scholarly journals Spatial analyses of wildlife contact networks

2015 ◽  
Vol 12 (102) ◽  
pp. 20141004 ◽  
Author(s):  
Stephen Davis ◽  
Babak Abbasi ◽  
Shrupa Shah ◽  
Sandra Telfer ◽  
Mike Begon
Keyword(s):  
Critical Role ◽  
Host Density ◽  
Spatial Arrangement ◽  
Spatial Proximity ◽  
Contact Network ◽  
Spatial Constraints ◽  
Contact Networks ◽  
Proximity Graphs ◽  
Contact Rates ◽  
Pathogen Persistence

Datasets from which wildlife contact networks of epidemiological importance can be inferred are becoming increasingly common. A largely unexplored facet of these data is finding evidence of spatial constraints on who has contact with whom, despite theoretical epidemiologists having long realized spatial constraints can play a critical role in infectious disease dynamics. A graph dissimilarity measure is proposed to quantify how close an observed contact network is to being purely spatial whereby its edges are completely determined by the spatial arrangement of its nodes. Statistical techniques are also used to fit a series of mechanistic models for contact rates between individuals to the binary edge data representing presence or absence of observed contact. These are the basis for a second measure that quantifies the extent to which contacts are being mediated by distance. We apply these methods to a set of 128 contact networks of field voles ( Microtus agrestis ) inferred from mark–recapture data collected over 7 years and from four sites. Large fluctuations in vole abundance allow us to demonstrate that the networks become increasingly similar to spatial proximity graphs as vole density increases. The average number of contacts, , was (i) positively correlated with vole density across the range of observed densities and (ii) for two of the four sites a saturating function of density. The implications for pathogen persistence in wildlife may be that persistence is relatively unaffected by fluctuations in host density because at low density is low but hosts move more freely, and at high density is high but transmission is hampered by local build-up of infected or recovered animals.

scholarly journals Seasonality and pathogen transmission in pastoral cattle contact networks

2017 ◽  
Vol 4 (12) ◽  
pp. 170808 ◽  
Author(s):  
Kimberly VanderWaal ◽  
Marie Gilbertson ◽  
Sharon Okanga ◽  
Brian F. Allan ◽  
Meggan E. Craft
Keyword(s):  
Water Resources ◽  
Disease Outbreaks ◽  
Dry Season ◽  
Pathogen Transmission ◽  
Contact Network ◽  
Wet Season ◽  
Contact Networks ◽  
Contact Rates ◽  
Animal Populations ◽  
The Impact

Capturing heterogeneity in contact patterns in animal populations is essential for understanding the spread of infectious diseases. In contrast to other regions of the world in which livestock movement networks are integral to pathogen prevention and control policies, contact networks are understudied in pastoral regions of Africa due to the challenge of measuring contact among mobile herds of cattle whose movements are driven by access to resources. Furthermore, the extent to which seasonal changes in the distribution of water and resources impacts the structure of contact networks in cattle is uncertain. Contact networks may be more conducive to pathogen spread in the dry season due to congregation at limited water sources. Alternatively, less abundant forage may result in decreased pathogen transmission due to competitive avoidance among herds, as measured by reduced contact rates. Here, we use GPS technology to concurrently track 49 free-roaming cattle herds within a semi-arid region of Kenya, and use these data to characterize seasonal contact networks and model the spread of a highly infectious pathogen. This work provides the first empirical data on the local contact network structure of mobile herds based on quantifiable contact events. The contact network demonstrated high levels of interconnectivity. An increase in contacts near to water resources in the dry season resulted in networks with both higher contact rates and higher potential for pathogen spread than in the wet season. Simulated disease outbreaks were also larger in the dry season. Results support the hypothesis that limited water resources enhance connectivity and transmission within contact networks, as opposed to reducing connectivity as a result of competitive avoidance. These results cast light on the impact of seasonal heterogeneity in resource availability on predicting pathogen transmission dynamics, which has implications for other free-ranging wild and domestic populations.

