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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    Quantification of different classical swine fever virus transmission routes within a single compartment
    Weesendorp, E. ; Backer, J. ; Loeffen, W.L.A. - \ 2014
    Veterinary Microbiology 174 (2014)3-4. - ISSN 0378-1135 - p. 353 - 361.
    between-pen transmission - within-pen - vaccination strategies - experimental-infection - airborne transmission - 1997-1998 epidemic - antibody-response - marker vaccine - low virulence - pigs
    During outbreaks of classical swine fever (CSF), CSF virus (CSFV) can be transmitted via different routes. Understanding these transmission routes is crucial in preventing the unlimited spread of the virus in a naïve population, and the subsequent eradication of the virus from that population. The objectives of the present study were to quantify virus transmission within a compartment, differentiating between transmission within a pen, transmission between pens via contact through (open) pen partitions, and transmission via the air. Furthermore, the possible contribution of each of these routes to infection of individual pigs was quantified. A CSFV outbreak was mimicked in a compartment housing 24 pigs in six different pens. Two pigs in one pen were inoculated with the moderately virulent Paderborn strain, and virus transmission to other pigs was followed in time. Virus transmission rates for transmission via the air (ß of 0.33 (0.14–0.64) per day) and transmission between adjacent pens (ß of 0.30 (0–0.88) per day) were comparable, but significantly lower than for virus transmission within a pen (ß of 6.1 (0.86–18) per day). The route via the air created new focal points of infection, from which virus transmission continued through other routes. This shows that, at least within a compartment, transmission via the air is expected to play a relevant role in the fast spread of the virus after an initial slow start. This will have consequences for efficacy of intervention measures, including vaccination during an outbreak.
    The effect of genetic selection for Johne's disease resistance n dairy cattle: Results of a genetic-epidemiological model
    Hulzen, K.J.E. van; Koets, A.P. ; Nielen, M. ; Heuven, H.C.M. ; Arendonk, J.A.M. van; Klinkenberg, D. - \ 2014
    Journal of Dairy Science 97 (2014)3. - ISSN 0022-0302 - p. 1762 - 1773.
    avium subspecies paratuberculosis - decision-analysis model - antibody-response - control program - fecal culture - holstein cows - mycobacterium - herd - infection - heritability
    The objective of this study was to model genetic selection for Johne’s disease resistance and to study the effect of different selection strategies on the prevalence in the dairy cattle population. In the Netherlands, a certification-and-surveillance program is in use to reduce prevalence and presence of sources of infection in milk by culling ELISA-positive dairy cows in infected herds. To investigate the additional genetic effect of this program, a genetic-epidemiological model was developed to assess the effect of selection of cows that test negative for Johne’s disease (dam selection). The genetic effect of selection at the sire level was also considered (sire selection), assuming selection of 80% of sires producing the most resistant offspring based on their breeding values, as well as the combined effect. Parameters assumed to be affected by genetic selection were the length of the latent period, susceptibility (i.e., the number of infectious doses needed to become infected), or the length of susceptible period as a calf. The effect of selection was measured by the time in years required to eliminate infection. Sensitivity analysis was performed for heritability, accuracy of selection, and intensity of selection. For dam selection, responses to selection were small, requiring 379 to 702 yr for elimination. For sire selection, responses were much larger, although elimination still required 147 to 223 yr. The response to selection was largest if genetic selection affected the length of the susceptible period, followed by the susceptibility, and finally the length of the latent period. Genetic selection for Johne’s disease resistance by certification and surveillance is too slow for practical purpose, but that selection on the sire level is able to contribute to the control of Johne’s disease in the long run.
    Transmission rate of African swine fever virus under experimental conditions
    Carvalho Ferreira, H.C. de; Backer, J.A. ; Weesendorp, E. ; Klinkenberg, D. ; Stegeman, J.A. ; Loeffen, W.L.A. - \ 2013
    Veterinary Microbiology 165 (2013)3-4. - ISSN 0378-1135 - p. 296 - 304.
