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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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
Estimation of the transmission of foot-and-mouth disease virus from infected sheep to cattle
Bravo De Rueda, C. ; Jong, M.C.M. de; Eble, P.L. ; Dekker, A. - \ 2014
Veterinary Research 45 (2014). - ISSN 0928-4249 - 11 p.
between-pen transmission - basic reproduction ratio - swine-fever virus - emergency vaccination - subclinical infection - within-pen - pigs - quantification - excretion - epidemic
The quantitative role of sheep in the transmission of foot-and-mouth disease virus (FMDV) is not well known. To estimate the role of sheep in the transmission of FMDV, a direct contact transmission experiment with 10 groups of animals each consisting of 2 infected lambs and 1 contact calf was performed. Secretions and excretions (oral swabs, blood, urine, faeces and probang samples) from all animals were tested for the presence of FMDV by virus isolation (VI) and/or RT-PCR. Serum was tested for the presence of antibodies against FMDV. To estimate FMDV transmission, the VI, RT-PCR and serology results were used. The partial reproduction ratio R0 p i.e. the average number of new infections caused by one infected sheep introduced into a population of susceptible cattle, was estimated using either data of the whole infection chain of the experimental epidemics (the transient state method) or the final sizes of the experimental epidemics (the final size method). Using the transient state method, R0 p was estimated as 1.0 (95% CI 0.2 - 6.0) using virus isolation results and 1.4 (95% CI 0.3 - 8.0) using RT-PCR results. Using the final size method, R0 p was estimated as 0.9 (95% CI 0.2 - 3.0). Finally, R0 p was compared to the R0’s obtained in previous transmission studies with sheep or cattle only. This comparison showed that the infectivity of sheep is lower than that of cattle and that sheep and cattle are similarly susceptible to FMD. These results indicate that in a mixed population of sheep and cattle, sheep play a more limited role in the transmission of FMDV than cattle.
Epidemic Threats to the European Union: Expert Views on Six Virus Groups
Kelly, L. ; Brouwer, A. ; Wilson, A. ; Gale, P. ; Snary, E. ; Ross, D. ; Vos, C.J. de - \ 2013
Transboundary and Emerging Diseases 60 (2013)4. - ISSN 1865-1674 - p. 360 - 369.
swine-fever virus - mouth-disease - risk - impact
In recent years, several animal disease epidemics have occurred within the European Union (EU). At the 4th Annual Meeting of the EPIZONE network (7-10 June 2010, St. Malo, France), an interactive session was run to elicit the opinions of delegates on a pre-defined list of epidemic threats to the EU. Responses from over 190 delegates, to questions relating to impact and likelihood, were used to rank six virus groups with respect to their perceived threat now (2010) and in 2020. The combined opinions of all delegates suggested that, from the pre-selected list of virus groups, foot-and-mouth disease and influenza are currently of most concern. Delegates thought that influenza would be less of a threat and zoonotic arboviruses would be more of a threat in 2020. Although the virus group rankings should not be taken as definitive, the results could be used in conjunction with experimental and field data, by scientists, policy-makers and stakeholders when assessing and managing risks associated with these virus groups.
Preliminary mapping of non-conserved epitopes on envelope glycoprotein E2 of bovine viral diarrhea virus type 1 and 2
Jelsma, H. ; Loeffen, W.L.A. ; Beuningen, A.R. van; Rijn, P.A. van - \ 2013
Veterinary Microbiology 166 (2013)1-2. - ISSN 0378-1135 - p. 195 - 199.