Effects of goldfish (Carassius auratus) population size and body condition on the transmission of Gyrodactylus kobayashii (Monogenea)

Parasitology ◽  
2017 ◽  
Vol 144 (9) ◽  
pp. 1221-1228 ◽  
Author(s):  
SHUN ZHOU ◽  
HONG ZOU ◽  
SHAN G. WU ◽  
GUI T. WANG ◽  
DAVID J. MARCOGLIESE ◽  
...  
Keyword(s):  
Population Size ◽  
Body Condition ◽  
Host Density ◽  
Host Population ◽  
Laboratory Model ◽  
Constant Density ◽  
Contact Rates ◽  
Effective Contact ◽  
Rate Of Increase ◽  
Population Sizes

SUMMARYField surveys indicate that host population size, rather than density, is the most important determinant of monogenean infection dynamics. To verify this prediction, epidemic parameters were monitored for 70 days at five host population sizes held at constant density using a goldfish – Gyrodactylus kobayashii laboratory model. During the first 20 days, the rate of increase of prevalence and mean abundance was faster in small host populations. Total mean prevalence and total mean abundance throughout the experiment were not significantly affected by host population sizes. Higher transmission rates were detected in larger host populations. However, there were no significant differences in effective contact rates among the five host populations on each sampling day during the first 20 days, implying that contact rates may be saturated at a sufficiently high host density. These results demonstrate that the epidemic occurs more quickly in smaller host populations at the beginning of the experiment. However, the epidemic is independent of the host population size due to the similar effective contact rates in the five population sizes. Significant negative influence of the initial body condition (Kn) of uninfected goldfish on total mean abundance of parasites suggests that susceptibility of hosts is also a determinant of parasite transmission.

scholarly journals Using network properties to predict disease dynamics on human contact networks

2011 ◽  
Vol 278 (1724) ◽  
pp. 3544-3550 ◽  
Author(s):  
Gregory M. Ames ◽  
Dylan B. George ◽  
Christian P. Hampson ◽  
Andrew R. Kanarek ◽  
Cayla D. McBee ◽  
...  
Keyword(s):  
Degree Distribution ◽  
Stochastic Simulations ◽  
Disease Spread ◽  
Contact Structures ◽  
Contact Network ◽  
Contact Networks ◽  
Human Contact ◽  
Differential Equation Models ◽  
Network Properties ◽  
Intermediate Density

Recent studies have increasingly turned to graph theory to model more realistic contact structures that characterize disease spread. Because of the computational demands of these methods, many researchers have sought to use measures of network structure to modify analytically tractable differential equation models. Several of these studies have focused on the degree distribution of the contact network as the basis for their modifications. We show that although degree distribution is sufficient to predict disease behaviour on very sparse or very dense human contact networks, for intermediate density networks we must include information on clustering and path length to accurately predict disease behaviour. Using these three metrics, we were able to explain more than 98 per cent of the variation in endemic disease levels in our stochastic simulations.

scholarly journals Incorporating genomic methods into contact networks to reveal new insights into animal behaviour and infectious disease dynamics

Behaviour ◽  
2018 ◽  
Vol 155 (7-9) ◽  
pp. 759-791 ◽  
Author(s):  
Marie L.J. Gilbertson ◽  
Nicholas M. Fountain-Jones ◽  
Meggan E. Craft
Keyword(s):  
Infectious Disease ◽  
Disease Ecology ◽  
Pathogen Transmission ◽  
Contact Network ◽  
Contact Networks ◽  
Host Behaviour ◽  
Infectious Disease Dynamics ◽  
Insight Into ◽  
Dynamic Interplay ◽  
Broad Overview

Abstract Utilization of contact networks has provided opportunities for assessing the dynamic interplay between pathogen transmission and host behaviour. Genomic techniques have, in their own right, provided new insight into complex questions in disease ecology, and the increasing accessibility of genomic approaches means more researchers may seek out these tools. The integration of network and genomic approaches provides opportunities to examine the interaction between behaviour and pathogen transmission in new ways and with greater resolution. While a number of studies have begun to incorporate both contact network and genomic approaches, a great deal of work has yet to be done to better integrate these techniques. In this review, we give a broad overview of how network and genomic approaches have each been used to address questions regarding the interaction of social behaviour and infectious disease, and then discuss current work and future horizons for the merging of these techniques.

