Epidemiology of malaria and leishmaniasis in Thailand (2004-2025): A systematic review.

Malaria and leishmaniasis remain major vector-borne parasitic diseases in tropical and subtropical regions. The aim of this systematic review was to synthesize evidence on the epidemiology and shared ecological and epidemiological characteristics of malaria and leishmaniasis in Thailand from 2004 to 2025. This systematic review was conducted in accordance with PRISMA guidelines and utilized three databases, PubMed, Scopus, and ScienceDirect, supplemented by grey literature and manual reference screening. From 1397 records, a total of 57 studies were included (36 on malaria and 21 on leishmaniasis). Malaria transmission persisted mainly in border and forest-associated areas, with nine Plasmodium species documented in Thailand across the included studies, including the emerging zoonotic parasites (Plasmodium knowlesi and Plasmodium cynomolgi). Plasmodium vivax and Plasmodium falciparum predominated nationwide; however, P. falciparum has shown a declining trend since 2012. Leishmaniasis was reported across multiple regions, with six Leishmania species identified. Leishmania martiniquensis and Leishmania orientalis were predominant species among people living with HIV. Seven provinces had reported occurrences of both diseases across the overall review period, associated with shared ecological conditions, forest-related occupational exposure, and population mobility. However, such findings reflect province-level co-occurrence based on aggregated evidence rather than confirmed concurrent transmission or co-infection. These findings highlight epidemiological characteristics and shared risk factors, particularly among immunocompromised populations and individuals engaged in forest-related activities. Integrated surveillance and control strategies within a One Health framework may strengthen the ability to eliminate malaria transmission and the expanding burden of leishmaniasis in Thailand.