swine-fever virus - random peptide library - hog-cholera virus - b-cell epitope - monoclonal-antibodies - strain brescia - vaccines - protein - identification - neutralization
Bovine viral diarrhea virus (BVDV) belongs together with Classical swine fever virus (CSFV) and Border disease virus (BDV) to the genus Pestivirus in the Flaviviridae family. BVDV has been subdivided into two different species, BVDV1 and BVDV2 based on phylogenetic analysis. Subsequent characterization of both strains revealed major antigenic differences. Because the envelope glycoprotein E2 is the most immunodominant protein for all pestiviruses, the present study focused on epitope mapping by constructing chimeric BVDV type 1 and 2 E2 genes in expression plasmids. These plasmids with chimeric E2-genes were transfected in SK6 cells and transient expression was studied by immunostaining with a panel of MAbs specific for E2 of BVDV1 or BVDV2, resulting in the localization of type-specific antigenic domains at similar regions. These results indicate that E2 glycoproteins of both BVDV types exhibit a comparable antigenic structure, but with type specific epitopes. In addition, the antigenic resemblance with envelope glycoprotein E2 of Classical swine fever virus is discussed.
Acidification of drinking water inhibits indirect transmission, but not direct transmission of Campylobacter between broilers
Bunnik, B.A.D. van; Katsma, W.E.A. ; Wagenaar, J.A. ; Jacobs-Reitsma, W.F. ; Jong, M.C.M. de - \ 2012
Preventive Veterinary Medicine 105 (2012)4. - ISSN 0167-5877 - p. 315 - 319.
swine-fever virus - reduces susceptibility - salmonella-enteritidis - feed - jejuni - chickens - risk
In this study the effect of acidification of the drinking water of broiler chickens on both direct and indirect transmission of Campylobacter was evaluated. In the direct transmission experiment both susceptible and inoculated animals were housed together. In the indirect transmission experiment the susceptible animals were spatially separated from the inoculated animals and no direct animal to animal contact was possible. The transmission parameter ß was estimated for the groups supplied with acidified drinking water and for the control groups. The results showed that acidification of the drinking water had no effect on direct transmission (ß=3.7 day(-1) for both control and treatment). Indirect transmission however was influenced by acidification of the drinking water. A significant decrease in transmission was observed (p
Modelling the wind-borne spread of highly pathogenic avian influenza virus between farms
Ssematimba, A. ; Hagenaars, T.H.J. ; Jong, M. de - \ 2012
PLoS ONE 7 (2012)2. - ISSN 1932-6203
mouth-disease virus - swine-fever virus - livestock buildings - commercial poultry - airborne spread - great-britain - risk-factors - a virus - epidemic - foot
A quantitative understanding of the spread of contaminated farm dust between locations is a prerequisite for obtaining much-needed insight into one of the possible mechanisms of disease spread between farms. Here, we develop a model to calculate the quantity of contaminated farm-dust particles deposited at various locations downwind of a source farm and apply the model to assess the possible contribution of the wind-borne route to the transmission of Highly Pathogenic Avian Influenza virus (HPAI) during the 2003 epidemic in the Netherlands. The model is obtained from a Gaussian Plume Model by incorporating the dust deposition process, pathogen decay, and a model for the infection process on exposed farms. Using poultry- and avian influenza-specific parameter values we calculate the distance-dependent probability of between-farm transmission by this route. A comparison between the transmission risk pattern predicted by the model and the pattern observed during the 2003 epidemic reveals that the wind-borne route alone is insufficient to explain the observations although it could contribute substantially to the spread over short distance ranges, for example, explaining 24% of the transmission over distances up to 25 km.
Interaction effects between sender and receiver processes in indirect transmission of Campylobacter jejuni between broilers.
