Serological surveillance of orally acquired acute Chagas disease in the Brazilian Amazon using conventional and in house assays

In the Brazilian Amazon, cases of acute Chagas disease (ACD) are mostly associated with the consumption of açaí juice contaminated with Trypanosoma cruzi have become frequent. A large proportion of diagnosed patients and exposed individuals after outbreaks are not followed-up clinically since they reside in the remote interior of the state of Amazonas with limited access to healthcare services. This study aims to conduct serological surveillance of populations exposed to T. cruzi in orally transmitted ACD. We evaluated 66 individuals with a history of diagnosis and treatment (G1), and 49 individuals without proven infection after exposure to outbreaks (G2). Serological surveillance was performed using 3 commercially available tests and 2 genotype-specific tests using antigens from T. cruzi strains TcI and TcIV. Among the G1, 34.8% presented serological cure whereas 6.1% in G2 presented seroconversion for IgG anti-T. cruzi while 22.5% (G2) had indeterminate results due to discordance between IIF and ELISA tests, which use different principles. Genotype-specific ELISA (TcI-TcIV) tests showed detection rates between 30.3 and 31.8% in G1, and 14.3-22.4% in G2. These results highlight the importance of follow-up serological surveillance among Amazonian populations exposed to ACD outbreaks. It also underscores the need for more sensitive serological tests with greater agreement for to ensure accurate diagnosis and monitoring of populations with a history of exposure.