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.

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    Protective Efficacy of Newcastle Disease Virus Expressing Soluble Trimeric Hemagglutinin against Highly Pathogenic H5N1 Influenza in Chickens and Mice
    Cornelissen, A.H.M. ; Leeuw, O.S. de; Tacken, M.G.J. ; Klos, H.C. ; Vries, R.P. de; Boer-Luijtze, E.A. de; Zoelen-Bos, D.J. van; Rigter, A. ; Rottier, P.J.M. ; Moormann, R.J.M. ; Haan, C.A.M. de - \ 2012
    PLoS ONE 7 (2012)8. - ISSN 1932-6203
    avian influenza - fusion protein - neutralizing antibodies - respiratory-tract - lethal challenge - vaccine vectors - fowlpox virus - recombinant - immunization - virulence
    Background: Highly pathogenic avian influenza virus (HPAIV) causes a highly contagious often fatal disease in poultry, resulting in significant economic losses in the poultry industry. HPAIV H5N1 also poses a major public health threat as it can be transmitted directly from infected poultry to humans. One effective way to combat avian influenza with pandemic potential is through the vaccination of poultry. Several live vaccines based on attenuated Newcastle disease virus (NDV) that express influenza hemagglutinin (HA) have been developed to protect chickens or mammalian species against HPAIV. However, the zoonotic potential of NDV raises safety concerns regarding the use of live NDV recombinants, as the incorporation of a heterologous attachment protein may result in the generation of NDV with altered tropism and/or pathogenicity. Methodology/Principal Findings: In the present study we generated recombinant NDVs expressing either full length, membrane-anchored HA of the H5 subtype (NDV-H5) or a soluble trimeric form thereof (NDV-sH5 3). A single intramuscular immunization with NDV-sH5 3 or NDV-H5 fully protected chickens against disease after a lethal challenge with H5N1 and reduced levels of virus shedding in tracheal and cloacal swabs. NDV-sH5 3 was less protective than NDV-H5 (50% vs 80% protection) when administered via the respiratory tract. The NDV-sH5 3 was ineffective in mice, regardless of whether administered oculonasally or intramuscularly. In this species, NDV-H5 induced protective immunity against HPAIV H5N1, but only after oculonasal administration, despite the poor H5-specific serum antibody response it elicited. Conclusions/Significance: Although NDV expressing membrane anchored H5 in general provided better protection than its counterpart expressing soluble H5, chickens could be fully protected against a lethal challenge with H5N1 by using the latter NDV vector. This study thus provides proof of concept for the use of recombinant vector vaccines expressing a soluble form of a heterologous viral membrane protein. Such vectors may be advantageous as they preclude the incorporation of heterologous membrane proteins into the viral vector particles.
    Intramuscular inoculation of calves with an experimental Newcastle disease virus-based vector vaccine elicits neutralizing antibodies against Rift Valley fever virus
    Kortekaas, J.A. ; Dekker, A. ; Boer, S.M. de; Weerdmeester, K. ; Vloet, R.P.M. ; Wit, A.A.C. de; Peeters, B.P.H. ; Moormann, R.J.M. - \ 2010
    Vaccine 28 (2010)11. - ISSN 0264-410X - p. 2271 - 2276.
    avian influenza - respiratory-tract - fusion protein - foreign gene - i interferon - cloned cdna - expression - humans - immunization - replication
    In the past decade, the use of Newcastle disease virus (NDV) as a vaccine vector for the prevention of economically important livestock diseases as well as for human diseases has been extensively explored. In this study, we have constructed a recombinant NDV vaccine virus, named NDFL-Gn, that produces the Rift Valley fever virus (RVFV) Gn glycoprotein. Calves were immunized via either the intranasal route or the intramuscular route. Delivery via the intranasal route elicited no detectable antibody responses, whereas delivery via the intramuscular route elicited antibodies against both NDV and the Gn protein. The RVFV-neutralizing activity of the antisera from intramuscularly vaccinated calves was demonstrated, suggesting that NDV is a promising vaccine vector for the prevention of RVF in calves.
    Vaccinatie van lelies tegen LMoV: een haalbare of ongewenste resistentiestrategie?
    Kock, M.J.D. de - \ 2009
    Lisse : PPO Bloembollen en Bomen - 27
    leliemozaïekvirus - lilium - lelies - plantenziekten - bloembollen - snijbloemen - plantenziektebestrijding - vaccinatie - immunisatie - nederland - lily mottle virus - lilium - lilies - plant diseases - ornamental bulbs - cut flowers - plant disease control - vaccination - immunization - netherlands
    Virusinfecties veroorzaken opbrengstverliezen en beperken tevens het internationale handelsverkeer tussen landen die strikte regelgeving hebben met betrekking tot de aanwezigheid van virussen in het plantenmateriaal. Wanneer een plant met een mild virusisolaat wordt geïnfecteerd, komt het vaak voor dat deze plant niet meer vatbaar (of minder vatbaar) is voor virusisolaten die heftige virussymptomen veroorzaken. Deze natuurlijke manier van geïnduceerde resistentie tegen agressieve virussen wordt cross: protectie genoemd. Het actief besmetten van een plant met een virusisolaat dat milde symptomen laat zien, wordt ook wel ‘vaccineren’ genoemd. Het vaccineren van planten wordt door het Japanse bedrijf Nippon Del Monte (NDM) in de praktijk reeds toegepast. NDM is in het bezit van een mild isolaat van Lilly mottle virus (leliemozaïekvirus, LMoV) dat geen of nauwelijks virussymptomen veroorzaakt en is op zoek naar partners in Nederland om voor dit isolaat de mogelijkheden van cross:protectie te bestuderen. Omdat de vaccinatietechnologie positieve verwachtingen heeft, maar ook onzekerheden, beperkingen en potentiële risico’s kent, wordt in dit rapport toegewerkt naar een collectief besluit of de vaccinatietechnologie in Nederland voeten aan de grond kan gaan krijgen. PPO:BBF heeft een stakeholder: en ketenanalyse gemaakt waarin aangegeven is welke nationale en internationale partijen in de keten betrokken zijn bij de implementatie van de vaccinatie technologie. Tevens is samen met Nederlandse lelieveredelingsbedrijven een lijst met criteria opgesteld waaraan een plantenvaccin (in algemene zin) moet voldoen. In een workshop is de vaccinatietechnologie van NDM getoetst aan deze criteria en vraagstellingen zijn geformuleerd die door middel van vervolgonderzoek beantwoord moeten worden of onderdeel kunnen zijn van validatieonderzoek van de vaccinatietechnologie tegen LMoV onder Nederlandse teeltomstandigheden. Er wordt vooral veel waarde gehecht aan de criteria dat de vaccinatietechnologie niet mag leiden tot teeltbeperkingen, niet mag leiden tot risico:inperkende maatregelen en niet mag leiden tot handelsbeperkingen. Juist omdat introductie van de door NDM voorgestelde vaccinatietechnologie volledig van toepassing is op deze criteria, en deze bezwaren niet eenvoudig op te lossen zijn, is gezamenlijk besloten dat er vanuit Nederland geen interesse is in de ontwikkeling van de vaccinatietechnologie tegen LMoV in lelie. Daarmee komt ook een potentiële collectieve samenwerking met NDM voor een gezamenlijke ontwikkeling van de technologie te vervallen. Tevens wordt er geen vervolgonderzoek opgestart waarin aanvullende onderzoeksvragen worden uitgewerkt. Deze conclusie is samengevat in een Memo die aan NDM is toegestuurd.
