In October 2017, a woman aged 53 years visited her local blood donation center to donate blood. On October 25, 2017, she was notified that a screening test (Abbott Prism Chagas; Abbott Laboratories) of the collected blood was positive for antibodies to T. cruzi. The follow-up confirmatory multistep enzyme strip immunoassay test (Abbott ESA Chagas; Abbott Laboratories) performed on November 8, 2017, also yielded a positive result. The patient was referred by her physician to an infectious disease specialist for further evaluation.
The patient reported no known triatomine bites. Her travel history was remarkable for a trip to California approximately 28 years earlier, when she crossed the Mexican border for a few hours to go shopping. She also traveled to Florida and Alabama for vacation but could not recall the specific year. She reported no insect bites or any medical complaints during those trips.
The patient underwent diagnostic testing at a commercial laboratory on November 28, 2017, with an enzyme-linked immunosorbent assay (ELISA) for T. cruzi immunoglobulin G (IgG), and the results were positive. After discussion with subject matter experts at CDC, confirmatory diagnostic testing was done on September 6, 2018. All diagnostic tests were developed at CDC's Parasitic Diseases laboratory. A Wiener recombinant antigen enzyme immunoassay (EIA) for T. cruzi antibody was positive, and the trypomastigote excreted secreted antigen (TESA) immunoblot assay, a laboratory-developed test, was negative. Because the first two test results were discordant, related to limitations of specificity and sensitivity associated with differences in T. cruzi strains endemic in different geographic areas, a third test, a laboratory-developed immunofluorescence assay (IFA) for T. cruzi IgG antibody, was conducted, and the result was positive.
Given the potential for T. cruzi infection to cause cardiomyopathy, an electrocardiogram was obtained, which showed arrhythmias, including primary atrioventricular block with prolonged PR interval (increased time between the beginning of the P wave and the start of the QRS complex). The patient also underwent echocardiography, which showed mild concentric left ventricular hypertrophy. Both findings were consistent with the chronic phase of infection. After all confirmatory testing, the patient completed a 60-day course of benznidazole (5 mg/kg/day) as treatment for Chagas disease. The patient's blood cell count and liver enzyme levels were monitored closely during her trypanocidal course for treatment side effects.
Morbidity and Mortality Weekly Report. 2020;69(7):193-195. © 2020 Centers for Disease Control and Prevention (CDC)