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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Dynamics of somatic cell count patterns as a proxy for transmission of mastitis pathogens
Dalen, Gunnar ; Rachah, Amira ; Nørstebø, Håvard ; Schukken, Ynte H. ; Reksen, Olav - \ 2019
Journal of Dairy Science 102 (2019)12. - ISSN 0022-0302 - p. 11349 - 11358.
intramammary infection - online cell count - somatic cell count - transmission

Management of udder health is particularly focused on preventing new infections. Data from the DeLaval Online Cell Counter (DeLaval, Tumba, Sweden) may be used in forecasting to improve decision support for improved udder health management. It provides online cell counts (OCC) as a proxy for somatic cell counts from every milking at the cow level. However, these values are typically too insensitive and nonspecific to indicate subclinical intramammary infection (IMI). Our aim was to describe and evaluate use of dynamic transmission models to forecast subclinical IMI episodes using milk cultures or changes in OCC patterns over time. The latter was expressed by an elevated mastitis risk variable. Data were obtained from the dairy herd of the Norwegian University of Life Sciences (Oslo, Norway). In total, 173 cows were sampled monthly for bacteriological milk culture during a 17-mo study period and 5,330 quarter milk samples were cultured. Mastitis pathogens identified were assigned to 1 of 2 groups, Pat 1 or Pat 2. Pathogens from which a high cell count would be expected during a subclinical IMI episode were assigned to the Pat 1 group. Pathogens not in the Pat 1 group were assigned to the Pat 2 group. Staphylococcus epidermidis, Staphylococcus aureus, and Streptococcus dysgalactiae were the most common Pat 1 pathogens. Corynebacterium bovis, Staphylococcus chromogenes, and Staphylococcus haemolyticus were the most common Pat 2 pathogens. The OCC were successfully recorded from 82,182 of 96,542 milkings. The current study included 324 subclinical IMI episodes. None of the mastitis pathogens demonstrated a basic reproduction number (R0) >1. Patterns of OCC change related to an episode of Pat 1 subclinical IMI at specificity levels of 80, 90, and 95% at sensitivity levels of 69, 59, and 48% respectively, demonstrated an R0 >1. An existing infection was significant for transmission for several Pat 2 pathogens, but only for Staphylococcus aureus and Staphylococcus epidermidis among Pat 1 pathogens. Dynamic transmission models showed that patterns of OCC change related to an episode of Pat 1 subclinical IMI were significantly related to the same pattern occurring in susceptible cows at specificity levels of 80, 90, and 99% at sensitivity levels of 69, 48, and 8%, respectively. We conclude that changes in herd prevalence of subclinical IMI can be predicted using dynamic transmission models based on patterns of OCC change. Choice of specificity level depends on management goals and tolerance for false-positive alerts.

Rift Valley fever: biology and epidemiology
Wright, Daniel ; Kortekaas, Jeroen ; Bowden, Thomas A. ; Warimwe, George M. - \ 2019
Journal of General Virology 100 (2019)8. - ISSN 0022-1317 - p. 1187 - 1199.
epidemiology - one health - pathogenesis - Rift Valley fever - transmission - vaccine

Rift Valley fever (RVF) is a mosquito-borne viral zoonosis that was first discovered in Kenya in 1930 and is now endemic throughout multiple African countries and the Arabian Peninsula. RVF virus primarily infects domestic livestock (sheep, goats, cattle) causing high rates of neonatal mortality and abortion, with human infection resulting in a wide variety of clinical outcomes, ranging from self-limiting febrile illness to life-threatening haemorrhagic diatheses, and miscarriage in pregnant women. Since its discovery, RVF has caused many outbreaks in Africa and the Arabian Peninsula with major impacts on human and animal health. However, options for the control of RVF outbreaks are limited by the lack of licensed human vaccines or therapeutics. For this reason, RVF is prioritized by the World Health Organization for urgent research and development of countermeasures for the prevention and control of future outbreaks. In this review, we highlight the current understanding of RVF, including its epidemiology, pathogenesis, clinical manifestations and status of vaccine development.

