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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Characterization of Coxiella burnetii outbreak strains
Kuley, Runa - \ 2017
University. Promotor(en): Mari Smits; Jerry Wells, co-promotor(en): Alex Bossers. - Wageningen : Wageningen University - ISBN 9789463431514 - 226
coxiella burnetii - q fever - outbreaks - strains - characterization - pathogenesis - zoonoses - virulence - dna sequencing - polymerase chain reaction - livestock farming - netherlands - q-koorts - uitbraken (ziekten) - stammen (biologisch) - karakterisering - pathogenese - zoönosen - virulentie - dna-sequencing - polymerase-kettingreactie - veehouderij - nederland

Q fever is a worldwide zoonotic infectious disease caused by the bacterium Coxiella burnetii. During 2007-2010, the largest Q fever outbreak was reported in The Netherlands, where more than 4000 human cases were registered showing a serious burden of the disease. During this outbreak, goats harboring predominantly the CbNL01 genotype strain were identified as the major source of disease in humans and drastic measures such as mass culling of infected goats were implemented to reduce the spread of the pathogen and control the disease. In order to minimize such complications in the future, it is crucial to have a thorough understanding of the disease causing pathogen and to develop effective Q fever vaccines. The causes of the large Dutch outbreak are not well-understood and one of the main reasons speculated were the hyper-virulent behavior of the circulating C. burnetii isolates. The research described in this thesis focuses on the characterization of C. burnetii outbreak strains isolated from infected goats, cattle, sheep and human clinical materials. Our studies were initiated to better understand the bacterial pathogenesis, virulence, evolution, adaptations in various environments, host immune responses and to identify pathogen related factors that have modulated the disease outbreak. We specifically aimed to identify the virulence factors and mechanisms that contributed to the increased zoonotic potential of the strain associated with the Dutch Q fever outbreak.

The studies presented in this thesis majorly applied Pathogenomic approaches at the genome and transcriptome level to decipher host-pathogen interactions and to develop new tools to study C. burnetii infections. A transcriptome analysis of the outbreak C. burnetii strain of the CbNL01 genotype grown under in vivo and in vitro conditions resulted in the identification of distinct metabolic adaptations and virulence mechanisms of the bacterium. Detailed comparative analysis of complete genome sequences of C. burnetii strains showed a high similarity between strains of the same genotype. Genome sequences of the Dutch outbreak CbNL01 genotype strains were more divergent than the genome sequences of the less prevalent CbNL12 genotype strains and the NM reference strain. The analysis also showed that the high virulence of the outbreak strains was not associated with acquiring novel virulence-related genes arguing against the idea that the Dutch outbreak was due to emergence of hyper-virulent strains though horizontal gene transfer. Among the prominent genetic differences in the CbNL01 outbreak strains compared to CbNL12 and NM, were the presence of several point mutations and increased transposon mediated genome plasticity, which might have contributed to its epidemic potential. Point mutations, especially in a large number of membrane proteins, could also have contributed to the increased zoonotic potential of CbNL01 strains allowing this clone to escape the host immune responses in goats and humans. In addition, mutations in critical genes involved in virulence and evasion of the host immune system could be potentially involved in the increased virulence of the CbNL01 outbreak strains. On the contrary, studies on host immune responses in an in vivo (experimental infections in mice) and an in vitro (human PBMC’s stimulation) model did not show any difference associated with the strain genotype. However, differences in immune responses were found to be associated with the host-origin of the C. burnetii strains. Among different host-origin strains, strains derived from goats and humans generated significantly lower innate and adaptive immune responses than strains derived from cattle, whereas no differences in immune responses were observed when strains were grouped based upon their genotype. These observations support immune evasions as a major virulence strategy of goat and human strains in hosts and further suggest that bacteria originating from goats have a greater potential to cause outbreaks in humans. This indicates that for Q fever prevention purposes goats should be efficiently monitored for the presence of C. burnetii. Taken together, the results described in this thesis suggest that the virulence potential of C. burnetii strains is not only based on genetic differences, but also on other host-adaptation mechanisms such as transposition of genomic elements and/or differential regulation of gene expression. Finally, the results from this thesis provide a framework for future studies in the development of vaccines and diagnostic tools for Q fever.

