Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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Thrips advisor : Exploiting thrips-induced defences to combat pests on crops
Steenbergen, Merel ; Abd-El-Haliem, Ahmed ; Bleeker, Petra ; Dicke, Marcel ; Escobar-Bravo, Rocio ; Cheng, Gang ; Haring, Michel A. ; Kant, Merijn R. ; Kappers, Iris ; Klinkhamer, Peter G.L. ; Leiss, Kirsten A. ; Legarrea, Saioa ; Macel, Mirka ; Mouden, Sanae ; Pieterse, Corné M.J. ; Sarde, Sandeep J. ; Schuurink, Robert C. ; Vos, Martin De; Wees, Saskia C.M. Van; Broekgaarden, Colette - \ 2018
Journal of Experimental Botany 69 (2018)8. - ISSN 0022-0957 - p. 1837 - 1848.
Cell-content feeder - effectors - herbivorous insect - phytohormone signalling - plant defence - specialized metabolites - thrips - virus - volatiles

Plants have developed diverse defence mechanisms to ward off herbivorous pests. However, agriculture still faces estimated crop yield losses ranging from 25% to 40% annually. These losses arise not only because of direct feeding damage, but also because many pests serve as vectors of plant viruses. Herbivorous thrips (Thysanoptera) are important pests of vegetable and ornamental crops worldwide, and encompass virtually all general problems of pests: they are highly polyphagous, hard to control because of their complex lifestyle, and they are vectors of destructive viruses. Currently, control management of thrips mainly relies on the use of chemical pesticides. However, thrips rapidly develop resistance to these pesticides. With the rising demand for more sustainable, safer, and healthier food production systems, we urgently need to pinpoint the gaps in knowledge of plant defences against thrips to enable the future development of novel control methods. In this review, we summarize the current, rather scarce, knowledge of thrips-induced plant responses and the role of phytohormonal signalling and chemical defences in these responses. We describe concrete opportunities for breeding resistance against pests such as thrips as a prototype approach for next-generation resistance breeding.

No significant differences in the breadth of the foot-and-mouth disease serotype A vaccine induced antibody responses in cattle, using different antigens, mixed antigens and different toutes of administration
Tekleghiorghis, T. ; Weerdmeester, K. ; Hemert-Kluitenberg, F. ; Moormann, R.J.M. ; Dekker, A. - \ 2014
Vaccine 32 (2014)41. - ISSN 0264-410X - p. 5330 - 5336.
aluminum hydroxide gel - emergency vaccination - immune-responses - cross-protection - fmd vaccines - virus - elisa - potency - tests - challenge
Inactivated whole virus foot-and-mouth disease (FMD) vaccines are used worldwide for protection against FMD, but not all vaccines induce protection against all genetic variants of the same FMD virus serotype. The aim of this study is to investigate whether the “breadth” of the antibody response against different strains of the same FMD virus serotype in cattle could be improved by using a different adjuvant, a mix of antigens and/or different routes of administration. To this end, six groups of five cattle were vaccinated with different FMD virus serotype A strain vaccines formulated with Montanide ISA 206 VG adjuvant. Antibody responses for homologous and heterologous cross-reactivity against a panel of 10 different FMD virus serotype A strains were tested by a liquid-phase blocking ELISA. Results of cattle vaccinated with ISA 206 VG adjuvanted vaccine were compared with results obtained in a previous study using aluminium hydroxide-saponin adjuvant. No significant effect of adjuvant on the breadth of the antibody response was observed, neither for mixing of antigens nor for the route of administration (subcutaneous vs. intradermal). Comparison of antigen payload, however, increased both homologous and heterologous titres; a 10-fold higher antigen dose resulted in approximately four times higher titres against all tested strains. Our study shows that breadth of the antibody response depends mainly on the vaccine strain; we therefore propose that, for vaccine preparation, only FMD virus strains are selected that, among other important characteristics, will induce a wide antibody response to different field strains.