A genome-wide association study for susceptibility and infectivity of Holstein Friesian dairy cattle to digital dermatitis
Biemans, F. ; Jong, M.C.M. de; Bijma, P. - \ 2019
Journal of Dairy Science 102 (2019)7. - ISSN 0022-0302 - p. 6248 - 6262.
claw health - generalized linear mixed model - genetic parameter - heritability - transmission

Selection and breeding can be used to fight transmission of infectious diseases in livestock. The prevalence in a population depends on the susceptibility and infectivity of the animals. Knowledge on the genetic background of those traits would facilitate efficient selection for lower disease prevalence. We investigated the genetic background of host susceptibility and infectivity for digital dermatitis (DD), an endemic infectious claw disease in dairy cattle, with a genome-wide association study (GWAS), using either a simple linear mixed model or a generalized linear mixed model based on epidemiological theory. In total, 1,513 Holstein-Friesian cows of 12 Dutch dairy farms were scored for DD infection status and class (M0 to M4.1) every 2 wk for 11 times; 1,401 of these cows were genotyped with a 75k SNP chip. We performed a GWAS with a linear mixed model on 10 host disease status traits, and with a generalized linear mixed model with a complementary log-log link function (GLMM) on the probability that a cow would get infected between 2 scorings. With the GLMM, we fitted SNP effects for host susceptibility and host infectivity, while taking the variation in exposure of the susceptible cow to infectious herd mates into account. With the linear model we detected 4 suggestive SNP (false discovery rate < 0.20), 2 for the fraction of observations a cow had an active lesion on chromosomes 1 and 14, one for the fraction of observations a cow had an M2 lesion on at least one claw on chromosome 1 (the same SNP as for the fraction of observations with an active lesion), and one for the fraction of observations a cow had an M4.1 lesion on at least one claw on chromosome 10. Heritability estimates ranged from 0.09 to 0.37. With the GLMM we did not detect significant nor suggestive SNP. The SNP effects on disease status analyzed with the linear model had a correlation coefficient of only 0.70 with SNP effects on susceptibility of the GLMM, indicating that both models capture partly different effects. Because the GLMM better accounts for the epidemiological mechanisms determining individual disease status and for the distribution of the y-variable, results of the GLMM may be more reliable, despite the absence of suggestive associations. We expect that with an extended GLMM that better accounts for the full genetic variation in infectivity via the environment, the accuracy of SNP effects may increase.

Clostridium difficile in wild rodents and insectivores in the Netherlands
Krijger, I.M. ; Meerburg, B.G. ; Harmanus, C. ; Burt, S.A. - \ 2019
Letters in Applied Microbiology (2019). - ISSN 0266-8254
animal to human - Clostridioides difficile - farms - house mouse - Mus musculus - Rattus rattus - transmission - zoonotic pathogen

With wild rodents and insectivores being present around humans and their living, working and food production environments, it is important to gain knowledge of the zoonotic pathogens present in these animals. The enteropathogen Clostridium difficile, an opportunistic anaerobic bacteria, can be carried by both animals and humans, and is distributed globally. It is known that there is genetic overlap between human and animal sources of C. difficile. In this study, the aim was to assess the presence of C. difficile in rodents and insectivores trapped on and around pig and cattle farms in the Netherlands. In total 347 rodents and insectivores (10 different species) were trapped and 39·2% tested positive for presence of C. difficile. For all positive samples the ribotype (RT) was determined, and in total there were 13 different RTs found (in descending order of frequency: 057, 010, 029, 005, 073, 078, 015, 035, 454, 014, 058, 062, 087). Six of the RTs isolated from rodents and insectivores are known to be associated with human C. difficile infection; RT005, RT010, RT014, RT015, RT078 and RT087. The presence of rodents and insectivores in and around food production buildings (e.g. farms) could contribute to the spread of C. difficile in the human environment. In order to enable on-farm management for pathogen control, it is essential to comprehend the role of wild rodents and insectivores that could potentially affect the ecology of disease agents on farms. Significance and Impact of the Study: This study shows that rodents and insectivores in and around food production buildings (e.g. farms) can carry Clostridium difficile ribotypes associated with human C. difficile infection (CDI). C. difficile spores in rodent and insectivore droppings are able to survive in the environment for prolonged periods, leading to host-to-host exposure and transmission. Therefore we can state that rodent and insectivore presence on farms is a risk for zoonotic pathogen transmission of C. difficile.

