2,628 research outputs found
Badgers, farm buildings and bovine tuberculosis (Mycobacterium bovis) in cattle: the practical importance of understanding host behavior
Delahay, R., Judge, J
Estimation of badger abundance using faecal DNA typing
1.Wildlife management and conservation programmes often require accurate information
on population density, but this can be difficult to obtain, particularly when the species in question is nocturnal or cryptic. Badger populations in Britain are of intense management interest because they are a wildlife reservoir host of bovine tuberculosis (TB). Attempts to manage this infection in badgers, whether by population control or vaccination, require reliable methods of estimating population size. In addition, such estimates are also required to support research into badger ecology and TB epidemiology. Currently, the most accurate estimates of local badger population size are
obtained from labour-intensive and time-consuming mark–recapture studies. 2. In recent years, DNA has been successfully extracted from the faeces of certain mammals,
and used to generate a genetic profile of the defecating individual. Here we report on an application of this technology to estimate badger abundance.3.Faecal samples were collected on 10 consecutive days from every freshly deposited dropping at latrine sites close to occupied setts in three badger social groups. Badger
DNA was extracted from 89% of samples, and 20 different individuals were reliably identified. The genotypes derived from the faecal samples were compared with those
obtained from blood or samples from badgers live trapped at the same setts.4.The faecal genotypes from badgers with known trap histories revealed that latrines were used equally by males and females, and by badgers ranging in age from cubs(< 1 year old) to 9 years old. Individual badgers used the latrines on between one and six different nights. Rarefaction analysis produced abundance estimates that closely matched those obtained from live trapping.
5.Synthesis and applications. Systematic sampling and genetic typing of fresh faeces from badger latrines can provide data that can be used to estimate abundance accurately.This approach requires considerably less human resources than repeated live trapping
and mark–recapture. The technique may be valuable for future badger research and management in relation to bovine TB, where accurate estimates of abundance at a local
scale are required
Estimation of the fatigue strength distribution in high-cycle multiaxial fatigue taking into account the stress–strain gradient effect
Based on the weakest link concept, a probabilistic approach in high-cycle multiaxial fatigue is developed to predict, for a given number of cycles, the probability distribution of the fatigue strength for metallic structural components. A three-parameter Weibull distribution is combined with the energy-based and volumetric high-cycle multiaxial fatigue criterion proposed by Banvillet et al. in 2002 [Banvillet A, Palin-Luc T, Lasserre S. A volumetric energy based high cycle multiaxial fatigue criterion. Int J Fatigue 2003;26(8):755–69; Banvillet A, Palin-Luc T, Lasserre, S, Vittori JF. Energy based high cycle multiaxial fatigue criterion depending on stress–strain distribution. In: Blom AF, editor. Fatigue 2002: Eighth international fatigue congress, vol. 1, EMAS: Stockholm; 2002, p. 283–90]. Whatever the stress state and the loading type are, the corresponding fatigue strength probability distribution can be deduced from three usual experimental fatigue limits. The scale effect is also predicted. Experimental probability distributions and theoretical predictions of the fatigue strength of smooth specimens are in good agreement for the five materials investigated: the 30NiCrMo16 and 35CrMo4 quenched and tempered steels, the C20 annealed steel, the EN-GJS800-2 nodular cast iron and the Ti–6Al–4V titanium alloy
Age-related declines and disease-associated variation in immune cell telomere length in a wild mammal
publication-status: Publishedtypes: Article© 2014 Beirne et al.The authors confirm that all data underlying the findings are fully available without restriction. All relevant data are within the paper and its
Supporting Information files.This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.Immunosenescence, the deterioration of immune system capability with age, may play a key role in mediating age-related
declines in whole-organism performance, but the mechanisms that underpin immunosenescence are poorly understood.
