Academic literature on the topic 'Pathogen reservoir'
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Journal articles on the topic "Pathogen reservoir"
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Brisson, Dustin, Catherine Brinkley, Parris T. Humphrey, Brian D. Kemps, and Richard S. Ostfeld. "It Takes a Community to Raise the Prevalence of a Zoonotic Pathogen." Interdisciplinary Perspectives on Infectious Diseases 2011 (2011): 1–6. http://dx.doi.org/10.1155/2011/741406.
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By definition, zoonotic pathogens are not strict host-species specialists in that they infect humans and at least one nonhuman reservoir species. The majority of zoonotic pathogens infect and are amplified by multiple vertebrate species in nature, each of which has a quantitatively different impact on the distribution and abundance of the pathogen and thus on disease risk. Unfortunately, when new zoonotic pathogens emerge, the dominant response by public health scientists is to search for a few, or even the single, most important reservoirs and to ignore other species that might strongly influence transmission. This focus on the single “primary” reservoir host species can delay biological understanding, and potentially public health interventions as species important in either amplifying or regulating the pathogen are overlooked. Investigating the evolutionary and ecological strategy of newly discovered or emerging pathogens within the community of potential and actual host species will be fruitful to both biological understanding and public health.
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Han, Barbara A., John Paul Schmidt, Sarah E. Bowden, and John M. Drake. "Rodent reservoirs of future zoonotic diseases." Proceedings of the National Academy of Sciences 112, no. 22 (May 18, 2015): 7039–44. http://dx.doi.org/10.1073/pnas.1501598112.
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The increasing frequency of zoonotic disease events underscores a need to develop forecasting tools toward a more preemptive approach to outbreak investigation. We apply machine learning to data describing the traits and zoonotic pathogen diversity of the most speciose group of mammals, the rodents, which also comprise a disproportionate number of zoonotic disease reservoirs. Our models predict reservoir status in this group with over 90% accuracy, identifying species with high probabilities of harboring undiscovered zoonotic pathogens based on trait profiles that may serve as rules of thumb to distinguish reservoirs from nonreservoir species. Key predictors of zoonotic reservoirs include biogeographical properties, such as range size, as well as intrinsic host traits associated with lifetime reproductive output. Predicted hotspots of novel rodent reservoir diversity occur in the Middle East and Central Asia and the Midwestern United States.
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Hoyt, Joseph R., Kate E. Langwig, Keping Sun, Katy L. Parise, Aoqiang Li, Yujuan Wang, Xiaobin Huang, et al. "Environmental reservoir dynamics predict global infection patterns and population impacts for the fungal disease white-nose syndrome." Proceedings of the National Academy of Sciences 117, no. 13 (March 16, 2020): 7255–62. http://dx.doi.org/10.1073/pnas.1914794117.
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Disease outbreaks and pathogen introductions can have significant effects on host populations, and the ability of pathogens to persist in the environment can exacerbate disease impacts by fueling sustained transmission, seasonal epidemics, and repeated spillover events. While theory suggests that the presence of an environmental reservoir increases the risk of host declines and threat of extinction, the influence of reservoir dynamics on transmission and population impacts remains poorly described. Here we show that the extent of the environmental reservoir explains broad patterns of host infection and the severity of disease impacts of a virulent pathogen. We examined reservoir and host infection dynamics and the resulting impacts of Pseudogymnoascus destructans, the fungal pathogen that causes white-nose syndrome, in 39 species of bats at 101 sites across the globe. Lower levels of pathogen in the environment consistently corresponded to delayed infection of hosts, fewer and less severe infections, and reduced population impacts. In contrast, an extensive and persistent environmental reservoir led to early and widespread infections and severe population declines. These results suggest that continental differences in the persistence or decay of P. destructans in the environment altered infection patterns in bats and influenced whether host populations were stable or experienced severe declines from this disease. Quantifying the impact of the environmental reservoir on disease dynamics can provide specific targets for reducing pathogen levels in the environment to prevent or control future epidemics.
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Wu, Ruonan, Gareth Trubl, Neslihan Taş, and Janet K. Jansson. "Permafrost as a potential pathogen reservoir." One Earth 5, no. 4 (April 2022): 351–60. http://dx.doi.org/10.1016/j.oneear.2022.03.010.
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Washburne, Alex D., Daniel E. Crowley, Daniel J. Becker, Kezia R. Manlove, Marissa L. Childs, and Raina K. Plowright. "Percolation models of pathogen spillover." Philosophical Transactions of the Royal Society B: Biological Sciences 374, no. 1782 (August 12, 2019): 20180331. http://dx.doi.org/10.1098/rstb.2018.0331.
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Predicting pathogen spillover requires counting spillover events and aligning such counts with process-related covariates for each spillover event. How can we connect our analysis of spillover counts to simple, mechanistic models of pathogens jumping from reservoir hosts to recipient hosts? We illustrate how the pathways to pathogen spillover can be represented as a directed graph connecting reservoir hosts and recipient hosts and the number of spillover events modelled as a percolation of infectious units along that graph. Percolation models of pathogen spillover formalize popular intuition and management concepts for pathogen spillover, such as the inextricably multilevel nature of cross-species transmission, the impact of covariance between processes such as pathogen shedding and human susceptibility on spillover risk, and the assumptions under which the effect of a management intervention targeting one process, such as persistence of vectors, will translate to an equal effect on the overall spillover risk. Percolation models also link statistical analysis of spillover event datasets with a mechanistic model of spillover. Linear models, one might construct for process-specific parameters, such as the log-rate of shedding from one of several alternative reservoirs, yield a nonlinear model of the log-rate of spillover. The resulting nonlinearity is approximately piecewise linear with major impacts on statistical inferences of the importance of process-specific covariates such as vector density. We recommend that statistical analysis of spillover datasets use piecewise linear models, such as generalized additive models, regression clustering or ensembles of linear models, to capture the piecewise linearity expected from percolation models. We discuss the implications of our findings for predictions of spillover risk beyond the range of observed covariates, a major challenge of forecasting spillover risk in the Anthropocene. This article is part of the theme issue ‘Dynamic and integrative approaches to understanding pathogen spillover’.
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Myers, B. R., S. Beecham, J. A. van Leeuwen, and A. Keegan. "Depletion of E. coli in permeable pavement mineral aggregate storage and reuse systems." Water Science and Technology 60, no. 12 (December 1, 2009): 3091–99. http://dx.doi.org/10.2166/wst.2009.753.