The real other? Museum objects in digital contact networks

2012 ◽  
Vol 17 (3) ◽  
pp. 265-286 ◽  
Author(s):  
Carl Hogsden ◽  
Emma K Poulter
Keyword(s):  
British Museum ◽  
Contact Network ◽  
Contact Networks ◽  
The Real ◽  
Meaning Change ◽  
Museum Objects ◽  
Digital Objects ◽  
To Come ◽  
The University ◽  
Relational Capacities

What can museum objects do when they are placed within a digital contact network – a system made up of reciprocally linked but otherwise separate nodes in which control and ownership of content lies with each location? What new connections are enabled through the placement of objects within this contact network and what are the new understandings that result? Dynamics of access, ownership and meaning change when museum collections are transformed into digital forms, in ways that require the reconceptualization of digital objects and their relational capacities. In theory and in practice, the ‘real’ and the digital object are often framed as disconnected and oppositional entities, a separation that hinders approaches to, and uses of, digital forms. Using examples of recent projects at the University of Cambridge Museum of Archaeology and Anthropology, and at the British Museum, it is argued that digital contact networks enable the unique qualities of digital objects to come to the fore, providing platforms for effective engagement and digital reciprocation.

Colloidal magnetic nanocrystal clusters: variable length-scale interaction mechanisms, synergetic functionalities and technological advantages

2015 ◽  
Vol 4 (6) ◽  
Author(s):  
Athanasia Kostopoulou ◽  
Alexandros Lappas
Keyword(s):  
Magnetic Particles ◽  
Critical Role ◽  
Exchange Interactions ◽  
Magnetic Behavior ◽  
Building Blocks ◽  
Spatial Arrangement ◽  
Magnetic Characteristics ◽  
Surface Functionality ◽  
Magnetic Nanocrystal

AbstractMagnetic particles of optimized nanoscale dimensions can be utilized as building blocks to generate colloidal nanocrystal assemblies with controlled size, well-defined morphology, and tailored properties. Recent advances in the state-of-the-art surfactant-assisted approaches for the directed aggregation of inorganic nanocrystals into cluster-like entities are discussed, and the synthesis parameters that determine their geometrical arrangement are highlighted. This review pays attention to the enhanced physical properties of iron oxide nanoclusters, while it also points to their emerging collective magnetic response. The current progress in experiment and theory for evaluating the strength and the role of intra- and inter-cluster interactions is analyzed in view of the spatial arrangement of the component nanocrystals. Numerous approaches have been proposed for the critical role of dipole-dipole and exchange interactions in establishing the nature of the nanoclusters’ cooperative magnetic behavior (be it ferromagnetic or spin-glass like). Finally, we point out why the purposeful engineering of the nanoclusters’ magnetic characteristics, including their surface functionality, may facilitate their use in diverse technological sectors ranging from nanomedicine and photonics to catalysis.

Spatial Proximity and its Importance for Cooperation in a Tourist Region - Complementary Use of Social Network Analysis and Agglomeration Theory

2019 ◽  
Vol 53 ◽  
pp. 4-4
Author(s):  
Katarzyna Czernek-Marszałek ◽  
Justyna Majewska
Keyword(s):  
Social Network ◽  
Social Network Analysis ◽  
Network Analysis ◽  
Spatial Arrangement ◽  
Economic Benefits ◽  
Spatial Proximity ◽  
Multidimensional Data ◽  
Structured Interviews ◽  
Logistic Regression Method ◽  
Tourist Region

Purpose. Evaluation of the importance of spatial proximity for undertaking business cooperation in a tourist region. Method. Agglomeration economy analysis was combined with the network approach (i.e. Social Network Analysis). The method of case study was used – cooperation between various entities (actors) in five tourist municipalities united in the “Beskid Five” agreement. Semi-structured interviews were conducted with 225 entities selected in purposeful sampling. Additionally, using the appropriate software, based on postal address and data on GPS coordinates of the location of the interviewed entities, were obtained. To analyse the data, some parameters of network analysis were used (i.e. the degree centrality – i.e. in-out and out-degree) and multidimensional data analysis. In particular, the logistic regression method was used, i.e. binary logic regressions were carried out in order to determine the significance of spatial proximity for undertaking cooperation and its intensity in a tourist region. In addition, Moran Ii local statistics were determined in order to measure the occurrence and direction of spatial autocorrelation (spatial correlation coefficient within Local Indicators of Spatial Associations, LISA). Visualisation techniques were also implemented in the work. Findings. In the research, it has been shown that spatial proximity is an important factor affecting cooperation in a tourist region, because it increases the likelihood of cooperation, although this relationship is not linear. Research and conclusion limitations. The study did not cover all entities from the region, but only the so-called key actors in a network. The region selected for research is so specific that the obtained results cannot be considered as representative for other regions in Poland or in the world. In addition, cooperation was analysed without division into various forms, which may also have influence on the obtained results. Practical implications. Entrepreneurs wishing to gain economic benefits regarding cooperation should consider the location and spatial arrangement of connections between potential partners of this cooperation, taking its various forms into account. In addition, by stimulating cooperation between entrepreneurs, local authorities should look at their (municipality office) location in the tourist region and the resulting spatial and functional structure of links between entities, which may determine the scope, intensity and level of effectiveness of the cooperation undertaken. Originality. To show the importance of geographic proximity with reference to intensity of cooperation in a tourist region, analysis of the agglomeration economies and social networks was combined for the first time. Type of paper. An article presenting the results of empirical research.