Bunnik, B.A.D. van; Hagenaars, T.H.J. ; Bolder, N.M. ; Nodelijk, G. ; Jong, M.C.M. de - \ 2012
BMC Veterinary Research 8 (2012). - ISSN 1746-6148
swine-fever virus - drinking-water - netherlands - epidemic - quantification - salmonella - resistance - bacteria - evaluate - design
Background: Infectious diseases in plants, animals and humans are often transmitted indirectly between hosts (or between groups of hosts), i.e. via some route through the environment instead of via direct contacts between these hosts. Here we study indirect transmission experimentally, using transmission of Campylobacter jejuni (C. jejuni) between spatially separated broilers as a model system. We distinguish three stages in the process of indirect transmission; (1) an infectious "sender" excretes the agent, after which (2) the agent is transported via some route to a susceptible "receiver", and subsequently (3) the receiver becomes colonised by the agent. The role of the sender and receiver side (stage 1 and stage 3) was studied here by using acidification of the drinking water as a modulation mechanism. Results: In the experiment one control group and three treatment groups were monitored for the presence of C. jejuni by taking daily cloacal swabs. The three treatments consisted of acidification of the drinking water of the inoculated animals (the senders), acidification of the drinking water of the susceptible animals (the receivers) or acidification of the drinking water of both inoculated and susceptible animals. In the control group 12 animals got colonised out of a possible 40, in each treatment groups 3 animals out of a possible 40 were found colonised with C. jejuni. Conclusions: The results of the experiments show a significant decrease in transmission rate (beta) between the control groups and treatment groups (p <0.01 for all groups) but not between different treatments; there is a significant negative interaction effect when both the sender and the receiver group receive acidified drinking water (p = 0.01). This negative interaction effect could be due to selection of bacteria already at the sender side thereby diminishing the effect of acidification at the receiver side.
Low Temperature-Dependent Salmonid Alphavirus Glycoprotein Processing and Recombinant Virus-Like Particle Formation
Metz, S.W.H. ; Feenstra, F. ; Villoing, S. ; Hulten, M.C. van; Lent, J.W.M. van; Koumans, J. ; Vlak, J.M. ; Pijlman, G.P. - \ 2011
PLoS ONE 6 (2011)10. - ISSN 1932-6203 - 10 p.
semliki-forest-virus - equine encephalitis-virus - nuclear polyhedrosis-virus - swine-fever virus - pancreas disease - atlantic salmon - spodoptera-frugiperda - nucleocapsid protein - baculovirus vectors - sleeping-disease
Pancreas disease (PD) and sleeping disease (SD) are important viral scourges in aquaculture of Atlantic salmon and rainbow trout. The etiological agent of PD and SD is salmonid alphavirus (SAV), an unusual member of the Togaviridae (genus Alphavirus). SAV replicates at lower temperatures in fish. Outbreaks of SAV are associated with large economic losses of ~17 to 50 million $/year. Current control strategies rely on vaccination with inactivated virus formulations that are cumbersome to obtain and have intrinsic safety risks. In this research we were able to obtain non-infectious virus-like particles (VLPs) of SAV via expression of recombinant baculoviruses encoding SAV capsid protein and two major immunodominant viral glycoproteins, E1 and E2 in Spodoptera frugiperda Sf9 insect cells. However, this was only achieved when a temperature shift from 27°C to lower temperatures was applied. At 27°C, precursor E2 (PE2) was misfolded and not processed by host furin into mature E2. Hence, E2 was detected neither on the surface of infected cells nor as VLPs in the culture fluid. However, when temperatures during protein expression were lowered, PE2 was processed into mature E2 in a temperature-dependent manner and VLPs were abundantly produced. So, temperature shift-down during synthesis is a prerequisite for correct SAV glycoprotein processing and recombinant VLP production
Opportunities and challenges for the baculovirus expression system
Oers, M.M. van - \ 2011
Journal of Invertebrate Pathology 107 (2011)Suppl.. - ISSN 0022-2011 - p. S3 - S15.
nuclear polyhedrosis-virus - envelope fusion protein - infected insect cells - swine-fever virus - occlusion-derived virus - n-linked glycosylation - escherichia-coli - endoplasmic-reticulum - surface display - recombinant baculoviruses
In this review background information on the baculovirus-insect cell expression system and its applications for producing protein subunits and virus-like particles for vaccine and other purposes is provided. This review will illustrate the principle structure of baculovirus vectors commonly used for heterologous gene expression in insect cells and describe adaptations that have been made over the last 10 years to improve the system in terms of quality of the protein produced and stability of the baculovirus genome. These improvements include enhanced trafficking, folding and glycosylation of the recombinant protein as well as preventing intracellular degradation. Challenges and progress in stabilizing the baculovirus genome in order not to lose the transgene cassette will also be discussed. Recent developments such as how to make multiple alterations in the baculovirus genome without accumulating marker genes are included
Virus inactivation by salt (NaCl) and phosphate supplemented salt in a 3D collagen matrix model for natural sausage casings
Wieringa-Jelsma, H. ; Wijnker, J.J. ; Zijlstra-Willems, E.M. ; Dekker, A. ; Stockhofe-Zurwieden, N. ; Maas, R. ; Wisselink, H.J. - \ 2011
International Journal of Food Microbiology 148 (2011)2. - ISSN 0168-1605 - p. 128 - 134.
