MRC Centre for Global Infectious Disease Analysis, Department of Infectious Disease Epidemiology, School of Public Health, Imperial College London, London, UK.
The Abdul Latif Jameel Institute for Disease and Emergency Analytics, School of Public Health, Imperial College London, London, UK.
BMC Med. 2022 Apr 20;20(1):135. doi: 10.1186/s12916-022-02324-1.
Sub-Saharan Africa has seen substantial reductions in cases and deaths due to malaria over the past two decades. While this reduction is primarily due to an increasing expansion of interventions, urbanisation has played its part as urban areas typically experience substantially less malaria transmission than rural areas. However, this may be partially lost with the invasion and establishment of Anopheles stephensi. A. stephensi, the primary urban malaria vector in Asia, was first detected in Africa in 2012 in Djibouti and was subsequently identified in Ethiopia in 2016, and later in Sudan and Somalia. In Djibouti, malaria cases have increased 30-fold from 2012 to 2019 though the impact in the wider region remains unclear.
Here, we have adapted an existing model of mechanistic malaria transmission to estimate the increase in vector density required to explain the trends in malaria cases seen in Djibouti. To account for the observed plasticity in An. stephensi behaviour, and the unknowns of how it will establish in a novel environment, we sample behavioural parameters in order to account for a wide range of uncertainty. This quantification is then applied to Ethiopia, considering temperature-dependent extrinsic incubation periods, pre-existing vector-control interventions and Plasmodium falciparum prevalence in order to assess the potential impact of An. stephensi establishment on P. falciparum transmission. Following this, we estimate the potential impact of scaling up ITN (insecticide-treated nets)/IRS (indoor residual spraying) and implementing piperonyl butoxide (PBO) ITNs and larval source management, as well as their economic costs.
We estimate that annual P. falciparum malaria cases could increase by 50% (95% CI 14-90) if no additional interventions are implemented. The implementation of sufficient control measures to reduce malaria transmission to pre-stephensi levels will cost hundreds of millions of USD.
Substantial heterogeneity across the country is predicted and large increases in vector control interventions could be needed to prevent a major public health emergency.
在过去的二十年中，撒哈拉以南非洲地区的疟疾病例和死亡人数大幅减少。虽然这种减少主要是由于干预措施的不断扩大，但城市化也起到了一定的作用，因为城市地区的疟疾传播通常比农村地区少得多。然而，随着入侵和建立的阿蚊斯蒂芬斯的建立，这种情况可能会部分丧失。A. 斯蒂芬斯，亚洲主要的城市疟疾传播媒介，于 2012 年首次在吉布提被发现，随后于 2016 年在埃塞俄比亚被发现，随后在苏丹和索马里也被发现。尽管在更广泛的地区的影响仍不清楚，但吉布提的疟疾病例从 2012 年到 2019 年增加了 30 倍。
在这里，我们对现有的疟疾传播机制模型进行了改编，以估计需要增加多少蚊子密度才能解释吉布提疟疾病例的趋势。为了说明阿蚊斯蒂芬斯行为的可观察到的可塑性，以及它在新环境中建立的未知情况，我们对行为参数进行了采样，以考虑到广泛的不确定性。然后，我们将这种量化应用于埃塞俄比亚，考虑到温度依赖性的外潜伏期、现有的媒介控制干预措施以及恶性疟原虫的流行率，以评估阿蚊斯蒂芬斯建立对恶性疟原虫传播的潜在影响。在此之后，我们估计了扩大经杀虫剂处理的蚊帐（ITN）/室内滞留喷洒（IRS）和实施胡椒基丁醚（PBO）ITN 和幼虫源管理以及它们的经济成本的潜在影响。
我们估计，如果不实施额外的干预措施，每年的恶性疟疾病例可能会增加 50%（95%CI14-90）。实施足以降低疟疾传播到斯蒂芬斯之前水平的控制措施将花费数亿美元。
预计全国各地存在显著的异质性，可能需要大幅增加蚊虫控制干预措施，以防止发生重大公共卫生紧急情况。