Estimating the between-farm transmission rates for highly pathogenic avian influenza subtype H5N1 epidemics in Bangladesh between 2007 and 2013
Ssematimba, A. ; Okike, I. ; Ahmed, G.M. ; Yamage, M. ; Boender, G.J. ; Hagenaars, T.J. ; Bett, B. - \ 2018
Transboundary and Emerging Diseases 65 (2018)1. - ISSN 1865-1674 - p. e127 - e134.
disease control - transmission - veterinary epidemiology - zoonosis/zoonotics
Highly Pathogenic Avian Influenza (HPAI) is classified by the World Organization for Animal Health as one of the notifiable diseases. Its occurrence is associated with severe socio-economic impacts and is also zoonotic. Bangladesh HPAI epidemic data for the period between 2007 and 2013 were obtained and split into epidemic waves based on the time lag between outbreaks. By assuming the number of newly infected farms to be binomially distributed, we fit a Generalized Linear Model to the data to estimate between-farm transmission rates (β). These parameters are then used together with the calculated infectious periods to estimate the respective basic reproduction numbers (R0). The change in β and R0 with time during the course of each epidemic wave was explored. Finally, sensitivity analyses of the effects of reducing the delay in detecting infection on a farm as well as extended infectiousness of a farm beyond the day of culling were assessed. The point estimates obtained for β ranged from 0.08 (95% CI: 0.06–0.10) to 0.11 (95% CI: 0.08–0.20) per infectious farm per day while R0 ranged from 0.85 (95% CI: 0.77–1.02) to 0.96 (95% CI: 0.72–1.20). Sensitivity analyses reveal that the estimates are quite robust to changes in the assumptions about the day in reporting infection and extended infectiousness. In the analysis allowing for time-varying transmission parameters, the rising and declining phases observed in the epidemic data were synchronized with the moments when R0 was greater and less than one, respectively. From an epidemiological perspective, the consistency of these estimates and their magnitude (R0 ≈ 1) indicate that the effectiveness of the deployed control measures was largely invariant between epidemic waves and the trend of the time-varying R0 supports the hypothesis of sustained farm-to-farm transmission that is possibly initiated by a few unique introductions.
Transmission dynamics of lumpy skin disease in Ethiopia
Molla, W. ; Frankena, Klaas ; Jong, Mart de - \ 2017
Epidemiology and Infection 145 (2017)13. - ISSN 0950-2688 - p. 2856 - 2863.
Cattle - Ethiopia - LSD - reproduction ratio - transmission
Lumpy skin disease (LSD) is a severe disease of cattle caused by a Capripoxvirus and often caused epidemics in Ethiopia and many other countries. This study was undertaken to quantify the transmission between animals and to estimate the infection reproduction ratio in a predominantly mixed crop–livestock system and in intensive commercial herd types. The transmission parameters were based on a susceptible-infectious-recovered (SIR) epidemic model with environmental transmission and estimated using generalized linear models. The transmission parameters were estimated using a survival rate of infectious virus in the environment equal to 0·325 per day, a value based on the best-fitting statistical model. The transmission rate parameter between animals was 0·072 (95% CI 0·068–0·076) per day in the crop–livestock production system, whereas this transmission rate in intensive production system was 0·076 (95% CI 0·068–0·085) per day. The reproduction ratio (R) of LSD between animals in the crop–livestock production system was 1·07, whereas it was 1·09 between animals in the intensive production system. The calculated R provides a baseline against which various control options can be assessed for efficacy.
