Interactions between Bacillus anthracis and Plants May Promote Anthrax Transmission

Ganz, Holly H.; Turner, Wendy C.; Brodie, Eoin L.; Küsters, Martina; Shi, Ying; Sibanda, Heniritha; Török, Tamás; Getz, Wayne M.

doi:10.1371/journal.pntd.0002903

Cited by 42 publications

(36 citation statements)

References 59 publications

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“…A total of 612 anthrax outbreaks were reported in India over a period of 5 years during 1991-1996 [16]. These spores can remain in avirulent form in the soil for several decades [8,11]. Under favourable soil conditions, they become viable and the herbivore animals like cattle may have a higher chance of contracting infection while grazing in the contaminated pasture land [17], as also found in this study.…”

Section: Discussionsupporting

confidence: 61%

“…Human anthrax cases range between 2 000 and 20 000 annually over the world with majority in cutaneous form [8]. Despite this, the ecology and transmission of anthrax are less understood because of the intermittent and variable nature of outbreaks, species affected, and associated environmental and climatic conditions [11]. As far as reports of anthrax cases from India are concerned, the actual incidence of this disease is not known exactly due to underreporting.…”

Section: Objectivementioning

confidence: 99%

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Epidemiological and laboratory investigation of a zoonotic anthrax outbreak in West Bengal, India

Chakrabarty¹,

Dey²,

Nanda³

et al. 2017

APJTD

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Section: Discussionsupporting

confidence: 61%

Section: Objectivementioning

confidence: 99%

Epidemiological and laboratory investigation of a zoonotic anthrax outbreak in West Bengal, India

Chakrabarty¹,

Dey²,

Nanda³

et al. 2017

APJTD

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“…Therefore, the environmental conditions in our study area may represent the environment in which the bacterium evolved much of its current life history. A recent experiment demonstrates that BA spores in soil enhance grass seedling establishment, and that even small additions of blood increase grass height [40]. This may indicate a BA -grass mutualism whereby BA benefits from a quick regeneration of nutrientrich grasses at carcass sites to attract herbivorous hosts.…”

Section: Discussionmentioning

confidence: 99%

Fatal attraction: vegetation responses to nutrient inputs attract herbivores to infectious anthrax carcass sites

et al. 2014

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Parasites can shape the foraging behaviour of their hosts through cues indicating risk of infection. When cues for risk co-occur with desired traits such as forage quality, individuals face a trade-off between nutrient acquisition and parasite exposure. We evaluated how this trade-off may influence disease transmission in a 3-year experimental study of anthrax in a guild of mammalian herbivores in Etosha National Park, Namibia. At plains zebra (Equus quagga) carcass sites we assessed (i) carcass nutrient effects on soils and grasses, (ii) concentrations of Bacillus anthracis (BA) on grasses and in soils, and (iii) herbivore grazing behaviour, compared with control sites, using motion-sensing camera traps. We found that carcass-mediated nutrient pulses improved soil and vegetation, and that BA is found on grasses up to 2 years after death. Host foraging responses to carcass sites shifted from avoidance to attraction, and ultimately to no preference, with the strength and duration of these behavioural responses varying among herbivore species. Our results demonstrate that animal carcasses alter the environment and attract grazing hosts to parasite aggregations. This attraction may enhance transmission rates, suggesting that hosts are limited in their ability to trade off nutrient intake with parasite avoidance when relying on indirect cues.

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“…The concentration of BA in soils and grasses was assessed via bacterial culture adapted from standard soil protocols101138. Five grams of homogenized soil was combined with 45 ml 0.1% sodium pyrophosphate in a sterile 50 ml centrifuge tube.…”

Section: Methodsmentioning

confidence: 99%

Lethal exposure: An integrated approach to pathogen transmission via environmental reservoirs

Turner

Kausrud

Beyer

et al. 2016

Sci Rep

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To mitigate the effects of zoonotic diseases on human and animal populations, it is critical to understand what factors alter transmission dynamics. Here we assess the risk of exposure to lethal concentrations of the anthrax bacterium, Bacillus anthracis, for grazing animals in a natural system over time through different transmission mechanisms. We follow pathogen concentrations at anthrax carcass sites and waterholes for five years and estimate infection risk as a function of grass, soil or water intake, age of carcass sites, and the exposure required for a lethal infection. Grazing, not drinking, seems the dominant transmission route, and transmission is more probable from grazing at carcass sites 1-2 years of age. Unlike most studies of virulent pathogens that are conducted under controlled conditions for extrapolation to real situations, we evaluate exposure risk under field conditions to estimate the probability of a lethal dose, showing that not all reservoirs with detectable pathogens are significant transmission pathways.Understanding the ecological processes that drive zoonotic disease outbreaks is important in mitigating their effects on human and animal populations. One critical factor affecting infectious disease dynamics is spatio-temporal heterogeneity in transmission 1,2 . For directly transmitted pathogens, this heterogeneity can be described through peer to peer contact rates and the structure of social networks in host populations [3][4][5] . When pathogens are acquired from environmental reservoirs, the pathogen's distribution in the environment and the interaction between host behavior and reservoir becomes the crucial link in transmission. Despite the global burden of diseases with environmental reservoirs (like cholera, tularemia, polio, botulism, anthrax, bubonic plague, leptospirosis, enteropathogenic E. coli and others 6 ), microbial ecology in the field is currently understudied due to the difficulties of monitoring microbes in their natural environment. Though progress is being made in risk assessment studies, more data are needed on diseases currently posing threats to public health, livestock health, and wildlife health. Moreover, to calibrate the risk and thus an appropriate response to emerging diseases following environmental change or the release of bioweapons, we need to know their long-term behavior in natural systems.The distribution of infectious agents in the environment is typically aggregated due to pulsed releases from infected hosts, creating heterogeneity in the risk of exposure for future hosts. Public health scientists assess risk of infection by identifying disease agents, quantifying exposure, and characterizing dose-response relationships 7,8 .

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Interactions between Bacillus anthracis and Plants May Promote Anthrax Transmission

Cited by 42 publications

References 59 publications

Epidemiological and laboratory investigation of a zoonotic anthrax outbreak in West Bengal, India

Epidemiological and laboratory investigation of a zoonotic anthrax outbreak in West Bengal, India

Fatal attraction: vegetation responses to nutrient inputs attract herbivores to infectious anthrax carcass sites

Lethal exposure: An integrated approach to pathogen transmission via environmental reservoirs

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