swine-fever virus - complete nucleotide-sequence - mouth-disease - mechanical-properties - vesicular disease - hog - pathogenesis - intestines - diagnosis - pigs
Due to possible presence and spread of contagious animal viruses via natural sausage casings the international trade in these food products is subject to veterinary and public health requirements. In order to manage these restrictions we determined the effect of casing preservation on four highly contagious viruses for livestock: foot-and-mouth-disease virus (FMDV), classical swine fever virus (CSFV), swine vesicular disease virus (SVDV) and African swine fever virus (ASFV). We used an in vitro 3D collagen matrix model in which cells, infected with the four different viruses were embedded in a bovine collagen type I gel matrix and treated with either saturated salt (NaCl) or phosphate supplemented saturated salt at four different temperatures (4, 12, 20 and 25 °C) during a period of 30 days. The results showed that all viruses were faster inactivated at higher temperatures, but that stability of the various viruses at 4 °C differed. Inactivation of FMDV in the 3D collagen matrix model showed a clear temperature and treatment effect on the reduction of FMDV titres. At 4 and 12 °C phosphate supplemented salt showed a very strong FMDV inactivation during the first hour of incubation. Salt (NaCl) only had a minor effect on FMDV inactivation. Phosphate supplemented salt treatment increased the effect temperature had on inactivation of CSFV. In contrast, the salt (NaCl) treatment only increased CSFV inactivation at the higher temperatures (20 °C and 25 °C). Also SVDV inactivation was increased by phosphate supplemented salt, but salt (NaCl) treatment only resulted in a significant decrease of SVDV titre at a few time points. The ASFV results showed that both salt (NaCl) and phosphate supplemented salt were capable to inactivate ASFV within 48 h. In contrast to the other viruses (FMDV, CSFV and SVDV), ASFV was the most stable virus even at higher temperatures. The results obtained in this in vitro model underline the efficacy of a combined treatment using phosphate supplemented salt and storage at 20 °C or higher for a period of 30 days. This treatment may therefore be useful in reducing the animal health risks posed by spread of contagious animal viruses by international trade of natural sausage casings
Functional processing and secretion of Chikungunya virus E1 and E2 glycoproteins in insect cells
Metz, S.W.H. ; Geertsema, C. ; Martina, Byron E. ; Andrade, Paulina ; Heldens, J. ; Oers, M.M. van; Goldbach, R.W. ; Vlak, J.M. ; Pijlman, G.P. - \ 2011
Virology journal 8 (2011). - ISSN 1743-422X - 12 p.
semliki-forest-virus - equine encephalitis-virus - envelope fusion protein - swine-fever virus - n-linked glycans - sindbis virus - structural proteins - baculovirus vectors - nucleotide-sequence - signal peptide
Background - Chikungunya virus (CHIKV) is a mosquito-borne, arthrogenic Alphavirus that causes large epidemics in Africa, South-East Asia and India. Recently, CHIKV has been transmitted to humans in Southern Europe by invading and now established Asian tiger mosquitoes. To study the processing of envelope proteins E1 and E2 and to develop a CHIKV subunit vaccine, C-terminally his-tagged E1 and E2 envelope glycoproteins were produced at high levels in insect cells with baculovirus vectors using their native signal peptides located in CHIKV 6K and E3, respectively. Results - Expression in the presence of either tunicamycin or furin inhibitor showed that a substantial portion of recombinant intracellular E1 and precursor E3E2 was glycosylated, but that a smaller fraction of E3E2 was processed by furin into mature E3 and E2. Deletion of the C-terminal transmembrane domains of E1 and E2 enabled secretion of furin-cleaved, fully processed E1 and E2 subunits, which could then be efficiently purified from cell culture fluid via metal affinity chromatography. Confocal laser scanning microscopy on living baculovirus-infected Sf21 cells revealed that full-length E1 and E2 translocated to the plasma membrane, suggesting similar posttranslational processing of E1 and E2, as in a natural CHIKV infection. Baculovirus-directed expression of E1 displayed fusogenic activity as concluded from syncytia formation. CHIKV-E2 was able to induce neutralizing antibodies in rabbits. Conclusions - Chikungunya virus glycoproteins could be functionally expressed at high levels in insect cells and are properly glycosylated and cleaved by furin. The ability of purified, secreted CHIKV-E2 to induce neutralizing antibodies in rabbits underscores the potential use of E2 in a subunit vaccine to prevent CHIKV infections.