Transmission of Actinobacillus pleuropneumoniae among weaned piglets on endemically infected farms
Tobias, T.J. ; Bouma, A. ; Broek, J. van den; Nes, A. van; Daemen, A.J.J.M. ; Wagenaar, J.A. ; Stegeman, J.A. ; Klinkenberg, D. - \ 2014
Preventive Veterinary Medicine 117 (2014)1. - ISSN 0167-5877 - p. 207 - 214.
between-pen transmission - acquired colostral antibodies - within-pen - airborne transmission - pigs - serotype-2 - virus - herd - quantification - colonization
Clinical outbreaks due to Actinobacillus pleuropneumoniae occur recurrently, despite the wide-scale use of antimicrobials or vaccination. Therefore, new approaches for the prevention and control of these outbreaks are necessary. For the development of alternative measures, more insight into the transmission of the bacterium on farms is necessary. The aim of this cohort study was to quantify transmission of A. pleuropneumoniae amongst weaned piglets on farms. We investigated three possible transmission routes: (i) indirect transmission by infected piglets within the same compartment, (ii) transmission by infected pigs in adjacent pens and (iii) transmission by direct contact within pens. Additionally, we evaluated the effect of independent litter characteristics on the probability of infection. Two farms participated in our study. Serum and tonsil brush samples were collected from sows pre-farrowing. Serum was analysed for antibodies against Apx toxins and Omp. Subsequently, tonsil brush samples were collected from all piglets from these dams (N = 542) in three cohorts, 3 days before weaning and 6 weeks later. Tonsil samples were analysed by qPCR for the presence of the apxIVA gene of A. pleuropneumoniae. Before weaning, 25% of the piglets tested positive; 6 weeks later 47% tested positive. Regression and stochastic transmission models were used to assess the contribution of each of the three transmission routes and to estimate transmission rates. Transmission between piglets in adjacent pens did not differ significantly from that between non-adjacent pens. The transmission rate across pens was estimated to be 0.0058 day(-1) (95% CI: 0.0030-0.010), whereas the transmission rate within pens was ten times higher 0.059 day(-1) (95% CI: 0.048-0.072). Subsequently, the effects of parity and serological response of the dam and litter age at weaning on the probability of infection of pigs were evaluated by including these into the regression model. A higher dam ApxII antibody level was associated with a lower probability of infection of the pig after weaning; age at weaning was associated with a higher probability of infection of the pig after weaning. Finally, transmission rate estimates were used in a scenario study in which the litters within a compartment were mixed across pens at weaning instead of raising litter mates together in a pen. The results showed that the proportion of infected piglets increased to 69% if litters were mixed at weaning, indicating that farm management measures may affect spread of A. pleuropneumoniae. (C) 2014 Elsevier B.V. All rights reserved.
Insect herbivore- associated organisms affect plant responses to herbivory
Zhu, F. ; Poelman, E.H. ; Dicke, M. - \ 2014
New Phytologist 204 (2014)2. - ISSN 0028-646X - p. 315 - 321.
spodoptera-littoralis - mediated interactions - indirect defense - host - virus - symbionts - parasites - caterpillars - arabidopsis - hypothesis
In nature, plants interact with many organisms and need to integrate their responses to these diverse community members. Knowledge on plant-insect relationships has accumulated rapidly during the last decades. Yet most studies on direct or indirect defences of plants against herbivory have treated herbivores as individual stressors. However, herbivores often consist of communities themselves, comprising organisms such as parasites and symbionts, which may have important effects on the herbivore phenotype, and consequently on interactions of the herbivore with its food plant. Here, we review how herbivore-associated organisms affect plant-herbivore interactions. Organisms associated with herbivores can directly affect how a plant interacts with their herbivorous hosts, by interfering with plant signal-transduction pathways, repressing the expression of plant defence-related genes, or altering plant secondary metabolism. In addition, herbivore-associated organisms can also affect plant responses indirectly by their effect on the behaviour and physiology of their herbivore host. The changes in plant phenotype that arise from herbivore-associated organisms may subsequently affect interactions with other community members, thereby impacting community dynamics. Furthermore, herbivore-associated organisms may act as a hidden driving force of plant-herbivore coevolution. Therefore, to understand plant-herbivore interactions it is important to realize that every single herbivorous insect constitutes a community in itself.
Seroprevalence and associated risk factors of important pig viral diseases in Bhutan
Monger, V.R. ; Stegeman, J.A. ; Koop, G. ; Dukpa, K. ; Tenzin, T. ; Loeffen, W.L.A. - \ 2014
Preventive Veterinary Medicine 117 (2014)1. - ISSN 0167-5877 - p. 222 - 232.