    basic reproduction ratio - between-pen transmission - experimental-infection - western hemisphere - antibody-response - disease virus - mouth-disease - hog-cholera - within-pen - pigs
    African swine fever (ASF) is a highly lethal, viral disease of swine. No vaccine is available, so controlling an ASF outbreak is highly dependent on zoosanitary measures, such as stamping out infected herds and quarantining of affected areas. Information on ASF transmission parameters could allow for more efficient application of outbreak control measures. Three transmission experiments were carried out to estimate the transmission parameters of two ASF virus isolates: Malta'78 (in two doses) and Netherlands'86. Different criteria were used for onset of infectiousness of infected pigs and moment of infection of contact pigs. The transmission rate (ß), estimated by a Generalized Linear Model, ranged from 0.45 to 3.63 per day. For the infectious period, a minimum as well as a maximum infectious period was determined, to account for uncertainties regarding infectiousness of persistently infected pigs. While the minimum infectious period ranged from 6 to 7 days, the average maximum infectious period ranged from approximately 20 to nearly 40 days. Estimates of the reproduction ratio (R) for the first generation of transmission ranged from 4.9 to 24.2 for the minimum infectious period and from 9.8 to 66.3 for the maximum infectious period, depending on the isolate. A first approximation of the basic reproduction ratio (R0) resulted in an estimate of 18.0 (6.90-46.9) for the Malta'78 isolate. This is the first R0 estimate of an ASFV isolate under experimental conditions. The estimates of the transmission parameters provide a quantitative insight into ASFV epidemiology and can be used for the design and evaluation of more efficient control measures.
    Trade-off between growth and immune function: a meta-analysis of selection experiments
    Most, P.J. van der; Jong, B. de; Parmentier, H.K. ; Verhulst, S. - \ 2011
    Functional Ecology 25 (2011)1. - ISSN 0269-8463 - p. 74 - 80.
    newcastle-disease virus - increased body-weight - random-bred strain - sheep erythrocytes - antibody-response - pasteurella-multocida - life-history - physiological-responses - ecological immunology - evolutionary ecology
    1. Evidence suggests that developing and maintaining an effective immune system may be costly and that an organism has to make a trade-off between immune function and other fitness-enhancing traits. To test for a trade-off between growth and immune function we carried out a meta-analysis of data from lines of poultry that had been divergently selected for either growth (body mass) or an aspect of immune function. This is relevant to our understanding of the evolution of immune function, but also because the increased prevalence of antibiotic-resistant bacteria and calls to restrict the use of antibiotics in the agricultural industry has made immune function of livestock an important theme. Has the selection of animals for rapid growth unintentionally resulted in reduced immune function? 2. The lines selected for increased growth all showed a strong and significant decrease in immune function (standard difference in means = 0·8; P <0·001). No difference was found between the effects on cellular or humoral immunity, although there were few data on cellular immunity, and hence this deserves more study. However, in the lines selected for immune function the effect on growth was heterogeneous and overall it was close to zero. 3. Testing for publication bias revealed that the effect of selection for body mass on immune function was robust. However, there was considerable heterogeneity in both body mass and immune function data. The heterogeneity in the growth-selected lines cannot be accounted for by gender or species: the only turkey line had an effect size between that of the two chicken lines. 4. In conclusion, we found that selection for growth does indeed compromise immune function, but selection for immune function did not consistently affect growth. This is in agreement with the supposition that the costs of growth are large relative to the costs of immune function, and on a practical level this suggests that it may be possible to breed animals for increased growth without loss of immune function.
    Using mortality data for early detection of Classical Swine Fever in The Netherlands
    Backer, J.A. ; Brouwer, H. ; Schaik, G. van; Roermund, H.J.W. van - \ 2011
    Preventive Veterinary Medicine 99 (2011)1. - ISSN 0167-5877 - p. 38 - 47.
    experimental-infection - antibody-response - weaner pigs - virus - transmission - disease - strategies - epidemics - vaccine - marker
    Early detection of the introduction of an infectious livestock disease is of great importance to limit the potential extent of an outbreak. Classical Swine Fever (CSF) often causes non-specific clinical signs, which can take considerable time to be detected. Currently, the disease can be detected by three main routes, that are all triggered by clinical signs. To improve the early detection of CSF an additional program, based on mortality data, aims to routinely perform PCR tests on ear notch samples from herds with a high(er) mortality. To assess the effectiveness of this new early detection system, we have developed a stochastic model that describes the virus transmission within a pig herd, the development of disease in infected animals and the different early detection programs. As virus transmission and mortality (by CSF and by other causes) are different for finishing pigs, piglets and sows, a distinction is made between these pig categories. The model is applied to an extensive database that contains all unique pig herds in The Netherlands, their herd sizes and their mortality reports over the CSF-free period 2001-2005. Results from the simulations suggest that the new early detection system is not effective in piglet sections, due to the high mortality from non-CSF causes, nor in sow sections, due to the low CSF-mortality. In finishing herds, the model predicts that the new early detection system can improve the detection time by two days, from 38 (27-53) days to 36(24-51) days after virus introduction, when assuming a moderately virulent virus strain causing a 50% CSF mortality. For this result up to 5 ear notch samples per herd from 8(0-13) finishing herds must be tested every workday. Detecting a source herd two days earlier could considerably reduce the number of initially infected herds. However, considering the variation in outcome and the uncertainty in some model assumptions, this two-day gain in detection time is too small to demonstrate a substantial effect of the new early detection system based on mortality data. But when the alertness of herd-owners and veterinarians diminishes during long CSF-free periods, the new early detection system might gain in effectiveness. (C) 2010 Elsevier B.V. All rights reserved.