Transmission through air as a possible route of exposure for MRSA
Bos, Marian E.H. ; Verstappen, Koen M. ; Cleef, Brigitte A.G.L. Van; Dohmen, Wietske ; Dorado-García, Alejandro ; Graveland, Haitske ; Duim, Birgitta ; Wagenaar, Jaap A. ; Kluytmans, Jan A.J.W. ; Heederik, Dick J.J. - \ 2016
Journal of Exposure Science and Environmental Epidemiology 26 (2016)3. - ISSN 1559-0631 - p. 263 - 269.
air - exposure - livestock - MRSA - transmission

Livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA) is highly prevalent in pigs and veal calves. The environment and air in pig and veal calf barns is often contaminated with LA-MRSA, and can act as a transmission source for humans. This study explores exposure-response relationships between sequence type 398 (ST398) MRSA air exposure level and nasal ST398 MRSA carriage in people working and/or living on farms. Samples and data were used from three longitudinal field studies in pig and veal calf farm populations. Samples consisted of nasal swabs from the human participants and electrostatic dust fall collectors capturing airborne settled dust in barns. In both multivariate and mutually adjusted analyses, a strong association was found between nasal ST398 MRSA carriage in people working in the barns for >20 h per week and MRSA air levels. In people working in the barns <20 h per week there was a strong association between nasal carriage and number of working hours. Exposure to ST398 MRSA in barn air seems to be an important determinant for nasal carriage, especially in the highly exposed group of farmers, next to duration of contact with animals. Intervention measures should therefore probably also target reduction of ST398 MRSA air levels.

Role of vaccination-induced immunity and antigenic distance in the transmission of highly pathogenic avian influenza H5N1.
Sitaras, I. ; Rousou, X. ; Kalthoff, D. ; Beer, M. ; Peeters, B.P.H. ; Jong, M.C.M. de - \ 2016
Journal of the Royal Society, Interface 13 (2016)114. - ISSN 1742-5689 - 13 p.
highly pathogenic avian influenza - transmission - antigenic distance - vaccine dose
Highly pathogenic avian influenza (HPAI) H5N1 epidemics in poultry cause
huge economic losses as well as sporadic human morbidity and mortality.
Vaccination in poultry has often been reported as being ineffective in preventing
transmission and as a potential driving force in the selection of immune
escape mutants.We conducted transmission experiments to evaluate the transmission
dynamics of HPAI H5N1 strains in chickens vaccinated with high and
low doses of immune escape mutants we have previously selected, and analysed
the data using mathematical models. Remarkably, we demonstrate
that the effect of antigenic distances between the vaccine and challenge strains
used in this study is too small to influence the transmission dynamics of the
strains used. This is because the effect of a sufficient vaccine dose on antibody
levels against the challenge viruses is large enough to compensate for any
decrease in antibody titres due to antigenic differences between vaccine and
challenge strains. Our results showthat at least under experimental conditions,
vaccination will remain effective even after antigenic changes as may be
caused by the initial selection in vaccinated birds.
Markt rijp voor betaalbaar kasdek met hoge isolatiewaarde en lichttransmissie : het Nieuwe Telen nog energiezuiniger maken
Rodenburg, J. ; Kempkes, F.L.K. - \ 2015
Onder Glas 12 (2015)6/7. - p. 34 - 35.
glastuinbouw - beglazing - bekleding, bouw - isolatie - transmissie - schermen - efficiëntie - folie - energiebesparing - lichtdoorlating - kastechniek - greenhouse horticulture - glazing - cladding - isolation - transmission - blinds - efficiency - foil - energy saving - light transmission - greenhouse technology
Precies een jaar geleden startte Wageningen UR Glastuinbouw en een consortium van bedrijven met de bouw van een nieuwe, energiezuinige kas. Sleutelcomponent is een ventileerbaar spouwdek dat bestaat uit helder glas waaronder een duurzaam diffuus folie is aangebracht. Dit najaar maken betrokkenen de balans op, maar nu al lijkt de innovatie een aanwinst voor Het Nieuwe Telen. Het systeem oogt professioneel en bezoekers reageren positief.