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Permeable pavement reservoirs provide an important opportunity for the harvesting and storage of stormwater for reuse. This research aims to determine whether storage in dolomite, calcite and quartzite mineral aggregates in the base course of a permeable pavement impacts on the survival of the pathogen indicator organism Escherichia coli (E. coli) in storage. The reasons for depletion were also investigated. Twelve model permeable pavement storage reservoirs were filled, in triplicate, with dolomite, calcite and quartzite. Three reservoirs contained no aggregate. After filling with pathogen spiked rainwater, the concentration of E. coli was examined for 22 days in the reservoirs. The reservoirs were then agitated to determine if there was E. coli present which was not in aqueous suspension. The results of the experiments show that there is no significant difference in the depletion of E. coli found in reservoirs without aggregate, and those filled with dolomite or calcite. The rate of depletion was found to be significantly lower in the quartzite filled reservoirs. Agitation of the reservoirs yielded increases in the aqueous concentration of E. coli in all reservoir types, suggesting that the bacteria are adhering to the surface of the mineral aggregate and to the reservoir walls.
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Cronin, James Patrick, Miranda E. Welsh, Martin G. Dekkers, Samuel T. Abercrombie, and Charles E. Mitchell. "Host physiological phenotype explains pathogen reservoir potential." Ecology Letters 13, no. 10 (July 6, 2010): 1221–32. http://dx.doi.org/10.1111/j.1461-0248.2010.01513.x.
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Worsley-Tonks, Katherine E. L., Luis E. Escobar, Roman Biek, Mariana Castaneda-Guzman, Meggan E. Craft, Daniel G. Streicker, Lauren A. White, and Nicholas M. Fountain-Jones. "Using host traits to predict reservoir host species of rabies virus." PLOS Neglected Tropical Diseases 14, no. 12 (December 8, 2020): e0008940. http://dx.doi.org/10.1371/journal.pntd.0008940.
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Wildlife are important reservoirs for many pathogens, yet the role that different species play in pathogen maintenance frequently remains unknown. This is the case for rabies, a viral disease of mammals. While Carnivora (carnivores) and Chiroptera (bats) are the canonical mammalian orders known to be responsible for the maintenance and onward transmission of rabies Lyssavirus (RABV), the role of most species within these orders remains unknown and is continually changing as a result of contemporary host shifting. We combined a trait-based analytical approach with gradient boosting machine learning models to identify physiological and ecological host features associated with being a reservoir for RABV. We then used a cooperative game theory approach to determine species-specific traits associated with known RABV reservoirs. Being a carnivore reservoir for RABV was associated with phylogenetic similarity to known RABV reservoirs, along with other traits such as having larger litters and earlier sexual maturity. For bats, location in the Americas and geographic range were the most important predictors of RABV reservoir status, along with having a large litter. Our models identified 44 carnivore and 34 bat species that are currently not recognized as RABV reservoirs, but that have trait profiles suggesting their capacity to be or become reservoirs. Further, our findings suggest that potential reservoir species among bats and carnivores occur both within and outside of areas with current RABV circulation. These results show the ability of a trait-based approach to detect potential reservoirs of infection and could inform rabies control programs and surveillance efforts by identifying the types of species and traits that facilitate RABV maintenance and transmission.
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Hoyer, Isaiah J., Erik M. Blosser, Carolina Acevedo, Anna Carels Thompson, Lawrence E. Reeves, and Nathan D. Burkett-Cadena. "Mammal decline, linked to invasive Burmese python, shifts host use of vector mosquito towards reservoir hosts of a zoonotic disease." Biology Letters 13, no. 10 (October 2017): 20170353. http://dx.doi.org/10.1098/rsbl.2017.0353.
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Invasive apex predators have profound impacts on natural communities, yet the consequences of these impacts on the transmission of zoonotic pathogens are unexplored. Collapse of large- and medium-sized mammal populations in the Florida Everglades has been linked to the invasive Burmese python, Python bivittatus Kuhl. We used historic and current data to investigate potential impacts of these community effects on contact between the reservoir hosts (certain rodents) and vectors of Everglades virus, a zoonotic mosquito-borne pathogen that circulates in southern Florida. The percentage of blood meals taken from the primary reservoir host, the hispid cotton rat, Sigmodon hispidus Say and Ord, increased dramatically (422.2%) from 1979 (14.7%) to 2016 (76.8%), while blood meals from deer, raccoons and opossums decreased by 98.2%, reflecting precipitous declines in relative abundance of these larger mammals, attributed to python predation. Overall species diversity of hosts detected in Culex cedecei blood meals from the Everglades declined by 40.2% over the same period ( H (1979) = 1.68, H (2016) = 1.01). Predictions based upon the dilution effect theory suggest that increased relative feedings upon reservoir hosts translate into increased abundance of infectious vectors, and a corresponding upsurge of Everglades virus occurrence and risk of human exposure, although this was not tested in the current study. This work constitutes the first indication that an invasive predator can increase contact between vectors and reservoirs of a human pathogen and highlights unrecognized indirect impacts of invasive predators.
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Shea, Dylan, Andrew Bateman, Shaorong Li, Amy Tabata, Angela Schulze, Gideon Mordecai, Lindsey Ogston, et al. "Environmental DNA from multiple pathogens is elevated near active Atlantic salmon farms." Proceedings of the Royal Society B: Biological Sciences 287, no. 1937 (October 21, 2020): 20202010. http://dx.doi.org/10.1098/rspb.2020.2010.
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The spread of infection from reservoir host populations is a key mechanism for disease emergence and extinction risk and is a management concern for salmon aquaculture and fisheries. Using a quantitative environmental DNA methodology, we assessed pathogen environmental DNA in relation to salmon farms in coastal British Columbia, Canada, by testing for 39 species of salmon pathogens (viral, bacterial, and eukaryotic) in 134 marine environmental samples at 58 salmon farm sites (both active and inactive) over 3 years. Environmental DNA from 22 pathogen species was detected 496 times and species varied in their occurrence among years and sites, likely reflecting variation in environmental factors, other native host species, and strength of association with domesticated Atlantic salmon. Overall, we found that the probability of detecting pathogen environmental DNA (eDNA) was 2.72 (95% CI: 1.48, 5.02) times higher at active versus inactive salmon farm sites and 1.76 (95% CI: 1.28, 2.42) times higher per standard deviation increase in domesticated Atlantic salmon eDNA concentration at a site. If the distribution of pathogen eDNA accurately reflects the distribution of viable pathogens, our findings suggest that salmon farms serve as a potential reservoir for a number of infectious agents; thereby elevating the risk of exposure for wild salmon and other fish species that share the marine environment.
Dissertations / Theses on the topic "Pathogen reservoir"
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Marien, Joachim, Benny Borremans, Sophie Gryseels, Barre Soropogui, Bruyn Luc De, Gedeon Ngiala Bongo, Beate Becker-Ziaja, et al. "No measurable adverse effects of Lassa, Morogoro and Gairo arenaviruses on their rodent reservoir host in natural conditions." BIOMED CENTRAL LTD, 2017. http://hdl.handle.net/10150/624077.