    Immuuninterventie : 'Drukken op de juiste knoppen van het afweersysteem'
    Schijns, V.E.J.C. - \ 2009
    Wageningen : Wageningen Universiteit - ISBN 9789085852773 - 32
    immunologie - immuniteitsreactie - immuniteit - immuunsysteem - immunisatie - vaccins - vaccinatie - immunology - immune response - immunity - immune system - immunization - vaccines - vaccination
    Molecular cloning and functional characterisation of a cathepsin L-like proteinases from the fish kinetoplastid parasite Trypanosoma carassii
    Ruszczyk, A. ; Forlenza, M. ; Savelkoul, H.F.J. ; Wiegertjes, G.F. - \ 2008
    Fish and Shellfish Immunology 24 (2008)2. - ISSN 1050-4648 - p. 205 - 214.
    carp cyprinus-carpio - fresh-water fish - cysteine proteinases - leishmania-mexicana - sequence alignment - danilewskyi - expression - cruzi - immunization - protease
    Trypanosoma carassii is a fish kinetoplastid parasite that belongs to the family Trypanosomatida. In the present study we cloned a cathepsin L-like proteinase from T. carassii. The nucleotide sequence of 1371 bp translated into a preproprotein of 456 amino acids. The preproprotein contained the oxyanion hole (Gln), the active triad formed by Cys, His and Asn and the conserved ERFNIN-like, GNFD and GCNGG motifs, characteristic for cathepsin L proteinases. Phylogenetic analysis showed that the T. carassii cysteine proteinase clustered with other cathepsin L-like proteinases from the Trypanosomatida. We produced a recombinant T. carassii cysteine proteinase in Escherichia coli and demonstrated that it has cathepsin L activity. Immunization of common carp (Cyprinus carpio L.) with the recombinant protein induced a very high increase in proteinase-specific antibodies but only slightly lowered parasitaemia. Our findings suggest that the T. carassii cysteine proteinase is highly conserved within the Trypanosomatida with respect to structure and activity but is not a major protective antigen in carp.
    Eenvoudige remedies voor stress bij weefselkweekplantjes
    Klerk, G.J.M. de - \ 2007
    Onder Glas 8 (2007)4. - p. 24 - 25.
    vermeerderingsmateriaal - weefselkweek - zaailingen - droogte - stress - genetische modificatie - beschermingsmiddelen - trehalose - immunisatie - proeven - glastuinbouw - propagation materials - tissue culture - seedlings - drought - stress - genetic engineering - protectants - trehalose - immunization - trials - greenhouse horticulture
    Als planten in de natuur onder stress staan, bijvoorbeeld door droogte, beschermen ze kwetsbare componenten door speciefieke stoffen, 'protectants', in grote hoeveelheden aan te maken. Deze manier van bescherming is ook bij weefselkweek te gebruiken. Telers kunnen planten voorbehandelen met milde stress. Daardoor kunnen ze daarna een zware stress doorstaan. Onderzoek met de modelplant Arabidopsis en met lelie, roos en appel geeft uitstekende resultaten. De methoden zijn eenvoudig. Op basis van deze resultaten kan de tuinbouw allerlei toepassingen ontwikkelen
    Effectiveness of simulated interventions in reducing the estimated prevalence of E. coli O157:H7 in lactating cows in dairy herds
    Vosough Ahmadi, B. ; Frankena, K. ; Turner, J. ; Velthuis, A.G.J. ; Hogeveen, H. ; Huirne, R.B.M. - \ 2007
    Veterinary Research 38 (2007). - ISSN 0928-4249 - p. 755 - 771.
    hemolytic-uremic-syndrome - semi-stochastic model - glycoconjugate vaccine - cattle - colonization - infections - pathogen - beef - transmission - immunization
    A transmission model developed to investigate the dynamics of Escherichia coli O157:H7 bacteria in a typical Dutch dairy herd was used to assess the effectiveness of vaccination, diet modification, probiotics (colicin) and hygienic measures as to water troughs and bedding, when they are applied single or in combination, in reducing the prevalence of infected animals. The aim was to rank interventions based on their effectiveness in reducing the baseline prevalence of infected animals in the lactating group. The baseline prevalence of the lactating group and the within-herd prevalence were estimated by the model to be 5.02% and 13.96% respectively. The results show that all four interventions, if applied to all four animal groups or only to young stock, are the most effective and will reduce the baseline prevalence by 84% to 99%. In general, combinations of hygiene (applied in all groups) and one other intervention had the highest effectiveness in reducing prevalence in the lactating group. Vaccination and diet modification show a slightly higher effectiveness than colicin and hygiene.
    Role of T-cell receptor V beta 8.3 peptide vaccine in the prevention of experimental autoimmune uveoretinitis
    Zhang, R. ; Yang, P.Z. ; Wu, C.Y. ; Jin, H.L. ; Li, B. ; Huang, X. ; Zhou, H. ; Gao, Y. ; Zhu, L. ; Kijlstra, A. - \ 2006
    Chinese Medical Journal 119 (2006)9. - ISSN 0366-6999 - p. 740 - 748.
    myelin basic-protein - multiple-sclerosis - rheumatoid-arthritis - cdr2 peptides - encephalomyelitis - disease - immunization - therapy - determinant - lymphocytes
    T-cell receptor (TCR) plays an important role in the development of autoimmune diseases. Recently, it was reported that immunization of animals with TCR peptide derived from the pathogenic cells could prevent autoimmune diseases. The aim of this study was to investigate whether vaccination with a synthetic peptide from the hypervariable region of TCR V(beta) 8.3, an experimental autoimmune uveoretinitis (EAU)-associated gene, was able to prevent the disease. METHODS: EAU was induced in Lewis rats by immunization with IRBP R16 peptide emulsified in complete Freund's adjuvant (CFA). The clinical and histological appearances were scored. Delayed type hypersensitivity (DTH) and lymphocyte proliferation were detected. Cytokine levels of aqueous humour, supernatants of cells from spleen and draining lymph nodes were measured by enzyme linked immunosorbent assay (ELISA). Gene expression of TCR V(beta) 8.3 on CD(4)(+) T cells was examined by real time quantitative polymerase chain reaction (PCR). RESULTS: After vaccination, the intraocular inflammation was significantly mitigated, antigen specific DTH and lymphocyte proliferation responses were suppressed, interleukin (IL)-2 in aqueous humour, interferon (IFN)-gamma and IL-2 produced by the spleen and draining lymph node cells were significantly decreased, whereas the production of IL-4 and IL-10 were increased. The response of draining lymph node cells to TCR V(beta) 8.3 peptide was enhanced after vaccination. Inoculation with CFA alone did not affect the severity of EAU and the above parameters. The suppression of EAU was much stronger in the group of four fold inoculations than the group of two fold inoculations. The expression of TCR V(beta) 8.3 gene was significantly reduced in the group of fourfold inoculations. CONCLUSION: Vaccination with the synthetic TCR V(beta) 8.3 peptide could remarkably inhibit the development of EAU.