classical swine-fever - influenza-a h1n1 - vaccination policy - antigenic drift - virus - infection - diagnosis - prrs
A cross-sectional serological study was conducted in Bhutan between October 2011 and February 2012 to determine the prevalence of antibodies to classical swine fever virus (CSFV), porcine reproductive and respiratory syndrome virus (PRRSV), porcine circovirus type 2 (PCV2), swine influenza virus (SIV) subtype H1N1 and Aujeszky's disease virus (ADV). Furthermore, risk factors for the seropositive status were investigated. Antibodies to SIV, subtype H1N1 (likely pandemic H1N1 2009) were detected in 49% of the pigs in the government farms, and 8% of the village backyard pigs. For PCV2, these percentages were 73% and 37% respectively. For CSFV, the percentages were closer together, with 62% and 52% respectively. It should be taken into consideration that vaccination of piglets is routine in the government herds, and that piglets distributed to backyard farms are also vaccinated. No direct evidence of CSFV infections was found, either by clinical signs or virus isolation. Antibodies to PRRSV and Aujeszky's disease, on the other hand, were not found at all. Risk factors found are mainly related to practices of swill feeding and other biosecurity measures. For CSFV, these were swill feeding (OR = 2.25, 95% CI: 1.01–4.99) and contact with neighbour's pigs (OR = 0.31, 95% CI: 0.13–0.75). For PCV2 this was lending of boars for local breeding purposes (OR = 3.30, 95% CI: 1.43–7.59). The results of this study showed that PCV2 and SIV infections are important in pigs in Bhutan and thus appropriate control strategies need to be designed and applied which could involve strict regulation on the import of live pigs and vaccination against these diseases.
Risk based surveillance for early detection of low pathogenic avian influenza outbreaks in layer chickens
Gonzales, J.L. ; Boender, G.J. ; Elbers, A.R.W. ; Stegeman, J.A. ; Koeijer, A.A. de - \ 2014
Preventive Veterinary Medicine 117 (2014)1. - ISSN 0167-5877 - p. 251 - 259.
transmission characteristics - virus - poultry - epidemic - netherlands - infection - spread - interventions - population - program
Current knowledge does not allow the prediction of when low pathogenic avian influenza virus (LPAIV) of the H5 and H7 subtypes infecting poultry will mutate to their highly pathogenic phenotype (HPAIV). This mutation may already take place in the first infected flock; hence early detection of LPAIV outbreaks will reduce the likelihood of pathogenicity mutations and large epidemics. The objective of this study was the development of a model for the design and evaluation of serological-surveillance programmes, with a particular focus on early detection of LPAIV infections in layer chicken flocks. Early detection is defined as the detection of an infected flock before it infects on average more than one other flock (between-flock reproduction ratio Rf <1), hence a LPAI introduction will be detected when only one or a few other flocks are infected. We used a mathematical model that investigates the required sample size and sampling frequency for early detection by taking into account the LPAIV within- and between-flock infection dynamics as well as the diagnostic performance of the serological test used. Since layer flocks are the target of the surveillance, we also explored whether the use of eggs, is a good alternative to sera, as sample commodity. The model was used to refine the current Dutch serological-surveillance programme. LPAIV transmission-risk maps were constructed and used to target a risk-based surveillance strategy. In conclusion, we present a model that can be used to explore different sampling strategies, which combined with a cost-benefit analysis would enhance surveillance programmes for low pathogenic avian influenza.
Economic Analysis of HPAI Control in the Netherlands II: Comparison of Control Strategies
Longworth, N.J. ; Mourits, Monique C.M. ; Saatkamp, H.W. - \ 2014
Transboundary and Emerging Diseases 61 (2014)3. - ISSN 1865-1674 - p. 217 - 232.
pathogenic avian influenza - poultry farms - mouth-disease - epidemic - virus - transmission - vaccination - simulation - spread - h7n7
A combined epidemiological-economic modelling approach was used to analyse strategies for highly pathogenic avian influenza (HPAI) control for the Netherlands. The modelling framework used was InterSpread Plus (ISP), a spatially based, stochastic and dynamic simulation model. A total of eight control strategies were analysed, including pre-emptive depopulation and vaccination strategies. The analysis was carried out for three different regions in the Netherlands: high-, medium- and low-density areas (HDA, MDA and LDA, respectively). The analysis included the veterinary impact (e.g. number of infected premises and duration), but was particularly focused on the impact on direct costs (DC) and direct consequential costs. The efficient set of control strategies for HDA and MDA included strategies based on either pre-emptive depopulation only or combined vaccination and pre-emptive depopulation: D2 (pre-emptive depopulation within a radius of 2 km), RV3 + D1 (ring vaccination within a radius of 3 km and additional pre-emptive depopulation within a radius of 1 km) and PV + D1 (preventive vaccination in non-affected HDAs and pre-emptive depopulation within a radius of 1 km in the affected HDA). Although control solely based on depopulation in most cases showed to be effective for LDA, pre-emptive depopulation showed to have an additional advantage in these areas, that is, prevention of 'virus jumps' to other areas. The pros and cons of the efficient control strategies were discussed, for example, public perception and risk of export restrictions. It was concluded that for the Netherlands control of HPAI preferably should be carried out using strategies including pre-emptive depopulation with or without vaccination. Particularly, the short- and long-term implications on export, that is, indirect consequential costs (ICC) and aftermath costs of these strategies, should be analysed further.
