Modelling the ecological niche of naturally occurring anthrax at global and circumpolar extents using an ensemble modelling framework

Abstract

Bacillus anthracis, the causative agent of anthrax, is a spore‐forming bacterium that primarily affects herbivorous livestock, wildlife and humans exposed to direct contact with infected animal carcasses or products. To date, there are a limited number of studies that have delineated the potential global distribution of anthrax, despite the importance of the disease from both an economic and public health standpoint. This study compiled occurrence data (n = 874) of confirmed human and animal cases from 1954 to 2021 in 94 countries. Using an ensemble ecological niche model framework, we developed updated maps of the global predicted ecological suitability of anthrax to measure relative risk at multiple scales of analysis, including a model for circumpolar regions. Additionally, we produced maps quantifying the disease transmission risk associated with anthrax to cattle, sheep and goat populations. Environmental suitability for B. anthracis globally is concentred throughout Eurasia, sub‐Saharan Africa, the Americas, Southeast Asia, Australia and Oceania. Suitable environments for B. anthracis at the circumpolar scale extend above the Arctic Circle into portions of Russia, Canada, Alaska and northern Scandinavia. Environmental factors driving B. anthracis suitability globally include vegetation, land surface temperature, soil characteristics, primary climate conditions and topography. At the circumpolar scale, suitability is influenced by soil factors, topography and the derived climate characteristics. The greatest risk to livestock is concentrated within the Indian subcontinent, Australia, Anatolia, the Caucasus region, Central Asia, the European Union, Argentina, Uruguay, China, the United States, Canada and East Africa. This study expands on previous work by providing enhanced knowledge of the potential spatial distribution of anthrax in the Southern Hemisphere, sub‐Saharan Africa, Asia and circumpolar regions of the Northern Hemisphere. We conclude that these updated maps will provide pertinent information to guide disease control programs, inform policymakers and raise awareness at the global level to lessen morbidity and mortality among animals and humans located in environmentally suitable areas.

Suitability of anthrax (Bacillus anthracis) in the Black Sea basin through the scope of distribution modelling

“…However, it is worth noting that during summer months, temperatures may still enable significant sporulation of B. anthracis [3]. In contrast, Deka et al [16] showed “very high” and “high” suitability for anthrax in parts of our northern region M, diverging from our findings. Additionally, anthrax cases in Ukraine and Belarus were reported sparingly, likely due to rigorous documentation of biothermal pits and infected burial grounds [49].…”

“…Suitable areas identified for anthrax spanned from central to eastern Türkiye, Armenia, southern Georgia, the southern Russian Federation, Bulgaria, southern and eastern Romania, Hungary, Moldova, and southern Ukraine. These areas are similar to those found by recent studies exploring the ecological niche of B. anthracis at a global scale [6,16], as well as a study specifically focused on northern latitudes [47]. Additionally, our model found anthrax-suitable areas with low uncertainty in northeast Azerbaijan, consistent with anthrax spatial clusters observed between 2000 and 2010 [48]; and the Odesa region in Ukraine, converging with a publication reporting B. anthracis in environmental samples and animal anthrax cases in this area [49].…”

“…(B) Depicts the 5% binary output of anthrax suitability with higher (orange) and lower (ochre) uncertainty. Graph and map were developed using R Statistical Software (v4.2.1) [16].…”

“…Furthermore, the lack of cases in these countries may be also explained by the prevalence of intensive livestock production systems where ruminants are often confined, and pastoral practices are uncommon, reducing opportunities for exposure to anthrax spores. Nevertheless, despite the current suboptimal environmental conditions for anthrax viability in this region, climate change- led extreme weather events, such as warmer temperatures, high precipitation and droughts [76] are expected to increase anthrax risk in these areas [16,47].…”

“…The consolidated database included international repositories, such as EMPRES-i and the World Animal Health Information System (WAHIS), regional sources, as the Animal Disease Information System (ADIS), and national databases from Moldova and Türkiye. Finally, it includes anthrax occurrences from Deka et al [16] (S1 File and S1 File Table 1).…”