Staff Publications

Staff Publications

  • external user (warningwarning)
  • Log in as
  • language uk
  • About

    '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.

    We have a manual that explains all the features 

    Current refinement(s):

    Records 1 - 20 / 274

    • help
    • print

      Print search results

    • export
      A maximum of 250 titles can be exported. Please, refine your queryYou can also select and export up to 30 titles via your marked list.
    • alert
      We will mail you new results for this query: keywords==contamination
    Check title to add to marked list
    Food safety hazards in the European seaweed chain
    Banach, J.L. ; Hoek-van den Hil, E.F. ; Fels-Klerx, H.J. van der - \ 2020
    Comprehensive Reviews in Food Science and Food Safety 19 (2020)2. - ISSN 1541-4337 - p. 332 - 364.
    contamination - food safety - hazard - seafood - seaweed

    Seaweed is a source of protein that can help overcome the anticipated challenges of a growing world population and the current challenges for finding alternatives for animal proteins in the Western diet. Thus far, data on the safety of seaweed for feed and food purposes in the Western world are scattered. This study aimed to review the available knowledge on the presence of food safety hazards in seaweed, including factors influencing their presence, and to prioritize the hazards that may pose a risk to human health. Given current knowledge from the literature, data from the Rapid Alert System for Food and Feed, and results from a stakeholder survey, 22 food safety hazards were ranked into major (4), moderate (5), and minor (13) hazards. Arsenic, cadmium, iodine, and Salmonella were identified as major hazards. Hazards, where data gaps exist, should be carefully assessed. These include pesticide residues, dioxins and polychlorinated biphenyls, brominated flame retardants, polycyclic aromatic hydrocarbons, pharmaceuticals, marine biotoxins, allergens, micro- and nanoplastics, other pathogenic bacteria, norovirus, and hepatitis E virus. It is recommended to collect more data on these hazards in future studies. Many factors can affect the presence of hazards including seaweed type, physiology, season, harvest and cultivation environment, geography including the location of cultivation, alongside further processing. Moreover, when seaweed is cultivated near industrialized or anthropogenic activities, these activities may negatively influence water quality, which can increase the likelihood of hazards in seaweed. Results of the ranking prioritized hazards can be used to prioritize monitoring programs and adjusted given future additional knowledge covering the data gaps.

    Assessing the impact of socio-economic development and climate change on faecal indicator bacteria in the Betna River, Bangladesh
    Islam, Majedul - \ 2017
    Wageningen University. Promotor(en): R. Leemans, co-promotor(en): N. Hofstra. - Wageningen : Wageningen University - ISBN 9789463436304 - 137
    climatic change - environmental impact - water quality - rivers - contamination - bacteria - coliform bacteria - faecal coliforms - bangladesh - south asia - klimaatverandering - milieueffect - waterkwaliteit - rivieren - besmetting - bacteriën - coliformbacteriën - fecale coliformen - bangladesh - zuid-azië

    Consumption of water that is contaminated with pathogens still causes high numbers of death and disease. Understanding the factors that influence the dynamic distribution of waterborne pathogens is important, as this will help understanding improvements and possible solutions. Such understanding is particularly important in a developing country like Bangladesh, where large proportions of the population often have little or no access to clean water. Despite the high relevance for public health, few studies currently exists on the fate and transport of pathogens and the so-called Faecal Indicator Bacteria (FIB, e.g. E. coli, enterococci) in (sub)tropical systems. FIB are susceptible to shifts in water flow and quality. The predicted increases in rainfall and floods due to climate change will exacerbate the faecal contamination scenarios. This could be further compounded by the rapid change in socio-economic conditions (population growth, urbanization, sanitation and agricultural management) in the developing countries. Therefore, to reduce future health risks, understanding the influence of changes in socio-economic conditions and climate on microbial dynamics is important.

    Very few studies have quantified the relationship between the waterborne pathogens/FIB concentrations and climate and socio-economic changes. In this study a process-based model was developed and a scenario analysis was performed based on the new combined climate and socio-economic changes scenarios, to assess the present and future river hydrodynamics, FIB sources, die-off processes and concentrations. We used FIB, because measuring FIB are cheaper than pathogens. FIB are usually not pathogenic but their presence indicates the likely presence of waterborne pathogens. These pathogens are expected to respond to climate change in a comparable way to FIB. The present study is based on the Betna River basin in southwestern Bangladesh, where faecal contamination is not monitored and very little knowledge exists on the distribution of contaminants.

    First of all, FIB concentrations of the river water were measured to identify the river’s faecal contamination levels that can be used to validate the water-quality model. In the study area, wastewater is not treated and this untreated wastewater is discharged directly into the river. This is evident from the measured FIB data. In 88% of the E. coli and all enterococci samples, the USEPA bathing water quality standards were violated (Chapter 2). Such violation indicates potential health risks associated with the use of the river water for domestic, bathing and irrigation purposes. The correlation between environmental variables (water temperature, precipitation and salinity) and FIB concentrations was also determined. A positive correlation was found with water temperature and precipitation, and a negative correlation with salinity. The positive correlation with temperature is due to the co-occurrence of high summer temperature with abundant monsoon rainfall. The positive correlation with precipitation can be explained by the increased runoff from agricultural lands and urban areas. This runoff contains many bacteria. In the study area, during the rainy season (July to September) precipitation increases and as a result water salinity decreases. The observed negative correlation with salinity is more likely due to the typical weather patterns during the rainy season when low salinity coincides with increased precipitation and high temperature, than to salinity dependent die-off of bacteria. A regression model was applied that explained almost half of E. coli and enterococci variability in river water. This, however, only considers water temperature and precipitation (Chapter 2).