Modelling seasonal and multi-annual variation in bank vole populations and nephropathia epidemica
Haredasht, S.A. ; Taylor, C.J. ; Maes, P. ; Clement, Jan ; Verstraeten, W.W. ; Ranst, M. van; Coppin, P. ; Berckmans, D. ; Aerts, J.M. - \ 2014
Biosystems Engineering 121 (2014). - ISSN 1537-5110 - p. 25 - 37.
puumala-hantavirus infection - clethrionomys-glareolus - indirect transmission - etiologic agent - belgium - dynamics - climate - virus - host - identification
Nephropathia epidemica (NE) is a human infection caused by Puumala virus (PUUV), which is naturally carried and shed by bank voles (Myodes glareolus). The objective was to develop a dynamic model of the NE cases and the bank vole population in both Finland and Belgium by defining the periodic components with a dynamic harmonic regression (DHR) model. The defined periodic components can be further used to adapt mechanistic Susceptible and Infective (SI) models regionally. Despite the difference in bank vole population dynamics and NE cases between the Western European temperate zone and boreal zones the DHR model was able to quantify the dynamics of NE cases in Belgium and Central Finland with a coefficient of determination (R2) of 0.70 and 0.82 respectively and to quantify the dynamics of bank vole population in Belgium and Central Finland with R2 of 0.80 and 0.98 respectively. DHR identified 18 month cycles in the bank vole population in Belgium. This approach demonstrated two year cycles in Belgian NE outbreaks. DHR identified three year cycles in Finnish bank vole populations which in turn cause three year cycles in the NE outbreaks in Central Finland. Because the bank vole population data in Finland was contemporary with the data of NE cases, the DHR showed a three month delay between the NE cases and the bank vole population in Central Finland. This approach may help us in our understanding of the spatial and temporal dynamics of NE cases and the bank vole populations in different regions.
A conceptual framework for economic optimization of single hazard surveillance in livestock production chains
Guo, X. ; Claassen, G.D.H. ; Oude Lansink, A.G.J.M. ; Saatkamp, H.W. - \ 2014
Preventive Veterinary Medicine 114 (2014)3-4. - ISSN 0167-5877 - p. 188 - 200.
classical swine-fever - animal-disease surveillance - control strategies - vesicular disease - pcr assay - virus - netherlands - simulation - system - pigs
Economic analysis of hazard surveillance in livestock production chains is essential for surveillance organizations (such as food safety authorities) when making scientifically based decisions on optimization of resource allocation. To enable this, quantitative decision support tools are required at two levels of analysis: (1) single-hazard surveillance system and (2) surveillance portfolio. This paper addresses the first level by presenting a conceptual approach for the economic analysis of single-hazard surveillance systems. The concept includes objective and subjective aspects of single-hazard surveillance system analysis: (1) a simulation part to derive an efficient set of surveillance setups based on the technical surveillance performance parameters (TSPPs) and the corresponding surveillance costs, i.e., objective analysis, and (2) a multi-criteria decision making model to evaluate the impacts of the hazard surveillance, i.e., subjective analysis. The conceptual approach was checked for (1) conceptual validity and (2) data validity. Issues regarding the practical use of the approach, particularly the data requirement, were discussed. We concluded that the conceptual approach is scientifically credible for economic analysis of single-hazard surveillance systems and that the practicability of the approach depends on data availability.
