Public Release: 

Transmission rates of vCJD

Reserach to be published in Royal Society Journals this week

Royal Society

Please find below the summaries of papers in Interface, Biology Letters, Proceedings B and Proceedings A that are due to be published onlinethis week.

Journal of the Royal Society Interface

Factors determining the potential for onward transmission of variant Creutzfeldt-Jakob disease via surgical instruments by Tini Garske, Hester J. T. Ward, Paul Clarke, Robert G. Will and Azra C. Ghani
(doi: 10.1098/rsif.2006.0142)

While the number of variant Creutzfeldt-Jakob disease (vCJD) cases continues to decline, concern has been raised that transmission could occur directly from one person to another through routes including the transfer of blood and shared use of surgical instruments. Here we present data on the surgical procedures undertaken on vCJD patients prior to onset of clinical symptoms, which supports the hypothesis that cases via this route are possible. Our results demonstrate that a key uncertainty determining the scale of an epidemic and whether it is self-sustaining is the number of times a single instrument is re-used, alongside the infectivity of contaminated instruments and the effectiveness of cleaning. A survey into the frequency of re-use of surgical instruments would help reducing these uncertainties.

Dr T Garske
London School of Hygiene and Tropical Medicine
tel. +44 (0)2079588208

Biology Letters

Chimpanzee and felid diet composition is influenced by prey brain size by Dr SMS Shultz and Professor R Dunbar
(doi: 10.1098/rsbl.2006.0519)

The underlying cause of brain evolution and intelligence has been an intriguing, yet elusive, problem. Various explanations have pointed to social cognition, tool use and behavioural flexibility as the key benefits of large brains. However, using predation rates for large cats and chimpanzees from five sites in Africa and South America we here show that predators deliberately target smaller brained prey species. These results provide an unexpected and novel perspective on mammalian brain evolution by showing that species with large brains avoid predation. Thus predators may be instrumental in driving brain evolution.

Dr SMS Shultz
School of Biological Sciences
Liverpool University
tel: +44 151 795 4417

Contrasting patterns of sequence divergence and base composition between Drosophila introns and intergenic regions by Dr. L Ometto, Dr. D De Lorenzo and Prof. W Stephan
(doi: 10.1098/rsbl.2006.0521)

We analyzed the nucleotide polymorphism and divergence in two non-coding DNA classes, introns and intergenic regions, of Drosophila melanogaster and found that they exhibit contrasting evolutionary patterns. In particular, GC content is significantly higher in intergenic regions and affects their degree of nucleotide variability. Moreover, divergence is positively correlated with recombination rate in intergenic regions, but not in introns. We argue that these differences in nucleotide composition and divergence pattern are due to different selective and functional constraints rather than mutational or recombinational mechanisms. Therefore, introns and intergenic regions represent two distinct classes of (weakly) selected DNA

Dr. L Ometto
Department of Ecology and Evolution
University of Lausanne
tel: +41 21 692 4165

Proceedings of the Royal Society B: Biological Sciences

Major cranial changes during triceratops ontogeny by Dr JR Horner and Mr. MB Goodwin

This is the first cranial ontogenetic assessment of Triceratops, the well-known Late Cretaceous dinosaur distinguished by three horns and a massive parietal-squamosal frill. Our analysis is based on a growth series of ten skulls, ranging from a 38 cm long baby skull to adult skulls over 2 m long. Four growth stages correspond to a suite of ontogenetic characters expressed in the postorbital horns, frill, nasal, epinasal horn, and epoccipitals. Postorbital horns are straight stubs early in ontogeny, curve posteriorly in juveniles, straighten in subadults, and recurve anteriorly in adults. The posterior margin of the baby frill is deeply scalloped. In early juveniles the frill margin becomes ornamented by 17 - 19 delta-shaped epoccipitals. Epoccipitals are dorso-ventrally compressed in subadults, strongly compressed and elongated in adults, and ultimately merge onto the posterior frill margin in older adults. Ontogenetic trends within and between growth stages include: posterior frill margin transitions from scalloped, to wavy, to smooth; progressive exclusion of the supraoccipital from the foramen magnum; internal hollowing at the base of the postorbital horns; closure of the midline nasal suture; fusion of the epinasal onto the nasals; and epinasal expansion into a morphologically variable nasal horn. We hypothesize that the changes in horn orientation and epoccipital shape functioned to allow visual identity of juveniles, and signaled their attainment of sexual maturity.

Mr. MB Goodwin
University of California
001 510-643-9745

Rapid adaptation of insect herbivores to an invasive plant by Dr E Siemann, Dr. WE Rogers and Dr. SJ DeWalt

Introduced plant success often is attributed to release from natural enemies in their new ranges. However, herbivores may accumulate over time and reduce invasiveness but evidence for this process to date is weak. We report here that enemy release is indeed limited to the early stages of introduction of Chinese Tallow Tree (Sapium sebiferum). In bioassays and gardens along a geographical gradient of time since Tallow Tree introduction, herbivory was highest and tree performance was poorest where Tallow Tree has been present longer (i.e. introduced earlier). Additionally, Asian ecotypes (grown from seeds collected in Asia) had lower survival than North American ecotypes (seeds collected in North America) which is consistent with genetic responses to low herbivory in the introduced range (EICA Hypothesis). Release from insect herbivores appears to contribute to early success of Tallow Tree, but accumulation of insect herbivores has apparently reduced this benefit over time.

