Public avoidance and epidemics: insights from an economic model

In this paper, we present a mathematical model of infectious disease transmission in which people can engage in public avoidance behavior to minimize the likelihood of acquiring an infection. The framework employs the economist's theory of utility maximization to model people's decision regarding their level of public avoidance. We derive the reproductive number of a disease which determines whether an endemic equilibrium exists or not. We show that when the contact function exhibits saturation, an endemic equilibrium must be unique. Otherwise, multiple endemic equilibria that differ in disease prevalence can coexist, and which one the population gets to depends on initial conditions. Even when a unique endemic equilibrium exists, people's preferences and the initial conditions may determine whether the disease will eventually die out or become endemic. Public health policies that increase the recovery rate or encourage self-quarantine by infected people can be beneficial to the community by lowering disease prevalence. However, it is also possible for these policies to worsen the situation and cause prevalence to rise since these measures give people less incentive to engage in public avoidance behavior. We also show that implementing policies that result in a higher level of public avoidance behavior in equilibrium does not necessarily lower prevalence and can result in more infections.     

Survey of Pestivirus infection in wild and domestic ungulates from south-western Italian Alps

The transmission of pestiviruses between domestic and wild ruminants has not been documented in communal alpine pastures shared between wildlife and livestock. The aim of this study was to investigate the role of domestic and wild ungulates species from Varaita Valley (SW Italian Alps) in the epidemiology of Pestivirus infections. Sera from free-ranging alpine chamois (Rupicapra rupicapra) and roe deer (Capreolus capreolus) were collected from 1994 to 2009 and 2001 to 2009, respectively. Also, sera from cattle and sheep sampled in 2009 were studied. Sera were tested for the presence of antibodies against pestivirus with an ELISA assay. Sera from positive animals were subsequently tested with a comparative virus neutralisation test using the BVDV-NADL and BDV-137/4 strains. Sera were tested for the presence of pestiviral antigen and the presence of viral RNA with a commercial ELISA assay and RT-PCR. Antibodies against Pestivirus were detected in 132 out of 312 (42%) chamois, in 30 out of 175 (17%) cattle and 6 out of 24 (25%) sheep. No antibodies were found in roe deer. No Pestivirus antigen or RNA was detected in any of the samples. Results indicate circulation of pestiviruses among the studied chamois, cattle and sheep populations. However the role of wild ungulates in the dynamics of Pestivirus infection is still unknown and monitoring the presence of these viruses in wild ungulates would be of importance, especially in the chamois population, where pestiviruses seem to circulate extensively.     

The food habits of wild ungulates in Uganda by analyses of stomach contents

Food eaten by six species of ungulates was studied by analysing stomach contents, using the method developed for faecal analyses. Frequency analyses showed that some herbivore species tend to be selective in their feeding. This suggested that availability and growth form of plants may be important in this respect. The observations agreed with those of other workers, which shows that feeding habits are consistent over large areas. In general, herbivores were classified in three groups with regard to preferences; namely pigs, certain antelope, and buffalo and waterbuck. Comparison of the proportions of epidermal fragments of particular grass species present in stomachs in wet and dry seasons showed that significant seasonal differences exist in the diet of most herbivores. Annuals and most members of the Andropogoneae were present in stomachs in larger proportions during the rains for reasons of availability and palatability. Chloris gayana and Sporobolus pyramidalis were usually present in greater proportions in dry seasons. Differences in the proportions of epidermal fragments of particular plant species present within wet or dry seasons were usually insignificant. A few herbivores, however, showed significant differences within seasons. This indicates that they are sensitive to small changes in plants and that they may have a feeding cycle involving a gradual and regular alternation of plant species. A comparison of the proportions of fragments of the same plant species in different herbivores showed that animal species usually avoided competition by their specialized food habits. There was greater separation in the longer dry season, but competition may have occurred when food supplies were reduced by large herbivores such as buffalo and hippopotamus.     

