First report of anti-Toxoplasma gondii antibodies in sea turtles.

Toxoplasma gondii is a zoonotic protozoan with an emerging ecological impact, particularly in coastal and marine ecosystems affected by terrestrial runoff. This study presents the first evidence of anti-T. gondii antibodies in sea turtles along the Espírito Santo coast, Brazil. A total of 102 serum samples were analyzed, primarily from green turtles (Chelonia mydas), with one loggerhead turtle (Caretta caretta). Samples were collected between 2017 and 2024 from two institutions: IPCMar and IPRAM. The modified agglutination test (MAT) revealed an overall seroprevalence of 8.8 % (9/102), with titers ranging from 1:25 to 1:100. Notably, most positive samples (80.0 %) were detected in 2024, suggesting a potential increase in environmental contamination, possibly linked to climate change and anthropogenic factors. The results provide serological evidence supporting the hypothesis that sea turtles might be susceptible to T. gondii exposure through contaminated prey, such as bivalves, algae, and fish, as well as runoff from terrestrial sources. Given their ecological importance and conservation status, these findings raise concerns about the health impacts of T. gondii on sea turtles and highlight the need for further research into their role in the parasite's transmission cycle. These findings underscore the significance of monitoring zoonotic pathogens in marine ecosystems to better understand the interplay between environmental changes, wildlife health, and pathogen spread.