scholarly journals Spatial Arrangement of the β-Glucoside Transporter from Escherichia coli

2009 ◽  
Vol 191 (9) ◽  
pp. 3086-3094 ◽  
Author(s):  
Sharon Yagur-Kroll ◽  
Ayelet Ido ◽  
Orna Amster-Choder
Keyword(s):  
Escherichia Coli ◽  
Transmembrane Domain ◽  
Protein A ◽  
Phosphorylation Site ◽  
Sugar Transport ◽  
Spatial Arrangement ◽  
Spatial Proximity ◽  
Transmembrane Helices ◽  
Phosphotransferase System ◽  
Hydrophilic Loop

ABSTRACT The Escherichia coli BglF protein, a sugar permease of the phosphoenolpyruvate-dependent phosphotransferase system (PTS), catalyzes concomitant transport and phosphorylation of β-glucosides across the cytoplasmic membrane. Despite intensive studies of PTS permeases, the mechanism that couples sugar translocation to phosphorylation and the nature of the translocation apparatus are poorly understood. Like many PTS permeases, BglF consists of a transmembrane domain, which in addition to transmembrane helices (TMs) contains a big cytoplasmic loop and two hydrophilic domains, one containing a conserved cysteine that phosphorylates the incoming sugar. We previously reported that the big hydrophilic loop, which connects TM VI to TM VII, contains regions that alternate between facing-in and facing-out states and speculated that it is involved in creating the sugar translocation channel. In the current study we used [2-(trimethylammonium)ethyl]methanethiosulfonate bromide (MTSET), a membrane-impermeative thiol-specific reagent, to identify sites that are involved in sugar transport. These sites map to the regions that border the big loop. Using cross-linking reagents that penetrate the cell, we could demonstrate spatial proximity between positions at the center of the big loop and the phosphorylation site, suggesting that the two regions come together to execute sugar phosphotransfer. Additionally, positions on opposite ends of the big loop were found to be spatially close. Cys accessibility analyses suggested that the sugar induces a change in this region. Taken together, our results demonstrate that the big loop participates in creating the sugar pathway and explain the observed coupling between translocation of PTS sugars from the periplasm to the cytoplasm and their phosphorylation.

Multiple warren use by subadult wild rabbits, Oryctolagus cuniculus, and its implications for disease transmission

2017 ◽  
Vol 44 (7) ◽  
pp. 582 ◽  
Author(s):  
Scott Jennings ◽  
Gregory Mutze
Keyword(s):  
Population Density ◽  
Breeding Season ◽  
Disease Transmission ◽  
Critical Role ◽  
Late Summer ◽  
Adult Size ◽  
Contact Rates ◽  
Rabbit Haemorrhagic Disease ◽  
European Rabbits ◽  
Haemorrhagic Disease

Context Contact rates are a key determinant of disease transmission. Territorial behaviour has generally been considered to limit contact between European rabbits occupying different warrens, particularly during the breeding season. Aims We investigated warren use by subadult rabbits during a period of low population density to determine their potential role in transmission of rabbit haemorrhagic disease and myxomatosis. Methods Subadult rabbits were radio-collared in late summer and relocated twice-weekly for 25 weeks, during which time they grew to adult size and breeding commenced. Key results Rabbits of both sexes used an average of four warrens each on a regular basis, even after older rabbits had commenced breeding. Warrens used by individual rabbits formed a continuously overlapping, irregular array. Subadult rabbits did not belong to separate social groups that utilised separate groups of warrens. Conclusions Subadult or young adult rabbits did not display the same territorial warren fidelity that had been previously described for rabbits. They have potential to carry pathogens between warrens at a landscape scale. Implications Movement of subadult rabbits between warrens is therefore likely to play a critical role in disease transmission, particularly when population density is low. This may help to explain the prevalent seasonality of RHD epizootics in spring when first-born litters of each breeding season typically reach that size.

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