Potential risk of heartworm infection in the United States of America and its projected incidence by 2100

BACKGROUND: Heartworm disease, caused by the parasitic roundworm Dirofilaria immitis, is a vector-borne zoonosis transmitted by culicid mosquitoes and widely distributed in the USA, where prevalence is highest in the southeastern states. Transmission dynamics are influenced by environmental and anthropogenic factors, and climate change is expected to modify its distribution. Within a One Health framework, this study generates monthly and annual risk maps for heartworm transmission in the USA and projects the habitat suitability of vectors to the year 2100. METHODS: Ecological niche models were constructed for Aedes albopictus and Aedes vexans using MaxEnt and occurrence data from the Global Biodiversity Information Facility (GBIF). Bioclimatic variables from WorldClim and environmental layers related to hydrology, vegetation, and human activity obtained from free global datasets were selected after multicollinearity testing. Growing degree days (GDD) were calculated to estimate monthly and annual D. immitis generations using CHELSA (Climatologies at high resolution for the Earth's land surface) temperature data. Habitat suitability models were combined with parasite generations to produce infection risk maps for the USA, validated against clinical case data. Future projections to 2100 were generated under the RCP (Representative Concentration Pathways) 8.5 scenario. RESULTS: Our results indicate that the highest risk of infection is concentrated in the southeastern states and Gulf Coast, where conditions are warmer and more humid, at least during certain periods of the year. In contrast, risk decreases towards the west, particularly in the Rocky Mountains, Sierra Nevada, and the deserts of Arizona and Nevada. Regarding seasonal variation, infection risk remains very low across most of the USA during the winter months, gradually increasing month by month and peaking in summer. Finally, projections for 2100 suggest a rise in infection risk, particularly in Midwest and Northeast regions and higher-altitude areas. CONCLUSIONS: Heartworm transmission risk in the USA shows strong geographical expansion potential driven by climate conditions. Our risk maps reveal emerging areas of suitability and provide an early warning tool for One Health surveillance and prevention strategies.