    Age at which dairy cattle become Mycobacterium avium subsp. paratuberculosis faecal culture positive
    Weber, M.F. ; Kogut, J. ; Bree, J. de; Schaik, G. van; Nielen, M. van - \ 2010
    Preventive Veterinary Medicine 97 (2010)1. - ISSN 0167-5877 - p. 29 - 36.
    genetic-variation - johnes-disease - ssp-paratuberculosis - antibody-response - immune-responses - diagnostic-tests - infection - calves - susceptibility - polymorphisms
    Age at which cattle become faecal culture positive for Mycobacterium avium subsp. paratuberculosis (Map) can be used as a proxy parameter for age at onset of faecal shedding, which is an important parameter in the control of Map in cattle herds. To investigate the age at becoming faecal culture positive, survival analysis methods were applied. The analyses were carried out on asynchronous interval censored data of faecal culture results of samples collected from 18,979 female Holstein-Frisian cattle in 353 Dutch herds between 1996 and 2002. The data were analysed with a Weibull proportional hazards model. The results indicate that the distribution of age at onset of faecal shedding in Holstein-Frisian dairy cattle in infected herds is associated with the within-herd prevalence. In higher classes of apparent prevalence, cattle started to shed Map at younger age on average. In herds with an apparent prevalence = 0.2, the proportion (95% CI) of cattle with onset of faecal shedding before 2 years of age was estimated at 1% (0.5%; 2%), 4% (3%; 5%), 8% (5%; 10%) and 20% (11%; 32%), respectively. This study indicates that a considerable proportion of young stock is shedding Map, especially in high prevalence herds. Therefore, infectious young stock should be a major concern in the control of paratuberculosis
    Across-line SNP association study of innate and adaptive immune response in laying hens
    Biscarini, F. ; Bovenhuis, H. ; Arendonk, J.A.M. van; Parmentier, H.K. ; Jungerius, B.J. ; Poel, J.J. van der - \ 2010
    Animal Genetics 41 (2010)1. - ISSN 0268-9146 - p. 26 - 38.
    quantitative trait loci - linkage disequilibrium - antibody-response - natural antibodies - chickens - populations - heritability - enteritidis - survival - disease
    The aim of the present study was to detect quantitative trait loci (QTL) for innate and adaptive immunity in laying hens. For this purpose, the associations between 1022 single nucleotide polymorphism (SNP) markers and immune traits were studied in 583 hens from nine different layer lines. Immune traits were natural antibodies for keyhole limpet haemocyanin (KLH) and lipopolysaccharide (LPS) at 20, 40 and 65 weeks, acquired antibodies to the vaccinal virus of Newcastle disease at 20 weeks, and complement activity measured on sheep and bovine red blood cells at 20, 40 and 65 weeks. We adopted a novel approach based on across-line analysis and testing of the SNP-by-line interaction. Among lines, linkage disequilibrium is conserved at shorter distances than in individual lines; therefore, SNPs significantly associated with immune traits across lines are expected to be near the functional mutations. In the analysis, the SNPs that had a significant across-line effect but did not show significant SNP-by-line interaction were identified to test whether the association was consistent in the individual lines. Ultimately, 59 significant associations between SNPs and immune traits were detected. Our results confirmed some previously identified QTL and identified new QTL potentially involved in the immune function. We found evidence for a role of IL17A (chromosome 3) in natural and acquired antibody titres and in the classical and alternative pathways of complement activation. The major histocompatibility genes on chromosome 16 showed significant association with natural and acquired antibody titres and classical complement activity. The IL12B gene on chromosome 13 was associated with natural antibody titres
    Effect of strain and inoculation dose of classical swine fever virus on within-pen transmission.
