Chagas Disease: Creeping into Family Practice in the United States

Chagas disease, a parasitic infection, is increasingly being detected in the United States, most likely due to immigration from endemic countries in South and Central America. Approximately 300,000 persons in the US have chronic Chagas disease, and up to 30% of them will develop clinically evident cardiovascular and/or gastrointestinal disease. Here’s practical guidance to help you recognize the features of symptomatic Chagas disease and follow up with appropriate evaluation and management.

Chagas disease, also known as American trypanosomiasis, is caused by the protozoan parasite Trypanosoma cruzi.¹ It is most commonly spread by triatomine bugs infected with T cruzi and is endemic in many parts of Mexico and Central and South America.² Chagas disease was first described in 1909 by Brazilian physician Carlos Chagas.³ Since its discovery, it has often been considered a disease affecting only the poor living in endemic areas of Latin America. However, 6 million to 7 million people are infected with T cruzi worldwide, and estimates suggest that Mexico and the US rank third and seventh, respectively, in the number of persons with T cruzi infection in the Western Hemisphere.^1,4

An estimated 300,000 persons in the US have Chagas disease; most of them are not aware that they are infected.^5,6 The increasing presence of the disease in the US, which traditionally has been considered a nonendemic area, is due to immigration from endemic areas, with subsequent infections occurring through mechanisms that do not require contact with the triatomine vector (eg, congenital transmission).¹ Between 1981 and 2005, more than 7 million people from T cruzi-endemic countries in Latin America moved to the US and became legal residents.³

Early detection and treatment of Chagas disease is important because up to 30% of patients with chronic infection will develop a heart disorder, which can range in severity from conduction system abnormalities to dilated cardiomyopathy.⁴ In some areas of southern Mexico, Chagas disease is the most common cause of dilated cardiomyopathy.¹ Equally concerning is the fact that untreated mothers with Chagas disease can transmit T cruzi to their infants.^1,3 An estimated 315 babies are born with congenital Chagas disease each year in the US, an incidence equivalent to that of phenylketonuria.⁷ It is estimated that congenital transmission is responsible for up to one-quarter of new infections worldwide.¹ Unfortunately, obstetricians are not well informed about the risk factors for congenital Chagas disease, and very limited screening of at-risk women is performed. In a 2008 survey exploring health care providers’ knowledge of and understanding about Chagas disease, obstetricians and gynecologists had the greatest knowledge deficits about the disease, although considerable deficits were also seen among other specialties.¹

KISSING BUG DISEASE: ETIOLOGY/PATHOPHYSIOLOGY

Exposure to the protozoan parasite T cruzi, the cause of Chagas disease, typically occurs following the bite of a triatomine bug. Also known as “kissing bugs” because they usually bite exposed areas of the skin such as the face, triatomine bugs feed on human blood, typically at night, and act as a vector for the parasite.⁸ The parasite lives in the feces and urine of the triatomine bugs and is excreted near the bite during or shortly after a blood meal. The bitten person will then unknowingly smear the infected feces into the bite wound, eyes, mouth, or any opening in the skin, which gives the parasites systemic access.⁴ Once in the host’s bloodstream, the parasite replicates in host cells, a process that ends in cell lysis and hematogenous spread. At this point, the parasites can be seen on peripheral blood smear. Noninfected triatomine insects become infected and continue the cycle when they feed on an infected human host (see Figure 1).³ Persons of lower socioeconomic status living in endemic areas in Latin America are at a higher risk for contracting Chagas disease because “kissing bugs” commonly live in wall or roof cracks of poorly built homes. Populations living in poverty are also at risk due to minimal access to health care and prenatal care.⁴ Transmission of T cruzi not involving triatomine vectors occurs congenitally or through blood transfusions, consumption of contaminated food, and organ donations.⁴