Abstract
Protozoan diseases remain a serious public health challenge, particularly in countries such as Brazil, whose continental dimensions and diverse ecological settings allow for multiple transmission cycles, involving a wide range of vectors, reservoirs, intermediate and definitive hosts, suitable habitats, and a complex socioeconomic context that increases exposure to various diseases due to social vulnerability. Consequently, diseases such as malaria, leishmaniasis, and Chagas disease are highly prevalent in Brazil, affecting a significant portion of the population, especially in regions marked by greater social inequality. In this context, this study aims to present the epidemiological landscape of these diseases and discuss the role of immunological and molecular diagnostic tools, as well as the fundamental concepts that are essential for evaluating these diagnostic approaches. Overall, this review provides a detailed summary of established diagnostic approaches of these diseases and emphasizes the integration of clinical and epidemiological information with the application of sensitive and specific diagnostic techniques aimed at promoting early detection, monitoring, and control of infections in endemic areas, highlighting the important role of diagnosis as a strategic tool in public health.