    Weesendorp, E. ; Backer, J.A. ; Stegeman, J.A. ; Loeffen, W.L.A. - \ 2009
    Veterinary Research 40 (2009)6. - ISSN 0928-4249 - p. 40 - 59.
    experimental-infection - replication kinetics - antibody-response - subunit vaccine - weaner pigs - rt-pcr - pathogenesis - virulence - moderate - disease
    To improve the understanding of the dynamics and options for control of classical swine fever (CSF), more quantitative knowledge is needed on virus transmission. In this study, virus excretion and within-pen transmission of a strain of low, moderate and high virulence were quantified. Furthermore, the effect of inoculation dose on excretion and transmission were studied. The transmission was quantified using a stochastic susceptible-exposed-infectious-recovered (SEIR) model. Five transmission trials were conducted with ten pigs each. In each trial, three pigs were inoculated with the low virulent strain Zoelen, a low (102 TCID50), middle (103 TCID50), or high dose (105 TCID50) of the moderately virulent strain Paderborn, or the highly virulent strain Brescia. The other seven pigs in each trial served as contact pigs. None of the pigs inoculated with the low dose of the Paderbom strain were infected. When it was assumed that the infectiousness of the pigs coincided with virus isolation positive oropharyngeal fluid and/or faeces, no significant differences in transmission rate ß and basic reproduction ratio R0 between the high inoculation dose of the Paderbom strain (ß = 1.62/day, R0 = 35.9) and the Brescia strain (ß = 2.07/day, Ro = 17.5) were observed. When the middle dose of the Paderbom strain was used for inoculation, the ß (5.38/day) was not significantly higher than the Brescia strain or the high inoculation dose of the Paderborn strain, but the Ro (148) was significantly higher. Infection with the Zoelen strain resulted in a significantly lower ß and Ro (ß = 0/day, Ro = 0) than the other strains
    Modeling Variability in Immunocompetence and Immunoresponsiveness
    Ask, B. ; Waaij, E.H. van der; Bishop, S.C. - \ 2008
    Poultry Science 87 (2008). - ISSN 0032-5791 - p. 1748 - 1759.
    acute-phase protein - escherichia-coli lipopolysaccharide - enterica serovar typhimurium - infectious-bronchitis virus - newly-hatched chick - red-blood-cells - immune-response - antibody-response - broiler-chickens - mareks-disease
    The purposes of this paper were to 1) develop a stochastic model that would reflect observed variation between animals and across ages in immunocompetence and responsiveness; and 2) illustrate consequences of this variability for the statistical power of genotype comparisons and selection. A stochastic model of immunocompetence development and responsiveness kinetics was developed. This model enabled variability in immunological variables to be taken into account in the evaluation of challenge and measurement strategies for selection. The characteristics of the variation in model output reflect those observed in the literature, to the extent that variation in the literature shows a consistent pattern; knowledge of true variation and patterns of variation in immunological variables is limited. The model created correlations between immunocompetence and immunoresponsiveness components, as well as correlations within each component across time. These correlations were generally in agreement with literature estimates, where available. The model enabled predictions of the effectiveness of selection for improved health through immunocompetence or immunoresponsiveness. It was predicted that effective selection for increased general immunocompetence to improve health should be done only when baseline immunity has matured. Further, the model implied that selection is unlikely to be successful if it is based only on a single measurement. Problems with low statistical power to detect differences between genotypes can be reduced by increasing challenge age in the experimental design, and one should ensure that the effects of maternal immunity are minimal when the challenge is done. The ability to detect differences between different groups of animals differs substantially with measurement timing because of low repeatabilities of immunocompetence and responsiveness across time. In general, the probability of detecting differences becomes higher when the challenge age is increased. Consequently, both the age at selection and the age at which information is gathered for selection must be considered carefully when designing genetic evaluations.