    Then, the present and future hydrodynamics of the river were simulated using a two dimensional hydrodynamic model (MIKE 21 FM). Although the main goal of this thesis is to assess the river’s present and future FIB concentrations, the reasons for this hydrodynamic modelling are twofold. Firstly, outputs of the hydrodynamic model are used as input into the water-quality model (Chapter 4). Secondly, hydrodynamics (i.e. water level and discharge) are simulated because increased water level and discharge together with sea level rise stimulate floods in the river basin. These floods are related to outbreaks of waterborne diseases. The modelled results corresponded very well with the measured water levels and discharges. The model was applied to simulate baseline and future water levels and discharge for Representative Concentration Pathway RCP4.5 and RCP8.5 scenarios using bias-corrected downscaled data from two climate models (IPSL-CM5A and MPI-ESM). The model results showed an expected increase in water level up to 16% by the 2040s and 23% by the 2090s (Chapter 3). The monsoon daily maximum discharge was expected to increase up to 13% by the 2040s and 21% by the 2090s. These model results also showed that the duration of the water level above the danger level and extreme discharge periods can increase by half a month by the 2040s and over a month by the 2090s. The coincidence of the water danger level with extreme discharge may cause disastrous floods in the study area.

    Next, the hydrodynamic model was coupled with a water-quality module (ECOLab). The fate and transport of FIB was simulated, the influence of different processes tested and the contribution from different sources to the total contamination quantified (Chapter 4). The model outputs corresponded very well with the measured FIB data. The present river microbial water quality based on measured and simulated results indicated, once again, noncompliance with bathing water standards. Primary and secondary levels of wastewater treatment were not sufficient to reach the standards most of the time, and discharges from sewer drains and incoming concentrations from the upstream boundary were found to be a major cause of water contamination. Tide, wind and diffuse sources (urban and agricultural runoff) contributed little. The high FIB inputs from the upstream open boundary come from untreated point source discharges from upstream urban areas and accumulation of diffuse contaminants from the large upstream areas. Therefore, this study underlines the need for establishment of wastewater treatment plants both in the studied basin and upstream urban areas. This study provides insight into bacterial fate and transport mechanisms, contribution of different sources to the faecal contamination and applicability of wastewater treatment in a river of a subtropical developing country where this type of study is lacking. Uncertainties are related to the lack of high temporal resolution measured FIB data and the lack of available data for contaminant loads from septic tank leakages, open defecation and sediment resuspension. However, the model well captured the measured FIB variability, suggesting that it can be applied for microbial water quality assessments in other watersheds of the world with similar characteristics.

    The developed model could be an ideal tool to forecast future impacts of climate and socioeconomic changes on FIB fate, transport and dynamics. Finally, future FIB concentrations were simulated using the coupled hydrodynamic and microbial model (MIKE 21 FM-ECOLab) and scenario analysis (Chapter 5). Scenarios have been developed building on the most recent Shared Socio-economic Pathways (SSPs) and Representative Concentration Pathways (RCPs) scenarios from the Intergovernmental Panel on Climate Change (IPCC). We developed a baseline scenario (October 2014–September 2015) reflecting the current conditions and two future scenarios, S1 (sustainability scenario) and S2 (uncontrolled scenario) mimicking different future developments of socio-economic (population, urbanization, sanitation, wastewater treatment development, land use) and climate-change factors (temperature, precipitation and sea-level rise). In S1 RCP4.5 was combined with socio-economic scenarios SSP1, and for S2 RCP8.5 was combined with SSP3 (S2). Assumptions on sanitation, waste water treatment and agricultural management in line with the storylines were made to quantify future changes in FIB concentrations and consequent health risk. Different future scenarios were found to have substantial impact on FIB concentrations in the river. By the 2090s, FIB concentrations are expected to decrease by 98% or increase by 75% for the sustainability scenario and uncontrolled scenario respectively. An uncontrolled future resulted in a deterioration of microbial water quality due to socio-economic developments, such as higher population growth, land-use change and increased sewage discharges and changes in rainfall patterns. Microbial water quality strongly improved under a sustainable climate and improved sewage treatment. FIB concentrations were much more sensitive to changes in socio-economic factors than to changes in climatic factors. This underlines the importance of socio-economic factors in assessing and improving microbial water quality.

    The results show the importance of improvements in sanitation and wastewater treatment in the Bangladeshi Betna River basin to ensure that future FIB concentrations in the river comply with the US-EPA bathing water quality standards. Major investments to construct wastewater treatment plants are necessary to compensate for the population growth and increased the volume of wastewater treatment. Although the current level of contamination is already too high, without wastewater treatment the water quality will further deteriorate.