The presence of Borrelia miyamotoi, a relapsing fever spirochaete, in questing Ixodes ricinus in Belgium and in The Netherlands
Cochez, C. ; Heyman, P. ; Heylen, D. ; Fonville, M. ; Hengeveld, P. ; Takken, W. ; Simons, L. ; Sprong, H. - \ 2015
Zoonoses and Public Health 62 (2015)5. - ISSN 1863-1959 - p. 331 - 333.
lyme-disease - meningoencephalitis - transmission
Borrelia miyamotoi is a tick-borne bacterium that may cause relapsing fever in humans. As this pathogen has been discovered in Europe only recently, only little is known about its local impact on human health and its spatial distribution. In this study, we show the results of PCR screenings for B. miyamotoi in flagged Ixodes ricinus from Belgium and the Netherlands. B. miyamotoi was detected in nine of thirteen, and three of five locations from the Netherlands and Belgium, respectively. These outcomes indicate that B. miyamotoi is more spread than previously thought. The mean infection rate B. miyamotoi was 1.14% for Belgium and 3.84% for the Netherlands.
Silent spread of highly pathogenic Avian Influenza H5N1 virus amongst vaccinated commercial layers
Poetri, O.N. ; Boven, M. ; Claassen, I.J.T.M. ; Koch, G. ; Wibawan, I.W. ; Stegeman, A. ; Broek, J. van den; Bouma, A. - \ 2014
Research in Veterinary Science 97 (2014)3. - ISSN 0034-5288 - p. 637 - 641.
transmission - chickens - poultry - evolution
The aim of this study was to determine whether a single vaccination of commercial layer type chickens with an inactivated vaccine containing highly pathogenic avian influenza virus strain H5N1 A/chicken/Legok/2003, carried out on the farm, was sufficient to protect against infection with the homologous virus strain. A transmission experiment was carried out with pairs of chicken of which one was inoculated with H5N1 virus and the other contact-exposed. Results showed that the majority of the vaccinated birds developed haemagglutination inhibition (HI) titres below 4log2. No clinical signs were observed in the vaccinated birds and virus shedding was limited. However, nearly all vaccinated birds showed a four-fold or higher increase of HI titres after challenge or contact-exposure, which is an indication of infection. This implies that virus transmission most likely has occurred. This study showed that a single vaccination applied under field conditions induced clinical protection, but was insufficient to induce protection against virus transmission, suggesting that silent spread of virus in vaccinated commercial flocks may occur. (C) 2014 Elsevier Ltd. All rights reserved.
Development of a Multiplexed Bead-Based Suspension Array for the Detection and Discrimination of Pospiviroid Plant Pathogens
Brunschot, S.L. van; Bergervoet, J.H.W. ; Pagendam, D.E. ; Weerdt, M. de; Geering, A.D.W. ; Drenth, A. ; Vlugt, R.A.A. van der - \ 2014
PLoS ONE 9 (2014)1. - ISSN 1932-6203
rt-pcr assay - 1st report - greenhouse tomatoes - natural infection - viroid disease - potato - identification - transmission - technology - strain
Efficient and reliable diagnostic tools for the routine indexing and certification of clean propagating material are essential for the management of pospiviroid diseases in horticultural crops. This study describes the development of a true multiplexed diagnostic method for the detection and identification of all nine currently recognized pospiviroid species in one assay using Luminex bead-based suspension array technology. In addition, a new data-driven, statistical method is presented for establishing thresholds for positivity for individual assays within multiplexed arrays. When applied to the multiplexed array data generated in this study, the new method was shown to have better control of false positives and false negative results than two other commonly used approaches for setting thresholds. The 11-plex Luminex MagPlex-TAG pospiviroid array described here has a unique hierarchical assay design, incorporating a near-universal assay in addition to nine species-specific assays, and a co-amplified plant internal control assay for quality assurance purposes. All assays of the multiplexed array were shown to be 100% specific, sensitive and reproducible. The multiplexed array described herein is robust, easy to use, displays unambiguous results and has strong potential for use in routine pospiviroid indexing to improve disease management strategies.