    Detection and quantification of classical swine fever virus in air samples originating from infected pigs and experimentally produced aerosols
    Weesendorp, E. ; Landman, W.J.M. ; Stegeman, A. ; Loeffen, W.L.A. - \ 2008
    Veterinary Microbiology 127 (2008)1-2. - ISSN 0378-1135 - p. 50 - 62.
    mouth-disease virus - hog-cholera - airborne transmission - enterococcus-faecalis - antibody-response - epidemic - netherlands - aerosolization - spread - area
    During epidemics of classical swine fever (CSF), neighbourhood infections occurred where none of the 'traditional' routes of transmission like direct animal contact, swill feeding, transport contact or transmission by people could be identified. A hypothesized route of virus introduction for these herds was airborne transmission. In order to better understand this possible transmission route, we developed a method to detect and quantify classical swine fever virus (CSFV) in air samples using gelatine filters. The air samples were collected from CSFV-infected pigs after experimental aerosolization of the virus. Furthermore, we studied the viability of the virus with time in aerosolized state. Three strains of CSFV were aerosolized in an empty isolator and air samples were taken at different time intervals. The virus remained infective in aerosolized state for at least 30 min with half-life time values ranging from 4.5 to 15 min. During animal experiments, concentrations of 100.3-101.6 TCID50/ m3 CSFV were detected in air samples originating from the air of the pig cages and 100.4-104.0 TCID50/m3 from the expired air of infected animals. This is the first study describing the isolation and quantification of CSFV from air samples originating from infected pigs and their cages, supporting previous findings that airborne transmission of CSF is feasible.
    Modeling Development Immunocompetence and Immunoresponsiveness to Challenge in Chicks
    Ask, B. ; Waaij, E.H. van der; Glass, E.J. ; Bishop, S.C. - \ 2007
    Poultry Science 86 (2007). - ISSN 0032-5791 - p. 1336 - 1350.
    infectious-bronchitis virus - escherichia-coli lipopolysaccharide - linked-immunosorbent-assay - phase protein response - immune-response - antibody-response - broiler-chickens - mareks-disease - bactericidal activities - divergent selection
    The purpose of this study was 2-fold: 1) to develop a deterministic model that describes the development of immunocompetence and the kinetics of immunoresponsiveness to a pathogenic challenge in chicks and 2) to use this model to illustrate the importance of factors in experimental design, such as type of variable measured, measurement timing, and challenge age. Difficulties in evaluating immunological variables hinder attempts to improve animal health through selection on immunological variables. In young chicks, evaluating immunological variables is additionally complicated by immune system development and maternal immunity. The evaluation of immunocompetence and immunoresponsiveness and the definition of appropriate challenge and measurement strategies may be enabled through a mathematical model that captures the key components of the immune system and its development. Therefore, a model was developed that describes the development of immunocompetence as well as the kinetics of immunoresponsiveness to a pathogenic extracellular bacterial challenge in an individual chick from 0 to 56 d of age. The model consisted of 4 components describing immunocompetence (maternal and baseline immunity) and immunoresponsiveness (acute phase and antibody response). Individual component equations generally fit published data adequately. Four scenarios that represented combinations of challenge age and measurement timing were simulated. In each scenario, the immunoresponsiveness to a particular challenge was compared for 3 different levels of baseline immunity, representing 3 broiler genotypes. It was illustrated that experimental design (type of immunoresponsiveness measured, measurement timing, and challenge age) can have an important effect on the ranking of genotypes, groups, or individuals and on the reliability of extrapolations based on this ranking. It is concluded that this model is a potentially useful tool in the definition of appropriate challenge and measurement strategies when evaluating immunocompetence and immunoresponsiveness. Further, it may be used as a generator of hypotheses on global immunological relationships to be tested experimentally.
    Serological and mucosal immune responses after vaccination and infection with FMDV in pigs.
    Eble, P.L. ; Bouma, A. ; Weerdmeester, K. ; Stegeman, J.A. ; Dekker, A. - \ 2007
    Vaccine 25 (2007)6. - ISSN 0264-410X - p. 1043 - 1054.
