Climate-warming shifts habitat risks for schistosomiasis-transmitting snails

Schistosomiasis, a parasitic disease transmitted by Schistosoma worms, affects more than 240 million people, while over 800 million live in areas at risk. In China, Schistosoma japonicum depends on the amphibious snail Oncomelania hupensis. Although China reached its criteria for transmission interruption by 2023, climate change and land-use changes can create new or re-emerging snail habitats. Understanding warming effects on snail survival and density is important for sustaining elimination gains.

Addressing this challenge, a research team led by Professor Jing Xu and Professor Shi‑Zhu Li from National Institute of Parasitic Diseases at Chinese Center for Disease Control and Prevention, China, with Dr. Li Qin as the first author, investigated O. hupensis responses to warming at individual, population, and ecosystem scales. They combined a 45-day temperature-controlled experiment with surveillance data from 34,554 villages across 12 provinces, covering 1990-2022. They analyzed temperature exposure across the snail's one-year life cycle, geographic and land-use factors, and future density under three climate scenarios. The study was published online in Volume 15 of the journal Infectious Diseases of Poverty on July 03, 2026.

The experiment showed that body size influenced survival of snails. Larger snails had the highest survival under low temperature, reaching 91.6%, compared with 64.3% for small snails. Under high temperature, survival rate was only 2.9% among small snails, compared with 45.7% among large snails. Across the dataset, 833 of 1,123 populations with sufficient records showed significant temperature responses, and 92.0% of these had positive temperature sensitivity. The strongest seasonal associations occurred during the coldest months and breeding periods, particularly January, February, April, and September-October.

Geography, land use, and historical climate variability also modified these responses. Waterbody-dominated areas had the highest density growth rate, while crop-dominated populations were especially responsive to land-cover change: a 1% increase in crop cover was associated with a 0.2 increase in population density. Higher latitude was associated with greater population density, whereas higher altitude was associated with lower density. Populations exposed to greater historical temperature variability showed higher densities and growth rates, but sensitivity differed by temperature measure.

"Climate warming does not affect O. hupensis populations uniformly. Our findings show that seasonal temperature exposure, geography, and land use together determine where snail populations may expand or become vulnerable," says Prof. Xu. Projections showed that populations benefiting from warming would decline to 24.6% under socioeconomic pathways (SSPs) SSP1-2.6, 21.5% under SSP2-4.5, and 19.0% under SSP5-8.5 by 2100. Croplands accounted for 72.0% of populations benefiting from warming, compared with 17.2% in forests and 8.3% in impervious-dominated areas.

Notably, regions around Poyang Lake emerged as major hotspots, while waterbodies had the highest predicted densities and impervious areas the lowest. These findings could support collaboration among disease-control, environmental, agricultural, and climate research sectors.

Overall, the findings indicate that climate warming may increase O. hupensis populations, but this benefit is not unlimited: higher-emission scenarios reduce the share of populations projected to benefit, suggesting that excessive warming could eventually suppress snail density.

"Ours is the first study to examine the impacts of climate warming on O. hupensis using daily temperature variation. It suggests that strengthening surveillance in vulnerable and expanding habitats, particularly around waterbodies and agricultural landscapes, may help China anticipate changes in schistosomiasis transmission risk and sustain elimination achievements," concludes Prof. Li.