From heat stress to health collapse: A global review of temperature-mediated disease risk in fish

Abstract

Aquatic ecosystem warming, brought on by climate change, has become a significant threat to fish health worldwide, with far-reaching effects on the viability of aquaculture and wild fisheries. As ectotherms, fish are vulnerable to temperature changes, which have a direct impact on immunological function, host-pathogen interactions, and metabolic processes. This paper summarizes the current understanding of how fish immunosuppression and disease outbreaks are mainly caused by heat stress. Based on empirical data from freshwater, marine, and aquaculture systems worldwide, we incorporate mechanistic insights into the temperature-mediated alteration of innate and adaptive immune responses. Documented case studies demonstrate that elevated temperatures frequently coincide with increased prevalence and severity of bacterial, parasitic, and fungal diseases, often amplified by concurrent stressors such as hypoxia, salinity fluctuations, poor water quality, and high stocking density. The review further examines how warming enhances pathogen growth, virulence, and geographic expansion, creating a critical host-pathogen thermal mismatch. Finally, we discuss the implications of these findings for climate-adaptive fish health management, highlighting the importance of early warning systems, adaptive husbandry practices, and selective breeding for thermal and disease resilience. By identifying key knowledge gaps and future research priorities, this review highlights the urgent need to shift from reactive disease control to proactive, climate-resilient strategies that safeguard fish health and aquatic food security in a warming world.