Using typing techniques in a specific outbreak : the ethical reflection of public health professionals
Rump, B. ; Cornelis, C. ; Woonink, F. ; Steenbergen, J. Van; Verweij, M. ; Hulscher, M. - \ 2017
Epidemiology and Infection 145 (2017)7. - ISSN 0950-2688 - p. 1431 - 1436.
Ethics - molecular epidemiology - outbreaks - public health ethics - typing
Typing techniques are laboratory methods used in outbreak management to investigate the degree to which microbes found within an outbreak are related. Knowledge about relational patterns between microbes benefits outbreak management, but inevitably also tells us something about the relational patterns of the people hosting them. Since the technique is often used without explicit consent of all individuals involved, this may raise ethical questions. The aim of this study was to unravel the complex ethical deliberation of professionals over the use of such techniques. We organised group discussions (n = 3) with Dutch outbreak managers (n = 23). The topic list was based on previously identified ethical issues and discussions were analysed for recurrent themes. We found that outbreak managers first and foremost reflect on the balance of individual harm with public health benefit. This key question was approached by way of discussing four more specific ethical themes: (1) justification of governmental intervention, (2) responsibility to prevent infections, (3) scientific uncertainty and (4) legal consequences. The themes found in this study, rephrased into accessible questions, represent the shared ethical understanding of professionals and can help to articulate the ethical dimensions of using molecular science in response to infectious disease outbreaks.
Markers inside wood : tree rings as archives of insect outbreaks, drift-sand dynamics, and spring flooding
Copini, P. - \ 2015
University. Promotor(en): Frits Mohren, co-promotor(en): Ute Sass-Klaassen; Jan den Ouden. - Wageningen : Wageningen University - ISBN 9789462574861 - 192
acer palmatum - quercus robur - hout - insectenplagen - jaarringen - uitbraken (ziekten) - inundatie - houtanatomie - bomen - wood - insect pests - growth rings - outbreaks - flooding - wood anatomy - trees


Trees are long-living organisms that record ecologically relevant information in their xylem that can be accessed by dendrochronology, the study of tree rings. Specific environmental events like frost, fire, floods, burial or wounding may drastically alter the anatomy of tree rings and consequently may leave markers inside trees. These wood-anatomical markers have shown a high potential for studying past environmental events with an annual or even intra-annual temporal resolution. In this thesis, the temporal resolution of wood-anatomical markers was studied to date wounds made by invasive Anoplophora beetles. In addition, the accuracy of dating drift-sand dynamics and spring flooding events was studied using wood-anatomical changes, which were expected to occur after drastic changes in the stem and root environment. It was hypothesised that all these wood-anatomical markers can be used with an intra-annual resolution. Field studies in combination with experiments were used to study tree growth and the formation of wood-anatomical markers in Japanese maple (Acer palmatum Thunb.) and pedunculate oak (Quercus robur L.).

It was shown that wounds in Japanese maple can be assigned to three different phases related to tree-ring development: (1) wounds that originated during dormancy are located at the tree-ring boundary; (2) wounds that originated during the growing season are located within the tree ring. If wound-xylem formation was observed locally around the wound (3), it could either imply that the wound originated at the very end of the growing season or just before the onset of radial growth or during dormancy when temperature was high. Dating wounds caused by the formation of exit holes has proved to be very significant in fighting invasive insect outbreaks. By pinpointing the exact year and season when Anoplophora beetles emerged, it can be substantiated whether exit holes in imported trees were formed at the location of import. This knowledge can subsequently be used to draw up customised eradication measures and allocate proper surveillance plans and population dynamics can be reconstructed.

Living trees in drift-sand areas may contain burial or exposure signals even if the sand under which they were buried has long since disappeared. Anatomical changes in pedunculate oak trees due to burial are not a result of physical changes in the stem environment that directly affect the cambium. Instead they are most likely the result of adventitious root formation that transforms lower parts of the stem into root, and concomitantly induces a change from stem to root anatomy. As the formation of a wood-anatomical marker caused by burial can be delayed by many years or might be entirely absent, depending on the formation of adventitious root formation, its presence only allows for an estimate on minimum burial age.

Flood rings containing anomalously small earlywood vessels in pedunculate oak are formed in response to spring flooding within a narrow time window related to cambial phenology. They can be induced if a flooding event has occurred for at least two weeks during spring. The extreme reduction in vessel size is a consequence of a delay in vessel formation due to anoxic conditions related to flooding. Flood rings however, provide only limited information on the duration of flooding, as the flooding may have lasted for months (during winter) before it is recorded.

It is concluded that the origin of wood-anatomical markers largely determines the temporal resolution. Markers induced by wounding or flooding show a high intra-annual temporal resolution and immediate effect on tree functioning, whereas burial might not be recorded three years after the triggering events. The different wood-anatomical markers addressed in this thesis illustrate the relevance of studying the mechanism behind the formation of markers for correct interpretation of the specific triggering factor as well as their temporal resolution. Only with this knowledge it becomes possible to reliably use wood-anatomical markers as archives to understand and reconstruct dynamics in geomorphic, entomologic, pathogenic or climatic factors.