Spatial constancy and the brain: insights from neural networks

To form an accurate internal representation of visual space, the brain must accurately account for movements of the eyes, head or body. Updating of internal representations in response to these movements is especially important when remembering spatial information, such as the location of an object, since the brain must rely on non-visual extra-retinal signals to compensate for self-generated movements. We investigated the computations underlying spatial updating by constructing a recurrent neural network model to store and update a spatial location based on a gaze shift signal, and to do so flexibly based on a contextual cue. We observed a striking similarity between the patterns of behaviour produced by the model and monkeys trained to perform the same task, as well as between the hidden units of the model and neurons in the lateral intraparietal area (LIP). In this report, we describe the similarities between the model and single unit physiology to illustrate the usefulness of neural networks as a tool for understanding specific computations performed by the brain.     

Host persistence or extinction from emerging infectious disease: insights from white-nose syndrome in endemic and invading regions

Predicting species'' fates following the introduction of a novel pathogen is a significant and growing problem in conservation. Comparing disease dynamics between introduced and endemic regions can offer insight into which naive hosts will persist or go extinct, with disease acting as a filter on host communities. We examined four hypothesized mechanisms for host–pathogen persistence by comparing host infection patterns and environmental reservoirs for Pseudogymnoascus destructans (the causative agent of white-nose syndrome) in Asia, an endemic region, and North America, where the pathogen has recently invaded. Although colony sizes of bats and hibernacula temperatures were very similar, both infection prevalence and fungal loads were much lower on bats and in the environment in Asia than North America. These results indicate that transmission intensity and pathogen growth are lower in Asia, likely due to higher host resistance to pathogen growth in this endemic region, and not due to host tolerance, lower transmission due to smaller populations, or lower environmentally driven pathogen growth rate. Disease filtering also appears to be favouring initially resistant species in North America. More broadly, determining the mechanisms allowing species persistence in endemic regions can help identify species at greater risk of extinction in introduced regions, and determine the consequences for disease dynamics and host–pathogen coevolution.     

Spatial pattern and process at the plant neighbourhood scale: insights from communities dominated by the clonal grass Elymus repens (L.) Gould

Question: How do clonal traits of a locally dominant grass (Elymus repens (L.) Gould.) respond to soil heterogeneity and shape spatial patterns of its tillers? How do tiller spatial patterns constrain seedling recruitment within the community? Locations: Artificial banks of the River Rhône, France. Material and Methods: We examined 45 vegetation patches dominated by Elymus repens. During a first phase we tested relationships between soil variables and three clonal traits (spacer length, number of clumping tillers and branching rate), and between the same clonal traits and spatial patterns (i.e. density and degree of spatial aggregation) of tillers at a very fine scale. During a second phase, we performed a sowing experiment to investigate effects of density and spatial patterns of E. repens on recruitment of eight species selected from the regional species pool. Results: Clonal traits had clear effects – especially spacer length – on densification and aggregation of E. repens tillers and, at the same time, a clear response of these same clonal traits as soil granulometry changed. The density and degree of aggregation of E. repens tillers was positively correlated to total seedling cover and diversity at the finest spatial scales. Conclusions: Spatial patterning of a dominant perennial grass responds to soil heterogeneity through modifications of its clonal morphology as a trade‐off between phalanx and guerrilla forms. In turn, spatial patterns have strong effects on abundance and diversity of seedlings. Spatial patterns of tillers most probably led to formation of endogenous gaps in which the recruitment of new plant individuals was enhanced. Interestingly, we also observed more idiosyncratic effects of tiller spatial patterns on seedling cover and diversity when focusing on different growth forms of the sown species.     