Suitability of faeces and tissue samples as a basis for non-invasive sampling for African swine fever in wild boar
Carvalho Ferreira, H.C. de; Weesendorp, E. ; Quak, S. ; Stegeman, J.A. ; Loeffen, W.L.A. - \ 2014
Veterinary Microbiology 172 (2014)3-4. - ISSN 0378-1135 - p. 449 - 454.
terrestrial ecosystems - sus-scrofa - virus - size - europe - pigs
A challenging aspect of ASFV control in wild boar populations is the design and implementation of effective surveillance and monitoring programmes, both for early warning, and to determine the ongoing epidemiological situation in an infected population. Testing blood samples requires invasive sampling strategies like hunting or capture of wild boar. Besides being biased towards healthy animals, such strategies are also linked to further spread of the virus. Non-invasive sampling strategies would increase the reliability of surveillance of ASFV in wild boar populations, without the negative side effects. This study evaluates the potential of faeces and tissue samples as a basis for non-invasive sampling strategies for ASFV in wild boar. In the acute phase (0–21 days after infection), in comparison with virus detection in blood, virus can be detected in faeces 50–80% of the time. This percentage decreases to below 10% for the subacute/chronic phase. ASFV DNA is quite stable in faeces. Half-lives range from more than 2 years at temperature up to 12 °C, to roughly 15 days at temperatures of 30 °C. In tissue samples, stored at 20 °C, half-lives mostly range from 1.7 to 7.4 days. The sample of preference is the spleen, where the highest titres and highest half-life of ASFV DNA are observed. The level and duration of excretion of ASFV in the faeces, combined with the stability of the DNA, suggest that sampling of faeces could be the basis for a non-invasive sampling strategy to monitor ASFV in wild boar.
The Influence of Between-Farm Distance and Farm Size on the Spread of Classical Swine Fever during the 1997-1998 Epidemic in The Netherlands
Boender, G.J. ; Hengel, R. van den; Roermund, H.J.W. van; Hagenaars, T.H.J. - \ 2014
PLoS ONE 9 (2014)4. - ISSN 1932-6203 - 7 p.
infectious-diseases - virus - transmission - strategies - model - risk
As the size of livestock farms in The Netherlands is on the increase for economic reasons, an important question is how disease introduction risks and risks of onward transmission scale with farm size (i.e. with the number of animals on the farm). Here we use the epidemic data of the 1997–1998 epidemic of Classical Swine Fever (CSF) Virus in The Netherlands to address this question for CSF risks. This dataset is one of the most powerful ones statistically as in this epidemic a total of 428 pig farms where infected, with the majority of farm sizes ranging between 27 and 1750 pigs, including piglets. We have extended the earlier models for the transmission risk as a function of between-farm distance, by adding two factors. These factors describe the effect of farm size on the susceptibility of a ‘receiving’ farm and on the infectivity of a ‘sending’ farm (or ‘source’ farm), respectively. Using the best-fitting model, we show that the size of a farm has a significant influence on both farm-level susceptibility and infectivity for CSF. Although larger farms are both more susceptible to CSF and, when infected, more infectious to other farms than smaller farms, the increase is less than linear. The higher the farm size, the smaller the effect of increments of farm size on the susceptibility and infectivity of a farm. Because of changes in the Dutch pig farming characteristics, a straightforward extrapolation of the observed farm size dependencies from 1997/1998 to present times would not be justified. However, based on our results one may expect that also for the current pig farming characteristics in The Netherlands, farm susceptibility and infectivity depend non-linearly on farm size, with some saturation effect for relatively large farm sizes.
Salmonid alphavirus replication in mosquito cells: towards a novel vaccine production system
Hikke, M.C. ; Verest, M. ; Vlak, J.M. ; Pijlman, G.P. - \ 2014
Microbial Biotechnology 7 (2014)5. - ISSN 1751-7907 - p. 480 - 484.
farmed atlantic salmon - salar l. - pancreas disease - rna interference - virus - line - sav - togaviridae - subtypes - ireland
Salmonid alphavirus (SAV) causes pancreas disease and sleeping disease in Atlantic salmon (Salmo salar) and rainbow trout (Oncorhynchus mykiss) and confers a major burden to the aquaculture industry. A commercial inactivated whole virus vaccine propagated in a salmon cell line at low temperature provides effective protection against SAV infections. Alphaviruses (family Togaviridae) are generally transmitted between vertebrate hosts via blood-sucking arthropod vectors, typically mosquitoes. SAV is unique in this respect because it can be transmitted directly from fish to fish and has no known invertebrate vector. Here, we show for the first time that SAV is able to complete a full infectious cycle within arthropod cells derived from the Asian tiger mosquito Aedes albopictus. Progeny virus is produced in C6/36 and U4.4. cells in a temperature-dependent manner (at 15°C but not at 18°C), can be serially passaged and remains infectious to salmonid Chinook salmon embryo cells. This suggests that SAV is not a vertebrate-restricted alphavirus after all and may have the potential to replicate in invertebrates. The current study also shows the ability of SAV to be propagated in mosquito cells, thereby possibly providing an alternative SAV production system for vaccine applications.
