Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, United Kingdom.
SACEMA, University of Stellenbosch, Stellenbosch, South Africa.
PLoS Med. 2018 Oct 22;15(10):e1002675. doi: 10.1371/journal.pmed.1002675. eCollection 2018 Oct.
Quantifying the effects of climate change on the entomological and epidemiological components of vector-borne diseases is an essential part of climate change research, but evidence for such effects remains scant, and predictions rely largely on extrapolation of statistical correlations. We aimed to develop a mechanistic model to test whether recent increases in temperature in the Mana Pools National Park of the Zambezi Valley of Zimbabwe could account for the simultaneous decline of tsetse flies, the vectors of human and animal trypanosomiasis.
The model we developed incorporates the effects of temperature on mortality, larviposition, and emergence rates and is fitted to a 27-year time series of tsetse caught from cattle. These catches declined from an average of c. 50 flies per animal per afternoon in 1990 to c. 0.1 in 2017. Since 1975, mean daily temperatures have risen by c. 0.9°C and temperatures in the hottest month of November by c. 2°C. Although our model provided a good fit to the data, it cannot predict whether or when extinction will occur.
The model suggests that the increase in temperature may explain the observed collapse in tsetse abundance and provides a first step in linking temperature to trypanosomiasis risk. If the effect at Mana Pools extends across the whole of the Zambezi Valley, then transmission of trypanosomes is likely to have been greatly reduced in this warm low-lying region. Conversely, rising temperatures may have made some higher, cooler, parts of Zimbabwe more suitable for tsetse and led to the emergence of new disease foci.
量化气候变化对虫媒病的昆虫学和流行病学因素的影响是气候变化研究的重要组成部分，但此类影响的证据仍然很少，预测主要依赖于统计相关性的推断。我们旨在开发一种机制模型，以检验津巴布韦赞比西河谷马纳波尔斯国家公园最近温度升高是否可以解释采采蝇（人体和动物锥虫病的传播媒介）同时减少的情况。
我们开发的模型纳入了温度对死亡率、产卵和羽化率的影响，并拟合了 27 年时间内从牛身上捕获的采采蝇的时间序列。这些捕获量从 1990 年每头动物每下午平均约 50 只下降到 2017 年的约 0.1 只。自 1975 年以来，平均日温度上升了约 0.9°C，11 月最热月份的温度上升了约 2°C。虽然我们的模型很好地拟合了数据，但它无法预测何时或是否会灭绝。
该模型表明，温度升高可能解释了采采蝇数量的观察性崩溃，并首次将温度与锥虫病风险联系起来。如果马纳波尔斯的影响扩展到整个赞比西河谷，那么在这个温暖的低地地区，锥虫的传播很可能大大减少。相反，温度升高可能使津巴布韦的一些较高、较冷的地区更适合采采蝇，并导致新的疾病焦点出现。