    The thesis assesses the present and future FIB dynamics in the Betna River through sampling, statistical and process-based modelling, and scenario analysis. The results contribute to increase the knowledge base on the dynamic distributions of the FIB in surface water in a developing country and in a subtropical system, where this type of study is lacking. It also reduces the knowledge gaps regarding future flooding scenarios at the local scale. While some earlier studies focused on only assessing climate-change impacts on microbial water quality, this study for the first time assessed the influence of combined climate and socio-economic scenarios (using scenarios based on the new SSP-RCP scenario matrix) on river FIB concentrations. This combined modelling and scenario approach enables the assessment of faecal contamination sources and dynamics at present and in the future. The developed model and scenario analysis approach provides a basis for the water managers to reduce the widespread faecal contamination and the risks of waterborne disease outbreaks, which are still a leading cause of deaths in developing countries.

    Dioxines, dioxineachtige- en niet dioxineachtige PCB’s in rode aal uit Nederlandse binnenwateren : resultaten van 2016
    Leeuwen, S.P.J. van; Hoogenboom, L.A.P. ; Kotterman, M.J.J. - \ 2016
    Wageningen : RIKILT Wageningen University & Research (RIKILT-rapport 2016.016) - 33
    palingen - osteichthyes - monitoring - dioxinen - polychloorbifenylen - binnenwateren - besmetting - nederland - eels - osteichthyes - monitoring - dioxins - polychlorinated biphenyls - inland waters - contamination - netherlands
    In 2016 zijn in het kader van het monitoringsprogramma “Monitoring contaminanten ten behoeve van de Nederlandse sportvisserij” 14 zoetwaterlocaties en één zoutwater locatie bemonsterd. Hiervan liggen twaalf locaties binnen het voor aalvisserij gesloten gebied en voor de overige 3 locaties is de aalvisserij toegestaan. Alle locaties zijn in voorgaande jaren al bemonsterd, behalve de Weespertrekvaart, die voor het eerst is bemonsterd in 2016. Dit jaar is voor de bemonstering van grote alen rekening gehouden met het zwaartepunt van de beroepsmatige vangst, waardoor meestal iets grotere aal is bemonsterd (>53 cm) dan in voorgaande jaren (was >45 cm).
    Dioxines, dioxineachtige- en niet dioxineachtige PCB's in rode aal uit Nederlandse binnenwateren 2015
    Kotterman, M.J.J. ; Dam, G. ten; Hoogenboom, L.A.P. ; Leeuwen, Stefan van - \ 2016
    IMARES (Rapport / IMARES C016/16) - 28
    palingen - osteichthyes - monitoring - dioxinen - polychloorbifenylen - binnenwateren - besmetting - nederland - eels - osteichthyes - monitoring - dioxins - polychlorinated biphenyls - inland waters - contamination - netherlands
    In 2015 zijn in het kader van het monitoringsprogramma “Monitoring contaminanten ten behoeve van de Nederlandse sportvisserij” 15 zoetwaterlocaties en één zoutwater locatie in Nederland bemonsterd. Elf locaties liggen binnen het voor aalvisserij gesloten gebied, op de andere vijf locaties is de aalvisserij toegestaan. Van de gevangen rode alen zijn mengmonsters samengesteld voor de lengteklassen 30-40 cm en >45 cm en geanalyseerd op de aanwezigheid van dioxines, dioxineachtige-PCBs (dl-PCB’s) en niet-dioxineachtige PCB’s (ndl-PCB’s).
    Grondbemonstering waardevol in de strijd tegen stengelaal
    Vreeburg, P.J.M. - \ 2015
    BloembollenVisie (2015)332. - ISSN 1571-5558 - p. 2 - 23.
    horticulture - ornamental bulbs - plant protection - agricultural research - sampling - contamination - plant disease control - knowledge transfer - ditylenchus dipsaci - tulips - hot water treatment - tuinbouw - bloembollen - gewasbescherming - landbouwkundig onderzoek - bemonsteren - besmetting - plantenziektebestrijding - kennisoverdracht - ditylenchus dipsaci - tulpen - heetwaterbehandeling
    Het Praktijknetwerk ‘Stengelaaltjes in het vizier’ heeft een belangrijke bijdrage geleverd in de strijd tegen stengelaaltjes door aan te tonen dat het nemen van grondmonsters veel inzicht kan geven in de mate van besmetting van grond en partijen en kan helpen bij het voorkomen van een aantasting en nieuwe besmettingen.
    Impact of climate change on microbial safety of leafy green vegetables
    Liu, C. - \ 2015
    Wageningen University. Promotor(en): Rik Leemans, co-promotor(en): Nynke Hofstra; Eelco Franz. - Wageningen : Wageningen University - ISBN 9789462574403 - 129
    klimaatverandering - bladgroenten - groenten - voedselveiligheid - micro-organismen - besmetting - voedselbesmetting - escherichia coli - salmonella - climatic change - leafy vegetables - vegetables - food safety - microorganisms - contamination - food contamination - escherichia coli - salmonella