Dr E Siemann
Rice University
001 713-348-5954

Modelling the initial spread of foot-and-mouth disease through animal movements by Dr DM Green, Dr IZ Kiss and Dr RR Kao

Livestock movements are now well recorded in the UK, showing how many pigs, sheep, and cattle move from where, to where, and when. We used these data to build a computer model of the spread of foot-and-mouth disease (FMD), and used the model to determine the susceptibility of the GB livestock industry to future outbreaks given current legislation. We show that movements could result in a large epidemic, but only if cattle are heavily involved, where FMD is more easily detected, or in late summer and early autumn. Larger epidemics are predicted in Scotland and the North.

Dr DM Green
University of Oxford
01865 281092

Can the common brain parasite, Toxoplasma gondii, influence human culture? by Dr D Lafferty

The latent prevalence of a long-lived and common brain parasite, Toxoplasma gondii, explains a statistically significant portion of the variance in aggregate neuroticism among populations, as well as in the "neurotic" cultural dimensions of sex roles and uncertainty avoidance. Spurious or non-causal correlations between aggregate personality and aspects of climate and culture that influence T. gondii transmission could also drive these patterns. A link between culture and T. gondii hypothetically results from a behavioural manipulation the parasite uses to increase its transmission to the next host in the life cycle, a cat. While latent toxoplasmosis is usually benign, the parasite's subtle effect on individual personality appears to alter aggregate personality at the population level. Drivers of the geographic variation in the prevalence of this parasite include the effects of climate on the persistence of infectious stages in soil, and the cultural practices of food preparation and cats as pets. Some variation in culture, therefore, may ultimately be related to how climate affects the distribution of T. gondii, though the results only explain a fraction of the variation in two of the four cultural dimensions, suggesting that if T. gondii does influence human culture, it is only one of many factors.

Dr D Lafferty
University of California
001 805 893 8778

Self-harm caused by innate immunity in an insect by Mr BM Sadd and Dr MT Siva-Jothy

It has been a long-held assumption that the innate immune system of insects causes self-harm when used to combat an immune insult: we show empirically that this assumption was correct. Invertebrate innate immunity relies heavily on effector systems which, when activated, produce cytotoxins that kill pathogens. Reliance on these robust, fast-acting, generic killing mechanisms ensures a potent and rapid response to pathogen invasion, but has the potential disadvantage of causing damage to self. We show that the innate immune response against an immune insult produces measurable phenotypic and functional damage to self-tissue in the beetle Tenebrio molitor. This type of self-harm (autoreactivity) and the life-history implications that arise from it, are central to understanding evolutionary phenomena such as the dynamics between hosts and parasites as well as the nature of immune system costs.

Dr MT Siva-Jothy
University of Sheffield

Evidence that female preferences have shaped male signal evolution in a clade of specialized plant-feeding insects by Dr RL Rodriguez, Dr K Ramaswamy and Dr. B Cocroft

Darwin proposed mate choice as an important source of selection on extravagant and rapidly evolving traits, such as mating signals. Testing this hypothesis requires evaluating the effect of changes in mate preferences on changes in mating signals. We conducted the most comprehensive test to date with Enchenopa treehoppers, plant-feeding insects that communicate with substrate vibrations. Males call with a slow whine followed by pulses, and females that like a male's call respond with a long "hum" that encourages him to look for her. The active role of females in pair formation allows discovering what they prefer in a call and how strongly they care. Comparing four closely related Enchenopa species, we found that species differ in their preferences and calls, and that for each species the closest fit between preference and call is found in those call features that females most care about. Our findings strongly support the hypothesis of mate choice as a main agent in signal evolution.

Dr RL Rodriguez
University of Missouri-Columbia
001 573-884-1080

Network frailty and the geometry of herd immunity by Mr. J Ferrari, Ms. none Bansal, Dr LA Meyers and Dr ON Bjornstad

The spread of infectious disease through communities depends fundamentally on the underlying patterns of contacts between individuals. Generally, the more contacts one has, the more vulnerable one is to infection during an epidemic. Thus, outbreaks disproportionately impact the most highly connected demographics. Epidemics can then lead to sparser networks, through immunization or removal of individuals, which are more resistant to future transmission of a given disease. Using several classes of contact networks - Poisson, scale-free, and small-world - we characterize the structural evolution of a network due to an epidemic in terms of frailty - the degree to which highly connected individuals are more vulnerable to infection - and interference - the extent to which the epidemic cuts off connectivity among the susceptible population that remains following an epidemic. The evolution of the susceptible network over the course of an epidemic differs among classes of networks; frailty, relative to interference, accounts for an increasing component of network evolution on networks with greater variance in contacts. The result is that immunization due to prior epidemics can provide greater community protection than random vaccination on networks with heterogeneous contact patterns, while the reverse is true for highly structured populations.

