scholarly journals Host community structure and the maintenance of pathogen diversity

2007 ◽  
Vol 274 (1619) ◽  
pp. 1715-1721 ◽  
Author(s):  
Caroline Buckee ◽  
Leon Danon ◽  
Sunetra Gupta
Keyword(s):  
Community Structure ◽  
Spatial Differentiation ◽  
Host Community ◽  
Contact Network ◽  
Strong Mixing ◽  
Metapopulation Model ◽  
Pathogen Population ◽  
Antigenic Diversity ◽  
Pathogen Diversity ◽  
Pathogen Populations

Community structure has been widely identified as a feature of many real-world networks. It has been shown that the antigenic diversity of a pathogen population can be significantly affected by the contact network of its hosts; however, the effects of community structure have not yet been explored. Here, we examine the congruence between patterns of antigenic diversity in pathogen populations in neighbouring communities, using both a deterministic metapopulation model and individual-based formulations. We show that the spatial differentiation of the pathogen population can only be maintained at levels of coupling far lower than that necessary for the host populations to remain distinct. Therefore, identifiable community structure in host networks may not reflect differentiation of the processes occurring upon them and, conversely, a lack of genetic differentiation between pathogens from different host communities may not reflect strong mixing between them.

Temperature and multiple parasites combine to alter host community structure

Oikos ◽  
2021 ◽  
Author(s):  
Olwyn Friesen ◽  
Robert Poulin ◽  
Clément Lagrue
Keyword(s):  
Community Structure ◽  
Host Community

scholarly journals Deforestation, host community structure, and amphibian disease risk

2016 ◽  
Vol 17 (1) ◽  
pp. 72-80 ◽  
Author(s):  
C. Guilherme Becker ◽  
David Rodriguez ◽  
Ana V. Longo ◽  
L. Felipe Toledo ◽  
Carolina Lambertini ◽  
...  
Keyword(s):  
Community Structure ◽  
Disease Risk ◽  
Host Community ◽  
Amphibian Disease

scholarly journals Community diversity reduces Schistosoma mansoni transmission, host pathology and human infection risk

2009 ◽  
Vol 276 (1662) ◽  
pp. 1657-1663 ◽  
Author(s):  
Pieter T.J Johnson ◽  
Peder J Lund ◽  
Richard B Hartson ◽  
Timothy P Yoshino
Keyword(s):  
Community Structure ◽  
Schistosoma Mansoni ◽  
Host Density ◽  
Biodiversity Loss ◽  
Infection Risk ◽  
Human Infection ◽  
Host Community ◽  
Community Diversity ◽  
Complex Life Cycle ◽  
Intermediate Hosts

Global biodiversity loss and disease emergence are two of the most challenging issues confronting science and society. Recently, observed linkages between species-loss and vector-borne infections suggest that biodiversity may help reduce pathogenic infections in humans and wildlife, but the mechanisms underlying this relationship and its applicability to a broader range of pathogens have remained speculative. Here, we experimentally evaluated the effects of host community structure on transmission of the human pathogen, Schistosoma mansoni , which alternates between snail intermediate hosts and vertebrate definitive hosts. By manipulating parasite exposure and community diversity, we show that heterospecific communities cause a 25–50 per cent reduction in infection among snail hosts ( Biomphalaria glabrata ). Infected snails raised alongside non-host snails ( Lymnaea or Helisoma sp.) also produced 60–80 per cent fewer cercariae, suggesting that diverse communities could reduce human infection risk. Because focal host density was held constant during experiments, decreases in transmission resulted entirely from diversity-mediated pathways. Finally, the decrease in infection in mixed-species communities led to an increase in reproductive output by hosts, representing a novel example of parasite-mediated facilitation. Our results underscore the significance of community structure on transmission of complex life-cycle pathogens, and we emphasize enhanced integration between ecological and parasitological research on the diversity–disease relationship.

scholarly journals Grafting for Disease Resistance

HortScience ◽  
2008 ◽  
Vol 43 (6) ◽  
pp. 1673-1676 ◽  
Author(s):  
Stephen R. King ◽  
Angela R. Davis ◽  
Wenge Liu ◽  
Amnon Levi
Keyword(s):  
Disease Resistance ◽  
Root Rot ◽  
Pathogen Resistance ◽  
Soilborne Pathogens ◽  
Pathogen Population ◽  
Soil Fumigant ◽  
Soil Microbial ◽  
The Future ◽  
Microbial Environment ◽  
Pathogen Populations

The primary purpose of grafting vegetables worldwide has been to provide resistance to soilborne diseases. The potential loss of methyl bromide as a soil fumigant combined with pathogen resistance to commonly used pesticides will make resistance to soilborne pathogens even more important in the future. The major disease problems addressed by grafting include fusarium wilt, bacterial wilt, verticillium wilt, monosporascus root rot, and nematodes. Grafting has also been shown in some instances to increase tolerance to foliar fungal diseases, viruses, and insects. If the area devoted to grafting increases in the future, there will likely be a shift in the soil microbial environment that could lead to the development of new diseases or changes in the pathogen population of current diseases. This shift in pathogen populations could lead to the development of new diseases or the re-emergence of previously controlled diseases. Although grafting has been demonstrated to control many common diseases, the ultimate success will likely depend on how well we monitor for changes in pathogen populations and other unexpected consequences.