A cohort study on Actinobacillus pleuropneumoniae colonisation in suckling piglets
Tobias, T.J. ; Klinkenberg, D. ; Bouma, A. ; Broek, J. van den; Daemen, A.J.J.M. ; Wagenaar, J.A. ; Stegeman, J.A. - \ 2014
Preventive Veterinary Medicine 114 (2014)3-4. - ISSN 0167-5877 - p. 223 - 230.
infection patterns - pigs - antibodies - transmission - efficacy - herds - sows - serotype-2 - hemolysin - vaccine
Actinobacillus pleuropneumoniae causes respiratory disease in pigs and despite the use of preventive measures such as vaccination and antimicrobials clinical outbreaks still occur. At weaning often many piglets are not colonised. If differences in prevalence between litters are large and if factors were known that could explain these differences, this may provide an opportunity to raise groups of A. pleuropneumoniae free piglets. To this end, a cohort study was performed on two endemically infected farrow-to-finish farms. Seventy-six of 133 sows were selected using stratified random selection by parity. Farmers complied with a strict hygiene and animal management protocol to prevent transmission between litters. Tonsil brush and serum samples taken three weeks before parturition were tested for antigen with an apxIVA qPCR and antibodies with Apx and Omp ELISAs, respectively. Three days before weaning tonsil brush samples from all piglets (n = 871) were collected and tested for antigen. Whereas all sows tested positive both in serology tests as well as qPCR, 0.41 of the litters tested fully negative and 0.73 of all piglets tested negative. The proportion of positively tested piglets in positive litters ranged from 0.08-1.0 (median= 0.36). A grouped logistic regression model with a beta binomial distribution of the probability for piglets to become infected was fitted to the data and associations with explanatory variables were explored. To test the possibility that alternatively the clustering was caused by onwards transmission among the piglets, a transmission model was fitted to the data incorporating sow-piglet and piglet-piglet transmission, but this model did not fit better. The results of this study showed that the number of colonised suckling piglets was highly clustered and mainly attributable to the variability of infectiousness of the dam, but no dam related risk factor for colonisation status of litter or piglets within litters could be identified. (C) 2014 Elsevier B.V. All rights reserved.
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.
Contagious animal diseases: The science behind trade policies and standards (Personal View)
Boqvist, S. ; Dekker, A. ; Depner, K. ; Grace, D. ; Hueston, W. ; Stark, K.D.C. ; Sternberg Lewerin, S. - \ 2014
The Veterinary Journal 202 (2014)1. - ISSN 1090-0233 - p. 7 - 10.
pcr detection methods - swine-fever virus - mouth-disease - ring test - vaccination - transmission - products - drivers - impacts - trends
Zuinig en efficiënt telen in 2SaveEnergy kas : tuinen bij Wageningen UR Glastuinbouw
Strating, J. ; Vries, J.W. de; Zwart, H.F. de - \ 2014
Kas techniek (2014)7. - p. 70 - 71.
glastuinbouw - kastechniek - kassen - diffuus glas - film - energiebesparing - innovaties - transmissie - plantenontwikkeling - cultuurmethoden - greenhouse horticulture - greenhouse technology - greenhouses - diffused glass - energy saving - innovations - transmission - plant development - cultural methods
In oktober wordt de 2SaveEnergy kas bij Wageningen UR Glastuinbouw in Bleiswijk in gebruik genomen. Het compleet nieuwe kasdekconcept combineert glas met folie en moet uiteindelijk een flinke energiebesparing opleveren, zo laten de initiatiefnemers weten.
