# Zoonotic trypanosomatids in small mammals at a wildlife-urban interface in southeastern Brazil: Implications for transmission risk

## TL;DR

This study found that small mammals in a forest near urban areas in Brazil can carry parasites that cause diseases in humans, highlighting the risk of transmission in these mixed environments.

## Contribution

The study is the first to detect Trypanosoma lainsoni in Nectomys squamipes and demonstrates the role of small mammals in zoonotic transmission at the wildlife-urban interface.

## Key findings

- Leishmania infantum, L. braziliensis, Trypanosoma cruzi DTU TcI, and T. lainsoni were detected in small mammals.
- Mammals in fragmented landscapes may sustain complex parasite assemblages and transmission cycles.
- Integrated diagnostic methods improve zoonotic surveillance at the wildlife-urban interface.

## Abstract

This study investigated the diversity of trypanosomatids infecting small mammals in a fragmented forest landscape in southeastern Brazil, to gain insight into their role in transmission cycles and to assess potential public health risks. Eighteen small mammals were captured; seventeen were included in laboratory analyses: Didelphis albiventris (n = 4), Marmosops incanus (n = 4), and Nectomys squamipes (n = 9) were captured in the Mata da Tapera Municipal Natural Park, Minas Gerais State. To detect infection and assess host infectiousness, we used xenodiagnoses (Rhodnius neglectus and Lutzomyia longipalpis), 18S rRNA nested PCR, molecular typing, and parasitological culture. Leishmania infantum was identified in three individuals (two N. squamipes and one D. albiventris), L. braziliensis in one M. incanus, Trypanosoma cruzi DTU TcI in two D. albiventris, and T. lainsoni was detected in one D. albiventris and one N. squamipes. This integrated diagnostic strategy illustrates the value of combining parasitological, molecular, and experimental approaches for zoonotic surveillance at the wildlife-urban interface. Our findings document the occurrence of zoonotic trypanosomatids in a human-modified landscape and highlight potential transmission risks to humans and domestic animals, particularly in an area with active ecotourism, emphasizing the need for targeted surveillance within a One Health framework.

In many parts of Brazil, forested areas are getting smaller and more fragmented due to urban growth. These changes increase the contact between wild animals, domestic animals, and humans, creating new opportunities for pathogen transmission. In this study, we examined small wild mammals living in a forest fragment close to human settlements in southeastern Brazil to find out if they carried parasites that can also infect humans. We used a combination of techniques, including allowing laboratory-raised sand flies and kissing bugs (triatomines) to feed on the animals, to detect the presence of parasites and assess whether they could be detected in vectors after blood feeding. We found that these mammals were naturally infected with species of Leishmania and Trypanosoma, including those that cause leishmaniasis and Chagas disease in humans. We also detected Trypanosoma lainsoni, a lesser-known parasite, for the first time in Nectomys squamipes. Our findings suggest that small mammals living in areas where forests meet cities may play an important role in maintaining and spreading parasites that affect public health. Although the number of animals examined was limited, the detection of multiple zoonotic parasites in this small sample underscores how even small fragments at the wildlife-urban interface can sustain complex assemblages of zoonotic parasites and potential transmission cycles.