    A DNA vaccine coding for gB and gD of pseudorabies virus (suid herpes type 1) primes the immune system in the presence of maternal immunity more efficiently than conventional vaccines
    Rooij, E.M.A. van; Moonen-Leusen, H.W.M. ; Visser-Hendriksen, Y.E. de; Middel, W.G. ; Boersma, W.J.A. ; Bianchi, A.T.J. - \ 2006
    Vaccine 24 (2006)9. - ISSN 0264-410X - p. 1264 - 1273.
    aujeszkys disease virus - cell-mediated-immunity - intranasal vaccination - antibody-titers - pigs - responses - protection - infection - glycoprotein - immunization
    DNA vaccines are capable of priming the immune system of neonates in the presence of maternal antibodies. However, it is still not clear whether the extent of priming and protection against challenge infections induced by a DNA vaccine in maternally immune newborns is better than that induced by conventional vaccines. To study this, we used the pseudorabies virus (PRV) infection model in the natural host, the pig. We compared the efficacy of a DNA vaccine with the efficacy of a conventional modified live vaccine (MLV) and an inactivated vaccine (IV) in maternally immune newborn piglets. We measured the priming of the immune response and the degree of protection against challenge infection for all vaccine types. We vaccinated piglets with or without maternal immunity twice, at the age of 5 and 9 weeks, and we assessed protection by challenge infection with virulent PRV at the age of 15 weeks. Vaccination with DNA or conventional vaccines induced both humoral and cell-mediated immune responses in maternally immune animals. DNA vaccination seemed not to suffer from suppression by maternal immunity and resulted in similar or stronger immune responses in maternally immune piglets as compared in naïve piglets. In contrast, vaccination with conventional vaccines resulted in weaker immune responses in maternally immune piglets than in naïve piglets. Moreover, DNA vaccination provided better protection against challenge infection in maternally immune piglets than in naive piglets, whereas vaccination with conventional vaccines did not.
    Quantification of the effect of vaccination on transmission of avian influenza (H7N7) in chickens
    Goot, A.J. van der; Koch, G. ; Jong, M.C.M. de; Boven, R.M. van - \ 2005
    Proceedings of the National Academy of Sciences of the United States of America 102 (2005)50. - ISSN 0027-8424 - p. 18141 - 18146.
    virus - vaccines - epidemic - immunization - efficacy - disease - turkeys - protein
    Recent outbreaks of highly pathogenic avian influenza (HPAI) viruses in poultry and their threatening zoonotic consequences emphasize the need for effective control measures. Although vaccination of poultry against avian influenza provides a potentially attractive control measure, little is known about the effect of vaccination on epidemiologically relevant parameters, such as transmissibility and the infectious period. We used transmission experiments to study the effect of vaccination on the transmission characteristics of HPAI A/Chicken/Netherlands/03 H7N7 in chickens. In the experiments, a number of infected and uninfected chickens is housed together and the infection chain is monitored by virus isolation and serology. Analysis is based on a stochastic susceptible, latently infected, infectious, recovered (SEIR) epidemic model. We found that vaccination is able to reduce the transmission level to such an extent that a major outbreak is prevented, important variables being the type of vaccine (H7N1 or H7N3) and the moment of challenge after vaccination. Two weeks after vaccination, both vaccines completely block transmission. One week after vaccination, the H7N1 vaccine is better than the H7N3 vaccine at reducing the spread of the H7N7 virus. We discuss the implications of these findings for the use of vaccination programs in poultry and the value of transmission experiments in the process of choosing vaccine.
    Novel baculovirus-derived p67 subunit vaccines efficacious against East Coast fever in cattle
    Kaba, S.A. ; Musoke, A.J. ; Schaap, D. ; Schetters, T. ; Rowlands, J. ; Vermeulen, A.J. ; Nene, V. ; Vlak, J.M. ; Oers, M.M. van - \ 2005
    Vaccine 23 (2005)21. - ISSN 0264-410X - p. 2791 - 2800.
    theileria-parva sporozoites - neutralizing epitopes - monoclonal-antibody - surface-antigen - protection - protein - stocks - immunogenicity - immunization - leukocytes
    Two novel baculovirus-derived recombinant Theileria parva p67 constructs were tested for their vaccine potential against East Coast fever. Boran calves were immunized with a his-GFP-p67 fusion protein (GFP:p67¿SS) or with GP64:p67C, a protein fusion between a C-terminal domain of p67 and the baculovirus envelope protein GP64. Both GFP:p67¿SS and GP64:p67C induced antibodies with high ELISA titers that neutralized T. parva sporozoites with high efficiency. Upon challenge, a correlation was observed between the in vitro neutralizing capacity and the reduction in severe ECF for individual animals. A protection level upto 85% was obtained. This level of protection was achieved with only two inoculations of 100 ¿g per dose, which is a major improvement over previous recombinant p67 products
    Vaccine-induced T cell-mediated immunity plays a critical role in early protection against pseudorabies virus (suid herpes virus type 1) infection in pigs
    Rooij, E.M.A. van; Bruin, M.G.M. de; Visser-Hendriksen, Y.E. de; Middel, W.G. ; Boersma, W.J.A. ; Bianchi, A.T.J. - \ 2004
    Veterinary Immunology and Immunopathology 99 (2004)1-2. - ISSN 0165-2427 - p. 113 - 125.
    aujeszkys disease virus - monoclonal-antibodies - interferon-gamma - b-cell - lymphocytes - responses - swine - mice - cytotoxicity - immunization
