Modeling the Ecological Niche of Bacillus anthracis to Map Anthrax Risk in Kyrgyzstan

Abstract

Abstract. Anthrax, caused by the environmental bacterium Bacillus anthracis, is an important zoonosis nearly worldwide. In Central Asia, anthrax represents a major veterinary and public health concern. In the Republic of Kyrgyzstan, ongoing anthrax outbreaks have been reported in humans associated with handling infected livestock and contaminated animal by-products such as meat or hides. The current anthrax situation has prompted calls for improved insights into the epidemiology, ecology, and spatial distribution of the disease in Kyrgyzstan to better inform control and surveillance. Disease control for both humans and livestock relies on annual livestock vaccination ahead of outbreaks. Toward this, we used a historic database of livestock anthrax reported from 1932 to 2006 mapped at high resolution to develop an ecological niche model-based prediction of B. anthracis across Kyrgyzstan and identified spatial clusters of livestock anthrax using a cluster morphology statistic. We also defined the seasonality of outbreaks in livestock. Cattle were the most frequently reported across the time period, with the greatest number of cases in late summer months. Our niche models defined four areas as suitable to support pathogen persistence, the plateaus near Talas and Bishkek, the valleys of western Kyrgyzstan along the Fergana Valley, and the low-lying areas along the shore of Lake Isyk-Kul. These areas should be considered "at risk" for livestock anthrax and subsequent human cases. Areas defined by the niche models can be used to prioritize anthrax surveillance and inform efforts to target livestock vaccination campaigns.

An Ecological Framework for Modeling the Geography of Disease Transmission

“…Ecological niche modeling (ENM) has proven useful to forecast the distribution of a vast number of organisms [10-13] and is increasingly employed to predict parasite distributions locally and globally [14][15][16][17]. Despite great strides made in the implementation of ENM to forecast complex biological phenomena such as disease systems [18], traditional frameworks may render biologically unrealistic predictions and thus must be revised, as we show in this review.…”

“…However, the black-box oversimplification may be perilous as it neglects ecological complexity (e.g., the identity of key host species for transmission). Alternatively, component-based approaches consider the individual ecologies of all species involved in disease transmission (e.g., parasites, hosts) [16,17,32]. This approach allows the identification of host species and prioritization of areas for disease surveillance and control.…”

“…As human activities intensify, contact with wildlife and exposure to novel parasites increase, potentially driving zoonotic disease emergence [1,7]. Given the threat that EIDs pose to human populations, understanding the underlying drivers of parasite geographic distribution and their spillover to humans is particularly relevant for epidemiologists, public-health practitioners, and policy makers [9].Ecological niche modeling (ENM) has proven useful to forecast the distribution of a vast number of organisms [10-13] and is increasingly employed to predict parasite distributions locally and globally [14][15][16][17]. Despite great strides made in the implementation of ENM to forecast complex biological phenomena such as disease systems [18], traditional frameworks may render biologically unrealistic predictions and thus must be revised, as we show in this review.…”

Spores and soil from six sides: interdisciplinarity and the environmental biology of anthrax (Bacillus anthracis)

“…It is worth noting that while anthrax is effectively cosmopolitan at a global scale, no global map of its distribution has ever been constructed; instead, most studies have mapped its distribution using ENMs constructed at the regional or national scale, often in close partnership with public health efforts. Studies using ENMs to map anthrax have been carried out in at least 12 countries, including Australia (Barro et al ., ), Cameroon, Chad, and Nigeria (Blackburn et al ., ), China (Chen et al ., ), Ghana (Kracalik et al ., ), Italy and Kazakhstan (Mullins et al ., ), Kyrgyzstan (Blackburn et al ., ), Mexico and the USA (Blackburn, ), and Zimbabwe (Chikerema et al ., ). In many of these regions, ENMs are the most accessible statistical tool for mapping risk, and therefore guide spatial prioritization for wildlife surveillance and livestock vaccination campaigns; however, follow‐up studies evaluating the efficacy of ENM‐based campaigns are currently rare (a problem not unique to anthrax work).…”

Spores and soil from six sides: interdisciplinarity and the environmental biology of anthrax (Bacillus anthracis)

“…It is worth noting that while anthrax is effectively cosmopolitan on a global scale, no global map of its distribution has ever been constructed; instead, most studies have mapped its distribution using ENMs constructed at the regional or national scale, often in close partnership with public health efforts. Studies using ENMs to map anthrax have been done in at least 12 countries, including Australia 141 ; Cameroon, Chad, and Nigeria 142 ; China 143 ; Ghana 144 ; Italy and Kazakhstan 145 ; Kyrgyzstan 146 ; Mexico and the United States 147 ; and Zimbabwe. 148 In many of these regions, ENMs are the most accessible statistical tool for mapping risk, and therefore guide spatial prioritization for wildlife surveillance and livestock vaccination campaigns; however, follow-up studies evaluating the efficacy of ENM-based campaigns are currently fairly lacking (a problem not unique to anthrax work).…”