Ochai Sunday O, Snyman Lourens, Dolfi Amelie C, Ramoelo Abel, Reilly Brian K, Botha Judith M, Dekker Edgar H, van Schalkwyk O Louis, Kamath Pauline L, Archer Emma, Turner Wendy C, van Heerden Henriette
Department of Veterinary Tropical Diseases, Faculty of Veterinary Science, University of Pretoria, Onderstepoort, South Africa.
Antimicrobial Research Unit, College of Health Sciences, University of KwaZulu-Natal, Durban, South Africa.
PLoS One. 2024 Dec 6;19(12):e0314103. doi: 10.1371/journal.pone.0314103. eCollection 2024.
Environmental and climatic factors, as well as host demographics and behaviour, significantly influence the exposure of herbivorous mammalian hosts to pathogens such as Bacillus anthracis, the causative agent of anthrax. Until the early 1990s in Kruger National Park (KNP), kudu (Tragelaphus strepsiceros) was the host species most affected by anthrax, with outbreaks occurring predominantly in the dry season, particularly during drought cycles. However, the most affected host species has shifted to impala (Aepyceros melampus), with more frequent anthrax outbreaks during the wet season. This study investigates the roles of environmental variation and other host species in this shift. Temporal trends in environmental variables such as precipitation, soil moisture, temperature, and normalised difference vegetation index (NDVI) were analyzed in relation to anthrax occurrence (presence/ absence and counts). Additionally, correlations between host species' densities and anthrax mortalities over time were examined. Anthrax cases in 1990 were concentrated in the central and northern regions of KNP(excluding Pafuri), primarily affected kudus; while subsequent mortalities affected mostly impala and were restricted to the far north, in Pafuri. Significant correlations were found between kudu anthrax mortality and a decrease in NDVI, average temperature, SPI-6 and SPI-12 (Standardised Precipitation Index in various time intervals. Conversely, anthrax occurrence in impalas was associated with a decline in SPI-3, and temperature rise, with increased mortality during the rainy season. Elephant density correlated negatively with kudu mortality, but a positive correlation with both impala mortality and impala density. The study concludes that environmental variables and species' densities may alter the diversity and frequency of hosts exposed to B. anthracis. Climate extremes and alterations therein may exacerbate anthrax severity by modifying species susceptibility and their probability of exposure over time.
环境和气候因素，以及宿主的人口统计学特征和行为，会显著影响食草哺乳动物宿主接触病原体（如炭疽杆菌，炭疽病的病原体）的情况。直到20世纪90年代初，在克鲁格国家公园（KNP），捻角羚（大羚羊）是受炭疽影响最严重的宿主物种，疫情主要发生在旱季，尤其是在干旱周期。然而，受影响最严重的宿主物种已转变为黑斑羚，炭疽疫情在雨季更为频繁。本研究调查了环境变化和其他宿主物种在这一转变中的作用。分析了降水、土壤湿度、温度和归一化植被指数（NDVI）等环境变量的时间趋势与炭疽发生情况（存在/不存在及数量）的关系。此外，还研究了宿主物种密度与炭疽死亡率随时间的相关性。1990年的炭疽病例集中在KNP的中部和北部地区（不包括帕富里），主要影响捻角羚；而随后的死亡病例大多影响黑斑羚，且仅限于最北部的帕富里。发现捻角羚炭疽死亡率与NDVI、平均温度、SPI - 6和SPI - 12（不同时间间隔的标准化降水指数）的下降之间存在显著相关性。相反，黑斑羚的炭疽发生与SPI - 3的下降和温度升高有关，雨季死亡率增加。大象密度与捻角羚死亡率呈负相关，但与黑斑羚死亡率和黑斑羚密度均呈正相关。该研究得出结论，环境变量和物种密度可能会改变接触炭疽杆菌的宿主的多样性和频率。极端气候及其变化可能会通过改变物种易感性及其随时间的接触概率来加剧炭疽的严重程度。