    The aim of our study was to evaluate the relative importance of antibody and T cell-mediated immunity in protection against pseudorabies virus (suid herpes virus type 1) infection in pigs. We induced different levels of immune responses by using: (1) a modified live vaccine; (2) the same modified live vaccine with an oil-in-water (o/w) adjuvant; (3) an inactivated vaccine; and (4) the same inactivated vaccine with an o/w adjuvant. Subsequently, we challenged pigs with virulent pseudorabies virus (PRV). We demonstrated that best-protected pigs stood out by maintaining strong T cell-mediated immune (CMI) responses after challenge. Of the immune parameters tested, protection against virus shedding was correlated best with the magnitude of the IFN-gamma-response of in vitro re-stimulated peripheral blood mononuclear cells (PBMC) with an additional role for PRV-specific IgG2 antibodies. The use of an o/w adjuvant resulted in higher antibody and CMI responses, in particular with an increased frequency of memory T helper blast cells of in vitro re-stimulated PBMC. However, this adjuvant-induced enhancement of the immune response had a limited additional effect on the efficacy of inactivated vaccines. This study suggests a major contribution of the CMI response in early protection against PRV infection and that PRV-induced IFN-gamma responses may serve as a suitable indicator for assessing the immune status of vaccinated pigs. (C) 2004 Elsevier B.V. All rights reserved.
    From phage display to plant expression: Fulfilling prerequisites for chicken oral immunotherapy against coccidiosis
    Wieland, W.H. - \ 2004
    Wageningen University. Promotor(en): Martin Verstegen, co-promotor(en): Arjen Schots; D.V. Orzaéz Calatayud. - Wageningen : S.n. - ISBN 9789085040736 - 132
    kippen - coccidiose - immunotherapie - iga - antilichamen - transgene planten - biotechnologie - immunisatie - immuniteit - immunologie - fowls - coccidiosis - immunotherapy - iga - antibodies - transgenic plants - biotechnology - immunization - immunity - immunology
    The frequency and spectrum of infections with pathogens harbouring resistance to antibiotics and other drugs has dramatically increased over the last years. One of the main causes is the extensive use of antibiotics and other drugs in human and veterinary medicine. Parasites, such as Eimeria causing coccidiosis in chicken and pathogenic bacteria like Salmonellae and Campylobacter are examples of pathogens that acquired resistance. Furthermore, continuous use of drugs in diets of animals kept for human consumption increases the risk of residues in food, that possibly affect human health. These drawbacks of antimicrobial drugs have led to a demand for alternative treatments. In this thesis an alternative approach for prevention of coccidiosis in chicken is described, based on immune intervention by passively administered, plant produced, secretory IgA.As a first step, Eimeria binding IgA fragments were selected using the phage display technique. The phage display system was adapted to be used for the display of chicken Fab fragments. A newly constructed vector, named pChick3, allows straightforward cloning of chicken variable antibody domains in frame with the constant domains of the chicken light chain and the first constant domain of the IgA heavy chain. In a following step, new plant expression vectors were designed and constructed. Ten antibodies, selected from the chicken phage antibody library were then transferred to this vector system and subsequently expressed in planta as full size IgA. Upon expression of the ten selected anti- Eimeria antibodies, differences up to 500-fold in yield were observed. Several factors on translational or protein level could cause the observed differences: e.g. processing, stability, assembly and silencing. Two were tested (silencing, chain compatibility i.e. assembly) and both have an influence on the levels of expression. An explanation may be found in the combination of several factors. These observations lead to the conclusion that an extra in planta selection step is inevitable for successful integration of phage display and plant expression systems. Finally, the structure of the chicken polymeric immunoglobulin receptor was elucidated. In a fashion similar to its mammalian counterpart, this receptor transports IgA to the gut lumen forming secretory IgA. This complex is highly stable, and IgA is protected against degradation by proteases or pH-fluctuation, which makes secretory IgA the most suitable form for passive immunization. Interestingly, the chicken SC comprises only four immunoglobulin-like domains compared to five found in mammals. Thus, an integrated system for both selection and expression of immunoglobulins was developed and with the final achievement of the production of Eimeria -specific secretory IgA in plants, the prerequisites for chicken passive immune therapy were fulfilled.
    Transmission of bovine herpesvirus 1 within and between herds on an island with a BHV1 control programme
    Hage, J.J. ; Schukken, Y.H. ; Schols, H. ; Maris-Veldhuis, M.A. ; Rijsewijk, F.A.M. ; Klaassen, C.H.L. - \ 2003
    Epidemiology and Infection 130 (2003)3. - ISSN 0950-2688 - p. 541 - 552.
    rhinotracheitis virus - infectious-diseases - marker vaccine - risk-factors - dairy farms - calves - immunity - type-1 - reactivation - immunization
    Transmission of bovine herpesvirus 1 (BHV1) within and between herds was studied on the island of Ameland, The Netherlands. There were 50 herds with 3300 head of cattle on the island. Herds were divided into three groups: (1) only containing seronegative cattle, (2) containing seronegative cattle and vaccinated seropositive cattle, and (3) containing only vaccinated cattle. All 23 herds in groups 1 and 2 were monitored. Three major outbreaks of BHV1 infections were observed due to the introduction of infectious cattle. Another major outbreak was most likely induced by reactivation of latent BHV1 in seropositive cattle. The basic reproduction ratio within these herds was estimated at least 4. Only one of these outbreaks led to three secondary outbreaks in susceptible herds in which all cattle were seronegative. These outbreaks were most likely due to respectively, direct animal contact, human transmission, and aerogenic transmission. The basic reproduction ratio between herds in this study was estimated to be 0(.)6.
    Seroepidemiology of diphtheria, tetanus, poliomyelitis and pertussis : evaluation of the national immunisation programme in the Netherlands
    Melker, H. de - \ 1999
    Agricultural University. Promotor(en): D. Kromhout; M.A.E. Conyn-van Spaendonck; J.F.P. Schellekens. - S.l. : S.n. - ISBN 9789058081285 - 205
    immunisatie - serologische overzichten - difterie - tetanus - poliomyelitis - kinkhoest - nederland - immunization - serological surveys - diphtheria - tetanus - poliomyelitis - pertussis - netherlands