The Mondrian Matrix: Culicoides prevalence and seasonal abundance during the 2006-2008 epizootic of bluetongue in the Netherlands
Meiswinkel, R. ; Scolamacchia, F. ; Dik, M. ; Mudde, J. ; Dijkstra, E. ; Ven, I.J.K. van der; Elbers, A.R.W. - \ 2014
Medical and Veterinary Entomology 28 (2014)1. - ISSN 0269-283X - p. 10 - 20.
diptera-ceratopogonidae culicoides - light-trap catches - serotype 8 - southern england - northern europe - virus - infection - vector - sweden - identification
During the northern Europe epidemic of bluetongue (BT), Onderstepoort-type blacklight traps were used to capture Culicoides Latreille (Diptera: Ceratopogonidae) biting midges weekly between November 2006 and December 2008 on 21 livestock farms in the Netherlands. Proven and potential vectors for the bluetongue virus (BTV) comprised almost 80% of the midges collected: the Obsoletus complex, constituting C. obsoletus (Meigen) and C. scoticus Downes & Kettle (44.2%), C. dewulfi Goetghebuer (16.4%), C. chiopterus (Meigen) (16.3%) and C. pulicaris (Linnaeus) (0.1%). Half of the 24 commonest species of Culicoides captured completed only one (univoltine) or two (bivoltine) generations annually, whereas multivoltine species (including all BTV vectors) cycled through five to six generations (exceeding the one to four generations calculated in earlier decades). Whether this increment signals a change in the phenology of northern Europe Culicoides or simply is an adaptive response that manifests during warmer episodes, thus heightening periodically the incursive potential of midge-borne arboviruses, remains to be clarified. Culicoides duddingstoni Kettle & Lawson, C. grisescens Edwards, C. maritimus Kieffer, C. pallidicornis Kieffer and C. riethi Kieffer are new records for the biting midge fauna of the Netherlands. It is suggested that C. punctatus (Meigen) be added to the European list of vector Culicoides
Cross-border collaboration in the field of highly contagious livestock diseases: A general framework for policy support
Hop, G.E. ; Mourits, M.C.M. ; Oude Lansink, A.G.J.M. ; Saatkamp, H.W. - \ 2014
Transboundary and Emerging Diseases 61 (2014)4. - ISSN 1865-1674 - p. 300 - 315.
classical swine-fever - veterinary epidemiology - international-trade - netherlands - virus
This paper analyses the potential gains and the main challenges for increased cross-border collaboration in the control of highly contagious livestock diseases in regions with cross-border reliance on production and consumption of livestock commodities. The aim of this intensification of cross-border collaboration is to retain the economic advantages of cross-border trade in livestock and livestock commodities while maintaining a low risk of highly contagious livestock diseases. From these two foci, possibilities for future policy making with respect to highly contagious livestock diseases are discussed: peacetime cross-border cooperation to improve the cost-effectiveness of routine veterinary measures and crisis time cross-border harmonization of current disease control strategies. A general disease management framework was used to describe the way in which these two fields are related to and affect the epidemiological system and, consequently, how they impact the stakeholders. In addition to this framework, the importance of a good understanding of influencing factors, that is, the production structure of livestock, was stressed because these factors are important determinants of the frequency and magnitude of highly contagious livestock diseases and their economic impact. The use of the suggested integrated approach was illustrated for the extended cross-border region of the Netherlands and Germany, that is, North Rhine Westphalia and Lower Saxony. For this region, current difficulties in cross-border trade in livestock and livestock commodities and possibilities for future cross-border collaboration were examined. The concepts and ideas presented in this paper should foster future development of cross-border collaboration in animal health control.
