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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Effect of challenge dose of plasmid-mediated extended-spectrum β-lactamase and AmpC β-lactamase producing Escherichia coli on time-until-colonization and level of excretion in young broilers
Dame-Korevaar, Anita ; Fischer, Egil A.J. ; Goot, Jeanet van der; Velkers, Francisca ; Broek, Jan van den; Veldman, Kees ; Ceccarelli, Daniela ; Mevius, Dik ; Stegeman, Arjan - \ 2019
Veterinary Microbiology 239 (2019). - ISSN 0378-1135
Animal model - Antibiotic resistance - Dose-response - Inoculation - Poultry - Transmission

Plasmid-mediated extended-spectrum β-lactamase and AmpC β-lactamase (ESBL/pAmpC) producing bacteria are present at all levels of the broiler production pyramid. Young birds can be found positive for ESBL/pAmpC-producing Escherichia coli shortly after arrival at farm. The aim of this study was to determine the effect of different challenge doses of ESBL/pAmpC-producing E. coli on time-until-colonization and the level of excretion in young broilers. One-day-old broilers (specific-pathogen free (SPF) and conventional Ross 308) were housed in isolators and challenged with 0.5 ml ESBL/pAmpC-producing E. coli strains of varying doses (101–105 CFU/ml). Presence and concentration (CFU/gram feces) of ESBL/pAmpC-producing E. coli and total E. coli were determined longitudinally from cloacal swabs, and in cecal content 72 h after challenge. Higher challenge doses resulted in shorter time-until-colonization. However, even the lowest dose (101 CFU/ml) resulted in colonization of the broilers which excreted >106 CFU/gram feces 72 h after inoculation. Conventional broilers were colonized later than SPF broilers, although within 72 h after challenge all broilers were excreting ESBL/pAmpC-producing E. coli. A probabilistic model was used to estimate the probability of colonization by initial inoculation or transmission. The higher the dose the higher the probability of excreting ESBL/pAmpC-producing E. coli as a result of inoculation. In conclusion, low initial doses of ESBL/pAmpC-producing E. coli can result in rapid colonization of a flock. Interventions should thus be aimed to eliminate ESBL/pAmpC-producing bacteria in the environment of the hatchlings and measures focusing at reducing colonization and transmission of ESBL/pAmpC-producing E. coli should be applied shortly after hatching.

Food Reformulation: Experts dagen voedingsindustrie uit
Renzetti, S. ; Noort, M.W.J. ; Janssen, A.M. ; Sman, R.G.M. van der - \ 2019
Kringlooplandbouw? Vergeet de dieren niet
Stegeman, Arjan ; Zwietering, M.H. ; Heederik, D.J.J. - \ 2019
De Volkskrant (2019).
Competition between Escherichia coli Populations with and without Plasmids Carrying a Gene Encoding Extended-Spectrum Beta-Lactamase in the Broiler Chicken Gut
Fischer, Egil A.J. ; Dierikx, Cindy M. ; Essen-Zandbergen, Alieda van; Mevius, Dik ; Stegeman, Arjan ; Velkers, Francisca C. ; Klinkenberg, Don - \ 2019
Applied and Environmental Microbiology 85 (2019)17. - ISSN 0099-2240
antibiotic resistance - Bayesian model - challenge - conjugation - experiment - poultry

