What is the prevalence of Chagas disease (American trypanosomiasis) in the US?

Updated: Apr 26, 2019
  • Author: Louis V Kirchhoff, MD, MPH; Chief Editor: Pranatharthi Haran Chandrasekar, MBBS, MD  more...
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Answer

Despite the presence of the sylvatic cycle of T cruzi transmission in the southern and southwestern United States, only 23 cases of autochthonous transmission of the parasite have been reported. [52, 73, 74] Although some cases of T cruzi infection probably go unnoticed or unreported, autochthonous acute Chagas disease is rare in the United States. This concept is supported by the extreme rarity of T cruzi infection among US blood donors who were not born in or who have not traveled extensively in endemic countries. The rarity of vector‑borne transmission of T cruzi to humans in the United States is likely due to the overall sparsity of vectors and the generally higher housing standards, which help prevent the vectors from becoming domiciliary. Despite this, triatomine insects have recently been reported as far north as Delaware [75] and the Carolinas [76] .

In contrast, the epidemiology of chronic T cruzi infection in the United States has changed markedly in the last few decades owing to the large number of people from endemic countries who have moved to the United States. According to one recent estimate, 23 million persons from endemic countries now live in the United States, 300,000 of whom have chronic T cruzi infection. [77, 78] Approximately two thirds of these immigrants are from Mexico, where the overall prevalence of T cruzi infection is 0.5%-1%. [79, 80]

Five cases of transfusion-associated transmission of T cruzi were reported in the United States prior to the implementation of donor screening in 2007, [81, 82] all of which occurred in immunocompromised patients. [83] Two additional such cases were found through trace-back studies after screening started. [84]

Two FDA‑approved tests are currently available for screening US blood donors for Chagas disease: the Ortho T cruzi ELISA Test System (Ortho Clinical Diagnostics, Rochester, NY) [85, 86] and the Abbott Prism Chagas assay (Abbott Laboratories, Abbott Park, IL). [87] Donor samples positive in either of the two screening assays generally undergo confirmatory testing with the Abbott Enzyme Strip Assay (ESA) Chagas, which is the only FDA‑approved option for this purpose. [88, 89] The Chagas RIPA, [90, 91] which was used for confirmatory testing from 2007-2014, is no longer available for this purpose.

The data accumulated to date indicate that about 1 in every 13,000 US blood donors is infected with T cruzi (ie, repeat reactive in the Ortho or Abbott screening assays and positive in the Chagas RIPA or the Abbott ESA), [92] which is consistent with estimates made prior to the initiation of screening by groups familiar with the epidemiology of T cruzi in the United States. No instances of transfusion transmission of T cruzi in the United States are known to have occurred since donor screening was implemented.

Five recipients of organ transplants from 3 donors with T cruzi infection developed acute Chagas disease in the United States, one of whom died of the illness. [33, 34]


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