McCreesh Nicky, Nikulin Grigory, Booth Mark
School of Medicine, Pharmacy and Health, Durham University, Durham, DH1 3LE, UK.
Swedish Meteorological and Hydrological Institute, Rossby Centre, Norrköping, SE-601 7, Sweden.
Parasit Vectors. 2015 Jan 6;8:4. doi: 10.1186/s13071-014-0617-0.
Survival and fitness attributes of free-living and sporocyst schistosome life-stages and their intermediate host snails are sensitive to water temperature. Climate change may alter the geographical distribution of schistosomiasis by affecting the suitability of freshwater bodies for hosting parasite and snail populations.
We have developed an agent-based model of the temperature-sensitive stages of the Schistosoma mansoni and intermediate host snail lifecycles. The model was run using low, moderate and high warming climate projections over eastern Africa. For each climate projection, eight model scenarios were used to determine the sensitivity of predictions to different relationships between air and water temperature, and different snail mortality rates. Maps were produced showing predicted changes in risk as a result of increasing temperatures over the next 20 and 50 years.
Baseline model output compared to prevalence data indicates suitable temperatures are necessary but not sufficient for both S. mansoni transmission and high infection prevalences. All else being equal, infection risk may increase by up to 20% over most of eastern Africa over the next 20 and 50 years. Increases may be higher in Rwanda, Burundi, south-west Kenya and eastern Zambia, and S. mansoni may become newly endemic in some areas. Results for 20-year projections are robust to changes in simulated intermediate host snail habitat conditions. There is greater uncertainty about the effects of different habitats on changes in risk in 50 years' time.
Temperatures are likely to become suitable for increased S. mansoni transmission over much of eastern Africa. This may reduce the impact of control and elimination programmes. S. mansoni may also spread to new areas outside existing control programmes. We call for increased surveillance in areas defined as potentially suitable for emergent transmission.
自由生活的血吸虫和孢子囊阶段及其中间宿主蜗牛的生存和适应性属性对水温敏感。气候变化可能会通过影响淡水水体对寄生虫和蜗牛种群的适宜性来改变血吸虫病的地理分布。
我们开发了一个基于主体的模型，用于模拟曼氏血吸虫和中间宿主蜗牛生命周期中对温度敏感的阶段。该模型使用东非地区低、中、高升温的气候预测数据运行。对于每种气候预测，使用八个模型情景来确定预测对气温与水温之间不同关系以及不同蜗牛死亡率的敏感性。制作了地图，显示了未来20年和50年因气温升高而预测的风险变化。
与流行率数据相比，基线模型输出表明适宜的温度对于曼氏血吸虫传播和高感染率是必要的，但并非充分条件。在其他条件相同的情况下，未来20年和50年，东非大部分地区的感染风险可能会增加高达20%。卢旺达、布隆迪、肯尼亚西南部和赞比亚东部的增幅可能更高，曼氏血吸虫可能会在一些地区成为新的地方病。20年预测结果对于模拟中间宿主蜗牛栖息地条件的变化具有稳健性。对于50年后不同栖息地对风险变化的影响，不确定性更大。
在东非大部分地区，温度可能会变得适宜于增加曼氏血吸虫的传播。这可能会降低控制和消除计划的影响。曼氏血吸虫也可能传播到现有控制计划之外的新地区。我们呼吁在被定义为可能适合新出现传播的地区加强监测。
