Natural Dissemination of
            <i>Bacillus anthracis</i>
            Spores in Northern Canada

Dragon, D. C.; Bader, Douglas E.; Mitchell, Jade; Woollen, Neal E.

doi:10.1128/aem.71.3.1610-1615.2005

Cited by 56 publications

(57 citation statements)

References 4 publications

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“…Experimental lethal doses for ingested anthrax are high in herbivores (around 10 7 -10 8 spores [20]), therefore transmission depends on BA aggregating in the environment and the behaviour of potential hosts at these aggregations. BA spores are known to be concentrated in soils at anthrax carcass sites and can persist there for several years [22,36], patterns that are not affected by scavenger presence or exclusion [37]. Despite the hypothesized importance of grazing in BA transmission [20,38], this is the first study to examine levels of BA contamination on grasses in the natural environment.…”

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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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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“…B. megaterium is able to grow in soil, as supported by proof for in situ transcription of the exponentially expressed protease gene nprM (14). Yet the recent literature implies that B. cereus sensu lato does not grow in soil (6,16). The current paradigm is that B. cereus sensu lato germinates and grows either in an animal host or in the rhizosphere, resulting in either symbiotic or pathogenic interactions.…”

mentioning

confidence: 99%

Analysis of the Life Cycle of the Soil Saprophyte Bacillus cereus in Liquid Soil Extract and in Soil

Vilain

Luo

Hildreth

et al. 2006

Appl Environ Microbiol

182

127

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Bacillus is commonly isolated from soils, with organisms of Bacillus cereus sensu lato being prevalent. Knowledge of the ecology of B. cereus and other Bacillus species in soil is far from complete. While the older literature favors a model of growth on soil-associated organic matter, the current paradigm is that B. cereus sensu lato germinates and grows in association with animals or plants, resulting in either symbiotic or pathogenic interactions. An in terra approach to study soil-associated bacteria is described, using filtersterilized soil-extracted soluble organic matter (SESOM) and artificial soil microcosms (ASM) saturated with SESOM. B. cereus ATCC 14579 displayed a life cycle, with the ability to germinate, grow, and subsequently sporulate in both the liquid SESOM extract and in ASM inserted into wells in agar medium. Cells grew in liquid SESOM without separating, forming multicellular structures that coalesced to form clumps and encasing the ensuing spores in an extracellular matrix. Bacillus was able to translocate from the point of inoculation through soil microcosms as shown by the emergence of outgrowths on the surrounding agar surface. Microscopic inspection revealed bundles of parallel chains inside the soil. The motility inhibitor L-ethionine failed to suppress outgrowth, ruling out translocation by a flagellar-mediated mechanism such as swimming or swarming. Bacillus subtilis subsp. subtilis Marburg and four Bacillus isolates taken at random from soils also displayed a life cycle in SESOM and ASM and were all able to translocate through ASM, even in presence of L-ethionine. These data indicate that B. cereus is a saprophytic bacterium that is able to grow in soil and furthermore that it is adapted to translocate by employing a multicellular mode of growth.

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“…Nevertheless, scavenging is frequently considered to play a critical role in the production of spores at carcass sites. The single study to empirically assess the relationship between scavengers and spore production found no significant difference between spore contamination at two carcasses, of which one was minimally scavenged while the other had been fully scavenged (27).…”

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confidence: 99%

Effects of Experimental Exclusion of Scavengers from Carcasses of Anthrax-Infected Herbivores on Bacillus anthracis Sporulation, Survival, and Distribution

Bellan

Turnbull²,

Beyer

et al. 2013

Appl Environ Microbiol

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e Scavenging of anthrax carcasses has long been hypothesized to play a critical role in the production of the infectious spore stage of Bacillus anthracis after host death, though empirical studies assessing this are lacking. We compared B. anthracis spore production, distribution, and survival at naturally occurring anthrax herbivore carcasses that were either experimentally caged to exclude vertebrate scavengers or left unmanipulated. We found no significant effect of scavengers on soil spore density (P > 0.05). Soil stained with terminally hemorrhaged blood and with nonhemorrhagic fluids exhibited high levels of B. anthracis spore contamination (ranging from 10 3 to 10 8 spores/g), even in the absence of vertebrate scavengers. At most of the carcass sites, we also found that spore density in samples taken from hemorrhagic-fluid-stained soil continued to increase for >4 days after host death. We conclude that scavenging by vertebrates is not a critical factor in the life cycle of B. anthracis and that anthrax control measures relying on deterrence or exclusion of vertebrate scavengers to prevent sporulation are unlikely to be effective.

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Natural Dissemination of Bacillus anthracis Spores in Northern Canada

Cited by 56 publications

References 4 publications

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

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

Analysis of the Life Cycle of the Soil Saprophyte Bacillus cereus in Liquid Soil Extract and in Soil

Effects of Experimental Exclusion of Scavengers from Carcasses of Anthrax-Infected Herbivores on Bacillus anthracis Sporulation, Survival, and Distribution

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