Chagas Disease in the United States: A Growing Public Health Concern

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Chagas disease is a parasitic infection caused by the protozoan parasite <i>Trypanosoma cruzi</i>.
Chagas disease is a parasitic infection caused by the protozoan parasite Trypanosoma cruzi.

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Chagas disease is a parasitic infection caused by the protozoan parasite Trypanosoma cruzi (T cruzi).  T cruzi infection can be acquired through the vector-borne route, transplacentally, through transfusion of contaminated blood products, from a transplanted organ of an infected donor, or rarely from contaminated food or laboratory accidents.1 A majority of infections are transmitted via the vector-borne route, which occurs only in the Americas. The vector for T cruzi is the triatomine bug, also known as the “kissing bug.” Infection is acquired through contact with the feces of an infected triatomine bug. The triatomine bug has been found in the southern United States, Mexico, Central America, and South America — as far south as Argentina. Chagas disease is endemic in Latin American countries, including Mexico and most countries in Central and South America.2 Although the triatomine bug survives in the southern United States, the vast majority of persons infected with T cruzi living in the United States acquired the infection while living in Latin American countries.

The United States is considered a nonendemic country for Chagas disease.  As of 2009, more than 300,000 persons living in the United States were believed to be infected with the T cruzi parasite.3 Although a 2016 review places this number closer to 240,000, this estimate does not include undocumented immigrants, who could account for more than 100,000 cases.4 If left untreated, the parasitic infection can lead to chronic disease with severe and life-threatening manifestations.  In approximately 20% to 30% of T cruzi infections, the disease progresses to Chagas cardiomyopathy and/or gastrointestinal Chagas disease.1 Practitioners serving communities with large populations of Latin American immigrants need to be aware of the disease prevalence in this population.

 

Epidemiology

An estimated 8 million people worldwide are infected with T cruzi, and the United States has the seventh highest prevalence of Chagas infections. Of the estimated 300,000 US individuals infected with the parasite, 30,000 to 45,000 will develop Chagas heart disease.5 Chagas infections represents a growing public health concern in the Western hemisphere, particularly in communities with high populations of Latin American immigrants.  The majority of cases of T cruzi infections in the United States are among immigrants from Latin American countries where T cruzi infections are endemic; few actual vector-borne cases of infection have been reported in the United States. According to Bern and Montgomery, only 7 cases of US vector-borne infections have been reported since 1955 despite the presence of the triatomine bug in the southern states.3

The kissing bug can be found in the southern half of the continental United States and large parts of Central and South America.1 The climate in the northern portions of North America and the southernmost portions of South America are not compatible for triatomine bug survival. Vector-borne transmission is prevalent in endemic countries where housing is poorly constructed as the bugs like to nest in cracks and holes in substandard housing.  Improved housing and less-efficient vectors may explain the low risk of vectorial transmission in the United States.1,2 Plastered walls and sealed entryways help to prevent bug infestations.

Risk Factors

Persons at highest risk of contracting T cruzi infection are those living or who have lived in poorly constructed, triatomine bug-infested houses in endemic countries.1 Other persons at risk are those who have received blood transfusions, transplant recipients, and offspring of infected mothers.  Since 2012, donated blood at all US blood centers undergoes screening for T cruzi infection; therefore, US blood transfusion recipients since 2012 are not considered high risk.1 Transplant recipients who receive an organ from a donor infected with T cruzi and children born to infected mothers are at risk of developing Chagas disease.1

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