    Climate change is generally recognized as a major threat to humans and the environment. With respect to food production, climate change does not only affect crop production or food security, but possibly also effects on food safety by affecting the prevalence and levels of bacteria, fungi or other pests and pesticides. Fresh-cut or ready-to-eat leafy vegetables (e.g. lettuce and spinach) are increasingly consumed because they are promoted as part of a healthy diet. Such leafy green vegetables (LGVs) are identified as the fresh produce commodity group of highest concern from a microbiological safety perspective, because they are often grown in the open field and therefore vulnerable to contamination and contact with (faeces of) wildlife. Moreover, they are grown and consumed in large volumes and often consumed raw. Bacteria, such as Salmonella spp. and pathogenic Escherichia coli strains are the main pathogens causing foodborne disease through LGVs. A major knowledge gap is understanding how climate change may directly or indirectly affect the contamination of LGVs. This primarily relates to the current lack of methods and tools to link climate data and climate change scenarios to food safety.

    My thesis aims to quantify the impacts of climate change on microbial safety of pre-harvested LGVs. To achieve this, I reviewed the literature and synthesised major impacts of climate change on contamination sources and pathways of foodborne pathogens (focussing on Escherichia coli O157 and Salmonella spp.) on pre-harvested LGVs (Chapter 2). Subsequently, I developed a statistical model that identifies the weather and management variables that are associated with the LGVs contamination with generic E. coli using regression analysis (Chapter 3). To apply suitable climate data to this statistical model to assess future impacts, I have prepared a tool to downscale coarse climate and climate change data for local food safety scenario analysis (Chapter 4). Finally, I applied the downscaled data to the statistical model and used multi-criteria scenario analysis to explore future food safety (Chapter 5). E.coli is used as a hygienic indicator in this thesis to study microbial safety of LGVs. Its presence is indicative for an increased pathogen presence probability. E. coli and many foodborne bacteria share the same contamination pathways and climate change is expected to similarly impact on both bacteria. Hygienic status is therefore used in my thesis as a proxy for the microbial safety of LGVs.

    The major result of the literature review in Chapter 2 is that the impact of climate change on LGV contamination depends on the resulting local balance of the positive and negative impacts. The review shows that the interactions between climate change and contamination are real but poorly understood. Therefore, integrative quantitative modelling approaches with scenario analyses and additional laboratory experiments are needed.

    With this knowledge background, mixed effect logistic regression and linear regression models were developed to identify the climate and management variables that are associated with the presence and concentration of E. coli on LGVs (Chapter 3). These models used E. coli data of 562 lettuce and spinach samples taken between 2011 and 2013 from 23 open-field farms from Belgium, Brazil, Egypt, Norway and Spain. Weather and agriculture management practices together had a systematic influence on E.coli presence and concentration. Temperature explained most of the observed variation on E. coli prevalence and concentration on LGVs. Minimum temperature of the sampling day (odds ratio [OR] 1.47), region and application of inorganic fertilizer explained a significant amount of variation in E. coli prevalence. Maximum temperature on three days before sampling and region best explained the variation in E. coli concentration (R2= 0.75). Region is a variable masking many management variables including use of rain water, surface water, manure, inorganic fertilizer and spray irrigation. Climate variables and E. coli presence and concentration are positively related. The results indicate that climate change will have an impact on microbiological safety of LGVs. These impacts can be directly through an increasing temperature, but also indirectly through changes in irrigation water type, fertilizer type and irrigation method. Therefore, climate change and farm management should be considered more systematically in an integrated way in future studies on fresh produce safety.

    To prepare climate data for local food safety scenario analysis, a climate data downscaling tool was presented and demonstrated (Chapter 4). Coarse gridded data from two general circulation models, HadGEM2-ES and CCSM4, were selected and downscaled using the ‘Delta method’ with quantile-quantile correction for the Belgium meteorological station in Ukkel. Observational daily temperature and precipitation data from 1981 to 2000 were used as a reference period for this downscaling. Data were provided for four future representative concentration pathways (RCPs) for the periods 2031–2050 and 2081–2100. These RCPs are radiative forcing scenarios for which future climate conditions are projected. The climate projections for these RCPs show that both temperature and precipitation will increase towards the end of the century in Ukkel. The climate change data were subsequently used with Ratkowsky's bacterial growth model to illustrate how projected climate data can be used for projecting bacterial growth in the future. In this example, the future growth rate of Lactobacillus plantarum and the number of days that the bacteria are able to grow are both projected to increase in Ukkel. This example illustrates that this downscaling method can be applied to assess future food safety. This downscaling tool is relatively straightforward compared to other more complex downscaling tools, so the food safety researchers can easily understand and apply it to their impact studies.

    With the statistical model (Chapter 3) and downscaled climate data (Chapter 4), a multi-criteria scenario analysis tool was developed to explore future food safety using pre-harvest spinach in Spain as an example (Chapter 5). The future E. coli concentrations on spinach were projected to change in RCP 8.5 and RCP 2.6 by the end of the century in Spain. The E. coli concentration was projected to increase between 0.2 log10 CFU/g and 0.3 log10 CFU/g (depending on the climate scenarios and management options applied) due to higher temperature by the end of the century compared to the concentrations by the end of the last century. This comparison assumed no changes in agricultural management practices. This tool can be used to help selecting the best management practices considering climate change and other indicators.