Puccinia striiformis in Australia: a review of the incursion, evolution, and adaptation of stripe rust in the period 1979 - 2006

2007 ◽  
Vol 58 (6) ◽  
pp. 567 ◽  
Author(s):  
C. R. Wellings
Keyword(s):  
Stripe Rust ◽  
Chemical Control ◽  
Puccinia Striiformis ◽  
Cool Temperature ◽  
Pathogen Population ◽  
European Origin ◽  
Yield And Quality ◽  
Eastern Australia ◽  
Major Shift ◽  
Pathogen Populations

The wheat stripe rust pathogen (Puccinia striiformis f. sp. tritici; Pst) was first detected in Australia in 1979. The features of the initial pathotype suggested that it was of European origin, and later work provided evidence that it was most likely transmitted as adherent spores on travellers’ clothing. Despite long-held views that this cool temperature pathogen would not adapt to Australian conditions, Pst became endemic and progressively adapted to commercial wheat production through step-wise mutation. Several of these mutant pathotypes became frequent in the Pst population, causing widespread infection and significant costs to production (yield and quality losses; chemical control expenditure) in certain cultivars and seasons. Pathotype evolution, including adaptation to native barley grass (Hordeum spp.) populations, is described. The occurrence of an exotic pathotype of Pst in Western Australia in 2002, and its subsequent spread to eastern Australia, represented a major shift in the pathogen population. This pathotype dominated pathogen populations throughout Australia from 2003, with chemical control expenditure estimated at AU$40–90 million annually. Another exotic introduction was detected in 1998. Initial data indicated that certain isolates collected from barley grass were highly avirulent to wheat differentials, with the exception of partial virulence to Chinese 166. Further seedling tests revealed that these isolates, tentatively designated barley grass stripe rust (BGYR), were virulent on several Australian barleys, notably those of Skiff parentage. Data, including molecular studies, suggest that BGYR is a new forma specialis of P. striiformis. Field nurseries indicate that BGYR is likely to have little impact on commercial barley, although this may change with further pathotype evolution or the release of susceptible cultivars.

scholarly journals Results of monitoring of the population of Blumeria graminis f.sp. hordei in Latvia in 2009-2010

2012 ◽  
Vol 66 (1-2) ◽  
pp. 41-47
Author(s):  
Inese Kokina ◽  
Isaak Rashal
Keyword(s):  
Blumeria Graminis ◽  
Shannon Index ◽  
Simpson Index ◽  
Pathogen Population ◽  
Random Samples ◽  
Barley Powdery Mildew ◽  
North Eastern ◽  
Pathogen Populations ◽  
North Western ◽  
High Diversity

Results of monitoring of the population ofBlumeria graminisf.sp.hordeiin Latvia in 2009-2010In 2009-2010, random samples of the causal agent of barley powdery mildew were collected in Daugavpils (south-eastern Latvia, Latgale region), Stende (north-western Latvia, Kurzeme region) and Priekuļi (north-eastern Latvia, Vidzeme region). Virulence frequency, complexity and pathotypes were calculated in the pathogen populations. Significant differences of virulence detected by the genesVa1, Va3and Va13occurred among samples of the pathogen population collected in different parts of Latvia. Nei index, Müller's index, Kosman index, Shannon index and Simpson index showed considerably higher diversity in Daugavpils and Stende during 2009-2010. In Daugavpils, the population ofBlumeria graminisf.sp.hordei was particularly characterised by high diversity.

scholarly journals Sensitivity of Nonexposed and Exposed Populations of Magnaporthe oryzae from Rice to Tricyclazole and Azoxystrobin

Plant Disease ◽  
2014 ◽  
Vol 98 (4) ◽  
pp. 512-518 ◽  
Author(s):  
Andrea Kunova ◽  
Cristina Pizzatti ◽  
Maria Bonaldi ◽  
Paolo Cortesi
Keyword(s):  
Magnaporthe Oryzae ◽  
Rice Blast ◽  
Cultivated Rice ◽  
Pathogen Population ◽  
Baseline Sensitivity ◽  
Mycelium Growth ◽  
Resistant Strains ◽  
Pathogen Populations ◽  
Continue Monitoring ◽  
Higher Sensitivity