Functional analysis of potato genes involved in quantitative resistance to Phytophthora infestans
Du, J. ; Tian, Z.D. ; Liu, J. ; Vleeshouwers, V.G.A.A. ; Shi, X.L. ; Xie, C.H. - \ 2013
Molecular Biology Reports 40 (2013)2. - ISSN 0301-4851 - p. 957 - 967.
systemic acquired-resistance - beta-aminobutyric acid - late blight - disease resistance - nicotiana-benthamiana - anionic peroxidase - durable resistance - genome sequence - virus - plant
The most significant threat to potato production worldwide is the late blight disease, which is caused by the oomycete pathogen Phytophthora infestans. Based on previous cDNA microarrays and cDNA-amplified fragment length polymorphism analysis, 63 candidate genes that are expected to contribute to developing a durable resistance to late blight were selected for further functional analysis. We performed virus-induced gene silencing (VIGS) to these candidate genes on both Nicotiana benthamiana and potato, subsequently inoculated detached leaves and assessed the resistance level. Ten genes decreased the resistance to P. infestans after VIGS treatment. Among those, a lipoxygenase (LOX; EC and a suberization-associated anionic peroxidase affected the resistance in both N. benthamiana and potato. Our results identify genes that may play a role in quantitative resistance mechanisms to late blight.
Fine mapping of the Ph-3 gene conferring resistance to late blight (Phytophthora infestans) in tomato
Zhang, C.Z. ; Liu, L. ; Zheng, Z. ; Sun, Y.Y. ; Zhou, L.X. ; Yang, Y.H. ; Cheng, F. ; Zhang, Z.H. ; Wang, X.W. ; Huang, S.W. ; Xie, B.Y. ; Du, Y.C. ; Bai, Y. ; Li, J.M. - \ 2013
Theoretical and Applied Genetics 126 (2013)10. - ISSN 0040-5752 - p. 2643 - 2653.
species solanum-pimpinellifolium - disease resistance - united-states - potato - cloning - virus - accession - effectors - genomics - venturii
Late blight, caused by the oomycete pathogen Phytophthora infestans (Mont.) de Bary, is a devastating disease for tomato and potato crops. In the past decades, many late blight resistance (R) genes have been characterized in potato. In contrast, less work has been conducted on tomato. The Ph-3 gene from Solanum pimpinellifolium was introgressed into cultivated tomatoes and conferred broad-spectrum resistance to P. infestans. It was previously assigned to the long arm of chromosome 9. In this study, a high-resolution genetic map covering the Ph-3 locus was constructed using an F-2 population of a cross between Solanum lycopersicum CLN2037B (containing Ph-3) and S. lycopersicum LA4084. Ph-3 was mapped in a 0.5 cM interval between two markers, Indel_3 and P55. Eight putative genes were found in the corresponding 74 kb region of the tomato Heinz1706 reference genome. Four of these genes are resistance gene analogs (RGAs) with a typical nucleotide-binding adaptor shared by APAF-1, R proteins, and CED-4 domain. Each RGA showed high homology to the late blight R gene Rpi-vnt1.1 from Solanum venturii. Transient gene silencing indicated that a member of this RGA family is required for Ph-3-mediated resistance to late blight in tomato. Furthermore, this RGA family was also found in the potato genome, but the number of the RGAs was higher than in tomato.
Ranking the microbiological safety of foods: A new tool and its application to composite products
Stella, P. ; Cerf, O. ; Hugas, M. ; Koutsoumanis, K.P. ; Nguyen-The, C. ; Sofos, J.N. ; Valero, A. ; Zwietering, M.H. - \ 2013
Trends in Food Science and Technology 33 (2013)2. - ISSN 0924-2244 - p. 124 - 138.
quantitative risk-assessment - yersinia-enterocolitica - escherichia-coli - moisture transfer - water - infection - outbreak - storage - virus
A methodology based on the combination of two complementary approaches to rank microbiological risks in foods is presented. In the forward approach data on the pathogenicity of hazards and their behaviour in food during processing and following steps, up to consumption, are used in decision trees to qualitatively estimate the risk associated with foods. In the backward approach risks are evaluated based on the analysis of data available on the past occurrence of hazards and foodborne outbreaks. The categorisation of foods using the forward approach should prevail, and whenever it leads to a likely risk for a given food, the risk can be further qualified with the results from the backward approach. The methodology developed was applied to rank the public health risk posed by certain composite products, which contain both processed products of animal origin and products of plant origin (e.g., bread, cakes, chocolate). Despite limitations in the data available for these foods, valuable results were obtained. The method is therefore considered suitable for application with success to other types of food, and is proposed as a tool for risk managers to rank foods based on their potential food safety risks
The potential of antiviral agents to control classical swine fever: A modelling study.