    In view of the evaluation of the National Immunisation Programme in the Netherlands the main objectives were to obtain insight into the immunity to diphtheria, tetanus and poliomyelitis, into the occurrence of pertussis and to improve serodiagnosis of pertussis.

    In a population-based nationwide sampling, 8359 sera (response 55%) were collected, and to gain access to orthodox reformed individuals refusing vaccination, in a sample from municipalities with low vaccine coverage 1589 sera (response 52.5%). In the nationwide sample, the prevalence of diphtheria and tetanus antibodies (≥0.01 IU/ml in toxin inhibition assay) was 88% and 84%, resp. In at least 90% antibodies (titre≥1:8 in neutralisation assay) against poliovirus types 1, 2 and 3 were measured. For those born after mass vaccination was introduced (<45 years) the prevalence of antibodies to diphtheria, tetanus, poliovirus types 1 and 2 was at least 92.5% and for poliovirus type 3 at least 80%. Diphtheria and tetanus antibodies decreased with age for those born before vaccination was introduced (≥45 years). Only 40% of orthodox reformed individuals had diphtheria and 60% had tetanus antibodies. Less than 70% had poliovirus type 1, 2 and/or 3 antibodies. We concluded that the Dutch immunisation programme induced long-term diphtheria, tetanus and poliomyelitis immunity. While adults are very well protected against poliomyelitis, a great number of adults lack diphtheria or tetanus antitoxin antibodies. These adults might benefit from diphtheria (re)vaccination; however, offering a primary tetanus vaccination to cohorts born before the introduction of vaccination would probably be more effective than routine revaccination. Introduction of C. diphtheriae or poliovirus in socio-geographically clustered orthodox reformed groups might constitute a danger of spread of these pathogens.

