cardiac or gastrointestinal disease. The cardiac form of the disease is typically characterized by potentially life-threatening arrhythmias and cardiomyopathy, and may result in sudden death, heart failure requiring cardiac transplantation, or stroke attributable to embolization of left ventricular thrombi.
Although vector-borne transmission (that is, disease organisms carried by an insect) of Chagas’ disease continues to be limited almost entirely to countries south of the U.S.-Mexico border, the disease can also be transmitted by blood transfusion, by organ and tissue transplantation, or congenitally from an infected mother to baby. In the United States, several cases of local vector-borne transmission have been reported, but risk is considered low. Transmissions by organ transplantation and blood transfusion have also been documented in the United States. Congenital transmission has been reported in other non-endemic countries with large immigrant populations from Latin American and may occur undetected in the United States.
Control efforts principally include spraying insecticide in areas where the vector has infected houses made from plant materials, or from stone with fractures or cavities where the insects can hide. These control efforts have reduced the number of infected persons from an estimated 16 million between 1975 and 1985 to 7.5 to 12 million currently. To help reduce transmission by contaminated blood transfusions, many countries, including the United States, now screen blood donors for Chagas’ infection.
Mexico, the principal country of origin of Latino immigrants to the United States, has made only limited efforts to control Chagas’ disease. Caryn Bern and Susan P. Montgomery, of the U.S. Centers for Disease Control and Prevention, estimated that about 300,000 persons with T.cruzi infection lived in the United States in 2005, resulting in approximately 30,000-45,000 cases of cardiomyopathy and an annual incidence of 63-315 congenital infections. Two drugs are currently available to treat Chagas’ infection -- benznidazole and nifurtimox. These drugs are not FDA-approved but are available from the CDC for treatment of patients under investigational protocols in the United States. Treatment has been shown to be effective in early, acute infection such as congenital infection, and a consensus is growing on the benefits of treatment of asymptomatic chronic disease, and even in the early stages of cardiac disease in an effort to slow or stop disease progression.
Unfortunately, few physicians in this country are familiar with Chagas’ disease, its management, or even its occurrence in the United States. In a recent survey of obstetricians, Verani and her colleagues found that only about 9 percent were aware that Chagas’ can cause congenital infection and the majority of respondents (77.9 percent) reported that they “never” considered the diagnosis, even among patients from endemic countries.
Given the importance of Chagas’ disease as a cause of heart disease and premature death, physicians in the United States should be aware of the importance of this often silent infection in the Latino population. Public health and clinical medical professionals should work together to increase awareness in Latino communities and to reduce the burden of premature deaths and disability among the 50 million Latinos living in the United States.
More information on Chagas’ disease is available at www.cdc.gov/chagas, including a free online CME/CNE course titled “Chagas’ disease: what U.S. clinicians need to know.”
Paul J. Edelson, MD. works for the Centers for Disease Control and Prevention in Jamaica, N.Y. and can be reached at dou9@cdc.gov.