    mouth-disease virus - direct-contact challenge - antibody-response - emergency vaccination - protection - cattle - transmission - vaccines - persistence - reduction
    The aim of this study was to determine a possible correlation between humoral immune responses shortly after vaccination and protection against foot-and-mouth disease virus (FMDV) infection and to study the serological and mucosal antibody responses after vaccination and infection. We used three groups of ten pigs, one non-vaccinated group, one group vaccinated with a single dose vaccine and one group vaccinated with a four-fold dose vaccine. At 7 days post vaccination, five pigs per group were challenged intra-dermally with FMDV O TAW 3/97 and the remaining pigs of each group were contact-exposed to the inoculated pigs. In each group, virus excretion and number of contact infections were quantified. The serological and mucosal antibody responses were evaluated until 116 days post infection. Vaccination resulted in a significant decrease of virus excretion. Stepwise linear regression analysis of variables from individual vaccinated pigs revealed the virus excretion after challenge to be correlated with neutralising antibody titres at the day of challenge (p <0.01). In serum and OPF samples comparable isotype-specific antibody responses (IgM, IgG and IgA), could be detected after vaccination as well as after infection. Remarkably, the pigs with the highest IgA responses after vaccination were protected against contact exposure. After infection, a long lasting (up to 116 dpi) IgA response was seen in the non-vaccinated and to a lesser extent in the single dose vaccinated pigs. The induction of NSP antibodies in the vaccinated pigs after infection was lower and of shorter duration as compared to the non-vaccinated infected pigs. This experiment shows that vaccination can reduce virus excretion in pigs, which will contribute to reduced transmission of FMDV in the field, even if the pigs are not fully protected. Moreover, vaccines that induce local IgA responses may be more effective, which merits further investigation.
    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.
    Genetic Variation among Broiler Genotypes in susceptibility to colibacillosis
    Ask, B. ; Waaij, E.H. van der; Stegeman, J.A. ; Arendonk, J.A.M. van - \ 2006
    Poultry Science 85 (2006)3. - ISSN 0032-5791 - p. 415 - 421.
    infectious-bronchitis virus - escherichia-coli - antibody-response - immune-response - disease virus - body-weight - food-intake - chickens - growth - resistance
    Selection for reduced susceptibility to colibacillosis in broilers may contribute to the prevention of colibacillosis. Such selection should focus on the responses to Escherichia coli rather than the associated primary agent(s). The purpose of the current study was to examine whether genetic variation is present in the susceptibility to colibacillosis. This was achieved through an evaluation of the susceptibility to primary colibacillosis in 5 pure broiler lines, a slow-growing line, and two 2-way crosses of the pure lines (altogether referred to as genotypes). A challenge experiment was executed in 2 trials. Per trial, 24 chicks per genotype were challenged and 20 chicks per genotype were controls. At 7 d of age, challenged chicks were intratracheally inoculated with 0.3 mL of E. coli O78K80 solution, and controls with 0.3 mL of PBS. All chicks were euthanized at 14 or 15 d. Traits measured were mortality, lesion scores (airsacculitis, pericarditis, and perihepatitis) at 14 or 15 d, and BW at 1, 4, 7, 10, 12, and 14 or 15 d. An effect of genotype on mortality, lesion prevalence, and growth retardation was found, indicating the presence of genetic variation in susceptibility to colibacillosis, and suggesting that selection for reduced susceptibility is possible. There were large between-genotype differences in mortality (up to 46%) and in lesion prevalence (up to 41%). Growth retardation was not observed for any genotype in chicks without lesions, whereas genotypes differed from none to 20% growth retardation for chicks with airsacculitis but no systemic lesions, and up to 13% for chicks with systemic lesions. The heterosis in susceptibility and growth retardation was found to be either negative or absent, indicating that crossbreeding would not be an advantage for the selection for reduced susceptibility, and that test crossing is essential
    Interaction between the blood fluke, Sanguinicola inermis and humoral components of the immune response of carp, Cyprinus carpio
    Roberts, M.L. ; Lewis, J.W. ; Wiegertjes, G.F. ; Hoole, D. - \ 2005
    Parasitology 131 (2005)2. - ISSN 0031-1820 - p. 261 - 271.
    salmo-gairdneri richardson - ligula-intestinalis cestoda - diplostomum-spathaceum digenea - rainbow-trout - schistosoma-mansoni - cryptobia-salmositica - alternative pathway - oncorhynchus-mykiss - ichthyophthirius-multifiliis - antibody-response
    The effect of Sanguinicola inermis on serum antibody and complement activity in Cyprinus carpio was assessed using an ELISA and haemolytic assays. Possible immune evasion strategies were assessed using immunodetection of host proteins on the surface of the parasite. Carp acclimatized to 20 or 25 °C were infected by exposure to 500 cercariae or injected intraperitoneally with 150 cercariae, and serum monitored over a 63-day period. In cercariae-injected carp, irrespective of time and temperature, a significant increase occurred in complement activity being greatest at 25 °C. In addition, fish exposed to the cercariae of S. inermis and maintained at 20 °C the level of complement activity was significantly higher after 5 weeks compared to controls. At 20 °C intraperitoneal injections of parasites increased serum antibody levels which peaked after 7 days. In contrast, at 25 °C, antibody levels were maintained over 63 days. Exposure offish to infection did not appear to stimulate antibody production. Immunofluorescence studies revealed 'host-like' molecules on the surface of the cercarial body exposed to carp serum and adult flukes obtained directly from the fish or cultured for 24 h in L15 medium. The possible role of 'host-like' molecules in immune evasion is discussed and the response at different temperatures is related to infection dynamics
    Genomics for food safety and sustainable animal production
    Harlizius, B. ; Wijk, H.J. van; Merks, J.W.M. - \ 2004
    Journal of Biotechnology 113 (2004)1-3. - ISSN 0168-1656 - p. 33 - 42.