Spatial avoidance of patches of polluted chernozem soils by soil invertebrates

Soil invertebrates and heavy metal concentrations are heterogeneously distributed in the soil of steppe plots surrounding an iron mining enterprise in southern Russia. This study assesses whether patches of high soil invertebrate abundance coincide with patches of low concentrations of pollutants. For this aim, spatial analysis by distance indices (SADIE) was applied. Three valleys in Belogorye Nature Reserve were chosen. One valley faced the tailing pond to the north and the other two faced south-east or south-west. Two sampling plots were chosen in each valley, 60 m apart from each other. On every plot 16 soil cores were collected from a grid of 4 × 4 units with a 5-m distance between each sample unit. Each soil core had an area of 76 cm² and was 12–15 cm deep. All macroinvertebrates were hand-sorted and identified to family. Abundance of soil invertebrates was not controlled by patches of metal concentration in the soil. Epigaeic groups, like insects and other invertebrates inhabiting the litter layer, were not directly associated with local parameters of the soil. On the contrary, belowground invertebrate abundance (elaterid larvae and earthworms) showed significant dissociation with some heavy metal (Fe, Pb, Zn) concentrations in the soil. The patchiness of soil pollution may act as a leading factor of belowground soil invertebrate distribution. The spatial structure of animal populations in industrially transformed soils needs further research.     

The spread of scientific information: insights from the web usage statistics in PLoS article-level metrics

The presence of web-based communities is a distinctive signature of Web 2.0. The web-based feature means that information propagation within each community is highly facilitated, promoting complex collective dynamics in view of information exchange. In this work, we focus on a community of scientists and study, in particular, how the awareness of a scientific paper is spread. Our work is based on the web usage statistics obtained from the PLoS Article Level Metrics dataset compiled by PLoS. The cumulative number of HTML views was found to follow a long tail distribution which is reasonably well-fitted by a lognormal one. We modeled the diffusion of information by a random multiplicative process, and thus extracted the rates of information spread at different stages after the publication of a paper. We found that the spread of information displays two distinct decay regimes: a rapid downfall in the first month after publication, and a gradual power law decay afterwards. We identified these two regimes with two distinct driving processes: a short-term behavior driven by the fame of a paper, and a long-term behavior consistent with citation statistics. The patterns of information spread were found to be remarkably similar in data from different journals, but there are intrinsic differences for different types of web usage (HTML views and PDF downloads versus XML). These similarities and differences shed light on the theoretical understanding of different complex systems, as well as a better design of the corresponding web applications that is of high potential marketing impact.     

Postconflict behaviour of wild Indian langur monkeys: avoidance of opponents but rarely affinity

Friendly postconflict (PC) interactions between former opponents have been described for a large number of primate species held in captivity. We investigated conflict management behaviour for wild Hanuman langurs, Semnopithecus (Presbytis) entellus entellus, in India, using a large sample of over 6000 agonistic and affinitive interactions recorded in one one-male/multifemale troop and three all-male bands. We compared dyadic PC affinity with the dyadic baseline affinity during the overall observation time to minimize biases of traditional matched-control samples. PC affinity was recorded during only 15% of all dyads (immature male-immature male 0%, adult male-adult male 0%, adult male-immature male 5%, adult male-adult female 0%, adult female-adult female 42%). PC affinity is probably absent amongst males because their dominance relationships are strongly asymmetrical, leaving little room for emotional insecurity. Dyads among females, on the other hand, reflect frequent rank changes and close kinship which probably corresponds to higher levels of emotional uncertainty and greater need for PC affinity. Overall, PC affinity reached only 26% of the randomly expected value. Thus, the vast majority of langur monkey opponents avoided each other after conflicts. Avoidance as a low-cost option for group-living animals to cope with conflicts is often not possible in captivity. This suggests that reports of high rates of reconciliation may be at least partly artefacts of captivity. Copyright 2002 The Association for the Study of Animal Behaviour. Published by Elsevier Science Ltd. All rights reserved.     

Trade-offs in the production of animal vocal sequences: insights from the structure of wild chimpanzee pant hoots

Background

Vocal sequences - utterances consisting of calls produced in close succession - are common phenomena in animal communication. While many studies have explored the adaptive benefits of producing such sequences, very little is known about how the costs and constraints involved in their production affect their form. Here, we investigated this issue in the chimpanzee (Pan troglodytes schweinfurthii) pant hoot, a long and structurally complex vocal sequence comprising four acoustically distinct phases – introduction, build-up, climax and let-down.