Extended-spectrum-beta-lactamase (ESBL)/AmpC-producing Escherichia coli strains are widely found in E. coli isolates from broiler feces, largely due to the presence of the blaCTX-M-1 gene on IncI1 plasmids. Plasmid carriage is theorized to cause fitness loss and thus should decrease under conditions of reduced antibiotic use. However, in vitro studies showed plasmid carriage to increase in the absence of antimicrobials, due to plasmid conjugation. We investigated whether this translates to increased levels of plasmid in the gastrointestinal tracts of chickens, where conjugation rates may be different and subtle differences in growth rates may have a larger impact on colonization. Eight groups of five chickens were orally inoculated at 4 days of age with a 0.5-ml volume containing 106 CFU/ml E. coli cells, of which 0%, 0.1%, 10%, or 100% carried the IncI1 plasmid with the gene blaCTX-M-1 At 13 time points during 41 days, fecal samples were taken from each chicken. E. coli strains with and without plasmids were quantified. Trends in E. coli subpopulations were analyzed using generalized linear mixed models, and population dynamics were studied by fitting to a mechanistic model. Trends in E. coli subpopulations were different between groups rather than between individual chickens, suggesting substantial levels of E. coli exchange between chickens in a group. The IncI1 plasmid carrying blaCTX-M-1 was transferred with conjugation coefficients at levels higher than those observed in vitro Across groups, the plasmids disappeared or were established independently of the initial fraction of plasmid-carrying E. coli, but no major increase occurred as observed in vitro Differences in growth rates were observed, but competitive exclusion of plasmid-carrying variants was counteracted by conjugation.IMPORTANCE Bacteria that produce extended-spectrum beta-lactamases are resistant to an important class of antimicrobials in human and veterinary medicine. Reduction in antibiotic use is expected to decrease the prevalence of resistance. However, resistance genes often lie on plasmids which can be copied and transferred to other bacteria by conjugation, so in vitro resistance was observed to increase in the absence of antimicrobials. We sought to determine whether this also occurs in the chicken gut and if competitive exclusion by similar E. coli variants without the resistance occurred. We studied the excretion of E. coli carrying IncI1 plasmids with the blaCTX-M-1 resistance gene in small groups of broiler chickens, after inoculating the chickens with E. coli suspensions containing different fractions of plasmid-carrying cells. Our results showed little variation between chickens within groups but large differences between groups that were independent of the ratio of variants with and without the plasmid and with persistence or extinction of the plasmid. However, there was no major plasmid increase as observed in vitro We conclude that in vivo studies with sufficient independent replications are important for intervention studies on plasmid-mediated antimicrobial resistance.

Dynamics of faecal shedding of ESBL- or AmpC-producing Escherichia coli on dairy farms
Hordijk, Joost ; Fischer, Egil A.J. ; Werven, Tine van; Sietsma, Steven ; Gompel, Liese Van; Timmerman, Arjen J. ; Spaninks, Mirlin P. ; Heederik, Dick J.J. ; Nielen, Mirjam ; Wagenaar, Jaap A. ; Stegeman, Arjan - \ 2019
Journal of Antimicrobial Chemotherapy 74 (2019)6. - ISSN 0305-7453 - p. 1531 - 1538.

OBJECTIVES: To explore the dynamics of faecal ESBL/AmpC shedding in dairy cattle and farmers, a study was conducted to examine changes in shedding by individual animals, as well as environmental exposure, and to study the association between antimicrobial use (AMU) and ESBL/AmpC shedding. METHODS: The study comprised a cross-sectional survey of 20 farms and a 1 year follow-up of 10 farms. Faecal samples were cultured by both direct inoculation on MacConkey agar + 1 mg/L cefotaxime (MC+) and enrichment in LB-broth + 1 mg/L cefotaxime with subsequent inoculation on MC+. Dust samples were collected using electrostatic dustfall collectors (EDCs). Human faecal samples were collected by the farmers. Presence of ESBL/AmpC genes was screened for by PCR and sequencing. Using mixed effects logistic regression, ORs were determined and population-attributable fractions (PAFs) calculated subsequently. RESULTS: In Phase 1, 8/20 farms were positive for ESBL/AmpC and, with 2 negative farms, were selected for Phase 2. Transient shedding of dominant allele variants was observed in the animals. EDCs and human faecal samples did not reflect what was observed in the animals. AMU was related to shedding of ESBLs in the next sampling moment [OR 14.6 (95% CI 3.0-80.0)] and the PAF of AMU was 0.36 (95% CI 0.08-0.77). Calves fed with colostrum from cows on dry-off therapy was not a risk factor [OR 1.7 (95% CI 0.7-4.9, P = 0.28)]. CONCLUSIONS: The presence of ESBL/AmpC could only be partly explained by AMU. No link was shown between shedding in cattle and humans or the environment. Interventions should focus on prevention of introduction.

Reassortments among avian influenza A(H5N1) viruses circulating in Indonesia, 2015-2016
Karo-Karo, Desniwaty ; Bodewes, Rogier ; Wibawa, Hendra ; Artika, I.M. ; Pribadi, Eko Sugeng ; Diyantoro, D. ; Pratomo, Widya ; Sugama, Agus ; Hendrayani, Nani ; Indasari, Iin ; Wibowo, Michael Haryadi ; Muljono, David Handojo ; Stegeman, Jan Arend ; Koch, Guus - \ 2019
Emerging Infectious Diseases 25 (2019)3. - ISSN 1080-6040 - p. 465 - 472.