The effect of inoculation dose of a highly pathogenic avian influenza virus strain H5N1 on the infectiousness of chickens
Spekreijse, D. ; Bouma, A. ; Stegeman, J.A. ; Koch, G. ; Jong, M.C.M. de - \ 2011
Veterinary Microbiology 147 (2011)1-2. - ISSN 0378-1135 - p. 59 - 66.
basic reproduction ratio - swine-fever virus - transmission experiments - pekin ducks - quantification - vaccination - epidemic - h7n7 - netherlands - diseases
Highly pathogenic avian influenza is of major concern for the poultry industry, as the virus can spread rapidly in and between flocks, causing high mortality and severe economic losses. The aim of this study was to determine the probability of infection and to determine dose-dependent virus transmission (direct transmission) for various inoculation doses. Two transmission experiments with pair-wise housed layer type chickens were performed, in which one bird per pair was inoculated with an HPAI H5N1 virus and the other contact-exposed. Various inoculation doses were used to determine the susceptibility (ID50), and possible relation between ID50, and infectiousness, expressed as the amount of virus shedding and the probability of contact birds becoming infected. The infectious H5N1 dose (CID50) in this study was an estimated 102.5 egg infectious dose (EID50). Increasing the dose increased the probability of infection but survival from infection was independent of dose. In addition, increasing the dose decreased the mean latent period in the inoculated chickens significantly. This could be important for determining the time of onset of infection in a flock and thus allowing more accurate identification of the source of infection. Moreover, the amount of virus shed in trachea and cloaca by the inoculated chickens in the time between inoculation and contact infection, also differed between the various dose groups. Despite differences in latent period and virus shedding, the transmission rate parameter ß and reproduction ratio R0 did not differ significantly between the various dose groups. This implies that in this experiment the amount of virus shedding is not a measure to predict transmission or the infectiousness of chickens.
No between-pen transmission of foot-and-mouth disease virus in vaccinated pigs
Roermund, H.J.W. van; Eblé, P.L. ; Jong, M.C.M. de; Dekker, A. - \ 2010
Vaccine 28 (2010)28. - ISSN 0264-410X - p. 4452 - 4461.
swine-fever virus - emergency vaccination - low virulence - within-pen - quantification - reduction - responses - fmdv - netherlands - protection
Many studies have shown transmission of foot-and-mouth disease virus (FMDV) within groups of pigs, even when vaccinated, but only limited information is available on transmission between pens. Three new experiments were carried out in two replicates, which consisted of infectious pigs housed in a central pen surrounded by four separate pens. First, all pigs were non-vaccinated and pens were separated by a walkway of 40-70 cm. Second, all pigs were non-vaccinated again but pens were adjacent. Third, this was repeated with all pigs vaccinated. From the experiments it is concluded that a single pen wall of solid wood between adjacent pens reduces the FMDV transmission 10- to 20-fold compared to within-pen transmission, for both non-vaccinated and for vaccinated pigs. Vaccination of pigs reduces the pen-to-adjacent pen R to values significantly below 1, whereas previous studies showed that it does not reduce the within-pen R(0) to values below 1
Multi Criteria Decision Making to evaluate control strategies of contagious animal diseases
Mourits, M.C.M. ; Asseldonk, M.A.P.M. van; Huirne, R.B.M. - \ 2010
Preventive Veterinary Medicine 96 (2010)3/4. - ISSN 0167-5877 - p. 201 - 210.
