Molecular survey of zoonotic protozoa in free-ranging marmosets (Callithrix penicillata) from Central Brazil: implications for One Health surveillance.

Urban expansion and environmental fragmentation have intensified contact among wildlife, domestic animals, and humans, reshaping infectious disease dynamics at the human-wildlife interface. Non-human primates (NHP), particularly the black-tufted marmoset (Callithrix penicillata), readily adapt to anthropogenic landscapes and may serve as sentinel hosts for zoonotic pathogens. This study investigated the occurrence of Leishmania spp., Plasmodium spp., Toxoplasma gondii, and Trypanosoma cruzi. in 232 free-ranging C. penicillata found dead in urban and peri-urban areas of the Federal District, central Brazil, between 2018 and 2023. Liver samples were analyzed by quantitative PCR. Plasmodium spp. was not detected (0/232). In contrast, 39.7% (92/232) of marmosets were positive for T. gondii, 32.4% (69/213) for Leishmania spp., and 21.1% (47/223) for T. cruzi. Overall, 71.6% of the animals tested positive for at least one protozoan agent, and 21.2% had coinfections, most commonly Leishmania spp. plus T. gondii. Positive cases were widely distributed across administrative regions, with evidence of spatiotemporal clustering in some urbanized areas. Parasitic loads varied substantially, and most infected animals showed no lesions attributable to these infections. These findings demonstrate the widespread circulation of zoonotic protozoa in free-ranging marmosets inhabiting anthropized environments and reinforce their epidemiological relevance within a One Health framework. Surveillance of urban NHP populations can contribute to understanding transmission networks and environmental contamination, thereby supporting public health strategies for the prevention and control of zoonotic diseases in central Brazil.