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Background: In order to optimize net transmission success, parasites are hypothesized to evolve towards causing minimal damage to their reservoir host while obtaining high shedding rates. For many parasite species however this paradigm has not been tested, and conflicting results have been found regarding the effect of arenaviruses on their rodent host species. The rodent Mastomys natalensis is the natural reservoir host of several arenaviruses, including Lassa virus that is known to cause Lassa haemorrhagic fever in humans. Here, we examined the effect of three arenaviruses (Gairo, Morogoro and Lassa virus) on four parameters of wild-caught Mastomys natalensis: body mass, head-body length, sexual maturity and fertility. After correcting for the effect of age, we compared these parameters between arenavirus-positive (arenavirus RNA or antibody) and negative animals using data from different field studies in Guinea (Lassa virus) and Tanzania (Morogoro and Gairo viruses). Results: Although the sample sizes of our studies (1297, 749 and 259 animals respectively) were large enough to statistically detect small differences in body conditions, we did not observe any adverse effects of these viruses on Mastomys natalensis. We did find that sexual maturity was significantly positively related with Lassa virus antibody presence until a certain age, and with Gairo virus antibody presence in general. Gairo virus antibody-positive animals were also significantly heavier and larger than antibody-free animals. Conclusion: Together, these results suggest that the pathogenicity of arenaviruses is not severe in M. natalensis, which is likely to be an adaptation of these viruses to optimize transmission success. They also suggest that sexual behaviour might increase the probability of M. natalensis to become infected with arenaviruses.
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Racicot, Bergeron Catherine. "Food animal reservoir for extraintestinal pathogenic «Escherichia coli» causing human infections." Thesis, McGill University, 2011. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=104886.
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Studies of extraintestinal infections caused by genetically related strains of Escherichia coli among unrelated people have demonstrated the epidemic potential of this group of bacteria. These related extraintestinal pathogenic E. coli (ExPEC) may have a common source. Our group recently described how retail meat, particularly chicken, may be a reservoir for ExPEC causing human urinary tract infections (UTIs). By moving upstream on the farm to fork continuum, this study tests whether the reservoir for ExPEC is in food animals themselves. A total of 824 geographically and temporally matched E. coli isolates from cecal contents of slaughtered food animals (n=349) and human UTI (n=475) sources were compared. Using 6 different typing methods, an evolutionary relationship was observed between E. coli isolates from the food animal reservoir and human UTI. Moreover, chicken was the predominant animal species from where the related isolates originated. Using an evolutionary model, chicken was determined to be the most likely source of the human UTI isolates. This study confirmed that an animal reservoir, principally in chicken, may exist for ExPEC causing community-acquired UTI.Les études portant sur les infections extra-intestinales causées par des souches d'Escherichia coli génétiquement apparentées, chez des personnes non reliées entre elles, ont démontré le potentiel épidémique de ce groupe de bactéries. Ces souches d'E. coli pathogènes extra-intestinales (ExPEC) apparentées auraient possiblement une source commune. Notre groupe a récemment décrit comment la viande de détail, plus particulièrement le poulet, pourrait être un réservoir d'ExPEC responsables d'infections urinaires (IUs) chez les humains. En se déplaçant plus en amont dans le continuum de la ferme à la fourchette, cette étude teste si le réservoir d'ExPEC se trouve dans les animaux de production eux-mêmes. Un total de 824 isolats d'E. coli de provenances géographique et temporelle communes, prélevés dans le contenu caecal d'animaux abattus (n=349) et de cas d'IU humaine (n=475) ont été comparés. Par l'utilisation de 6 différentes méthodes de typage, une relation évolutionnaire a été observée entre les isolats d'E. coli provenant du réservoir animal et d'IU humaine. De plus, le poulet était l'espèce animale prédominante parmi les isolats parentés. L'utilisation d'un modèle évolutionnaire a permis de déterminer que le poulet est la source la plus probable des isolats d'IU humaine. Cette étude a confirmé qu'un réservoir animal, principalement chez le poulet, pourrait exister pour les ExPEC qui causent des IUs acquises en communauté.
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Perkins, Tracy. "The role of estuarine sediments as a reservoir for pathogenic microorganisms." Thesis, Bangor University, 2015. https://research.bangor.ac.uk/portal/en/theses/the-role-of-estuarine-sediments-as-a-reservoir-for-pathogenic-microorganisms(3683144c-e7f1-4753-8749-72f3e0378935).html.
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Estuarine environments are biologically productive ecosystems that are both economically and socially important. Consequently, a decline in the microbiological water quality can pose a risk to human health and have severe socioeconomic consequences, especially for areas that rely on tourism and shellfisheries for income. The enumeration of faecal indicator bacteria (FIB) in water samples has been the paradigm for estimating water quality in coastal zones, but there is an emerging view that sediments are a poorly studied and yet a significant reservoir of FIB. The aims of this thesis were: (I) to investigate the role of sediments as a reservoir for FIB and other potentially pathogenic bacteria; (II) to examine the spatial ecology of FIB in relation to sediment composition (grain size and organic matter content); (III) to investigate the influence of point and diffuse pollution sources on the abundance of bacteria in marine and estuarine sediments; (IV) to investigate the abundance of human pathogenic bacteria in the Conwy estuary, North Wales, UK, and (V) to investigate the influence of suspended particulate matter (SPM) on the survival of FIB in both fresh and brackish water. Culturable E. coli, total coliforms, enterococci (FIB), Salmonella, Campylobacter, Vibrio spp. and heterotrophic bacteria were enumerated in sediments and water from the Conwy estuary that is subject to various point and diffuse sources of pollution. FIB counts were three orders of magnitude greater in sediments compared with the overlying water column, demonstrating that estuarine sediments are a significant reservoir for FIB and other potential pathogens. In addition, sediment grain size analysis and organic matter content determinations revealed that finer sediments such as clay, silt and very fine sand contained significantly higher concentrations of all bacterial groups enumerated. The enumeration of FIB in marine sediments surrounding an offshore sewage outfall pipe revealed that spatial variations in FIB abundance reflected the course of the sewage effluent plume as predicted by a hydrodynamic model, demonstrating the impact of point sources of microbial pollution on the underlying sediments. To address the actual pathogen content of sediments in the Conwy estuary (rather than only indicator bacteria), PCR and qPCR were utilized to detect and quantify known pathogen virulence genes, revealing that estuarine sediments are a reservoir for pathogenic bacteria. Furthermore, qPCR suggested greater concentrations of FIB compared with culture counts from the same sample, indicating the possible presence of viable but non-culturable (VBNC) bacteria. Consequently, sediment-associated bacteria pose a risk to human health if they are resuspended into the water column under certain hydrodynamic processes, as tide-dominated estuaries usually contain large areas of fine sand that are easily mobilized. To investigate the influence of SPM concentration on FIB survival, fresh and brackish water containing low (~16 mg/l), high (~160 mg/l) and extreme (~1650 mg/l) SPM concentrations were inoculated with crude sewage and sheep faeces. FIB were enumerated every 24 hrs for 5 days, revealing that SPM concentrations influence FIB survival in brackish water but had minimal influence in freshwater over time. In general, FIB concentrations increased with a decrease in SPM concentration. These data add to a limited body of evidence on the role of sediments as a reservoir for pathogenic bacteria, with implications for routine monitoring protocols that assess the microbial pollution of environmental waters. In addition, these data suggest that catchment-based risk assessments of microbial pollution in aquatic systems should consider the source of FIB, the hydrodynamics of the environment, and the subsequent influence of SPM concentrations, all of which determine the survival of FIB in aquatic environments.
