# Assessment of Leishmania exposure in blood donors from a non‐endemic urban area: A study in São Paulo

## TL;DR

This study found no active Leishmania infections in blood donors from São Paulo, a non-endemic area, despite some positive antibody tests, suggesting limitations in current screening methods.

## Contribution

The study evaluates the reliability of serological screening for Leishmania in non-endemic regions and recommends molecular methods for improved transfusion safety.

## Key findings

- 2.82% of blood donors had ELISA-reactive results, but none tested positive by PCR for Leishmania DNA.
- Non-specific reactivity in serological tests may be due to inflammatory conditions like pregnancy or abortion.
- Molecular methods and universal leukoreduction are recommended to improve transfusion safety in low-endemicity areas.

## Abstract

According to the World Health Organization, more than 1 billion people are at risk of leishmaniasis in over 89 countries. Environmental changes such as deforestation, urban expansion and climate change facilitate the spread of sand fly vectors and reservoirs, increasing disease transmission. The introduction of Leishmania into non‐endemic regions may be further driven by globalization and ecotourism. Transfusion transmission, particularly of Leishmania infantum, remains a concern due to the parasite's ability to survive under blood storage conditions and its prolonged latent phase. We aimed to determine the prevalence of Leishmania spp. among blood donors in a non‐endemic region.

A prospective, cross‐sectional study was conducted with 5145 blood donor samples collected from January to December 2023. Serological screening was performed using an in‐house immunoglobulin G (IgG) ELISA based on Leishmania chagasi antigen. Samples with positive or inconclusive ELISA results were further tested by real‐time PCR targeting internal transcribed spacer (ITS) and kinetoplast DNA (kDNA) regions, according to Pirmez et al.

Among samples tested, 2.82% (141/5145) were ELISA‐reactive. None of these were positive by PCR for ITS or kDNA.

The absence of Leishmania DNA in ELISA‐reactive samples highlights the limitations of serological screening in low‐endemicity areas. Inflammatory physiological conditions, such as pregnancy and abortion, may contribute to non‐specific reactivity. The incorporation of molecular methods and the adoption of universal leukoreduction are recommended measures to ensure transfusion safety and avoid unnecessary donor deferrals.