High-resolution climate modelling of fasciolosis risk in Australia: A One Health early-warning framework.

Fasciolosis, caused by the liver fluke Fasciola hepatica, is a climate-sensitive parasitic disease that threatens livestock health, productivity and farm profitability, with broader implications for food security, rural livelihoods, and sustainable food systems. The disease is endemic in Victoria, Australia, where environmental and climatic conditions favour parasite transmission at the livestock-environment interface. This study used high-resolution (5 km2) climate data from 40,504 grid points across Victoria to validate a Growing Degree Days (GDD) model for estimating fasciolosis risk over the past 50 years (1975-2024) and to project future risk for 2050 and 2090 under medium (RCP 4.5) and high (RCP 8.5) representative concentration pathways. Linear regression analysis identified a strong relationship between observed fasciolosis prevalence and modelled risk values (R2 = 0.94, p < 0.003). Historical data analyses showed substantial interannual variability, with consistently higher risk in eastern Victoria, followed by the western and northern regions. Under future climate scenarios, fasciolosis risk increased spatially 2-fold in Barwon and 3-fold in the Great South Coast, particularly under the RCP 8.5 scenario in 2090. Risk remained sustained in Gippsland, especially in southern areas, covering 35% of the region, while a modest increase (5%) was projected for Greater Melbourne relative to a baseline risk of 45%. These findings highlight important One Health implications, as climate-driven changes in fasciolosis risk may undermine livestock productivity, and challenge the resilience of livestock-derived food systems. The study provides an evidence base to support climate-responsive surveillance, risk-based control strategies, and integrated animal health and environmental policy development.