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Nowak, Kathrin [Verfasser]. "African fruit bats as potential reservoir for zoonotic pathogens - the example of Escherichia coli / Kathrin Nowak." Berlin : Freie Universität Berlin, 2018. http://d-nb.info/1176639382/34.
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Nowak, Astrid Kathrin [Verfasser]. "African fruit bats as potential reservoir for zoonotic pathogens - the example of Escherichia coli / Kathrin Nowak." Berlin : Freie Universität Berlin, 2018. http://nbn-resolving.de/urn:nbn:de:kobv:188-refubium-23453-4.
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Maaz, Denny [Verfasser]. "The influence of co-infections on the reservoir competence of peridomestic rodents for tick-borne pathogens / Denny Maaz." Berlin : Freie Universität Berlin, 2019. http://d-nb.info/1176634933/34.
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Sproston, Emma L. "Ruminant reservoirs and invertebratevectors for transfer of human pathogens to vegetable crops and ready-to-eat foods." Thesis, University of Aberdeen, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.495927.
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This was a study to determine if invertebrate vectors (i.e. flies and slugs) were able to acquire human pathogens from local ruminant faeces and potentially transfer them to vegetables or ready-to-eat food. A field survey revealed that slugs are able to acquire pathogenic strains of E. coli O.157 that were indistinguishable from those isolated from local sheep faeces. Laboratory experiments demonstrated that commensal E. coli had relatively long survival rates on and in slugs, where the slugs were able to transfer E. coli by direct contact or excretion. Escherichia coli had a slow decline rate in excreted slug faeces with a decimal reduction time of 13.9 days. The results suggest that slugs have the potential to transfer pathogenic E. coli to vegetables. The second part of this work aimed at identifying temporal or host related relationships in the Campylobacter population of cattle and sheep. The Multi-locus sequence typing (MLST) technique was used in addition to quantifying the prevalence and concentrations of Campylobacter excreted by cattle and sheep present on the same farm. Statistically significant temporal variations were identified in addition to differences between the two hosts. During the faecal sampling, flies were also collected. Flies were found to carry identical sequence types (STs) to those present in local ruminant faecal samples. However, despite the relatively low Campylobacter prevalence in flies, certain STs were over represented, suggesting some degree of host restriction. A low number of slugs were also sampled where the Campylobacter ST isolated, had not been identified on this farm or elsewhere. Flies and slugs are able to acquire E. coli O157 and Campylobacter strains, thus posing a potential risk of transfer to vegetable crops.
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Nygren, Tomas, and Claes Johansson. "Draining the Pathogenic Reservoir of Guilt? : A study of the relationship between Guilt and Self-Compassion in Intensive Short-Term Dynamic Psychotherapy." Thesis, Linköpings universitet, Institutionen för beteendevetenskap och lärande, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-119217.
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Objective: One of the main theoretical proposals of Intensive Short-term Dynamic Psychotherapy (ISTDP; Davanloo, 1990) is that experiencing of previously unconscious guilt over aggressive impulses associated with attachment trauma leads to increase in self-compassion. The present study aimed to test this assumption. Method: Videotaped sessions from five therapies from a randomized controlled trial of 20-sessions of time-limited ISTDP for treatment-refractory depression were rated with the Achievement of Therapeutic Objectives Scale (ATOS; McCullough, Larsen, Schanche, Andrews& Kuhn, 2003b). Degree of patient guilt arousal and self-compassion were rated on all available sessions. Data were analyzed using a replicated single-subject time-series approach. Results: Guilt arousal was not shown to positively predict self-compassion for any of the five patients. For one patient guilt arousal negatively predicted self-compassion two sessions ahead in time. Conclusion: The current study yields no support that the experience of guilt over aggressive feelings and impulses leads to increases in self-compassion. On the contrary, the finding that guilt negatively predicted self-compassion for one patient must be considered as an indication that this treatment process might negatively impact self-compassion for some patients in some contexts. However, there are several methodological limitations to the current study in the light of which the results should be regarded as tentative.
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Staley, Christopher. "Investigation of Reservoirs of Fecal Indicator Bacteria and Water Quality on the Presence of Allochthonous Pathogens and the Ecology and Virulence of Vibrio vulnificus." Scholar Commons, 2012. http://scholarcommons.usf.edu/etd/4228.
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The quality of recreational and shellfishing waters has historically been monitored using commensal, allochthonous bacteria shed in feces (fecal indicator bacteria, FIB). The fate of FIB in the environment should mimic that of bacterial, protozoan, and viral human pathogens, which may also be allochthonous (e.g. Salmonella, Cryptosporidium, or enteric viruses) or autochthonous (e.g. Vibrio spp.) to aquatic environments. FIB are contributed to water from human and animal sources; however, pollution source cannot be determined by conventional FIB measurements. Because fecal source determination is important for pollution remediation and assessment of human health risks, microbial source tracking (MST) methods are increasingly used in water quality studies.
The host-specific genes (markers) used for MST include the 16S rRNA of Bacteroides HF183 and the T-antigen of human polyomaviruses (HPyVs). In my work, correlations among FIB, MST markers, and autochthonous pathogens were explored in the context of factors that may influence these relationships. Specifically, the effects of stormwater runoff, sediment resuspension, and survival/persistence of FIB on submerged aquatic vegetation were investigated in a recreational lake. Furthermore, the relationship between FIB and concentrations of the autochthonous pathogen, V. vulnificus, was investigated at water bodies surrounding Tampa Bay. I hypothesized that degraded water quality would influence the concentration and/or population structure of V. vulnificus, a potentially lethal human pathogen. Finally, I hypothesized that the gene encoding a sodium-phosphate transporter (nptA) would be differentially expressed in V. vulnificus strains under varying conditions of salinity and phosphate concentration.
I hypothesized that stormwater infrastructure/runoff, SAV, and sediments would serve as reservoirs for FIB, human-associated microbes (HF183 and HPyVs), and allochthonous pathogens (Salmonella, Cryptosporidium, Giardia, and enteric viruses). FIB concentrations in the water were positively associated with those in the sediment, SAV, and with 24hr antecedent rainfall. At least one MST marker or pathogen was found in 35% of samples following rain events. These data were incorporated into a Bayesian model, which predicted pathogen absence when fecal coliform concentrations were low. Stormwater was also shown to be an important reservoir/conveyance system for FIB, human-associated microbes, and pathogens.