Mr. J Ferrari
The Pennsylvania State University
001 814-863-1815

Spatio-temporal expression of the settlement-inducing protein complex (SIPC) in the barnacle, Balanus amphitrite by Dr C Dreanno, Dr RR Kirby and Professor AS Clare

Barnacles are prominent members of hard substratum benthic communities and their study has been important to advances in experimental ecology and contemporary ecological theory. Having recently characterised the cue to gregarious settlement of Balanus amphitrite, the settlement-inducing protein complex (SIPC), we use two polyclonal antibodies to examine the tissue distribution and ontogenetic expression of this glycoprotein. These antibodies were raised against two separate peptides located near the N- and C-termini of SIPC and were used to detect the glycoprotein by western blotting and immunohistochemistry. By in situ hybridisation we also show that the SIPC mRNA co-occurs with the expressed glycoprotein in the cuticles of both nauplius and cypris larval stages and the adult. In the larvae, the SIPC is expressed most strongly in the mouthparts and the hindgut of the stage 2 nauplius and in the thoracopods, antennules and bivalved carapace of the cyprid. In adult B. amphitrite, the expressed SIPC is present in protein extracts of the shell and in all organs that are lined by cuticular tissues. We suggest that the SIPC is produced by the epidermal cells that produce the cuticle and discuss these observations with regard to earlier studies and the role of SIPC as a contact pheromone.

Professor AS Clare
University of Newcastle Upon Tyne
0191 222 5918

Himalayan porter's specialization: metabolic power, economy and skill by Professor AE Minetti, Mr F Formenti and Mr LP Ardigo
(doi:10.1098/ rspb.2006.3653)

Carrying heavy loads in the Himalayan region is a real challenge. Porters face extreme ranges in terrain condition, path steepness, altitude hypoxia and climate for 6-8 hours a day, many months a year, since they are boys. It has been previously shown that, when carrying loads on level terrain, porters' metabolic economy is higher than in Caucasians, but the reasons for that are still unknown. We monitored Nepalese porters both during 90 km trekking in Khumbu Valley and at two different altitudes (3490 and 5050 m a.s.l.) where they were compared to Caucasian mountaineers during (22%) gradient walking. Both subject groups carried a load of up to 90% body mass. The remarkably higher performance of porters during uphill locomotion (+60% in speed, +39% mechanical power) is only partly explained by the lower cost of loaded walking (-20%), being also the result of a better cardio-circulatory adaptation to altitude, which generates a higher mass specific metabolic power (+30%). Consequently, Nepalese porters show higher efficiency, both during uphill and downhill loaded walking. Their higher economy on steep paths cannot be ascribed to a better exchange between potential and kinetic energy, as in our experiments the body centre of mass travelled monotonically uphill (or downhill). A different oscillation pattern of the loaded head-trunk segment, together with the analysis of the different components of the mechanical work during load carrying, suggests that achieved motor skills in balancing the loaded body segment above the hip could play a role in determining the better economy of porters.

Professor AE Minetti
University of Milan

Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences

'Morphing' bistable orthotropic elliptical shallow shells by Dr KA Seffen.

This study is concerned with the equilibrium shapes of orthotropic, elliptical plates and shells deforming elastically without initial stresses. The aim is to explore potential bistable configurations and their dependencies on material parameters and initial shape for elucidating novel morphing structures. A strain energy formulation gives way to a compact set of governing equations of deformation, which can be solved in closed form for some isotropic and orthotropic conditions. It is shown that bi-stability depends on the change in Gaussian curvature of the shell, in particular, for initially untwisted shells, isotropy precludes bi-stability, where there is negative initial Gaussian curvature, but orthotropic materials yield bi-stability irrespective of the sign of the initial Gaussian curvature. This improved range of performance stems from increasing the independent shear modulus, which imparts sufficient torsional rigidity to stabilize against perturbations in the deformed state. It is also shown that the range of bistable configurations for initially twisted shells generally diminishes as the degree of twist increases.

Dr KA Seffen
University of Cambridge
Tel : 00 44 1223 764137

Observations on the Evolution of Wave Modulation by Professor HH Hwung, Dr. WS Chiang and Dr. S Hsiao.

This paper aims to investigate the evolutions of nonlinear wave trains in a super wave flume (300 M. x 5.0 M. x 5.2 M.). The evolutions including transient wave front, fastest growth mode, energy transfer, and initial wave steepness effect are discussed and their results are compared with the existing experimental data and theoretical predictions. A frequency downshift is observed in initial uniform wave trains experiment, while a multiple-downshift found in the initial imposed sidebands wave trains. Furthermore, the permanent frequency downshift induced by wave breaking observed by previous researchers may are not permanent.

Professor HH Hwung
National Cheng-Kung University
Tel: 00 886-6-3840207


Interface, Biology Letters, Proceedings B and Proceedings A are published by the Royal Society but do not necessarily reflect the views of the Royal Society

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