    The pioneering research presented in my thesis brought new methods and tools, and another mind set to food safety research. The climate-change data downscaling tool provides detailed temporal and spatial climate data for climate scenario analysis in food safety assessment studies. The multi-criteria scenario analysis tool provides a platform to study changes in weather or climate, and management impacts on future food safety. This tool also allows for inclusion of different stakeholders’ perspectives or interests and supports their decision making processes. Moreover, the thesis presents a statistical model that can be used to study the relationship between climate and E. coli contamination.

    My thesis quantified the impacts of climate change on microbial safety of pre-harvested LGVs contaminated with generic E. coli for the first time. With one degree increase in minimum temperature of the sampling day, the odds of having E. coli presence on LGVs increase by a factor of 1.5. The mean E. coli concentrations are also expected to increase. Climate change should not be ignored in food safety management and research.

    Comparative analysis of biofilm formation by Bacillus cereus reference strains and undomesticated food isolates and the effect of free iron
    Hayrapetyan, H. ; Muller, L.K. ; Tempelaars, M.H. ; Abee, T. ; Nierop Groot, M.N. - \ 2015
    International Journal of Food Microbiology 200 (2015). - ISSN 0168-1605 - p. 72 - 79.
    pseudomonas-aeruginosa - stainless-steel - processing environments - twitching motility - adhesion - surface - attachment - contamination - typhimurium - sporulation
    Biofilm formation of Bacillus cereus reference strains ATCC 14579 and ATCC 10987 and 21 undomesticated food isolates was studied on polystyrene and stainless steel as contact surfaces. For all strains, the biofilm forming capacity was significantly enhanced when in contact with stainless steel (SS) as a surface as compared to polystyrene (PS). For a selection of strains, the total CFU and spore counts in biofilms were determined and showed a good correlation between CFU counts and total biomass of these biofilms. Sporulation was favoured in the biofilm over the planktonic state. To substantiate whether iron availability could affect B. cereus biofilm formation, the free iron availability was varied in BHI by either the addition of FeCl3 or by depletion of iron with the scavenger 2,2-Bipyridine. Addition of iron resulted in increased air-liquid interface biofilm on polystyrene but not on SS for strain ATCC 10987, while the presence of Bipyridine reduced biofilm formation for both materials. Biofilm formation was restored when excess FeCl3 was added in combination with the scavenger. Further validation of the iron effect for all 23 strains in microtiter plate showed that fourteen strains (including ATCC10987) formed a biofilm on PS. For eight of these strains biofilm formation was enhanced in the presence of added iron and for eleven strains it was reduced when free iron was scavenged. Our results show that stainless steel as a contact material provides more favourable conditions for B. cereus biofilm formation and maturation compared to polystyrene. This effect could possibly be linked to iron availability as we show that free iron availability affects B. cereus biofilm formation.
    Leverbot in kaart gebracht
    Verkaik, J.C. ; Verwer, C. - \ 2015
    V-focus 12 (2015)3. - ISSN 1574-1575 - p. 27 - 29.
    melkveehouderij - leverbot - diergeneeskunde - diergezondheid - dierziektepreventie - besmetting - ziektebestrijding - dairy farming - liver flukes - veterinary science - animal health - animal disease prevention - contamination - disease control
    Leverbotinfecties zijn in toenemende mate een knelpunt bij melkgevende koeien die weiden of vers gras op stal gevoerd krijgen. Leverbotinfecties brengen verliezen met zich mee die onderschat worden, zoals verminderde groei van jongvee, verminderde weerstand, verminderde melkproductie en afkeuring van levers van geslachte dieren.
    Ultratrace LC-MS/MS Analysis of Segmented Calf Hair for Retrospective Assessment of Time of Clenbuterol Administration in Agriforensics
    Duvivier, W.F. ; Beek, T.A. van; Meijer, T. ; Peeters, R.J.P. ; Groot, M.J. ; Sterk, S.S. ; Nielen, M.W.F. - \ 2015
    Journal of Agricultural and Food Chemistry 63 (2015)2. - ISSN 0021-8561 - p. 493 - 499.
    tandem mass-spectrometry - performance liquid-chromatography - beta-agonist residues - equine hair - bovine hair - human urine - cattle - calves - contamination - samples
    In agriforensics, time of administration is often debated when illegal drug residues, such as clenbuterol, are found in frequently traded cattle. In this proof-of-concept work, the feasibility of obtaining retrospective timeline information from segmented calf tail hair analyses has been studied. First, an ultraperformance liquid chromatography–tandem mass spectrometry (UPLC-MS/MS) hair analysis method was adapted to accommodate smaller sample sizes and in-house validated. Then, longitudinal 1 cm segments of calf tail hair were analyzed to obtain clenbuterol concentration profiles. The profiles found were in good agreement with calculated, theoretical positions of the clenbuterol residues along the hair. Following assessment of the average growth rate of calf tail hair, time of clenbuterol administration could be retrospectively determined from segmented hair analysis data. The data from the initial animal treatment study (n = 2) suggest that time of treatment can be retrospectively estimated with an error of 3–17 days.