I hypothesized that polluted estuarine waters in Tampa Bay, and oysters harvested from them, would contain higher V. vulnificus concentrations, and that the population structure would be altered compared to unpolluted waters. Enumeration included direct plating, enrichment followed by plating, and quantitative PCR (qPCR). V. vulnificus colonies isolated directly on mCPC agar were rarely PCR-confirmed, although enrichment and qPCR methods yielded a higher confirmation frequency. Unconfirmed colonies resembling V. vulnificus were identified as V. sinaloensis via 16S rRNA sequence analysis and were more frequently detected in less polluted waters. Comparison of growth rates among V. vulnificus and V. sinaloensis strains in enrichment media and seawater showed that V. vulnificus had faster growth rates (µ) in enrichment media, but that µ of V. sinaloensis strains was greater in seawater. V. sinaloensis presence can therefore lead to overestimation of V. vulnificus concentrations when samples are directly plated. These results highlight a need for better understanding of the ecology and virulence potential of this newly-described species.
Finally, I hypothesized that V. vulnificus strains with varying virulence potential would differentially express the nptA gene in response to changes in environmental conditions. Expression studies were performed on biotype 1, 2, and 3 strains, and strains more closely associated with environmental reservoirs (water or oysters) showed up to 100-fold greater nptA expression than strains isolated from clinical cases. Gene expression in environmentally-associated, but not clinically-isolated, strains was highest in media at pH 6.0 vs. those at pH ≥ 7.0 and at 10 / salinity. In contrast, expression was highest among clinical strains at 10 / salinity, pH 8.0 media. Sequence analysis of the nptA gene also divided strains into environmentally- and clinically-isolated groups. These results suggest that differences in gene expression may be related to host preference and may be associated with differential virulence of strains in humans.
These studies demonstrate a relationship between water quality (determined by FIB concentrations) and the prevalence of allochthonous and autochthonous human pathogens, and reveal that many environmental habitats may serve as reservoirs for FIB and pathogens. Differences in water quality were further demonstrated to impact the community structure of Vibrio spp. and may affect the relative abundance of strains with greater virulence potential.
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Thelaus, Johanna. "The aquatic microbial food web and occurence of predation-resistant and potentially pathogenic bacteria, such as Francisella tularensis." Doctoral thesis, Umeå universitet, Ekologi, miljö och geovetenskap, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-1620.
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All natural aquatic systems harbour a vast variety of microorganisms. In the aquatic microbial food web, the larger microorganisms (i.e. protozoa) feed on the smaller microorganisms (i.e. bacteria and phytoplankton). An increase in nutrient availability results in changes of the microbial food web structure, like altered community composition and blooms of toxic phytoplankton. In this thesis work I hypothesised that nutrient-rich aquatic environments, with strong protozoan predation, favour the occurrence of predation-resistant bacteria like F. tularensis, and that the microbial food web may provide a reservoir for the bacterium between outbreaks. By using a size-structured ecosystem food web model it was shown that the protozoan predation pressure on bacteria, defined as protozoan predation per bacterial biomass, increases with increasing nutrient availability in aquatic systems (estimated chlorophyll a 0.2 to 112 μg L-1). This dynamics was caused by increasing growth-rate of a relatively constant number of bacterial cells, maintaining the growth of an increasing number of protozoan cells. The results were supported by meta-analysis of field studies. Thus my results suggest that protozoa control the bacterial community by predation in nutrient-rich environments. In a field study in a natural productivity gradient (chlorophyll a 1.4 to 31 μg L-1) it was shown that intense selection pressure from protozoan predators, favours predation-resistant forms of bacteria. Thus, the abundance of predation-resistant bacteria increases with increasing nutrient availability in lakes. Furthermore, I could demonstrate that the bacterium Francisella tularensis, the causative agent of tularemia, was present in eutrophic aquatic systems in an emerging tularemia area. Isolated strains of the bacterium were found to be resistant to protozoan predation. In a microcosm study, using natural lake water, high nutrient availability in combination with high abundance of a small colourless flagellate predator favoured the occurrence of F. tularensis holarctica. In laboratory experiments F. tularensis strains were able to form biofilm at temperatures between 30-37°C, but not below 30°C. In conclusion, I have shown that the protozoan predation pressure on bacteria increases with increasing nutrient availability in aquatic systems. Predation-resistant forms of bacteria, such as F. tularensis are favoured in nutrient-rich environments. The complexity of the microbial food web and nutrient-richness of the water, influence the transmission of the pathogenic F. tularensis holarctica. However, over long periods of time, the bacterium survives in lake water but may lose its virulence. The temperature-regulated biofilm formation by F. tularensis may play a role in colonization of vectors or for colonization of hosts, rather than for survival in aquatic environments.
Books on the topic "Pathogen reservoir"
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Shearer, Judy F. Potential of a pathogen, Mycoleptodiscus terrestris, as a biocontrol agent for the management of Myriophyllum spicatum in Lake Guntersville Reservoir. [Vicksburg, Miss: U.S. Army Engineer Waterways Experiment Station, 1996.
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Hipsey, Matthew R. Hydrodynamic distribution of pathogens in lakes and reservoirs. Denver, CO: Awwa Research Foundation, 2005.
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Bonthius, Daniel J. Lymphocytic Choriomeningitis Virus. Oxford University Press, 2018. http://dx.doi.org/10.1093/med/9780190604813.003.0011.
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Lymphocytic choriomeningitis virus (LCMV), an arenavirus, is a prevalent pathogen and an important and underrecognized cause of neurologic birth defects. LCMV utilizes rodents as its principal reservoir. Rodents that acquire the virus transplacentally often remain asymptomatic because congenital infection provides immunological tolerance for the virus. Humans typically acquire LCMV by direct contact with fomites contaminated with infectious virus, from rodents, or by inhalation of aerosolized virus. Congenital LCMV infection occurs when a woman acquires the virus during pregnancy. The virus is passed to the fetus transplacentally, presumably during maternal viremia. Published reports of LCMV infection during pregnancy make it clear that LCMV can be a severe neuroteratogen. Prospective epidemiological or clinical studies of congenital LCMV infection are needed to gain more knowledge about the incidence and spectrum of LCMV-induced teratogenicity. The clinical presentation of congenital LCMV is reviewed, along with recommendations for diagnostic studies and information about long-term prognosis.
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Smith, Robert M., and Wendy J. Zochowski. Leptospirosis. Oxford University Press, 2011. http://dx.doi.org/10.1093/med/9780198570028.003.0027.