    Pertussis surveillance data from notifications, positive serology and hospital admissions (1976-98) showed a sudden increase in the number of pertussis cases in 1996-97. According to notifications and serology data, the increase among, mostly unvaccinated, children less than 1 year was similar to the increase in hospital admissions. For older, mostly vaccinated, individuals the increase in hospital admissions was relatively small. The increase of reported vaccinated patients of all ages was higher than for unvaccinated patients. We postulated that the proportion of pertussis infections resulting in recognizable symptoms has increased among vaccinated individuals due to a mismatch of the vaccine strain and circulating B. pertussis strains.

    To investigate at which level IgG antibodies against pertussis toxin (IgG-PT) in a single serum sample are indicative for recent pertussis, IgG-PT was analysed in 7756 population-based sera, in sera of 3491 patients with at least a fourfold IgG-PT increase, in paired sera of 89 patients with positive cultures or polymerase chain reactions and in sera of 57 pertussis patients with a median follow-up of 1.4 years. IgG-PT levels of at least 100 U/ml were present in less than 1% of the population, are reached by most pertussis patients within 4 weeks after disease onset and persist only temporarily. We concluded that such levels are diagnostic for recent or actual infection with B. pertussis .

    Our results not only show that childhood vaccination should be sustained, but that adult vaccination could be considered. We have to anticipate long-term effects of mass vaccination, such as gaps in immunity as a result of decreased circulation of the pathogens and waning immunity. Epidemiological studies directed towards evaluation of vaccination should continue to provide a scientific basis for vaccination strategy.

    Besmettelijke dierziekten: geintegreerd aanpakken
    Hanekamp, W. ; Snoep, J. - \ 1998
    Praktijkonderzoek Rundvee, Schapen en Paarden. Praktijkonderzoek 11 (1998)4. - ISSN 1386-8470 - p. 25 - 29.
    diergeneeskunde - melkvee - melkveehouderij - infectieziekten - vaccinatie - immunisatie - immunotherapie - vaccins - preventieve geneeskunde - ziektepreventie - preventie - diergezondheid - hygiëne - ziekteoverdracht - dieren - zoönosen - veterinary science - dairy cattle - dairy farming - infectious diseases - vaccination - immunization - immunotherapy - vaccines - preventive medicine - disease prevention - prevention - animal health - hygiene - disease transmission - animals - zoonoses
    Omdat het dier de belangrijkste besmettingsbron is, is aankoop van vee een grote risicofactor en dienen mensen die veel in contact komen met dieren bedrijfskleding aan te trekken.
    Immunological aspects of oral vaccination in fish
    Joosten, P.H.M. - \ 1997
    Agricultural University. Promotor(en): W.B. van Muiswinkel; J.H.W.M. Rombout. - S.l. : Joosten - ISBN 9789054856986 - 134
    vissen - diergeneeskunde - vaccinatie - immunisatie - immunotherapie - vaccins - geneesmiddelen - farmacologie - toedieningswijzen - reticulo-endotheliaal systeem - antilichamen - immunoglobulinen - immunologische technieken - elisa - immunochemie - fishes - veterinary science - vaccination - immunization - immunotherapy - vaccines - drugs - pharmacology - application methods - reticuloendothelial system - antibodies - immunoglobulins - immunological techniques - elisa - immunochemistry

    In this thesis immunological consequences of oral vaccination in fish have been described. The efficacy of oral vaccination can be increased by protection of the antigen against degradation in the foregut, in order to reach the hindgut in sufficient quantities for uptake and subsequent activation of the mucosal and systemic immune system. Using a specific monoclonal antibody, in addition to mucosal B cells, a distinct mucosal T cell population was demonstrated, which may play an important role in local immunity. Furthermore, two approaches to protect antigens against digestive degradation are described: bioencapsulation and microencapsulation. For the first approach antigen is encapsulated in living food, and subsequently fed to juvenile carp and seabream. In carp, oral vaccination at 2 and 4 weeks old resulted in immunological tolerance. However, in older carp (8 weeks old) and seabream (8 and 10 weeks old), immunological memory was induced. It can be concluded that oral vaccination with bioencapsulated bacterial antigens is effective for oral vaccination of juvenile fish, when applied at the right age. For microencapsulation an alginate microparticle system was studied, which may be more suitable for vaccination of older fish. The supernatant appeared to be the most immunogenic fraction of a bacterin, which is taken up in the hindgut and evokes best memory formation. This fraction was encapsulated in alginate microparticles and fed to adult carp and trout. Different microparticle preparations, with respect to release time and antigen concentration, were needed for immunological memory formation in each fish species. Therefore, oral vaccination with bacterial antigens in alginate microparticles can be effective. Oral tolerance against protein antigens was demonstrated in animals fed with ferritin or recombinant VHS G protein. However, the immune response to ovalbumin appeared to be carp strain dependent. A carp strain that produced specific antibodies after injection with OVA was selected and repeated feeding of OVA, prior to injection, resulted in increased antibody titres in serum. Oral tolerance induction in fish therefore appeared to depend on the protein and possibly also on genetic factors.