    quantitative trait loci - leukocyte adhesion deficiency - meat quality traits - linkage map - dairy-cattle - muscle mass - photoperiod sensitivity - antibody-response - holstein cattle - flowering time
    There is a growing concern in society about the safety of animal-derived food, the health and welfare of farm animals and the sustainability of current animal production systems. Along farm animal, breeding genomics may contribute to a solution for these concerns. The use of genomic analysis tools, to achieve genetic progress in typical out-bred populations of farm animals, seems to be more difficult compared to `model` organisms or plants. However, identification of positional candidate genes may be accelerated by linkage disequilibrium (LD) mapping. Recording of sustainable traits requires a large financial and logistic input and the economic advantages for the market are not as clear as for traditional selection traits. Examples show that the major genes causing variability for similar traits in different species are rarely the same. Therefore, for breeding purposes genomic analysis of the species of interest is needed. The fundamental knowledge obtained on the genetic architecture of complex traits will open new perspectives for the use of DNA tests in selection schemes. For food safety and traceability, DNA-based techniques evolve for monitoring and early warning systems
    Overproduction of corticotropin-releasing hormone blocks germinal center formation: role of corticosterone and impaired follicular dendritic cell networks
    Murray, S.E. ; Rosenzweig, H.L. ; Johnson, M. ; Huising, M.O. ; Sawicki, K. ; Stenzel-Poore, M.P. - \ 2004
    Journal of Neuroimmunology 156 (2004)1-2. - ISSN 0165-5728 - p. 31 - 41.
    stress-induced enhancement - lymphotoxin beta-receptor - tumor-necrosis-factor - b-cells - mediated-immunity - splenic microarchitecture - deficient mice - immunological memory - antibody-response - human neutrophils
    xCorticotropin-releasing hormone (CRH) is a central mediator in the response to stress, coordinating behavioral, autonomic and neuroendocrine activation. CRH overproduction is implicated in several affective disorders, including major depression, panic-anxiety disorder and anorexia-diseases also associated with altered immune function. We investigated the link between CRH overdrive and immune function using CRH transgenic mice. Following immunization, CRH transgenic mice fail to form germinal centers; chronic glucocorticoid administration recapitulates this effect in wild-type mice. Regulation of germinal centers by glucocorticoids appears to be mediated, in part, through effects on follicular dendritic cells (FDC), providing a novel mechanism by which CRH dysregulation may significantly impair humoral immune responses. (C) 2004 Elsevier B.V. All rights reserved.
    Vaccination of pigs two weeks before infection significantly reduces transmission of foot-and-mouth disease virus
    Eble, P.L. ; Bouma, A. ; Bruin, M.G.M. de; Hemert-Kluitenberg, F. van; Oirschot, J.T. van; Dekker, A. - \ 2004
    Vaccine 22 (2004)11-12. - ISSN 0264-410X - p. 1372 - 1378.
    antibody-response - cattle - computation - reduction - emergency - epidemic - exposure - models
    The objective of this study was to investigate whether and at what time interval could vaccination reduce transmission of foot-and-Mouth disease virus (FMDV) among pigs. Reduction of virus transmission by vaccination was determined experimentally. Transmission of FMDV was studied in three groups of ten pigs: one non-vaccinated group and two groups that were vaccinated 7 days (-7 dpi) and 14 days before inoculation (-14 dpi), respectively. Five randomly selected pigs from each group were inoculated with FMDV type O Taiwan, while the other five pigs left in the groups were exposed to the inoculated pigs by direct contact. Clinical signs were recorded, virus isolation and RT-PCR were carried out on oropharyngeal fluid (OPF), and the neutralizing antibody titres and the antibody response against non-structural (NS) proteins of FMDV were determined. No virus transmission was observed in the -14 dpi group, whereas virus transmission was observed in all contact pigs affecting both the non-vaccinated and the -7 dpi group. The reproduction ratio R in the -14 dpi vaccinated group was significantly lower than that of the non-vaccinated group. This study confirms the potential of vaccination as an important tool to reduce transmission of FMDV. (C) 2003 Elsevier Ltd. All rights reserved.