swine-fever virus - epidemic - netherlands - transmission
The decision on which strategy to use in the control of contagious animal diseases involves complex trade-offs between multiple objectives. This paper describes a Multi Criteria Decision Making (MCDM) application to illustrate its potential support to policy makers in choosing the control strategy that best meets all of the conflicting interests. The presented application focused on the evaluation of alternative strategies to control Classical Swine Fever (CSF) epidemics within the European Union (EU) according to the preferences of the European Chief Veterinary Officers (CVO). The performed analysis was centred on the three high-level objectives of epidemiology, economics and social ethics. The appraised control alternatives consisted of the EU compulsory control strategy, a pre-emptive slaughter strategy, a protective vaccination strategy and a suppressive vaccination strategy. Using averaged preference weights of the elicited CVOs, the preference ranking of the control alternatives was determined for six EU regions. The obtained results emphasized the need for EU region-specific control. Individual CVOs differed in their views on the relative importance of the various (sub)criteria by which the performance of the alternatives were judged. Nevertheless, the individual rankings of the control alternatives within a region appeared surprisingly similar. Based on the results of the described application it was concluded that the structuring feature of the MCDM technique provides a suitable tool in assisting the complex decision making process of controlling contagious animal diseases.
A meta-analysis quantifying transmission parameters of FMDV strain O Taiwan among non-vaccinated and vaccinated pigs
Eble, P.L. ; Koeijer, A.A. de; Jong, M.C.M. de; Engel, B. ; Dekker, A. - \ 2008
Preventive Veterinary Medicine 83 (2008)1. - ISSN 0167-5877 - p. 98 - 106.
basic reproduction ratio - mouth-disease outbreak - swine-fever virus - immune-responses - infection - strategies
Our aim was to provide additional estimates of main parameters for the transmission of foot-and-mouth disease virus (FMDV) strain O Taiwan (3/97). We used the data of previous experiments in non-vaccinated and vaccinated pigs and combined the data of experiments with the same treatment(s). First, we quantified the reproduction ratio R for the various groups using a final-size method. Our final-size results predicted that vaccination with a four-fold vaccine dose (but not with a single dose) at 1 week before inoculation (-7 dpi) would reduce R compared to the non-vaccinated group. Secondly, we used the daily results of virus excretion to quantify the transmission rate beta (by using generalized linear modelling), and the infectious period T(by using survival analysis). We used the estimates of and T to estimate R more precisely as compared to the final-size method and also for the groups for which a finite estimate could not be obtained using a final-size method. Our modelling results predicted that beta for non-vaccinated, for single-dose and four-fold-dose groups would be 6.1 (3.7, 10) day(-1), 2.0 (1.0,4.0) day(-1) and 0.4 (0.1, 1.4) day(-1), Tat 6.5 (5.7, 7.3), 5.3 (4.7, 6.0) and 2.3 (0.9, 5.7) days and R at 40 (21, 74), 11 (4.9, 24) and 1.0 (0. 1, 7.8), respecfively. These results predicted that both vaccination with a four-fold vaccine dose and with a single dose at -7 dpi would reduce beta, T and R significantly as compared to the non-vaccinated pigs, thereby showing that vaccination will reduce transmission of FMDV significantly already I week post vaccination. (C) 2007 Elsevier B.V. All rights reserved.
