Department of Ecology & Evolutionary Biology and Biodiversity Institute, University of Kansas, Lawrence, Kansas, United States of America.
Bacterial Special Pathogens Branch, Division of High-Consequence Pathogens and Pathology, National Center for Emerging and Zoonotic Infectious Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia, United States of America.
PLoS Negl Trop Dis. 2020 Mar 9;14(3):e0008131. doi: 10.1371/journal.pntd.0008131. eCollection 2020 Mar.
Bacillus cereus biovar anthracis (Bcbva) is an emergent bacterium closely related to Bacillus anthracis, the etiological agent of anthrax. The latter has a worldwide distribution and usually causes infectious disease in mammals associated with savanna ecosystems. Bcbva was identified in humid tropical forests of Côte d'Ivoire in 2001. Here, we characterize the potential geographic distributions of Bcbva in West Africa and B. anthracis in sub-Saharan Africa using an ecological niche modeling approach.
METHODOLOGY/PRINCIPAL FINDINGS: Georeferenced occurrence data for B. anthracis and Bcbva were obtained from public data repositories and the scientific literature. Combinations of temperature, humidity, vegetation greenness, and soils values served as environmental variables in model calibrations. To predict the potential distribution of suitable environments for each pathogen across the study region, parameter values derived from the median of 10 replicates of the best-performing model for each pathogen were used. We found suitable environments predicted for B. anthracis across areas of confirmed and suspected anthrax activity in sub-Saharan Africa, including an east-west corridor from Ethiopia to Sierra Leone in the Sahel region and multiple areas in eastern, central, and southern Africa. The study area for Bcbva was restricted to West and Central Africa to reflect areas that have likely been accessible to Bcbva by dispersal. Model predicted values indicated potential suitable environments within humid forested environments. Background similarity tests in geographic space indicated statistical support to reject the null hypothesis of similarity when comparing environments associated with B. anthracis to those of Bcbva and when comparing humidity values and soils values individually. We failed to reject the null hypothesis of similarity when comparing environments associated with Bcbva to those of B. anthracis, suggesting that additional investigation is needed to provide a more robust characterization of the Bcbva niche.
CONCLUSIONS/SIGNIFICANCE: This study represents the first time that the environmental and geographic distribution of Bcbva has been mapped. We document likely differences in ecological niche-and consequently in geographic distribution-between Bcbva and typical B. anthracis, and areas of possible co-occurrence between the two. We provide information crucial to guiding and improving monitoring efforts focused on these pathogens.
蜡状芽孢杆菌炭疽亚种（Bcbva）是一种与炭疽芽孢杆菌密切相关的新兴细菌，后者在全球范围内分布广泛，通常在与热带稀树草原生态系统相关的哺乳动物中引起传染病。Bcbva 于 2001 年在科特迪瓦的潮湿热带雨林中被发现。在这里，我们使用生态位建模方法来描述西非 Bcbva 和撒哈拉以南非洲的炭疽芽孢杆菌的潜在地理分布。
方法/主要发现：从公共数据库和科学文献中获取炭疽芽孢杆菌和 Bcbva 的地理位置数据。温度、湿度、植被绿色度和土壤值的组合作为模型校准中的环境变量。为了预测每个病原体在研究区域内适宜环境的潜在分布，使用从每个病原体表现最佳模型的 10 个重复的中位数中得出的参数值。我们发现，在撒哈拉以南非洲确认和疑似炭疽活动的地区，炭疽芽孢杆菌的适宜环境得到了预测，包括从埃塞俄比亚到塞拉利昂的萨赫勒地区的东西走廊和非洲东部、中部和南部的多个地区。Bcbva 的研究区域仅限于西非和中非，以反映可能通过扩散而使 Bcbva 到达的区域。模型预测值表明，在潮湿的森林环境中存在潜在的适宜环境。地理空间中的背景相似性测试表明，当比较与炭疽芽孢杆菌相关的环境与 Bcbva 的环境时，以及当比较湿度值和土壤值时，统计上支持拒绝相似性的零假设。当比较与 Bcbva 相关的环境与炭疽芽孢杆菌的环境时，我们未能拒绝相似性的零假设，这表明需要进一步调查以更准确地描述 Bcbva 的生态位。
结论/意义：这是首次对 Bcbva 的环境和地理分布进行了映射。我们记录了 Bcbva 与典型炭疽芽孢杆菌之间生态位（因此地理分布）的可能差异，以及两者之间可能发生的共存区域。我们提供了对指导和改进这些病原体监测工作至关重要的信息。