    Detection of QTL for immune response to Sheep Red Blood Cells in laying hens
    Siwek-Gapinska, M.Z. ; Cornelissen, S.J.B. ; Nieuwland, M.G.B. ; Buitenhuis, A.J. ; Bovenhuis, H. ; Crooijmans, R.P.M.A. ; Groenen, M.A.M. ; Vries Reilingh, G. de; Parmentier, H.K. ; Poel, J.J. van der - \ 2003
    Animal Genetics 34 (2003)6. - ISSN 0268-9146 - p. 442 - 428.
    quantitative trait loci - antibody-response - divergent selection - genetic dissection - biozzi mice - chickens - responsiveness - pigs - populations - resistance
    The aim of this study is to detect quantitative trait loci (QTL) involved in the regulation of the primary and the secondary immune response to sheep red blood cells (SRBC) in a resource population using microsatellite DNA markers. The F2 resource population originates from a cross of two divergently selected lines for either high (H line) or low (L line) primary antibody response to SRBC. The F2 population consisted of six half-sib families, three families per each of reciprocal crosses. Total antibody titres to SRBC were determined by agglutination in serum from all birds. F2, F1 and F0 generations were genotyped for 170 microsatellite markers, using a whole-genome scan approach. The half-sib and the line-cross analyses were performed to determine QTL regions associated with regulation of the immune response. In the half-sib analysis, four QTL for SRBC primary response have been identified: on GGA3, GGA5, GGA16 and GGA23. No QTL was identified for SRBC secondary response under the half-sib model. In the line-cross analysis, three QTL were identified on GGA10, GGA16 and GGA27 for SRBC primary response and five QTL were identified on GGA6, GGA9, GGA15, GGA16 and GGA27 for SRBC secondary response. Subsequently, the family contribution of individual families to the QTL was analysed. The family with the largest contribution was genotyped with additional microsatellite markers in the QTL region on GGA5. The extended half-sib analysis with additional genotype information results in narrowing down the QTL region on GGA5.
    Neighbourhood infections of classical swine fever during the 1997-1998 epidemic in the Netherlands
    Crauwels, A.P.P. ; Nielen, M. ; Elbers, A.R.W. ; Stegeman, J.A. ; Tielen, M.J.M. - \ 2003
    Preventive Veterinary Medicine 61 (2003). - ISSN 0167-5877 - p. 263 - 277.
    hog-cholera virus - antibody-response - transmission - disease - herds - diptera - pigs - area
    Data of the 1997-1998 epidemic of classical swine fever (CSF) in The Netherlands were analysed in survival analysis to identify risk factors that were associated with the rate of neighbourhood infections. The study population consisted of herds within 1000 m of exclusively one previously infected herd. Dates of virus introduction into herds were drawn randomly from estimated probability distributions per herd of possible weeks of virus introduction. (To confirm the insensitivity of the results for this random data-selection procedure, the procedure was repeated 9 times (resulting in 10 different datasets).) The dataset had 906 non-infected and 59 infected neighbour herds, which were distributed over 215 different neighbourhoods. Neighbour herds that never became infected were right-censored at the last date of the infectious period of the infected source herd. Neighbour herds that became empty within the infectious period or within the following 21 days due to preventive depopulation or due to the implemented buying-out programme were right-censored 21 days before the moment of becoming empty. This was done as a correction for the time a herd could be infected without being noticed as such. The median time to identified infection of neighbour herds was 2 weeks, whereas the median time to right censoring of non-infected neighbour herds was 3 weeks. The risk factors, radial distance less than or equal to500 m, cattle present on source herd and increasing herd size of the neighbour herd were associated multivariably with the hazard for neighbour herds to become infected. We did not find an association between time down wind and-infection risk for neighbour herds. Radial dispersion of CSFV seemed more important in neighbourhood infections than dispersion along the road on which the infected source herd is situated. The results of this study support the strategy of preventive depopulation in the neighbourhood of an infected herd. Recommendations are presented to adapt the applied control strategy for neighbourhood infections. (C) 2003 Elsevier B.V. All rights reserved.
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