Comparing methods to quantify experimental transmission of infectious agents
Velthuis, A.G.J. ; Jong, M.C.M. de; Bree, J. de - \ 2007
Mathematical Biosciences 210 (2007)1. - ISSN 0025-5564 - p. 157 - 176.
swine-fever virus - basic reproduction ratio - pseudorabies virus - actinobacillus-pleuropneumoniae - pigs - vaccine - populations - quantification - excretion - immunity
Transmission of an infectious agent can be quantified from experimental data using the transient-state (TS) algorithm. The TS algorithm is based on the stochastic SIR model and provides a time-dependent probability distribution over the number of infected individuals during an epidemic, with no need for the experiment to end in final-size (e.g., where no more infections can occur). Because of numerical limitations, the application of the TS algorithm is limited to populations with only a few individuals. We investigated the error of using the easily applicable, time-independent final-size (FS) algorithm knowing that the FS situation was not reached. We conclude that the methods based on the FS algorithm: (i) underestimate R0, (ii) are liberal when testing H0:R0 1 against H1:R0 <1, (iii) are conservative when testing H0:R0 1 against H1:R0 > 1, and (iv) are conservative when testing H0:Rcontrol = Rtreatment against H1:Rcontrol > Rtreatment. Furthermore, a new method is presented to find a difference in transmission between two treatment groups (MaxDiff test). The MaxDiff test is compared to tests based on FS and TS algorithms. The TS test and the MaxDiff test were most powerful (approximately equally powerful) in finding a difference, whereas the FS test was less powerful (especially, when both Rcontrol and Rtreatment are >1).
Quantification of within- and between-pen transmission of Fouth-and-Mouth disease virus in pigs
Eble, P.L. ; Koeijer, A.A. de; Bouma, A. ; Stegeman, J.A. ; Dekker, A. - \ 2006
Veterinary Research 37 (2006)5. - ISSN 0928-4249 - p. 647 - 654.
swine-fever virus - experimental-infection - antibody-response - great-britain - vaccination - epidemic - impact - calves
Quantified transmission parameters of Foot-and-Mouth Disease Virus (FMDV) are needed for epidemic models used for control and surveillance. In this study, we quantified the within- and between-pen transmission of FMDV in groups of pigs by estimating the daily transmission rate , i.e. the number of secondary infections caused by one infectious pig during one day, using an SIR (susceptible-infectious-removed) model. Within-pen transmission was studied in four groups of ten pigs in which 5 infected and 5 susceptible pigs had direct contact; between-pen transmission was studied in one group of ten pigs in which 5 infected and 5 susceptible pigs had indirect contact. Daily results of virus isolation of oropharyngeal fluid were used to quantify the transmission rate , using Generalised Linear Modelling (GLM) and a maximum likelihood method. In addition, we estimated the expected time to infection of the first pig within a pen Tw and in the indirect-contact pen Tb. The between-pen transmission rate b was estimated to be 0.59 (0.083-4.18) per day, which was significantly lower than the within-pen transmission rate w of 6.14 (3.75-10.06). Tw was 1.6 h, and Tb was 16 h. Our results show that the transmission rate is influenced by contact structure between pigs.
Vaccines for viral and parasitic diseases produced with baculovirus vectors
Oers, M.M. van - \ 2006
Advances in Virus Research 68 (2006). - ISSN 0065-3527 - p. 193 - 253.
virus-like particles - respiratory syncytial virus - infectious bursal disease - swine-fever virus - nuclear polyhedrosis-virus - influenza-a virus - merozoite surface protein-1 - chimeric fg glycoprotein - parvovirus empty capsids - hemagglutinin-neuraminidase gl
The baculovirus¿insect cell expression system is an approved system for the production of viral antigens with vaccine potential for humans and animals and has been used for production of subunit vaccines against parasitic diseases as well. Many candidate subunit vaccines have been expressed in this system and immunization commonly led to protective immunity against pathogen challenge. The first vaccines produced in insect cells for animal use are now on the market. This chapter deals with the tailoring of the baculovirus¿insect cell expression system for vaccine production in terms of expression levels, integrity and immunogenicity of recombinant proteins, and baculovirus genome stability. Various expression strategies are discussed including chimeric, viruslike particles, baculovirus display of foreign antigens on budded virions or in occlusion bodies, and specialized baculovirus vectors with mammalian promoters that express the antigen in the immunized individual. A historical overview shows the wide variety of viral (glyco)proteins that have successfully been expressed in this system for vaccine purposes. The potential of this expression system for antiparasite vaccines is illustrated. The combination of subunit vaccines and marker tests, both based on antigens expressed in insect cells, provides a powerful tool to combat disease and to monitor infectious agents.