    Measuring microbial food safety output and comparing self-checking systems of food business operators in Belgium
    Jacxsens, L. ; Kirezieva, K. ; Luning, P.A. ; Ingelrham, J. ; Diricks, H. ; Uyttendaele, M. - \ 2015
    Food Control 49 (2015). - ISSN 0956-7135 - p. 59 - 69.
    management-system - processing plants - performance - contamination - programs - quality
    The Belgian food safety authority has provided incentives for food business operators to set-up a certified self-checking system (SCS), based upon good practices and HACCP principles. A selection of food processing companies in Belgium was invited to take part in a self-assessment study to evaluate the effect of SCS certification on the performance of an implemented food safety management system (FSMS) and on company’s microbiological food safety output according to their sector and company size and to compare the added value of SCS against voluntary standard certification. Results revealed that the majority of food processing companies (90%) were already certified for a voluntary standard such as BRC or IFS prior to or next to the Belgian SCS certification (50%). Although five clusters could be identified among the eighty-two participating companies in the performance profiles of their food safety management system and microbiological food safety output, overall no significant difference could be identified between SCS certified and non-certified SCS food processing companies. However, assurance activities (i.e. set-up of sampling plan, validation and verification of the FSMS) were elaborated at a more advanced, tailored level in SCS certified companies. No significant differences were found according to company size, but depending on the sector more robust FSMS could be identified (e.g. animal products processing sector). The benefits of the widespread presence of a third party certified food safety management system (whether voluntary standard or national SCS) as a basis for governing food safety are also reflected in the favourable inspection results obtained by Belgian food safety authority (76.90%e78.71% compliance in years 2009e2011; 12 823 SCS certified companies being visited) at the processing level. Whereas higher non-compliance in inspection results is noted (47.55e52.45% compliance in years 2009e2011; 4 415 SCS certified companies being visited) in the distribution sector, encompassing a large amount of small food service operations and retail outlets. The introduction of certified SCS is still exceptional in that sector (4.11% in 2011) and the introduction of voluntary standards is less common due to lack of incentives, capacity and resources. Thus, there are indications that a certification system based on audits is an appropriate approach in pro-actively governing food safety and supporting the implementation of control and assurance activities at advanced level, hence increasing the robustness of the food safety management systems as a basis for good microbiological food safety output.
    Dioxines en PCB's in Chinese wolhandkrab
    Kotterman, M.J.J. ; Leeuwen, S.P.J. van; Hoogenboom, L.A.P. - \ 2014
    IJmuiden : IMARES (Rapport / IMARES C120/14) - 36
    krabben (schaaldieren) - dioxinen - polychloorbifenylen - besmetting - toxinen - zeevisserij - crabs - dioxins - polychlorinated biphenyls - contamination - toxins - marine fisheries
    Natuurlijke selectie van varroaresistente bijenvolken. Bijennieuws 28
    Blacquière, T. - \ 2014
    Wageningen : Bijen@wur
    apidae - wilde bijenvolken - dierveredeling - rassen (dieren) - ziekteresistentie - selectiemethoden - diergezondheid - varroa - besmetting - mijten - apidae - wild honey bee colonies - animal breeding - breeds - disease resistance - selection methods - animal health - varroa - contamination - mites
    Naar aanleiding van in het wild gevonden (Noord Amerika, Frankrijk) en via experimenten verkregen (Gotland, Zweden) min of meer resistente volken, althans natuurlijk overlevende volken, hebben wij in 2007 met een nateelt van Gotland koninginnen en in 2008 met een Nederlands mengsel van bijenvolken twee teelten van bijenvolken opgezet zonder varroa te bestrijden. Bij de 2008-serie hebben we ook een groep volken als controle meegenomen, waarin varroa twee keer per jaar wordt bestrede
    Aanpak van Burkholderia gladioli in gladiool
    Dam, M.F.N. van; Dijkema, M.H.G.E. - \ 2014
    Lisse : Praktijkonderzoek Plant & Omgeving, Sector Bomen, Bollen & Fruit - 29
    bloembollen - gladiolus - burkholderia - bacterieziekten - bestrijdingsmethoden - ziekteoverdracht - besmetting - tests - verdedigingsmechanismen - ziekteresistentie - ornamental bulbs - gladiolus - burkholderia - bacterial diseases - control methods - disease transmission - contamination - tests - defence mechanisms - disease resistance