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Leptospirosis is one of the most widespread and important zoonotic pathogens and is of global medical and veterinary importance. Clinical disease ranges from mild self-limiting influenza – like illness to fulminating repeats-several failure.It is caused by bacterial spirochaetes of the genus Leptospira, family Leptospiraceae. Pathogenic Leptospira interrogans strains, of which there are over 230 serovars in 24 serogroups, are morphologically identical in that they are thin, helical highly motile Gram-negative bacteria, hooked at one or both ends.Natural hosts of pathogenic strains, generally referred to as serovars, may cause infection in man and include wild animals (rodents), livestock (cattle and pigs) and pets (dogs). Most, if not all mammals may become long-term carriers (maintenance hosts). Leptospires become located in the renal tubules and excreted in the urine of infected reservoir animals, humans becoming infected through broken skin, mucous membranes and the conjunctivae.Leptospirosis is most commonly found in tropical or sub-tropical countries in both urban and rural settings. It causes major economic losses, to the highly intensive cattle and pig industries in developed countries, primarily through their effects on reproduction. It is still an important occupational disease risk for people working in agriculture or those living in unsanitary conditions. It is increasingly recognised as a recreational and travel-associated disease.
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Hydrodynamic Distribution of Pathogens in Lakes and Reservoirs: Awwarf Report 91073f (Awwarf Report). Intl Water Assn, 2006.
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Oakley, Stewart M. Integrated Wastewater Management for Health and Valorization: A Design Manual for Resource Challenged Cities. IWA Publishing, 2022. http://dx.doi.org/10.2166/9781789061536.
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Abstract Adequate wastewater treatment in low to medium income cities worldwide has largely been a failure despite decades of funding. The still dominant end-of-pipe paradigm of treatment for surface water discharge, focusing principally on removal of organic matter, has not addressed the well-published problems of pathogen and nutrient release with continued contamination of surface waters. This book incorporates the new paradigm of integrated wastewater management for valorization without surface water discharge using waste stabilization pond systems and wastewater reservoirs. In this paradigm the purpose of treatment is to protect health by reducing pathogens to produce an effluent that is valorized for its fertilizer and water value for agriculture and aquaculture. Methane production as a sustainable energy source is also considered for those applications where it is appropriate. Emphasis is on sustainable engineering solutions for low to medium income cities worldwide. Chapters present the theory of design, followed by design procedures, example design problems, and case study examples with data, diagrams and photos of operating systems. Excel spreadsheets and the FAO program CLIMWAT/CROPWAT are included in examples throughout. Sections on engineering practice include technical training, operation and maintenance requirements, construction and sustainability. The book incorporates design and operating data and case studies from Africa, Australia, Latin America, Europe, New Zealand, and the US, including studies that have been published in French, Portuguese, and Spanish. The book is designed for upper-division and graduate level engineering students, practicing engineers, regulatory professionals who help establish and enforce effluent standards, international development professionals, and policy stakeholders. ISBN: 9781789061529 (paperback) ISBN: 9781789061536 (eBook) ISBN: 9781789061543 (ePUB)
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Ball, Jonathan. Antimicrobial stewardship in the intensive care setting. Oxford University Press, 2016. http://dx.doi.org/10.1093/med/9780198758792.003.0012.
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Intensive care units (ICUs) care for patients with life-threatening infections and thus harbour reservoirs of pathogenic microorganisms. Furthermore, as a direct consequence of their critical illness/injury, ICU patients commonly have a significant degree of acutely acquired, innate, and adaptive immune system dysfunction. Critically ill patients therefore present unique challenges for antibiotic stewardship. Antibiotic stewardship in ICUs should address both the timely delivery of effective empiric therapy and the minimization of the use of broad-spectrum agents. Solutions to these challenges are usually adaptations of general principles rather than novel interventions. In ICUs, as elsewhere, antibiotic stewardship should be viewed as a key component of the overall infection control strategy.
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Palmer, Stephen. The global challenge of zoonoses control. Oxford University Press, 2011. http://dx.doi.org/10.1093/med/9780198570028.003.0001.
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Zoonotic diseases are now recognized as a major global threat to human health and sustainable development and a major concern for national and international agencies (Marano et al. 2006). There was a period in the 1960s and 70s when it was widely expected that the antibiotic and vaccine era would relegate infectious diseases to footnotes of history, and in many countries communicable control systems were neglected (Keusch et al. 2009) but the frequent and often dramatic appearance of new infectious agents or the reappearance of well recognized zoonoses has changed perceptions. ‘A wide variety of animal species, domesticated, peri-domesticated and wild, can act as reservoirs for these pathogens, which may be viruses, bacteria, parasites or prions. Considering the wide variety of animal species involved and the often complex natural history of the pathogens concerned, effective surveillance, prevention and control of zoonotic diseases pose a real challenge to public health’ (WHO 2004). No country has been able to anticipate the sudden and sometimes devastating impact of novel agents, and international trade and transport of people, animals and goods have ensured that wherever zoonoses emerge they have to be considered as global issues. The cost of zoonoses can be enormous. The H1N1v pandemic which began in pig herds on the Mexico-US border resulted in major losses to the pork industry amounting to US$25 million per week; fear that transmission could occur from meat led to the banning of importation of pigs and pork products by at least 15 countries (Keusch et al. 2009). And in addition to these ‘natural’ threats, several zoonoses are prime agents for deliberate release by disaffected groups. A more esoteric threat, though nonetheless a real cause of concern, is the possibility of zoonotic emergence from xenotransplantation (Mattiuzzo et al. 2008).
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Rello, Jordi, and Bárbara Borgatta. Pathophysiology of pneumonia. Oxford University Press, 2016. http://dx.doi.org/10.1093/med/9780199600830.003.0115.
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Airway colonization, ventilator-associated tracheobronchitis (VAT), and hospital-acquired (HAP) and ventilator-associated pneumonia (VAP) are three manifestations having the presence of micro-organisms in airways in common. Newer definitions have to consider worsening of oxygenation, in addition to purulent respiratory secretions, chest-X rays opacities, and biomarkers of inflammation. Bacteria are the main causes of HAP/VAP. During hospitalization there’s a shift of airway’s colonizing flora from core organisms to enteric and non-fermentative ones. Macro- and micro-aspiration is the most important source of pneumonia. Endotracheal tube secretion leakage is an important source, serving biofilm as a reservoir. Exogenous colonization is infrequent, but it may contribute to cross-infection with resistant species. Prevention of VAP can be achieved by implementing multidisciplinary care bundles focusing on oral/hand hygiene and control of sedation. Pneumonia develops when micro-organisms overwhelm host defences, resulting in a multifocal process. Risk and severity of pneumonia is determined by bacterial burden, organism virulence and host defences. Innate and adaptive immune responses are altered, decreasing clearing of pathogens. Some deficits of the complement pathway in intubated patients are associated with increased risk for VAP and higher mortality. Micro-arrays have demonstrated specific different immunological signatures for VAP and VAT. Early antibiotic therapy is associated with a decrease in early HAP/VAP incidence, but selects for MDR organisms. Attributable mortality is lower than 10%, but HAP/VAP prolongs length of stay, and dramatically increase costs and use of health care resources.