Highly pathogenic avian influenza (HPAI) A(H5N1) viruses have been circulating since 2003 in Indonesia, with major impacts on poultry health, severe economic losses, and 168 fatal laboratory-confirmed human cases. We performed phylogenetic analysis on 39 full-genome H5N1 virus samples collected during outbreaks among poultry in 2015-2016 in West Java and compared them with recently published sequences from Indonesia. Phylogenetic analysis revealed that the hemagglutinin gene of all samples belonged to 2 genetic groups in clade 2.3.2.1c. We also observed these groups for the neuraminidase, nucleoprotein, polymerase, and polymerase basic 1 genes. Matrix, nonstructural protein, and polymerase basic 2 genes of some HPAI were most closely related to clade 2.1.3 instead of clade 2.3.2.1c, and a polymerase basic 2 gene was most closely related to Eurasian low pathogenicity avian influenza. Our results detected a total of 13 reassortment types among HPAI in Indonesia, mostly in backyard chickens in Indramayu.

Transmission routes of ESBL/pAmpC producing bacteria in the broiler production pyramid, a literature review
Dame-Korevaar, Anita ; Fischer, Egil A.J. ; Goot, Jeanet van der; Stegeman, Arjan ; Mevius, Dik - \ 2019
Preventive Veterinary Medicine 162 (2019). - ISSN 0167-5877 - p. 136 - 150.
Antimicrobial resistance - Evidence - Mechanisms - Poultry - Spread

Plasmid mediated Extended Spectrum Beta-Lactamase and AmpC Beta-Lactamase (ESBL/pAmpC) producing bacteria are resistant to beta-lactam antimicrobials and are widespread in humans, the environment and animals. Animals, especially broilers, are an important reservoir of ESBL/pAmpC producing bacteria. To control ESBL/pAmpC prevalence in broilers, transmission within the entire broiler production pyramid should be considered. This study, including 103 articles originating from two electronic databases, searched for evidence for possible routes of transmission of ESBL/pAmpC producing bacteria in the broiler production pyramid. Possible routes of transmission were categorised as 1) vertical between generations, 2) at hatcheries, 3) horizontal on farm, and 4) horizontal between farms and via the environment of farms. This review presents indications for transmission of ESBL/pAmpC producing bacteria for each of these routes. However, the lack of quantitative results in the literature did not allow an estimation of the relative contribution or magnitude of the different routes. Future research should be specifically targeted towards such information as it is crucial to guide reduction strategies for the spread of ESBL/pAmpC producing bacteria in the broiler production chain.

Veterinary medicinal product usage among food animal producers and its health implications in Central Ethiopia
Tufa, Takele Beyene ; Gurmu, Feraol ; Beyi, Ashenafi Feyisa ; Hogeveen, Henk ; Beyene, Tariku Jibat ; Ayana, Dinka ; Woldemariyam, Fanos Tadesse ; Hailemariam, Eyerusalem ; Gutema, Fanta Desissa ; Stegeman, J.A. - \ 2018
BMC Veterinary Research 14 (2018)1. - ISSN 1746-6148
Antimicrobial resistance - Antimicrobial usage - Central Ethiopia - Farmers' knowledge, awareness, and practices - Food animals

Background: Antimicrobials and anthelmintics are the most commonly used veterinary drugs to control animal diseases. However, widespread use of these drugs could contribute to the emergence of drug resistance. Information on the practice of antimicrobial usage among food animal raising communities in Central Ethiopia is scarce. We used a standardised questionnaire survey to assess knowledge, awareness, and practices related to drug use and resistance in food animals among the farmers in and around Bishoftu town. Results: Of the total of 220 livestock owners interviewed, around 80% of the respondents were not able to define what antimicrobials are and for what purposes they are used. Only 14.1% (n = 31) of the respondents had awareness about antimicrobial resistance (AMR) and its consequences; and 35.5% (n = 11/31) and 9.7% (n = 3/31) of them agreed that the irrational use of antimicrobials in animals could lead to AMR in animals and humans. Oxytetracycline was the most commonly available antibiotic in veterinary drug shops/pharmacies and the most widely used drug in the area. However, 43.3% of the respondents did not see clinical improvements after using antibiotics. Similarly, the respondents explained that no response was observed in 73.3, 70.8 and 52.5% of the cases after medication with anthelmintics, antiprotozoal and acaricides, respectively. About 56.7% of the respondents considered traditional medicines equally important to modern medicines. It was also noted that there were illegal drug vendors, dispensing medicines under unfavourable conditions which include a direct exposure to sunlight, which practice violates the drug handling and storage recommendations given by WHO. Conclusion: The study revealed that there is a general lack of awareness among food animal owners about the correct use of antibiotics and anthelmintics. The widespread misuse and improper drug dispensing and handling practices observed in this study can affect the drug quality and can also contribute to the development of drug resistance in central Ethiopia.