Magnaporthe oryzae is the major pathogen of cultivated rice worldwide, which can cause substantial losses to rice production. Rice blast management is based predominantly on the application of fungicides; however, only a little is known about responses of pathogen populations to the most widely used fungicides. In this work, the baseline sensitivity of the Italian M. oryzae population to tricyclazole and azoxystrobin in terms of mycelium growth was determined, and the possible adaptation of the pathogen population after several years of repeated exposure to fungicide treatments was evaluated. All the analyzed strains demonstrated higher sensitivity and variability to azoxystrobin (concentration of fungicide causing 50% growth inhibition [ED50] = 0.063 mg liter–1) than to tricyclazole (99.289 mg liter–1). After comparing two additional populations collected from fields repeatedly treated with fungicides to the baseline, no decrease in sensitivity toward these fungicides was observed and no resistant strains were detected. The shift of the pathogen sensitivity toward these fungicides has not occurred, although we observed slightly increased variance associated with ED50 of azoxystrobin. Therefore, both azoxystrobin and tricyclazole can be used to manage rice blast in Italy but it will be important to continue monitoring M. oryzae population to early detect possible azoxystrobin resistance.

scholarly journals Pathogen clonal expansion underlies multiorgan dissemination and organ-specific outcomes during systemic infection

2021 ◽  
Author(s):  
Karthik Hullahalli ◽  
Matthew K Waldor
Keyword(s):  
Genetic Factors ◽  
Systemic Infection ◽  
Clonal Expansion ◽  
Inoculum Size ◽  
Pathogen Population ◽  
E Coli ◽  
Highly Sensitive ◽  
Organ Specific ◽  
Bacterial Genetic ◽  
Pathogen Populations

The dissemination of pathogens through blood and their establishment within organs lead to severe clinical outcomes. However, the within-host dynamics that underly pathogen spread to and clearance from systemic organs remain largely uncharacterized. Here, we investigate the population dynamics of extraintestinal pathogenic E. coli, a common cause of bacteremia, during systemic infection. We show that while bacteria are largely cleared by most organs, organ-specific clearance failures are pervasive and result from dramatic expansions of clones representing less than 0.0001% of the inoculum. Clonal expansion underlies the variability in bacterial burden between animals, and stochastic dissemination of clones profoundly alters the pathogen population structure within organs. Despite variable pathogen expansion events, host bottlenecks are consistent yet highly sensitive to infection variables, including inoculum size and macrophage depletion. Finally, we identify organ-specific bacterial genetic factors that distinguish between establishment of within-organ pathogen populations and subsequent survival or expansion.

scholarly journals The effect of host community functional traits on plant disease risk varies along an elevational gradient

eLife ◽  
2021 ◽  
Vol 10 ◽  
Author(s):  
Fletcher W Halliday ◽  
Mikko Jalo ◽  
Anna-Liisa Laine
Keyword(s):  
Community Structure ◽  
Disease Risk ◽  
Environmental Gradients ◽  
Elevational Gradient ◽  
Host Community ◽  
Interactive Effects ◽  
Life History Strategies ◽  
Herbaceous Plant ◽  
Field Evidence ◽  
Increasing Temperature

Quantifying the relative impact of environmental conditions and host community structure on disease is one of the greatest challenges of the 21st century, as both climate and biodiversity are changing at unprecedented rates. Both increasing temperature and shifting host communities towards more fast-paced life-history strategies are predicted to increase disease, yet their independent and interactive effects on disease in natural communities remains unknown. Here, we address this challenge by surveying foliar disease symptoms in 220, 0.5 meter-diameter herbaceous plant communities along a 1100-meter elevational gradient. We find that increasing temperature associated with lower elevation can increase disease by (1) relaxing constraints on parasite growth and reproduction, (2) determining which host species are present in a given location, and (3) strengthening the positive effect of host community pace-of-life on disease. These results provide the first field evidence, under natural conditions, that environmental gradients can alter how host community structure affects disease.

OPINION DYNAMICS IN POPULATIONS WITH IMPLICIT COMMUNITY STRUCTURE

2009 ◽  
Vol 20 (12) ◽  
pp. 2013-2026 ◽  
Author(s):  
XIAMENG SI ◽  
YUN LIU ◽  
ZHENJIANG ZHANG
Keyword(s):  
Community Structure ◽  
Opinion Dynamics ◽  
Initial Distribution ◽  
Contact Network ◽  
Space And Time ◽  
Opinion Evolution ◽  
Majority Model

Web encounter facilitate contacts between people from different communities outside space and time. Implicit Community Structure is exhibited because of highly connected links within community and sparse encounters between communities. Considering the imperceptible influence of encounter on opinions, Sznajd updating rules are used to mimic people's behaviors after encountering a stranger in another community. We introduce a model for opinion evolution, in which the interconnectivity between different communities is represented as encounter frequency, and leadership is introduced to control the strength of community's opinion guide. In this scenario, the effects of Implicit Community Structure of contact network on opinion evolution, for asymmetric and random initial distribution but with heterogeneous opinion guide, are investigated respectively. It is shown that large encounter frequency favors consensus of the whole populations and successful opinion spreading, which is qualitatively agree with the results observed in Majority model defined on substrates with predefined community structure.

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