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Zinsstag, Jakob, Borna Müller, and Ivo Pavlik. Mycobacterioses. Oxford University Press, 2011. http://dx.doi.org/10.1093/med/9780198570028.003.0015.
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The Mycobacterium tuberculosis complex MTC is composed of several species of mycobacteria which are M. tuberculosis, the main cause of human tuberculosis, M. canetti, M. africanum, M. microti, M. pinnipedii, M. caprae, and M. bovis. Cattle are the principal host of M. bovis, but a large number of other ruminants and other mammals, particularly wildlife are infected. Human tuberculosis is a global problem of huge proportions. More than 95% of human tuberculosis cases occur in developing and transition countries, of which one third are in Africa but the proportion of cases caused by M. bovis is still not known. Today, bovine tuberculosis (BTB) is re-emerging and threatens the livestock industry in industrialized countries with wildlife reservoirs like the wild tailed deer (Odocoileus virginianus) in the USA or the badger (Meles meles) in the UK. Most developing countries lack the means and capacity for effective control of BTB. A better understanding of its epidemiology is required to identify novel, locally adapted options for control in a given context. BTB in Africa is emphasized here because of the special importance of multiple transmission interfaces between wildlife, livestock and humans.In addition to obligatory pathogenic mycobacteria (esp. members of the MTC), potentially pathogenic mycobacteria (PPM) previously designated as ‘mycobacteria other than tubercle bacilli’ (MOTT) are increasingly important causes of mycobacterioses in humans and animals. Most of them are opportunistic in humans and occur mostly in immunocompromised patients. The mycobacteria that cause human disease are both the M. avium complex (MAC) members and other mycobacterial species MAC members have been detected in more than 95% of cases; this chapter will mainly focus on M. avium subsp. avium, M. a. hominissuis, and M. intracellulare.
Book chapters on the topic "Pathogen reservoir"
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Eisen, Lars, and Rebecca Eisen. "Climate and vector potential of medically important North American ticks." In Climate, ticks and disease, 188–92. Wallingford: CABI, 2021. http://dx.doi.org/10.1079/9781789249637.0028.
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Abstract This expert opinion focuses on climate-related factors and how these interact with landscape and tick host/pathogen reservoir factors to impact the vector potential for the three most notable North American human-biting tick species: Ixodes scapularis, Amblyomma americanum and the American dog tick, Dermacentor variabilis.
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Daniels, P. W., K. Halpin, A. Hyatt, and D. Middleton. "Infection and Disease in Reservoir and Spillover Hosts: Determinants of Pathogen Emergence." In Current Topics in Microbiology and Immunology, 113–31. Berlin, Heidelberg: Springer Berlin Heidelberg, 2007. http://dx.doi.org/10.1007/978-3-540-70962-6_6.
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Wille, Michelle, Neus Latorre-Margalef, and Jonas Waldenström. "Of Ducks and Men: Ecology and Evolution of a Zoonotic Pathogen in a Wild Reservoir Host." In Modeling the Transmission and Prevention of Infectious Disease, 247–86. Cham: Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-60616-3_9.
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Tyndall, R. L. "Pathogenic microorganisms in thermally altered reservoirs and other waters." In Microbial Processes in Reservoirs, 135–54. Dordrecht: Springer Netherlands, 1985. http://dx.doi.org/10.1007/978-94-009-5514-1_8.
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Manges, Amee R., and James R. Johnson. "Reservoirs of Extraintestinal Pathogenic Escherichia coli." In Urinary Tract Infections, 159–77. Washington, DC, USA: ASM Press, 2016. http://dx.doi.org/10.1128/9781555817404.ch9.
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van der Linden, Leon, Matthew R. Hipsey, Michael D. Burch, and Justin D. Brookes. "Myponga Reservoir, South Australia: The Influence of Nutrients, Phytoplankton, Pathogens, and Organic Carbon on Water Quality." In Encyclopedia of Lakes and Reservoirs, 530–39. Dordrecht: Springer Netherlands, 2012. http://dx.doi.org/10.1007/978-1-4020-4410-6_130.
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Berg, Gabriele, Mohammadali Alavi, Michael Schmid, and Anton Hartmann. "The Rhizosphere as a Reservoir for Opportunistic Human Pathogenic Bacteria." In Molecular Microbial Ecology of the Rhizosphere, 1209–16. Hoboken, NJ, USA: John Wiley & Sons, Inc., 2013. http://dx.doi.org/10.1002/9781118297674.ch116.
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Boschiroli, Maria Laura, Joseph Falkinham, Sabine Favre-Bonté, Sylvie Nazaret, Pascal Piveteau, Michael Sadowsky, Murulee Byappanahalli, Pascal Delaquis, and Alain Hartmann. "Natural Soil Reservoirs for Human Pathogenic and Fecal Indicator Bacteria." In Manual of Environmental Microbiology, 3.3.2–1–3.3.2–12. Washington, DC, USA: ASM Press, 2015. http://dx.doi.org/10.1128/9781555818821.ch3.3.2.
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Marín-Angel, Edgar, Martín Rivera-Toledo, and Iván R. Quevedo. "Modelling the Migration of Pathogens in Agricultural Settings: From Surface Land to Groundwater Reservoirs." In Microbial Biodiversity, Biotechnology and Ecosystem Sustainability, 271–94. Singapore: Springer Nature Singapore, 2023. http://dx.doi.org/10.1007/978-981-19-4336-2_13.
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Mohamed Hatha, A. A., Puthenkandathil Sukumaran Divya, Silvester Reshma, and John Nifty. "Polluted Coastal and Estuarine Environments: A Potential Reservoir for AMR Determinants in Various Pathogenic Bacteria." In Antimicrobial Resistance, 101–34. Singapore: Springer Singapore, 2020. http://dx.doi.org/10.1007/978-981-15-3658-8_5.
Full textConference papers on the topic "Pathogen reservoir"
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Carrie Elizabeth Shaffer and Shane W Rogers. "Wild Deer as reservoirs of manure pathogens and resistance genes." In International Symposium on Air Quality and Manure Management for Agriculture Conference Proceedings, 13-16 September 2010, Dallas, Texas. St. Joseph, MI: American Society of Agricultural and Biological Engineers, 2010. http://dx.doi.org/10.13031/2013.32667.
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Đukić, Dragutin, Leka Mandić, Monika Stojanova, Vesna Đurović, and Bojana Trifunović. "INFICIRANJE HIDROBIONATA SA POTENCIJALNO PATOGENIM MIKROORGANIZMIMA." In XXVII savetovanje o biotehnologiji. University of Kragujevac, Faculty of Agronomy, 2022. http://dx.doi.org/10.46793/sbt27.383dj.
