Abstract and Introduction

Abstract

We combined American Community Survey data with age-specific Trypanosoma cruzi prevalence derived from US surveys and World Health Organization reports to yield estimates of Chagas disease in the United States, which we mapped at the local level. In addition, we used blood donor data to estimate the relative prevalence of autochthonous T. cruzi infection. Our estimates indicate that 288,000 infected persons, including 57,000 Chagas cardiomyopathy patients and 43,000 infected reproductive-age women, currently live in the United States; 22–108 congenital infections occur annually. We estimated ≈10,000 prevalent cases of locally acquired T. cruzi infection. Mapping shows marked geographic heterogeneity of T. cruzi prevalence and illness. Reliable demographic and geographic data are key to guiding prevention and management of Chagas disease. Population-based surveys in high prevalence areas could improve the evidence base for future estimates. Knowledge of the demographics and geographic distribution of affected persons may aid practitioners in recognizing Chagas disease.

Introduction

Six million persons are estimated to have Chagas disease in the Americas; 20%–30% of those cases will progress to cardiac or gastrointestinal disease^[1]. Early treatment of infection with the causative parasite, Trypanosoma cruzi, provides the best chance to decrease progression risk; cure rates are ≥60% in those treated as children^[2,3]. Cure rates among adults are unclear; the accepted test of cure is reversion to negative serologic test results, which requires years to decades, and the time to negative serologic results is inversely proportional to the duration of infection^[4]. Because the date of T. cruzi infection is nearly always unknown, age is commonly used as a proxy for duration. Infected persons are typically asymptomatic for decades. In those with established Chagas cardiomyopathy, antiparasitic treatment is unlikely to alter heart disease progression^[5]. Thus, early, active screening during the asymptomatic period is essential to achieve timely diagnosis and effective treatment. Since the establishment of regional control programs in the 1990s, many Latin America countries have mounted community- and facility-based programs, most commonly focused on screening of children and pregnant women^[6,7]. No such large-scale programs exist in the United States.

Enzootic transmission by local triatomine species occurs across the southern United States from coast to coast; Lynn et al. summarized 76 suspected or confirmed autochthonous human T. cruzi infections^[8]. However, locally acquired infections are vastly outnumbered by those acquired by immigrants from Latin America in their countries of origin before arrival in the United States. No nationally representative T. cruzi prevalence data exist for the United States; disease burden estimates have been based on reported national prevalence figures from Latin America countries. These estimates suggest that 240,000–350,000 US residents of Latin America origin may have T. cruzi infection^[9]. However, infection rates are heterogeneous within countries, so national-level prevalence estimates may not reflect prevalence among US immigrants.

Calls for more widespread screening and diagnostic testing for Chagas disease in the United States are growing^[10–12]. Finer-scale geographic data would be of great help in the targeting of such efforts. Local screening of at-risk populations in Los Angeles, California; the District of Columbia; and the Boston, Massachusetts, metropolitan areas provide a more accurate reflection of prevalence in some US populations^[13–15]. Using data from the American Community Survey (ACS)^[16], we developed new age-structured estimates and interactive maps of Chagas disease prevalence at the local level. We present these data to support geographic targeting of screening efforts and setting priorities for healthcare providers and public health outreach to address Chagas disease in the United States.