Biomedical research on humans and laboratory models has documented age and disease related declines in the telomere
lengths of leukocytes (‘immune cells’), stimulating interest their having a potentially general role in the emergence of
immunosenescent phenotypes. However, it is unknown whether such observations generalise to the immune cell
populations of wild vertebrates living under ecologically realistic conditions. Here we examine longitudinal changes in the
mean telomere lengths of immune cells in wild European badgers (Meles meles). Our findings provide the first evidence of
within-individual age-related declines in immune cell telomere lengths in a wild vertebrate. That the rate of age-related
decline in telomere length appears to be steeper within individuals than at the overall population level raises the possibility
that individuals with short immune cell telomeres and/or higher rates of immune cell telomere attrition may be selectively
lost from this population. We also report evidence suggestive of associations between immune cell telomere length and
bovine tuberculosis infection status, with individuals detected at the most advanced stage of infection tending to have
shorter immune cell telomeres than disease positive individuals. While male European badgers are larger and show higher
rates of annual mortality than females, we found no evidence of a sex difference in either mean telomere length or the
average rate of within-individual telomere attrition with age. Our findings lend support to the view that age-related declines
in the telomere lengths of immune cells may provide one potentially general mechanism underpinning age-related declines
in immunocompetence in natural populations.Biotechnology and Biological Sciences Research Council (BBSRC)The Food and Environmental Research Agency (FERA
Phylogeographic diversity and mosaicism of the Helicobacter pylori tfs integrative and conjugative elements.
Background: The genome of the gastric pathogen Helicobacter pylori is characterised by considerable variation of both gene sequence and content, much of which is contained within three large genomic islands comprising the cag pathogenicity island (cagPAI) and two mobile integrative and conjugative elements (ICEs) termed tfs3 and tfs4. All three islands are implicated as virulence factors, although whereas the cagPAI is well characterised, understanding of how the tfs elements influence H. pylori interactions with different human hosts is significantly confounded by limited definition of their distribution, diversity and structural representation in the global H. pylori population.
Results: To gain a global perspective of tfs ICE population dynamics we established a bioinformatics workflow to extract and precisely define the full tfs pan-gene content contained within a global collection of 221 draft and complete H. pylori genome sequences. Complete (ca. 35-55kbp) and remnant tfs ICE clusters were reconstructed from a dataset comprising >12,000 genes, from which orthologous gene complements and distinct alleles descriptive of different tfs ICE types were defined and classified in comparative analyses. The genetic variation within defined ICE modular segments was subsequently used to provide a complete description of tfs ICE diversity and a comprehensive assessment of their phylogeographic context. Our further examination of the apparent ICE modular types identified an ancient and complex history of ICE residence, mobility and interaction within particular H. pylori phylogeographic lineages and further, provided evidence of both contemporary inter-lineage and inter-species ICE transfer and displacement.
Conclusions: Our collective results establish a clear view of tfs ICE diversity and phylogeographic representation in the global H. pylori population, and provide a robust contextual framework for elucidating the functional role of the tfs ICEs particularly as it relates to the risk of gastric disease associated with different tfs ICE genotypes
Mating system of the Eurasian badger, Meles meles, in a high density population
Badgers are facultatively social, forming large groups at high density. Group-living appears
to have high reproductive costs for females, and may lead to increased levels of inbreeding.