    Wateroverlast in een Teelt de grond uit-systeem kan grote schade geven aan lelies. Drie dagen wateroverlast in augustus leidde in dit onderzoek tot grote opbrengstderving. Eén dag wateroverlast in september of in oktober veroorzaakte nauwelijks uitval of een lager bolgewicht bij de oogst. Wateroverlast leidt tot ethanolvorming in de bollen. De ethanolvorming vertoonde dit jaar geen mooi verband met de tijd: drie dagen wateroverlast gaf meer ethanol dan één of twee dagen, maar twee dagen niet meer dan één. In 2013 vertoonde de concentratie ethanol een rechtlijnig verband met de duur van de wateroverlast. De voorspellende waarde van een ethanolmeting blijkt na de experimenten in 2014 minder zeker. Het beluchten van het natte substraat door het doorblazen van perslucht leidde bij de behandeling in augustus tot minder ethanolvorming, maar juist tot meer opbrengstderving. Het systeem van beluchting via een slang onderin het substraat had een iets gunstiger effect op de ethanolvorming dan beluchting via slangetjes, die in het substraat gestoken waren. De grotere opbrengstderving door beluchting tijdens de periode van wateroverlast is mogelijk een gevolg van mechanische beschadiging van de (haar)wortels door de beweging, of van structuurbederf die optreedt als het doorborrelde substraat weer droogvalt. Dit onderzoek bevestigt de conclusie uit 2013 dat lelies bestand zijn tegen maximaal 1 dag wateroverlast (anaerobie). Een periode van anaerobie leidt tot ethanolvorming in de bollen, maar de correlatie tussen duur van de anaerobie is te zwak om het ethanolgehalte als indicator toe te passen. Het beluchten van grond tijdens periodes van wateroverlast is geen oplossing voor het anaerobieprobleem.
    Kruiscontaminatie van antibiotica : onderzoek naar de aanwezigheid van antibioticaresiduen in mest van vleesvarkens en vleeskalveren en op pluimveebedrijven
    Zuidema, T. ; Stolker, A.A.M. ; Ginkel, L.A. van - \ 2014
    Wageningen : RIKILT Wageningen UR (RIKILT rapport 2014.015) - 47
    antibioticumresiduen - plattelandsomgeving - mest - drinkwater - blootstelling - besmetting - varkens - vleeskuikens - vleeskalveren - pluimvee - rundvee - antibiotic residues - rural environment - manures - drinking water - exposure - contamination - pigs - broilers - veal calves - poultry - cattle
    Dit onderzoek heeft tot doel een eerste indicatie te krijgen over het voorkomen van antibioticaresiduen in dieren en hun directe omgeving. Het gaat daarbij met name om de onbedoelde blootstelling als gevolg van kruiscontaminatie. Hiertoe is een onderzoek gedaan naar de aanwezigheid van antibioticaresiduen in mestmonsters van vleesvarkens, vleeskalveren en vleeskuikens. Bij vleeskuikens is ook onderzoek gedaan in omgevingsmonsters (blootstelling vanuit de omgeving) en in watermonsters (blootstelling van dieren via water).
    Effect varroa op volksgrootte pas zichtbaar als het te laat is?
    Dooremalen, C. van; Cornelissen, B. ; Langevelde, F. van - \ 2014
    Bijenhouden 8 (2014)3, juni 2014. - ISSN 1877-9786 - p. 20 - 22.
    apidae - honingbijen - varroa destructor - mijten - bijenziekten - bijensterfte - besmetting - bestrijdingsmethoden - maatregelen - onderzoek - apidae - honey bees - varroa destructor - mites - bee diseases - bee mortality - contamination - control methods - measures - research
    De parasitaire mijt Varroa destructor is altijd en overal aanwezig in volken van onze honingbijen. Varroa verkot het leven van de volwassen bij, wat resulteert in een verhoogde kans op wintersterfte. Ondanks leen relatief geringe wintersterfte in 2012-2013 en 2013-2014 is het identificeren van een variabele om in een vroeg stadium wintersterfte te kunnen voorkomen nog steeds hard nodig. Met behulp van zo'n variabele kunnen er maatregelen genomen worden om sterfte te voorkomen.
    Temporal variability in groundwater and surface water quality in humid agricultural catchments; driving processes and consequences for regional water quality monitoring
    Rozemeijer, J. ; Velde, Y. van der - \ 2014
    Fundamental and Applied Limnology 184 (2014)3. - ISSN 1863-9135 - p. 195 - 209.
    flow route contributions - land-use - nutrient concentrations - nitrate concentrations - network design - storm events - phosphorus - dynamics - contamination - netherlands
    Considering the large temporal variability in surface water quality is essential for adequate water quality policy and management. Neglecting these dynamics may easily lead to decreased effectiveness of measures to improve water quality and to inefficient water quality monitoring. The objective of this paper is to summarise our understanding of temporal variability in surface water and upper groundwater quality and to discuss the consequences and opportunities for regional water quality monitoring. In regional monitoring networks, measurement frequencies are typically too low to capture the short-term temporal variations in solute concentrations. This causes large uncertainty in the assessment of (trends in) average concentrations and contaminant loads. The most important driver for short-term variations in water quality in most catchments is the variability in meteorological conditions, which induces changes in the relative discharge contributions of water from different flow routes and different chemical compositions. Various options exist for dealing with the transient behavior of water quality in regional water quality monitoring. Estimates of average concentrations and loads from low-frequency concentration data can be improved by using the explanatory strength of commonly available measurements of quantitative hydrological data like precipitation, discharge, and groundwater levels. This paper provides examples of the relationship between water quality and explanatory variables in conceptual, statistical, or process-based models. Another strategy for dealing with short-term variability in water quality monitoring is to measure long-term average solute concentrations using passive samplers. Similarly, on-site auto analyzers and ion specific electrodes provide opportunities for continuous water quality measurements.