The European Food Safety Authority's risk assessment of vector-borne diseases: An example focusing on the risk of mosquite-borne viruses
Dhollander, S. ; Beltran-Beck, B. ; Bicout, D. ; Czwienczek, E. ; Koeijer, A.A. de; Vos-de Jong, C.J. de; Gogin, A. ; Miguel, Miranda ; Thulke, H.H. ; Stegeman, J. - \ 2018
In: Proceedings of the Annual Scientific Conference and the Annual General Meeting of the European College of Veterinary Public Health, 17-19 October 2018, University of Perugia, Italy. - Perugia : - p. 19 - 19.
Exploring contacts facilitating transmission of influenza A(H5N1) virus between poultry farms in West Java, Indonesia : A major role for backyard farms?
Wibawa, Hendra ; Karo-Karo, Desniwaty ; Pribadi, Eko Sugeng ; Bouma, Annemarie ; Bodewes, Rogier ; Vernooij, Hans ; Diyantoro, ; Sugama, Agus ; Muljono, David H. ; Koch, Guus ; Tjatur Rasa, Fadjar Sumping ; Stegeman, Arjan - \ 2018
Preventive Veterinary Medicine 156 (2018). - ISSN 0167-5877 - p. 8 - 15.
Avian influenza - Contact structure - H5N1 - Indonesia - Poultry - Transmission
Highly pathogenic avian influenza virus (HPAIV) H5N1 has been reported in Asia, including Indonesia since 2003. Although several risk factors related to the HPAIV outbreaks in poultry in Indonesia have been identified, little is known of the contact structure of farms of different poultry production types (backyard chickens, broilers, layers, and ducks). This study aims to quantify the contact rates associated with the movement of people, and movements of live birds and products and equipment that affect the risk of HPAIV H5N1 transmission between poultry farms in Indonesia. On 124 poultry farms in 6 districts in West Java, logbooks were distributed to record the movements of farmers/staff and visitors and their poultry contacts. Most movements in backyard chicken, commercial native chicken, broiler and duck farms were visits to and from other poultry farms, whilst in layer farms visits to and from poultry companies, visits to egg collection houses and visit from other poultry farms were most frequent. Over 75% of persons visiting backyard chicken and duck farms had previously visited other poultry farms on the same day. Visitors of backyard chicken farms had the highest average contact rate, either direct contact with poultry on other farms before the visits (1.35 contact/day) or contact during their visits in the farms (10.03 contact/day). These results suggest that backyard chicken farms are most at risk for transmission of HPAIV compared to farms of the other poultry production types. Since visits of farm-to-farm were high, backyard farms could also a potential source for HPAIV transmission to commercial poultry farms.
Advice of the Scientific Advisory Committee on Seal Rehabilitation in the Netherlands
Zande, A.N. van der; Alphen, J.J.M. van; Goodman, S.J. ; Meijboom, F.L.B. ; Stegeman, A.J. ; Thompson, D. ; Kuindersma, W. ; Latour, J.B. - \ 2018
Wageningen : Wageningen Environmental Research - 90 p.
animal welfare - wild animals - seals - animal health - animal housing
Host and environmental factors affecting the intestinal microbiota in chickens
Kers, Jannigje G. ; Velkers, Francisca C. ; Fischer, Egil A.J. ; Hermes, Gerben D.A. ; Stegeman, J.A. ; Smidt, Hauke - \ 2018
Frontiers in Microbiology 9 (2018)FEB. - ISSN 1664-302X
16S rRNA - Confounding factors - Gut health - Gut microbiota - Microbiome - Poultry
The initial development of intestinal microbiota in poultry plays an important role in production performance, overall health and resistance against microbial infections. Multiplexed sequencing of 16S ribosomal RNA gene amplicons is often used in studies, such as feed intervention or antimicrobial drug trials, to determine corresponding effects on the composition of intestinal microbiota. However, considerable variation of intestinal microbiota composition has been observed both within and across studies. Such variation may in part be attributed to technical factors, such as sampling procedures, sample storage, DNA extraction, the choice of PCR primers and corresponding region to be sequenced, and the sequencing platforms used. Furthermore, part of this variation in microbiota composition may also be explained by different host characteristics and environmental factors. To facilitate the improvement of design, reproducibility and interpretation of poultry microbiota studies, we have reviewed the literature on confounding factors influencing the observed intestinal microbiota in chickens. First, it has been identified that host-related factors, such as age, sex, and breed, have a large effect on intestinal microbiota. The diversity of chicken intestinal microbiota tends to increase most during the first weeks of life, and corresponding colonization patterns seem to differ between layer- and meat-type chickens. Second, it has been found that environmental factors, such as biosecurity level, housing, litter, feed access and climate also have an effect on the composition of the intestinal microbiota. As microbiota studies have to deal with many of these unknown or hidden host and environmental variables, the choice of study designs can have a great impact on study outcomes and interpretation of the data. Providing details on a broad range of host and environmental factors in articles and sequence data repositories is highly recommended. This creates opportunities to combine data from different studies for meta-analysis, which will facilitate scientific breakthroughs toward nutritional and husbandry associated strategies to improve animal health and performance.