Results

We found that in each of these phases, and for the sequence as a whole, there was a negative relationship between the number of calls produced and their average duration. There was also a negative relationship between the total duration of some adjacent phases. Significant relationships between the fundamental frequency of calls and their number or duration were found for some phases of the sequence, but the direction of these relationships differed between particular phases.

Conclusions

These results indicate that there are trade-offs in terms of signal duration at two levels in pant-hoot production: between call number and duration, and between the relative durations of successive phases. These trade-offs are likely to reflect biomechanical constraints on vocal sequence production. Phase-specific trade-offs also appear to occur between fundamental frequency and call number or duration, potentially reflecting that different phases of the sequence are associated with distinct types of information, linked in different ways to call pitch. Overall, this study highlights the important role of costs and constraints in shaping the temporal and acoustic structure of animal vocal sequences.

     

New insights into the infection process of Rhynchosporium secalis in barley using GFP

Through the use of a Rhynchosporium secalis isolate transformed with the green fluorescent protein gene and LASER scanning confocal microscopy (LSCM), fungal development during the R. secalis/barley interaction was analysed. Each infection stage was investigated from 0.5h to 14 days post-inoculation (p.i.) with extensive sampling within the first 48 h p.i. Early germination events were observed that had not been previously described. A specific time of germination was noted, with germ tube formation appearing as early as 1h p.i. Conidia were observed within anticlinal grooves of epidermal cells and the formation of bubbles within these pectin-rich regions was observed within 24h p.i. The study reports R. secalis pectinase production and suggests degradation of these pectin-rich regions. Reactive oxygen species were present during early penetration, 3h p.i. and co-localised with fungal development. LSCM allowed the visualisation of fungal growth deep within tissues at the later stage of the infection.     

Ecology of the invading moss species Orthodontium lineare in Sweden: Spatial distribution and population structure

The moss species Orthodontium lineare , originally from the southern hemisphere, has been spreading in Europe during this century. We have monitored the distribution patterns of the species in Sweden.
The age distribution differed between localities due to variation in the proportion of colonies in old age classes. We attributed this to differences in colony mortality. Although O. lineare had a high spore output in most localities, the colonies showed a clumped pattern, indicating strong neighbourhood effects in the colonization of new spots within the locality.
The regional distribution was uneven and markedly southwestern. The distribution was related to regional and local availability of suitable habitats (decaying wood in not-too-dense forests), and to a lesser extent to climatic variables.
Spore transport and establishment are suggested to be the limiting factors for colonization of suitable habitats of O. lineare .     

Detection of Dichelobacter nodosus in wild ungulates (Capra ibex ibex and Ovis aries musimon) and domestic sheep suffering from foot rot using a two-step polymerase chain reaction

Severe keratinous hoof afflictions have been recorded in ibex (Capra ibex ibex) since 1995 and more recently in mouflon (Ovis aries musimon) in Switzerland. Based on clinical observations and comparison with diseases known to affect domestic ungulates, it was hypothesized these wild ungulates were affected by foot rot associated with infection with Dichelobacter nodosus. Dichelobacter nodosus has been shown to be the essential pathogen for initiation and establishment of foot rot, a highly contagious foot disease of sheep and goats. Because these bacteria could not be cultivated from affected ibex, we developed a nested polymerase chain reaction that allowed detection of D. nodosus without culture. Using this assay, we were able to diagnose D. nodosus infections of ibex, mouflon, and domestic sheep in natural outbreaks. From these results we conclude that D. nodosus plays an etiological role in foot rot not only in domestic but also in wild Caprinae.     

Comparisons of mutation rate variation at genome-wide microsatellites: evolutionary insights from two cultivated rice and their wild relatives

Background  

Mutation rate (μ) per generation per locus is an important parameter in the models of population genetics. Studies on mutation rate and its variation are of significance to elucidate the extent and distribution of genetic variation, further infer evolutionary relationships among closely related species, and deeply understand genetic variation of genomes. However, patterns of rate variation of microsatellite loci are still poorly understood in plant species. Furthermore, how their mutation rates vary in di-, tri-, and tetra-nucleotide repeats within the species is largely uninvestigated across related plant genomes.