Airborne virus sampling - Efficiencies of samplers and their detection limits for infectious bursal disease virus (IBDV)
Yang Zhao, Yang ; Aarnink, A.J.A. ; Wang, Wei ; Fabri, T. ; Groot Koerkamp, P.W.G. ; Jong, M.C.M. de - \ 2014
Annals of Agricultural and Environmental Medicine 21 (2014)3. - ISSN 1232-1966 - p. 464 - 471.
bioaerosol samplers - collection efficiency - relative-humidity - newcastle-disease - influenza-virus - united-kingdom - vaccine virus - 2001 epidemic - transmission - enumeration
Introduction. The airborne transmission of infectious diseases in livestock production is increasingly receiving research attention. Reliable techniques of air sampling are crucial to underpin the findings of such studies. This study evaluated the physical and biological efficiencies and detection limits of four samplers (Andersen 6-stage impactor, all-glass impinger "AGI-30", OMNI-3000 and MD8 with gelatin filter) for collecting aerosols of infectious bursal disease virus (IBDV). Materials and Method. IBDV aerosols mixed with a physical tracer (uranine) were generated in an isolator, and then collected by the bioaerosol samplers. Samplers' physical and biological efficiencies were derived based on the tracer concentration and the virus/tracer ratio, respectively. Detection limits for the samplers were estimated with the obtained efficiency data. Results. Physical efficiencies of the AGI-30 (96%) and the MD8 (100%) were significantly higher than that of the OMNI-3000 (60%). Biological efficiency of the OMNI-3000 (23%) was significantly lower than 100% (P <0.01), indicating inactivation of airborne virus during sampling. The AGI-30, the Andersen impactor and the MD8 did not significantly inactivate virus during sampling. The 2-min detection limits of the samplers on airborne IBDV were 4.1 log(10) 50% egg infective dose (EID50) m(-3) for the Andersen impactor, 3.3 log(10) EID50 m(-3) for the AGI-30, 2.5 log(10) EID50 m(-3) for the OMNI-3000, and 2.9 log(10) EID50 m(-3) for the MD8. The mean half-life of IBDV aerosolized at 20 degrees C and 70% was 11.9 min. Conclusion. Efficiencies of different samplers vary. Despite its relatively low sampling efficiency, the OMNI-3000 is suitable for use in environments with low viral concentrations because its high flow rate gives a low detection limit. With the 4 samplers investigated, negative air samples cannot guarantee virus-free aerial environments, which means that transmission of infectious agents between farms may still occur even when no virus has been detected.
Pulmonary immunization of chickens using non-adjuvanted spray-freeze dried whole inactivated virus vaccine completely protects against highly pathogenic H5N1 avian influenza virus.
Peeters, B.P.H. ; Tonnis, W.F. ; Murugappan, S. ; Rottier, P. ; Koch, G. ; Frijlink, H.W. ; Huckriede, A. ; Hinrichs, W.L.J. - \ 2014
Vaccine 32 (2014)48. - ISSN 0264-410X - p. 6445 - 6450.
a h5n1 - aerosol vaccination - immune-responses - mass vaccination - powder - transmission - delivery - poultry - inulin - birds
Highly pathogenic avian influenza (HPAI) H5N1 virus is a major threat to public health as well as to the global poultry industry. Most fatal human infections are caused by contact with infected poultry. Therefore, preventing the virus from entering the poultry population is a priority. This is, however, problematic in emergency situations, e.g. during outbreaks in poultry, as there are currently no mass application methods to effectively vaccinate large numbers of birds within a short period of time. To evaluate the suitability of needle-free pulmonary immunization for mass vaccination of poultry against HPAI H5N1, we performed a proof-of-concept study in which we investigated whether non-adjuvanted spray-freeze-dried (SFD) whole inactivated virus (WIV) can be used as a dry powder aerosol vaccine to immunize chickens. Our results show that chickens that received SFD-WIV vaccine as aerosolized powder directly at the syrinx (the site of the tracheal bifurcation), mounted a protective antibody response after two vaccinations and survived a lethal challenge with HPAI H5N1. Furthermore, both the number of animals that shed challenge virus, as well as the level of virus shedding, were significantly reduced. Based on antibody levels and reduction of virus shedding, pulmonary vaccination with non-adjuvanted vaccine was at least as efficient as intratracheal vaccination using live virus. Animals that received aerosolized SFD-WIV vaccine by temporary passive inhalation showed partial protection (22% survival) and a delay in time-to-death, thereby demonstrating the feasibility of the method, but indicating that the efficiency of vaccination by passive inhalation needs further improvement. Altogether our results provide a proof-of-concept that pulmonary vaccination using an SFD-WIV powder vaccine is able to protect chickens from lethal HPAI challenge. If the efficacy of pulmonary vaccination by passive inhalation can be improved, this method might be suitable for mass application.