In silico identification of putative promoter motifs of White Spot syndrome virus
Marks, H. ; Ren, X.Y. ; Sandbrink, H. ; Hulten, M.C.W. van; Vlak, J.M. - \ 2006
BMC Bioinformatics 7 (2006)309. - ISSN 1471-2105 - 13 p.
swine-fever virus - nuclear polyhedrosis-virus - virion protein genes - transcriptional analysis - penaeus-monodon - structural proteins - proteomic analysis - genome sequence - shrimp - baculovirus
Background: White Spot Syndrome Virus, a member of the virus family Nimaviridae, is a large dsDNA virus infecting shrimp and other crustacean species. Although limited information is available on the mode of transcription, previous data suggest that WSSV gene expression occurs in a coordinated and cascaded fashion. To search in silico for conserved promoter motifs (i) the abundance of all 4 through 8 nucleotide motifs in the upstream sequences of WSSV genes relative to the complete genome was determined, and (ii) a MEME search was performed in the upstream sequences of either early or late WSSV genes, as assigned by microarray analysis. Both methods were validated by alignments of empirically determined 5' ends of various WSSV mRNAs. Results: The collective information shows that the upstream region of early WSSV genes, containing a TATA box and an initiator, is similar to Drosophila RNA polymerase II core promoter sequences, suggesting utilization of the cellular transcription machinery for generating early transcripts. The alignment of the 5' ends of known well-established late genes, including all major structural protein genes, identified a degenerate motif (ATNAC) which could be involved in WSSV late transcription. For these genes, only one contained a functional TATA box. However, almost half of the WSSV late genes, as previously assigned by microarray analysis, did contain a TATA box in their upstream region. Conclusion: The data may suggest the presence of two separate classes of late WSSV genes, one exploiting the cellular RNA polymerase II system for mRNA synthesis and the other generating messengers by a new virus-induced transcription mechanism
Detection of economically important viruses in boar semen by quantitative RealTime PCRtm technology
Rijn, P.A. van; Wellenberg, G.J. ; Hakze-van der Honing, R.W. van der; Jacobs, C.E. ; Moonen, P.L.J.M. ; Feitsma, H. - \ 2004
Journal of Virological Methods 120 (2004)2. - ISSN 0166-0934 - p. 151 - 160.
mouth-disease virus - linked-immunosorbent-assay - polymerase chain-reaction - swine-fever virus - respiratory syndrome - artificial-insemination - transmission
The objective of this study was to develop quantitative real-time polymerase chain reaction (ReTi-PCR) tests for the detection of five economically important viruses in swine semen namely, pseudorabies virus (PRV), classical swine fever virus (CSFV), foot-and-mouth disease virus (FMDV), swine vesicular disease virus (SVDV), and porcine reproductive and respiratory syndrome virus (PRRSV). Each ReTi-PCR test was validated for specificity, analytical sensitivity (detection limits), and experimental infection studies were performed to compare the conventional virus isolation methods with the newly developed ReTi-PCR tests. All five developed ReTi-PCR tests are very rapid compared to virus isolation, highly specific, and even more sensitive (lower detection limits) than conventional virus isolation methods for the detection of mentioned viruses in semen. In semen of experimentally infected boars, viruses were detected much earlier after infection and more frequently by ReTi-PCR tests than by virus isolations. The high throughput of these rapid ReTi-PCR tests makes it possible to screen large number of semen samples for the presence of viruses prior to insemination. This is a substantial advantage, in particular for boar semen the quality of which deteriorates quickly after storage. In general, the newly developed ReTi-PCR tests are valuable tools for the early, reliable and rapid detection of five economically important viruses, namely PRV, CSFV, FMDV, SVDV, and PRRSV in boar semen. These ReTi-PCR tests will improve the control of viral diseases transmitted via semen. (C) 2004 Elsevier B.V. All rights reserved.
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