    Computer simulation to support policy-making in Aujeszky's disease control
    Buijtels, J.A.A.M. - \ 1997
    Agricultural University. Promotor(en): A.A. Dijkhuizen; R.B.M. Huirne; M.C.M. de Jong. - S.l. : Buijtels - ISBN 9789054856528 - 187
    ziekte van marek - ziekte van aujeszky - varkens - diergeneeskunde - vaccinatie - immunisatie - immunotherapie - vaccins - investering - kosten-batenanalyse - economische evaluatie - computersimulatie - simulatie - simulatiemodellen - dynamisch programmeren - markov-processen - economie - gebruikswaarde - economische impact - nederland - marek's disease - aujeszky's disease - pigs - veterinary science - vaccination - immunization - immunotherapy - vaccines - investment - cost benefit analysis - economic evaluation - computer simulation - simulation - simulation models - dynamic programming - markov processes - economics - use value - economic impact - netherlands

    Aujeszky's disease is a contagious viral disease that affects the central nervous system of pigs. Several eradication programs or measures are available, each of them providing different results. Determining the preferred strategy is to a large extent a matter of economic consideration.

    Under the EU rules, countries or regions that are Aujeszky-free can ban imports of breeding animals carrying antibodies of the disease; movements to Aujeszky-free areas from other areas of both breeding and rearing pigs are subject to strict conditions and controls, which differ depending on whether or not the area of origin has an EU-approved eradication program. If important import destinations achieve disease-free status, exporting countries that have failed to eradicate the disease will be severely penalized. Therefore, sterner demands are to be expected considering control and eradication of Aujeszky's disease in the Netherlands in the future. To meet these demands, the objective of this study was to develop a computer simulation environment in which "what-if' scenarios can be performed to explore the epidemiological and economic effects of different Aujeszky's disease control programs. The model can be used to support the choice of the optimal eradication program under various conditions, in particular from an epidemiological and economic point of view.

    First, a flexible economic framework to evaluate Aujeszky's disease eradication programs was developed, and illustrated with an example (Chapter 2). The framework has four elements: changes in percentage of infectious herds, changes in product quantities, changes in product prices and economic integration. Each of these elements is defined as a separate module in the simulation model and has its own input and output data, depending on the control strategy under consideration. With these elements all epidemiological and economic aspects of the disease can be monitored over time.

    In an illustrative example, probability distributions of the number of infectious herds corresponding to each control strategy were compared and the optimal strategy was chosen, according to the risk attitude of the decision maker. The framework can be considered a standardized approach in comparing and selecting animal health control strategies by integrating technical and economic data and principles.

    To obtain epidemiological information with respect to the control of Aujeszky's disease virus, an epidemiological state-transition simulation model was constructed to evaluate the spread of the virus (Chapter 3). In the model, the population of herds in the Netherlands is subdivided into four herd types: great-grandparent stock+multiplier, rearing, farrowing and fattening. Every time step, each herd is in one of 32 states per herd type. The states are based on (1) the reproduction ratio R ind , which is the number of individuals infected by one infectious individual, (2) the prevalence for each value of R ind and (3) the expected number of infectious animals in an infectious herd within each prevalence range of the herds. The different values Of R ind are based as much as possible on field data and experiments, where different vaccination strategies were applied.

    The transition matrix with the probabilities of every possible transition from one state to another was calculated on a weekly base. With this matrix the distribution of herds over states from week to week was derived. To include the non-linearity of the transmission process, the transmission probabilities from non-infectious to either non-infectious or infectious were developed such that they depend on the state vector itself The fraction of herds that becomes infectious equals one minus the fraction of herds that has not been infected by the virus emitted by infectious herds.

    Calculations revealed that infection in the Dutch pig population would not disappear without vaccination, nor with a vaccination scheme in which sows were vaccinated less than 3 times per year and fattening pigs once per cycle (Chapter 4). The infection, however, would be eradicated within 2 to 3 years, if sows were vaccinated 3 or 4 times per year and fattening pigs twice per cycle. The outcome turned out to be sensitive to the impact of other than animal contacts on the number of new effective virus introductions per time unit.

    The structure of the production pyramid and herd density in the affected regions were other important factors which influenced the course of infection. To examine the impact of these factors the total number of herds in the Netherlands were further subdivided into four regions (North, East, West-Middle, South).

    Outcomes showed that the percentage of infectious herds in equilibrium was highest for rearing herds (76.3%) and lowest for great-grandparent stock+multiplier herds (20.0%) if no vaccination was done. The herd type "fattening" had more impact on the effectivity of the different vaccination strategies than the herd type "farrowing". This difference is becoming less if more intensive vaccination strategies are applied. Besides the difference in herd type, also herd density and the percentage of non-vaccinated herds were an important factor in the eradication process.

