Serology reveals comparable patterns in the transmission intensities of and in Langkat district, North Sumatera Province, Indonesia.

Introduction: The incidence of malaria in Indonesia has declined significantly over the last few decades. Thus, a demand for more sensitive techniques to describe low levels of transmission in the country is important. This study was conducted to evaluate antibody response to and in an area nearing elimination in North Sumatera Province, Indonesia.

Methods: A cross-sectional survey was conducted in Langkat district, North Sumatera Province, in June 2019. Basic demographic data and filter paper blood spots were collected from 339 participants. Antibody responses to two (PfAMA-1 and PfMSP-1) and two (PvAMA-1 and PvMSP-1) antigens were measured using indirect enzyme-linked immunosorbent assay (ELISA). Seroconversion rates (SCR) were estimated by fitting a simple reversible catalytic model to seroprevalence data for each antibody. Multiple logistic regression was used to investigate factors associated with exposure.

Results: The overall malaria seroprevalence was 10.6% for PfAMA-1, 13% for PfMSP-1, 18.6% for PvAMA-1, and 7.4% for PvMSP-1. Seropositive individuals for (PfAMA-1/PfMSP-1) and (PvAMA-1/PvMSP-1) were similar at 20.7%, with no significant differences observed between age groups (p > 0.05). Based on the reversible catalytic model, the calculated SCRs indicated a higher level of transmission than using all tested antigens. In the adjusted model, only spending nights in the forest was associated with seropositivity (odd ratio: 3.93, p < 0.001).

Conclusion: The analysis of community-based serological data helps describe the similar levels of and transmission in the Langkat district. The use of a serological approach enhances the detection of past exposure, aiding in the identification of epidemiological risk factors and malaria surveillance in low transmission settings in Indonesia.