Deaths among wild birds during highly pathogenic avian influenza A(H5N8) virus outbreak, the Netherlands
Kleyheeg, Erik ; Slaterus, Roy ; Bodewes, Rogier ; Rijks, Jolianne M. ; Spierenburg, Marcel A.H. ; Beerens, Nancy ; Kelder, Leon ; Poen, Marjolein J. ; Stegeman, Jan A. ; Fouchier, Ron A.M. ; Kuiken, Thijs ; Jeugd, Henk P. van der - \ 2017
Emerging Infectious Diseases 23 (2017)12. - ISSN 1080-6040 - p. 2050 - 2054.
During autumn–winter 2016–2017, highly pathogenic avian influenza A(H5N8) viruses caused mass die-offs among wild birds in the Netherlands. Among the ≈13,600 birds reported dead, most were tufted ducks (Aythya fuligula) and Eurasian wigeons (Anas penelope). Recurrence of avian influenza outbreaks might alter wild bird population dynamics.
Comparison of Eimeria Infection Dynamics between Broiler Flocks with a Conventional or On-farm Hatching System.
Velkers, Francisca ; Jong, I.C. de; Ven, Lotte van de; Reep, L. Van de; Stegeman, A. - \ 2017
In: Proceedings of the XXthe Veterinary Poultry Congress, Edinburg. - - p. 197 - 197.
Broiler Chickens, Coddidiosis, Eimeria, Enteric Disease, On-farm hatching
An increasing trend in Europe is placing 18 days incubated eggs on trays in broiler houses for on-farm hatching. Chicks are not transported and have immediate access to food and water, which promotes early intestinal tract and immune system development. It was hypothesized that these physiological effects may affect the response to intestinal infections. Moreover, on-farm hatched chicks may be exposed to environmental Eimeria oocysts earlier than hatchery chicks. Therefore we compared Eimeria infection dynamics for in hatchery (R) and on-farm hatched (F) Ross 308 broilers in two field studies on commercial broiler farms and in one study in an experimental facility.
In field study 1, a poultry house was divided in a part with F and R hatching for two rounds. Ten flocks on four farms were included in field study 2 with on each farm F flocks and R flocks originating from the same parent flock. In study 3, four groups of F and R broilers were placed in experimental pens, each with 1150 birds from the same parent flock. From the second week of life onwards, oocyst excretion in faeces (OPG = oocysts per g), collected in weekly (study 2) or biweekly (studies 1 and 3) intervals, was determined with the McMaster counting technique. In both field studies an Eimeria-species specific OPG was determined with qPCR (GD Deventer, the Netherlands) on weekly pools of colonic and caecal faeces collected three times per week. Lesion scores for E. acervulina, E. maxima and E. tenella were determined during post-mortem examinations of five to six randomly selected birds on one to three occasions per production round from the third week of life onwards. Use of coccidiostats, antibiotics and production performance was recorded.
Results of qPCR showed that E. acervulina, E. tenella (studies 1 and 2) and E. maxima (study 2) were detected, without differences in species distribution between F and R flocks. In study 3, where qPCR results were not available, lesion scores indicated presence of E. acervulina and E. maxima, but not E. tenella in both F and R flocks. In all studies lesion scores were generally mild and not significantly different between F and R flocks. Oocyst excretion patterns throughout the production period were similar for F and R flocks in study 1, but in study 2 F flocks on average showed a later excretion peak (R peaked between day 22-28 and F between days 22-28 or 28-34). In study 3 oocyst output dynamics were comparable in F and R pens. In this study oocyst excretion did not reach a clear peak by the end of the round at day 40, due to a late (day 33) start of excretion. OPG determined by qPCR and the McMaster technique in studies 1 and 2 gave similar results. Production performance could not be compared between F and R flocks in the field studies, due to differences in disease occurrence and antibiotic treatments.
Only small differences in the course of Eimeria infections were detected, but the number of flocks was too small to draw accurate conclusions about effects of hatching system on coccidiosis and how this affects production performance. Small differences in infection dynamics, e.g. time of peak excretion, may affect body weight at slaughter or influence opportunities for secondary infections. Therefore, if more commercial on-farm hatching and comparable reference flocks become available, further research is warranted.
Dynamics of CMY-2 producing E. coli in a broiler parent flock
Dame-Korevaar, Anita ; Fischer, Egil A.J. ; Stegeman, Arjan ; Mevius, Dik ; Essen-Zandbergen, Alieda van; Velkers, Francisca ; Goot, Jeanet van der - \ 2017
Veterinary Microbiology 203 (2017). - ISSN 0378-1135 - p. 211 - 214.
Antibiotic resistance - Broiler parent stock - CMY - Escherichia coli - Poultry