    After simulating these epidemiological characteristics of Aujeszky's disease virus, market outcomes and pig producers' returns were simulated under different scenarios with respect to closure of export markets for live piglets and fattened pigs (Chapter 5). If the Netherlands fails to eradicate Aujeszky's disease before its trading partners in these markets, live piglet exports would be banned, reducing industry revenue and export earnings by about 9% and 10% respectively in the medium term. If exports of live fattened pigs are also banned, the reductions are 26 and 32% respectively. The piglet-producing sector would be more
    severely affected than the fattening sector. The model also showed that, if export markets for carcasses were also to close for an unspecified food safety reason, capacity of the industry would fall over 50%.

    Lastly four control strategies to eradicate Aujeszky's disease virus in the Netherlands were compared epidemiologically and economically (Chapter 6). Vaccination decreased the number of cases per production loss. The decrease was largest if vaccination strategy changed from "no vaccination" to the less intensive vaccination. Extra vaccinations under more intensive vaccination strategies, however, still had impact. The attendant costs were highest per dead animal (especially for gilts) and per abortion. Growth delay of gilts and piglets turned out to be of minor importance.

    The sales distribution on the piglet markets (import, export and on the domestic markets) was particularly influenced by vaccination, but the decreases in revenues were only less than 4.3%. The only exception was the number of piglets and live animals that were imported into the Netherlands, which decreased by more than 15% and about 9% respectively. The accompanying revenues from piglets and fattened pigs were highest if "no vaccination" was done. Compared with the revenue in this strategy, this difference is greatest on the piglet market, as the decrease in revenue was about 3.6%, while the decrease was about 0.55% on the market of fattened pigs.

    According to the resulting present values over a period of 10 years, "no vaccination" is economically the best solution only if no trade restrictions are to be expected. Economically speaking, however, the most intensive vaccination strategy should be applied, if an export ban of two years on live animals to, for instance, Germany is expected within 10 years after the start of the vaccination strategy. A prolonged export ban makes this strategy even more favourable. From an economic point of view intermediate vaccination strategies are never preferred.

    The main conclusions of this thesis are:
    - State-transition simulation proves to be an appropriate method to evaluate transmission of Aujeszky's disease virus. The epidemiological information obtained can well be used in economic evaluation of different control strategies.
    - Aujeszky's disease is only eradicated in the Netherlands if the most intensive vaccination strategy (≥3 times per year) is applied for breeding sows, and fattening pigs are vaccinated at least once per cycle.
    - If applying the most intensive vaccination strategy, it takes about 200 weeks for an average herd to become non-infectious.
    - The relative impact of other than animal contacts on the number of new virus introductions increases from 4% to 98%, if the vaccination strategy is changed from "no vaccination" to the most intensive vaccination program.
    - Subdivision of the total population into herd types and regions is important to enhance insight into transmission of infection in the pig population and to support decision making at regional level.
    - Price equilibrium models can well estimate the short-term changes in prices as well as those in the medium term. To accomplish this, it is of importance that sufficient historical data about quantities, prices and the infections occurred are available to estimate the required parameters accurately. A monthly data-set of about 10 years turned out to be sufficient.
    - Direct production losses from Aujeszky's disease virus are less than 6% of the vaccination costs when vaccination is carried out. More than 80% of these losses are caused by growth delay of fattening pigs.
    - The most intensive vaccination strategy (i.e., sows are vaccinated 3 or 4 times per year and fattening and rearing pigs twice per cycle) is economically preferred if an export ban on part of the live animals is expected during at least 2 years within 10 years after the start of the vaccination program. If this is not to be expected then "no vaccination" turns out to be the best strategy. The risk of an export ban on live animals should justify the eradication of the virus from the population.
    - For the current situation in the Netherlands it is economically preferred to start blood sampling all sows and remove the gE-positive animals instead of continuing vaccination, provided that the additional risk of new introductions of the virus is sufficiently limited.

    Introductie van virusresistentie in lelie door middel van genetische modificatie : eindverslag van het project 'Inbouw van virusresistentie in lelies via genetische manipulatie'
    Langeveld, S.A. ; Bol, J.F. ; Boonekamp, P.M. - \ 1996
    Lisse : Laboratorium voor Bloembollenonderzoek (Urgentieprogramma Bollenziekte- en veredelingsonderzoek ) - 19
    plantenziekten - plantenvirussen - bloembollen - plantenveredeling - ziekteresistentie - plaagresistentie - genetische modificatie - recombinant dna - planten - immunisatie - geïnduceerde resistentie - onderzoek - lilium - plant diseases - plant viruses - ornamental bulbs - plant breeding - disease resistance - pest resistance - genetic engineering - plants - immunization - induced resistance - research
    Effect van moment van vlekziektevaccinatie op het interval spenen-bronst
    Riel, J. van; Vesseur, P. - \ 1996
    Praktijkonderzoek varkenshouderij 10 (1996)2. - ISSN 1382-0346 - p. 5 - 5.
    erysipelothrix - vruchtbaarheid - immunisatie - immunotherapie - infectieziekten - oestrus - biggen - zeugen - vaccinatie - vaccins - diergeneeskunde - spenen - erysipelothrix - fertility - immunization - immunotherapy - infectious diseases - oestrus - piglets - sows - vaccination - vaccines - veterinary science - weaning
    In de praktijk zijn er vragen over de gevolgen van vlekziektevaccinaties voor de vruchtbaarheid. Een oriënterende studie heeft aanwijzingen opgeleverd dat enten in de eerste week van de lactatie een negatieve invloed heeft op het interval spenen-bronst.
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