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The results of isolation and identification (API test-systems) of the cultures of Enterobacteria and “non-fermentating” microorganisms from water, zooplankton (protozoa, cyclopes, daphnias), chironomids larvae of natural and anthropogenic water reservo- irs are produced. Spectrum of potentially pathogenic bacteria in water and in the hydrobionts was rather wide (16 genera) and of similar composition. Microflora of chironomids proved to be less heterogenous than that of zooplankton. The most frequently observed microbes were found to belong to Klebsiella, Pseudomonas, Acinetobacter, as well as to Actinomyces and Candida. Both aquatic and overground ecosystems can be a habitat of microorganisms that are potentially pathogenic to man and animals.
Reports on the topic "Pathogen reservoir"
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Shearer, Judy F. Potential of a Pathogen, Mycoleptodiscus Terrestris, as a Biocontrol Agent for the Management of Myriophyllum Spicatum in Lake Guntersville Reservoir. Fort Belvoir, VA: Defense Technical Information Center, February 1996. http://dx.doi.org/10.21236/ada305309.
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Gunnison, Douglas. Evaluating Microbial Pathogens in Reservoirs. Fort Belvoir, VA: Defense Technical Information Center, July 1999. http://dx.doi.org/10.21236/ada367728.
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Davis, Robert E., Edna Tanne, James P. Prince, and Meir Klein. Yellow Disease of Grapevines: Impact, Pathogen Molecular Detection and Identification, Epidemiology, and Potential for Control. United States Department of Agriculture, September 1994. http://dx.doi.org/10.32747/1994.7568792.bard.
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Grapevine yellows diseases characterized by similar symptoms have been reported in several countries including Israel, the United States, France, Italy, Spain, Germany and Australia. These diseases are among the most serious known in grapevine, but precise knowledge of the pathogens' identities and modes of their spread is needed to devise effective control stratgegies. The overall goals of this project were to develop improved molecular diagnostic procedures for detection and identification of the presumed mycoplasmalike organism (MLO) pathogens, now termed phytoplasmas, and to apply these procedures to investigate impact and spread and potential for controlling grapevine yellows diseases. In the course of this research project, increased incidence of grapevine yellows was found in Israel and the United States; the major grapevine yellows phytoplasma in Israel was identified and tis 16S rRNA gene characterized; leafhopper vectors of this grapevine yellows phytoplasma in Israel were identified; a second phytoplasma was discovered in diseased grapevines in Israel; the grapevine yellows disease in the U.S. was found to be distinct from that in Israel; grapevine yellows in Virginia, USA, was found to be caused by two different phytoplasmas; both phytoplasmas in Virginia grapevines were molecularly characterized and classified; commercial grapevines in Europe were discovered to host a phytoplasma associated with aster yellow disease in the USA, but this phytoplasma has not been found in grapevine in the USA; the Australian grapevine yellows phytoplasma was found to be distinct from the grapevine phytoplasmas in Israel, the United States and Europe and was described and named "Candidatus phytoplasma australiense", and weed host plants acting as potential reservoirs of the grapevine phytoplasmas were discovered. These and other findings from the project should aid in the design and development of strategies for managing the grapevine yellows disease problem.
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Sela, Hanan, Eduard Akhunov, and Brian J. Steffenson. Population genomics, linkage disequilibrium and association mapping of stripe rust resistance genes in wild emmer wheat, Triticum turgidum ssp. dicoccoides. United States Department of Agriculture, January 2014. http://dx.doi.org/10.32747/2014.7598170.bard.
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The primary goals of this project were: (1) development of a genetically characterized association panel of wild emmer for high resolution analysis of the genetic basis of complex traits; (2) characterization and mapping of genes and QTL for seedling and adult plant resistance to stripe rust in wild emmer populations; (3) characterization of LD patterns along wild emmer chromosomes; (4) elucidation of the multi-locus genetic structure of wild emmer populations and its correlation with geo-climatic variables at the collection sites. Introduction In recent years, Stripe (yellow) rust (Yr) caused by Pucciniastriiformis f. sp. tritici(PST) has become a major threat to wheat crops in many parts of the world. New races have overcome most of the known resistances. It is essential, therefore, that the search for new genes will continue, followed by their mapping by molecular markers and introgression into the elite varieties by marker-assisted selection (MAS). The reservoir of genes for disease and pest resistance in wild emmer wheat (Triticumdicoccoides) is an important resource that must be made available to wheat breeders. The majority of resistance genes that were introgressed so far in cultivated wheat are resistance (R) genes. These genes, though confering near-immunity from the seedling stage, are often overcome by the pathogen in a short period after being deployed over vast production areas. On the other hand, adult-plant resistance (APR) is usually more durable since it is, in many cases, polygenic and confers partial resistance that may put less selective pressure on the pathogen. In this project, we have screened a collection of 480 wild emmer accessions originating from Israel for APR and seedling resistance to PST. Seedling resistance was tested against one Israeli and 3 North American PST isolates. APR was tested on accessions that did not have seedling resistance. The APR screen was conducted in two fields in Israel and in one field in the USA over 3 years for a total of 11 replicates. We have found about 20 accessions that have moderate stripe rust APR with infection type (IT<5), and about 20 additional accessions that have novel seedling resistance (IT<3). We have genotyped the collection using genotyping by sequencing (GBS) and the 90K SNP chip array. GBS yielded a total 341K SNP that were filtered to 150K informative SNP. The 90K assay resulted in 11K informative SNP. We have conducted a genome-wide association scan (GWAS) and found one significant locus on 6BL ( -log p >5). Two novel loci were found for seedling resistance. Further investigation of the 6BL locus and the effect of Yr36 showed that the 6BL locus and the Yr36 have additive effect and that the presence of favorable alleles of both loci results in reduction of 2 grades in the IT score. To identify alleles conferring adaption to extreme climatic conditions, we have associated the patterns of genomic variation in wild emmer with historic climate data from the accessions’ collection sites. The analysis of population stratification revealed four genetically distinct groups of wild emmer accessions coinciding with their geographic distribution. Partitioning of genomic variance showed that geographic location and climate together explain 43% of SNPs among emmer accessions with 19% of SNPs affected by climatic factors. The top three bioclimatic factors driving SNP distribution were temperature seasonality, precipitation seasonality, and isothermality. Association mapping approaches revealed 57 SNPs associated with these bio-climatic variables. Out of 21 unique genomic regions controlling heading date variation, 10 (~50%) overlapped with SNPs showing significant association with at least one of the three bioclimatic variables. This result suggests that a substantial part of the genomic variation associated with local adaptation in wild emmer is driven by selection acting on loci regulating flowering. Conclusions: Wild emmer can serve as a good source for novel APR and seedling R genes for stripe rust resistance. APR for stripe rust is a complex trait conferred by several loci that may have an additive effect. GWAS is feasible in the wild emmer population, however, its detection power is limited. A panel of wild emmer tagged with more than 150K SNP is available for further GWAS of important traits. The insights gained by the bioclimatic-gentic associations should be taken into consideration when planning conservation strategies.