Extended-spectrum β-lactamase and plasmid mediated AmpC β-lactamase (ESBL/pAmpC) producing bacteria are resistant to Extended Spectrum Cephalosporins (ESC), and are present in all levels of the broiler production chain. We determined the prevalence, concentration, and persistence of ESBL/pAmpC-Escherichia coli in a broiler parent flock during the rearing and laying period. One-day old chickens were housed in four separate pens. Until week 33 no antibiotics or coccidiostatics were used. During rearing 57 chickens in each pen (n = 228), and in the laying period two groups of 33 chickens were individually sampled (n = 66). Environmental samples were taken from week 16 onwards. ESBL/pAmpC-E. coli presence was determined by selective culturing. In the samples of week 16–19 the concentration of ESBL/pAmpC-E. coli was determined. All ESC-resistant isolates found were positive for pAmpC gene blaCMY-2 located on IncA/C plasmids, in several E. coli MLST types. CMY-2-E. coli prevalence decreased from 91% (95%CI 86–94%) at day 7 (week 1) to 0% (95%CI 0–5%) in week 21. However, CMY-2-E. coli remained present in the environmental samples during the whole study. CMY-2-E. coli concentration varied between detection limit (<10^3) and 2·10^4 cfu/g faeces. The sharp reduction of CMY-2-E. coli in this broiler parent flock in absence of antibiotics suggests a selective disadvantage of blaCMY-2 on IncA/C plasmids on animal level. The underlying mechanism should be studied further as this may provide new insights on how to reduce ESBL/pAmpC prevalence and transmission in the broiler production chain.