    René van der Vlugt over schade aan landbouwgewassen
    Vlugt, R.A.A. van der - \ 2014
    landbouw - gewasbescherming - plantenvirussen - niet-geclassificeerde plantenvirussen - voedselgewassen - besmetting - kennisniveau - agro-ecologie - ecologie - agriculture - plant protection - plant viruses - unclassified plant viruses - food crops - contamination - knowledge level - agroecology - ecology
    In de natuur zijn vele ongetwijfeld heel veel plantenvirussen die niet bij mensen bekend zijn. Maar die visrussen kunnen op een gegeven moment overslaan van de wilde natuur naar landbouwgewassen. Dat kan zorgen voor veel schade en zelfs hongersnoden veroorzaken. Die ‘wilde’ virussen vroegtijdig in de smiezen krijgen is dus bittere noodzaak, bepleit René van der Vlugt, buitengewoon hoogleraar Ecologische plantenvirologie aan Wageningen University.
    Vogelgriepvirus kwam aanvliegen uit Azië
    Sikkema, A. ; Bouwstra, R.J. - \ 2014
    Resource: weekblad voor Wageningen UR 9 (2014)8. - ISSN 1874-3625 - p. 8 - 8.
    aviaire influenza - aviaire influenzavirussen - besmetting - pluimveehouderij - pluimvee - diergezondheid - dierenwelzijn - ziekteoverdracht - dierlijke productie - avian influenza - avian influenza viruses - contamination - poultry farming - poultry - animal health - animal welfare - disease transmission - animal production
    CVI acht besmetting via trekvogels 'waarschijnlijk.' Het virus komt oorspronkelijk uit China.
    Levels of polychlorinated dibenzo-p-dioxins, dibenzofurans (PCDD/Fs) and dioxin-like PCBs in free range eggs from Vietnam, including potential health risks
    Hoang, T.T. ; Traag, W.A. ; Murk, A.J. ; Hoogenboom, L.A.P. - \ 2014
    Chemosphere 114 (2014). - ISSN 0045-6535 - p. 268 - 274.
    home-produced eggs - bien-hoa-city - southern vietnam - chicken eggs - contamination - exposure - residents - bioassay - food - soil
    Chicken and duck eggs collected from three different areas in Vietnam were examined for polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs). These regions included a background area, an area sprayed with Agent Orange and the Bien Hoa airbase area where Agent Orange was handled by the US Army. The latter area now is inhabited and people keep their own laying hens. Egg samples were first screened with an in vitro reporter gene bioassay and a selection was analyzed by GC/HRMS. Samples from Bien Hoa airbase showed very high PCDD/F levels, up to 249 pg dioxin-equivalents (TEQ)/g fat, mainly due to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). In the sprayed areas, levels (3.2–8.2 pg TEQ g-1) were comparable to those observed in background areas (3.2–8.2 pg TEQ g-1 fat). The estimated average consumption of 22 g d-1 of the highly contaminated eggs will result in a 2-fold exceedance of the current exposure limits for adults and 5-fold for children, even without considering other contaminated food sources. This indicates a potential health risk from consumption of these highly contaminated eggs, which were not yet considered as a source for exposure to PCDD/Fs of people living in the highly contaminated areas.
    Overdracht en bestrijding van fytoplasma’s in hyacint : overdracht en bestrijding van het fytoplasma, dat Lissers veroorzaakt in hyacint
    Vreeburg, P.J.M. ; Korsuize, C.A. - \ 2014
    Lisse : Praktijkonderzoek Plant & Omgeving, Business Unit Bloembollen, Bomen en Fruit - 31
    bloembollen - hyacinthus - plantenziekteverwekkende bacteriën - vectoren, ziekten - macrosteles sexnotatus - besmetting - landbouwkundig onderzoek - dalbulus - ornamental bulbs - hyacinthus - plant pathogenic bacteria - disease vectors - macrosteles sexnotatus - contamination - agricultural research - dalbulus
    De laatste jaren (2007 t/m 2010) is er in de broeierij van hyacinten en hyacint-achtigen (met name Muscari) een duidelijke toename van zogenaamde ‘Lissers’ waargenomen. ‘Lissers’, een ziekte die wordt gekenmerkt door een iele plant, die niet of nauwelijks bloeit en een slechte beworteling heeft, wordt veroorzaakt door een infectie met een fytoplasma (uit de “Aster Yellows” groep), een celwandloze bacterie die door (dwerg)cicaden (met name Macrosteles sexnotatus) van plant tot plant wordt verspreid. Het is het zelfde fytoplasma dat de vergelings-heksembezemziekte bij gladiool veroorzaakt. Er wordt verwacht dat door de klimaatsveranderingen de komende jaren het aantal besmettingen met fytoplasma’s in het voorjaar zal toenemen. Gedurende 3 jaar is onderzocht of de ligging van het teeltperceel van invloed is op het voorkomen van ‘Lissers’. Ook is het moment van voorkomen van (besmette) cicaden gemonitord en is de periode waarin besmetting met het fytoplasma plaatsvindt onderzocht.
    Check title to add to marked list
    << previous | next >>

    Show 20 50 100 records per page

    Please log in to use this service. Login as Wageningen University & Research user or guest user in upper right hand corner of this page.