South Asian Journal of Parasitology

Climate change is altering the environmental conditions that constrain vectors, intermediate hosts and parasites, but the public-health consequences cannot be reduced to a simple expectation that warming will expand transmission. This critical narrative review evaluates how climatic change, vector and intermediate-host adaptation, parasite development, and non-climatic determinants interact to shape emerging risks from malaria, leishmaniasis, Chagas disease, human African trypanosomiasis, schistosomiasis, babesiosis and selected filarial infections. Literature published from 2000 to 6 August, 2026 was identified through multidisciplinary biomedical and scholarly databases, supplemented by citation searching and authoritative global-health sources. Evidence was appraised for biological realism, study design, treatment of confounding, external validity and correspondence between climatic suitability and observed transmission. Across disease systems, temperature acts nonlinearly on survival, biting, development and parasite incubation, while humidity, hydrology, thermal variability and extreme events can modify or reverse mean-temperature effects. Phenotypic plasticity, local adaptation, altered phenology and range movement can relax static climatic constraints, yet direct demonstrations of evolutionary adaptation in field vector populations remain uncommon. Malaria provides the most developed mechanistic evidence, including strong support for nonlinear thermal limits and growing recognition that hydrology and species-specific vector ecology materially change projections. Evidence for sand flies, triatomines, schistosome snails, ticks, tsetse and filarial vectors likewise indicates redistribution rather than uniform expansion, with gains in some margins and losses in overheated or desiccating areas. Crucially, vector establishment is not equivalent to parasite establishment or clinical disease: mobility, reservoirs, land use, poverty, housing, surveillance and control frequently determine whether climatic opportunity becomes realised transmission. Climate-resilient disease control therefore requires locally validated early warning, longitudinal entomological and parasitological surveillance, flexible integrated vector management, One Health coordination and explicit attention to uncertainty and equity. Future research should prioritise coupled vector–parasite experiments under realistic climate variability, field tests of adaptive capacity, causal attribution designs and prospective evaluation of climate-informed interventions.