Different cross protection scopes of two avian influenza H5N1 vaccines against infection of layer chickens with a heterologous highly pathogenic virus
Poetri, Okti Nadia ; Boven, Michiel van; Koch, Guus ; Stegeman, Arjan ; Claassen, Ivo ; Wisaksana, I.W. ; Bouma, Annemarie - \ 2017
Research in Veterinary Science 114 (2017). - ISSN 0034-5288 - p. 143 - 152.
Archetti-Horsfall ratio - Avian influenza - Cross protection - H5N1

Avian influenza (AI) virus strains vary in antigenicity, and antigenic differences between circulating field virus and vaccine virus will affect the effectiveness of vaccination of poultry. Antigenic relatedness can be assessed by measuring serological cross-reactivity using haemagglutination inhibition (HI) tests. Our study aims to determine the relation between antigenic relatedness expressed by the Archetti-Horsfall ratio, and reduction of virus transmission of highly pathogenic H5N1 AI strains among vaccinated layers. Two vaccines were examined, derived from H5N1 AI virus strains A/Ck/WJava/Sukabumi/006/2008 and A/Ck/CJava/Karanganyar/051/2009. Transmission experiments were carried out in four vaccine and two control groups, with six sets of 16 specified pathogen free (SPF) layer chickens. Birds were vaccinated at 4 weeks of age with one strain and challenge-infected with the homologous or heterologous strain at 8 weeks of age. No transmission or virus shedding occurred in groups challenged with the homologous strain. In the group vaccinated with the Karanganyar strain, high cross-HI responses were observed, and no transmission of the Sukabumi strain occurred. However, in the group vaccinated with the Sukabumi strain, cross-HI titres were low, virus shedding was not reduced, and multiple transmissions to contact birds were observed. This study showed large differences in cross-protection of two vaccines based on two different highly pathogenic H5N1 virus strains. This implies that extrapolation of in vitro data to clinical protection and reduction of virus transmission might not be straightforward.

Genetic Characterization of Porcine Circovirus Type 2 (PCV2) in Pigs of Bhutan
Monger, V.R. ; Loeffen, W.L.A. ; Kus, K. ; Stegeman, J.A. ; Dukpa, K. ; Szymanek, K. ; Podgórska, K. - \ 2017
Transboundary and Emerging Diseases 64 (2017)2. - ISSN 1865-1674 - p. 442 - 448.
Bhutan - genome - phylogenetic analysis - pigs - porcine circovirus type 2 - sequence

Porcine circovirus (PCV) is a small non-enveloped virus with a single-stranded circular DNA with two antigenically and genetically different species, PCV1 and PCV2. Among these two, PCV2 is responsible for multifactorial disease syndromes, the most important disease known as PCV2-systemic disease (PCV2-SD), previously known as post-weaning multisystemic wasting syndrome (PMWS). The epidemiological situation is dynamically changing and new strains including recombinant PCV2 have emerged in Asia. In Bhutan, pigs are important livestock and play a very important role in providing meat and income for rural farmers. Although high rate of pigs seropositive against PCV2 was described in Bhutan, there was no virological evidence for PCV2 infections. This study was conducted to confirm the presence of PCV2 through detection of PCV2 DNA and molecular characterization of PCV2 strains in tissue and blood samples collected from Bhutanese pigs. Porcine circovirus type 2 genome was detected in 16 of 34 tissue samples pigs from the government farm. In 9 pigs, very high level of viral replication indicated that PCV2-SD was detected. Phylogenetic analysis performed with a set of GenBank sequences revealed that the Bhutanese PCV2 strains belonged to the PCV2b genotype and grouped with cluster 1C.