Significant increase of Echinococcus multilocularis prevalencein foxes, but no increased predicted risk for humans
Maas, M. ; Dam-Deisz, W.D.C. ; Roon, A.M. van; Takumi, K. ; Giessen, J.W.B. van der - \ 2014
Veterinary Parasitology 206 (2014)3-4. - ISSN 0304-4017 - p. 167 - 172.
human alveolar echinococcosis - red foxes - netherlands - transmission - switzerland - city - dogs
The emergence of the zoonotic tapeworm Echinococcus multilocularis, causative agent ofalveolar echinococcosis (AE), poses a public health risk. A previously designed risk mapmodel predicted a spread of E. multilocularis and increasing numbers of alveolar echinococ-cosis patients in the province of Limburg, The Netherlands. This study was designed todetermine trends in the prevalence and worm burden of E. multilocularis in foxes in a popu-lar recreational area in the southern part of Limburg to assess the risk of infection for humansand to study the prevalence of E. multilocularis in dogs in the adjacent city of Maastricht.Thirty-seven hunted red foxes were tested by the intestinal scraping technique and nestedPCR on colon content. Additionally, 142 fecal samples of domestic dogs from Maastrichtwere analyzed by qPCR for the presence of E. multilocularis.In foxes, a significantly increased prevalence of 59% (95% confidence interval 43–74%)was found, compared to the prevalence of 11% (95% CI 7–18%) in 2005–2006. Average wormburden increased to 37 worms per fox, the highest since the first detection, but consistentwith the prediction about the parasite population for this region. Updated prediction onthe number of AE cases did not lead to an increase in previous estimates of human AE casesup to 2018. No dogs in the city of Maastricht tested positive, but results of questionnairesshowed that deworming schemes were inadequate, especially in dogs that were consideredat risk for infection.
Hybridization studies to modify the host preference of Anopheles gambiae
Pates, H.V. ; Curtis, C.F. ; Takken, W. - \ 2014
Medical and Veterinary Entomology 28 (2014)S1. - ISSN 0269-283X - p. 68 - 74.
candidate odorant receptors - malaria vector mosquito - feeding preferences - quadriannulatus - behavior - arabiensis - culicidae - diptera - transmission - responses
A strategy to decrease the vector competence of Anopheles gambiae sensu stricto (Diptera: Culicidae), the most efficient malaria vector in Africa, may consist of exploiting the genes involved in zoophily. Crossing and backcrossing experiments were performed between An.¿gambiae s.s. and the zoophilic sibling species Anopheles quadriannulatus. Mosquito strains were tested in a dual-choice olfactometer to investigate their responses to cow odour. Totals of 12% of An.¿gambiae s.s. and 59% of An.¿quadriannulatus selected the port with the cow odour. Crosses and backcrosses did not show a significant preference for the cow-baited port. The results indicated that anthropophilic behaviour in An.¿gambiae s.s. is a dominant or partially dominant trait, which, in conjunction with the unstable zoophilic behaviour observed in An.¿quadriannulatus, poses a serious obstacle to plans to decrease vector competence by modifying the anthropophilic trait.
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