The extent of female competition for reproduction has been estimated from field data, but
knowledge of male reproductive success and the extent of extra-group paternity remains
limited. Combining field data with genetic data (16 microsatellite loci), we studied the mating
system of 10 badger social groups across 14 years in a high-density population. From 923
badgers, including 425 cubs, we were able to assign maternity to 307 cubs, with both parents
assigned to 199 cubs (47%) with 80% confidence, and 14% with 95% confidence. Age had a
significant effect on the probability of reproduction, seemingly as a result of a deficit of
individuals aged two years and greater than eight years attaining parentage. We estimate
that approximately 30% of the female population successfully reproduced in any given
year, with a similar proportion of the male population gaining paternity across the same
area. While it was known there was a cost to female reproduction in high density populations,
it appears that males suffer similar, but not greater, costs. Roughly half of assigned paternity
was attributed to extra-group males, the majority of which were from neighbouring social
groups. Few successful matings occurred between individuals born in the same social group
(22%). The high rate of extra-group mating, previously unquantified, may help reduce inbreeding,
potentially making philopatry a less costly strategy
Density and abundance of badger social groups in England and Wales in 2011-2013
This is the final version of the article. Available from Nature Publishing Group via the DOI in this record.In the United Kingdom, European badgers Meles meles are a protected species and an important wildlife reservoir of bovine tuberculosis. We conducted a survey of badger dens (main setts) in 1614 1 km squares across England and Wales, between November 2011 and March 2013. Using main setts as a proxy for badger social groups, the estimated mean density of badger social groups in England and Wales was 0.485 km(-2) (95% confidence interval 0.449-0.521) and the estimated abundance of social groups was 71,600 (66,400-76,900). In the 25 years since the first survey in 1985-88, the annual rate of increase in the estimated number of badger social groups was 2.6% (2.2-2.9%), equating to an 88% (70-105%) increase across England and Wales. In England, we estimate there has been an increase of 103% (83-123%) in badger social groups, while in Wales there has been little change (-25 to +49%).We are grateful to the thousands of landowners for their kind co-operation in granting access to their land. This study was funded by the Department for Environment, Food and Rural Affairs, as part of England and Wales national research activities. Fieldwork was conducted by staff of the National Wildlife Management Centre. Access to data from the 1985–88 survey was licensed by the Joint Nature Conservation Committee, to whom the rights of the Nature Conservancy Council had passed
Contact chains of cattle farms in Great Britain
This is the final version. Available from the publisher via the DOI in this record.Further information and figures supporting this article have been uploaded as part of the electronic
supplementary material. Underlying data consist of every movement of cattle between all farms in Great Britain.
Aside from the size of the dataset, there are substantial issues of confidentiality (locations, trading practices) and
commercial sensitivity in these data. They are collated and managed by Defra, via the Animal and Plant Health
Agency, who grant access to the data with specific permissions for specific studies. In practice, this means that the
data can be used for the stated purpose only, and making the data publicly accessible would not conform to the
licence the authors have been granted to use these data. With the agreement of the journal’s Editorial Office, the
authors will not be able to make the dataset available on this occasion, but encourage readers, referees and editors
to contact the Animal and Plant Health Agency data manager for data access requests. At the time of submission,
the data manager is Andy Mitchell ([email protected])Network analyses can assist in predicting the course of epidemics.
Time-directed paths or ‘contact chains’ provide a measure of hostconnectedness across specified timeframes, and so represent
potential pathways for spread of infections with different
epidemiological characteristics. We analysed networks and
contact chains of cattle farms in Great Britain using Cattle
Tracing System data from 2001 to 2015. We focused on the
potential for between-farm transmission of bovine tuberculosis,
a chronic infection with potential for hidden spread through
the network. Networks were characterized by scale-free type
properties, where individual farms were found to be influential
‘hubs’ in the network. We found a markedly bimodal
distribution of farms with either small or very large ingoing and
outgoing contact chains (ICCs and OCCs). As a result of their
cattle purchases within 12-month periods, 47% of British farms
were connected by ICCs to more than 1000 other farms and 16%
were connected to more than 10 000 other farms. As a result of
their cattle sales within 12-month periods, 66% of farms had
OCCs that reached more than 1000 other farms and 15% reached
more than 10 000 other farms. Over 19 000 farms had both ICCs
and OCCs reaching more than 10 000 farms for two or more
years. While farms with more contacts in their ICCs or OCCs
might play an important role in disease spread, farms with
extensive ICCs and OCCs might be particularly important by
being at higher risk of both acquiring and disseminatinginfections.Biotechnology and Biological Science Research Council (BBSRC
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