Coxiella burnetii (Q fever) prevalence in associated populations of humans and small ruminants in The Gambia
Bok, Jeroen ; Hogerwerf, L. ; Germeraad, Eveline A. ; Roest, H.I.J. ; Faye-Joof, Tisbeh ; Jeng, M. ; Nwakanma, D. ; Secka, A. ; Stegeman, A. ; Goossens, B. ; Wegmüller, Rita ; Sande, M.T. van der; Hoek, W. ; Secka, A. - \ 2017
Tropical Medicine and International Health 22 (2017)3. - ISSN 1360-2276 - p. 323 - 331.
Objectives To simultaneously estimate the prevalence of antibodies against Coxiella burnetii (Q fever) among adults and small ruminants, and C. burnetii shedding prevalence among small ruminants in households in the Kiang West district of The Gambia; and to assess associated risk factors. Methods Sera of 599 adults and 615 small ruminants from 125 compounds within 12 villages were tested for antibodies against C. burnetii using ELISA. Vaginal swabs and milk samples of 155 small ruminants were tested using PCR to investigate shedding of C. burnetii. Results 3.8% to 9.7% of adults, depending on ELISA test cutoff, and 24.9% of small ruminants in Kiang West were seropositive. Having at least one seropositive animal in one's compound was a risk factor for human seropositivity (OR 3.35, 95% CI: 1.09-14.44). A grazing area within a village was a risk factor for seropositivity in small ruminants (OR 2.07, 95% CI: 1.26-3.50); others were having lambed (OR 2.75, 95% CI: 1.37-5.76), and older age of the animals (OR 2.75, 95% CI: 1.37-5.76 for 1-3 years and OR 5.84, 95% CI: 3.10-11.64 for >3 years). 57.4% of sampled small ruminants were shedding C. burnetii. Conclusion C. burnetii infection is endemic among both humans and small ruminants in this area of The Gambia. Human and animal exposure to C. burnetii were related at compound-level. Further research into the clinical relevance of C. burnetii infection in West Africa is needed.
Effects of on-farm hatching on Eimeria infection dynamics
Velkers, F.C. ; Jong, I.C. de; Ven, L.J.F. van de; Reep, L. Van de; Stegeman, J.A. - \ 2016
An increasing trend in Europe is placing 18 days incubated eggs on trays in broiler houses for on-farm hatching. Chicks are not transported and have immediate access to food and water, which promotes early intestinal tract and immune system development1. These chicks may be exposed to environmental Eimeria oocysts earlier than hatchery chicks. Therefore we compared Eimeria infection dynamics for in hatchery (R) and on-farm hatched (F) Ross 308 broilers in 2 field studies. In study 1 a poultry house was divided in a part with F and R hatching for 2 rounds. Study 2 consisted of 10 flocks on 4 farms. For each F flock an R flock on the same farm, originating from the same parent flock, was compared. Oocysts per g (OPG) was determined weekly from wk 2-6 of age with qPCR (GD Deventer, the Netherlands) on pooled colonic and cecal feces, collected 3 times per wk. For comparisons, OPG was determined with a McMaster counting technique2 twice per wk from wk 2 onwards (study 1) and in wk 4 and 5 (study 2). Lesion scores for E. acervulina, E. maxima and E. tenella3 in 5 randomly selected birds from F and R flocks at post-mortem were assessed weekly in wk 3-6 (study 1) and once in wk 4 (study 2). Use of coccidiostats, antibiotics and production performance was recorded. E. acervulina, E. tenella (study 1 & 2) and E. maxima (study 2) were detected, without differences in species distribution between F and R flocks. In both studies lesion scores were generally mild and not significantly different between F and R flocks. Oocyst excretion patterns throughout the production period were similar for F and R flocks in study 1, but in study 2 F flocks on average showed a later excretion peak (R peaked between day 22-28 and F between days 22-28 or 28-34). OPG for qPCR and McMaster technique gave similar results. Production performance could not be compared between F and R flocks, due to differences in disease occurrence and antibiotic treatments. Only small differences in the course of Eimeria infections were detected, but the number of flocks was too small to draw accurate conclusions about effects of hatching system on coccidiosis. Small differences, e.g. time of peak excretion, may affect body weight at slaughter or affect opportunities for secondary infections. Therefore, if more on-farm hatching and comparable reference flocks become available, further research is warranted.
Evaluation of Oral Bait Vaccine Efficacy Against Classical Swine Fever in Village Backyard Pig Farms in Bhutan
Monger, V.R. ; Stegeman, J.A. ; Dukpa, K. ; Gurung, R.B. ; Loeffen, W.L.A. - \ 2016
Transboundary and Emerging Diseases 63 (2016)6. - ISSN 1865-1674 - p. e2111 - e218.
Bhutan - Classical swine fever - Exotic pigs - Local pigs - Oral bait vaccine - Village backyard farms - Virus neutralization test

Control and eradication of classical swine fever (CSF) in countries with a high proportion of backyard holdings is a challenge. Conventional attenuated Chinese C-strain vaccines, though safe and effective, are difficult to use in backyard farms due to various practical reasons. The aim of this study was to evaluate the efficacy of the CSF oral bait vaccine in village backyard pig farms and to assess the farmers' knowledge on CSF and motivation on using oral vaccines. The pigs were fed the bait by the farmers themselves; one bait was given on day 0, followed by second bait on the next day. Seventy-three per cent (140 of 193 pigs) of vaccinated pigs had either a slight (2-fold-3-fold; 60 pigs) or significant (at least 4-fold; 80 pigs) increase of the antibody titre against CSFV. A significant increase of the antibody titres was mainly observed in pigs with no pre-vaccination titre (OR = 12, 95% CI = 4-40). The number of pigs with protective antibody titres (≥40) rose from 47 (24%) to 115 (60%) following vaccination. Only 30% of the farmers claimed to be familiar with CSF, although clinical signs they mentioned were rather unspecific and could relate to many other pig diseases. Most of the farmers claimed to be motivated to use oral vaccines if made available. The oral vaccine could be a substitute for the conventional attenuated CSF vaccines in areas where it is logistically difficult for veterinarians to visit. It may therefore be a useful tool to combat endemic CSF disease in regions where the disease continues to have a serious impact on the backyard farmers who depend on pig farming for their sustenance and livelihoods.

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