Backer, J.A. ; Vrancken, R. ; Neyts, J. ; Goris, N. - \ 2013
Antiviral Research 99 (2013)3. - ISSN 0166-3542 - p. 245 - 250.
virus - netherlands - pigs - transmission - vaccination - strategies - epidemics - marker
Classical swine fever (CSF) represents a continuous threat to pig populations that are free of disease without vaccination. When CSF virus is introduced, the minimal control strategy imposed by the EU is often insufficient to mitigate the epidemic. Additional measures such as preemptive culling encounter ethical objections, whereas emergency vaccination leads to prolonged export restrictions. Antiviral agents, however, provide instantaneous protection without inducing an antibody response. The use of antiviral agents to contain CSF epidemics is studied with a model describing within- and between-herd virus transmission. Epidemics are simulated in a densely populated livestock area in The Netherlands, with farms of varying sizes and pig types (finishers, piglets and sows). Our results show that vaccination and/or antiviral treatment in a 2 km radius around an infected herd is more effective than preemptive culling in a 1 km radius. However, the instantaneous but temporary protection provided by antiviral treatment is slightly less effective than the delayed but long-lasting protection offered by vaccination. Therefore, the most effective control strategy is to vaccinate animals when allowed (finishers and piglets) and to treat with antiviral agents when vaccination is prohibited (sows). As independent control measure, antiviral treatment in a 1 km radius presents an elevated risk of epidemics running out of control. A 2 km control radius largely eliminates this risk.
Rift Valley Fever Risk Map Model and Seroprevalence in Selected Wild Ungulates and Camels from Kenya
Britch, S.C. ; Binepal, Y.S. ; Ruder, M.G. ; Kariithi, H.M. ; Linthicum, K.J. ; Anyamba, A. ; Small, J.L. ; Tucker, C.J. ; Ateya, L.O. ; Oriko, A.A. ; Gacheru, S. ; Wilson, W.C. - \ 2013
PLoS ONE 8 (2013)6. - ISSN 1932-6203 - 16 p.
saudi-arabia - vertical transmission - vegetation index - african buffalo - virus - outbreak - antibody - humans - prevalence - prevention
Since the first isolation of Rift Valley fever virus (RVFV) in the 1930s, there have been multiple epizootics and epidemics in animals and humans in sub-Saharan Africa. Prospective climate-based models have recently been developed that flag areas at risk of RVFV transmission in endemic regions based on key environmental indicators that precede Rift Valley fever (RVF) epizootics and epidemics. Although the timing and locations of human case data from the 2006–2007 RVF outbreak in Kenya have been compared to risk zones flagged by the model, seroprevalence of RVF antibodies in wildlife has not yet been analyzed in light of temporal and spatial predictions of RVF activity. Primarily wild ungulate serum samples from periods before, during, and after the 2006–2007 RVF epizootic were analyzed for the presence of RVFV IgM and/or IgG antibody. Results show an increase in RVF seropositivity from samples collected in 2007 (31.8%), compared to antibody prevalence observed from 2000–2006 (3.3%). After the epizootic, average RVF seropositivity diminished to 5% in samples collected from 2008–2009. Overlaying maps of modeled RVF risk assessments with sampling locations indicated positive RVF serology in several species of wild ungulate in or near areas flagged as being at risk for RVF. Our results establish the need to continue and expand sero-surveillance of wildlife species Kenya and elsewhere in the Horn of Africa to further calibrate and improve the RVF risk model, and better understand the dynamics of RVFV transmission.
A bead-based suspension array for the serological detection of Trichinella in pigs
Wal, F.J. van der; Achterberg, R.P. ; Kant, A. ; Maassen, C.B.M. - \ 2013
The Veterinary Journal 196 (2013)3. - ISSN 1090-0233 - p. 439 - 444.
linked-immunosorbent-assay - multiplexed luminex assay - nonstructural proteins - antibodies - trichinosis - virus - spiralis - animals - serodiagnosis - immunoassay
The feasibility of using bead-based suspension arrays to detect serological evidence of Trichinella in pigs was assessed. Trichinella spiralis excretory–secretory antigen was covalently coupled to paramagnetic beads and used to bind serum antibodies, which were subsequently detected using anti-swine antibody. The assay was evaluated by testing pig sera from farms where trichinellosis was endemic and comparing the results with those obtained using two commercially available ELISAs. With cut-offs established by receiver operating characteristic (ROC) analysis, digestion-negative sera from a Trichinella-free population of pigs were deemed seronegative. When anti-swine antibody was replaced with protein A/G, higher test sensitivity (94% vs. 88%) at similar test specificity (95%), was achieved. The potential use of this assay in species other than swine was also demonstrated by testing human sera.
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