The Schmallenberg virus epidemic in Europe 2011-2013
Afonso, A. ; Abrahantes, J.C. ; Conraths, F. ; Veldhuis, A.E. ; Elbers, A.R.W. - \ 2014
Preventive Veterinary Medicine 116 (2014)4. - ISSN 0167-5877 - p. 391 - 403.
congenital-abnormalities - akabane virus - newborn lambs - infection - cattle - sheep - seroprevalence - outbreaks - france
During the Schmallenberg virus (SBV) epidemic, the European Food Safety Authority (EFSA) collected data on SBV occurrence across Europe in order to provide an assessment of spread and impact. By May 2013, twenty-nine countries were reporting to EFSA and twenty-two countries had reported cases of SBV. The total number of SBV herds reported was 13,846 and the number of SBV laboratory confirmed herds was 8730. The surveillance activities were based on the detection of SBV clinical cases (either adults or newborns). Malformation in newborns was the most commonly reported clinical sign of SBV-infection. All countries were able to provide the date when the first suspicion of SBV in the herd was reported and nineteen could report the location of the herd at a regional level. This allowed the spread of SBV in Europe to be measured both temporally and spatially. The number of SBV confirmed herds started to increase in December 2011 and two peaks were observed in 2012 (February and May). Confirmed herds continued to be reported in 2012 and into 2013. An increase during winter 2012 and spring 2013 was again observed, but the number of confirmed herds was lower than in the previous year. SBV spread rapidly throughout Europe from the initial area of detection. SBV was detected above the latitude of 60° North, which exceeds the northern expansion observed during the bluetongue virus serotype 8 epidemic in 2006-2009. The impact of SBV was calculated as ratio of the number of herds with at least one malformed SBV positive foetus and the total number of herds in this region. The 75th percentile of the malformations ratio in the various affected countries for the whole reporting period was below 1% and 3% for cattle and sheep herds, respectively. International data collection on emerging diseases represents a challenge as the nature of available data, data quality and the proportion of reported cases may vary widely between affected countries. Surveillance activities on emerging animal diseases are often structured only for case detection making the estimation of infection/diseases prevalence and the investigation of risk factors difficult. The impact of the disease must be determined to allow risk managers to take appropriate decisions. Simple within-herd impact indicators suitable for emerging disease outbreaks should be defined that could be measured as part of routine animal health surveillance programmes and allow for rapid and reliable impact assessment of emerging animal health diseases.
Intervention methods to control the transmission of noroviruses and other enteric and respiratory viruses
Tuladhar, E. - \ 2014
University. Promotor(en): Marcel Zwietering, co-promotor(en): E. Duizer; Rijkelt Beumer. - Wageningen : Wageningen University - ISBN 9789462571129 - 163
norovirus - gastro-enteritis - uitbraken (ziekten) - ziekteoverdracht - voedselbesmetting - ademhalingsziekten - voedselmicrobiologie - gastroenteritis - outbreaks - disease transmission - food contamination - respiratory diseases - food microbiology

Intervention methods to control the transmission of noroviruses and other enteric and respiratory viruses

Era Tuladhar


Human noroviruses are the leading cause of acute and outbreak associated gastroenteritis worldwide. The outbreaks occur often in hospitals, nursing homes, health care centers as well as in individual homes. Due to the high number of outbreaks and frequency of infection, the burden of disease is high. The virus transmission takes place from person to person directly through the fecal oral route or indirectly through contaminated surfaces or consumption of contaminated food. This study aimed to investigate methods to reduce the burden of disease caused by norovirus and focuses on reducing the transmission through hands and contaminated surfaces. Besides human norovirus, other enteric and respiratory viruses are also transmitted through these routes and were included in the study. Enteric viruses included in the study were human norovirus GI.4 and GII.4, poliovirus Sabin1, rotavirus SA11, parechovirus 1 and murine norovirus 1 (MNV1). The respiratory viruses were adenovirus type 5 and influenza A (H1N1) virus. These viruses can contaminate food through food handler-related contamination. Heating and pasteurizing is a commonly used method for inactivation of microorganisms in food. Heating at commonly used temperatures of 56°C and 73°C showed that thermo-stability of parechovirus and influenza virus was found to be similar to that of proven foodborne viruses and heating at 73°C for 3 min is sufficient to reduce the infectivity of the tested viruses > 4 log10. Not only food, contaminated hands can also transfer viruses to different surfaces, which are then sources of further transmission of the viruses. Cleaning and disinfection of contaminated surfaces are common intervention methods used in health care and kitchen facilities. The enteric and respiratory viruses showed varying susceptibility to cleaning and disinfection procedures applied. Data on infectious doses and transfer efficiencies was used to estimate a target level to which the residual contamination should be reduced and it was found that a single wipe with liquid soap followed by a wipe with 250 ppm free chlorine solution was sufficient to reduce the residual contamination to below the target level for most of the pathogens tested. Spot disinfection by 1000 ppm chlorine solution after wiping with liquid soap was sufficient to reduce the genomic copies of human norovirus GI.4 and GII.4 (> 5 log10 PCRU) completely within 10 min. In addition to manual cleaning and disinfection, non-touch disinfection of contaminated surfaces by vaporized hydrogen peroxide disinfection at 127 ppm for 1 h, as approved disinfection in the Netherlands for hospitals and health care centers, is effective against poliovirus Sabin 1, rotavirus SA11, adenovirus type 5 and MNV1 on stainless steel, framing panel (> 4 log10 infectivity reduction) and gauze (> 2 log10 infectivity reduction). Beside non-touch disinfection, immobilized biocidals have been tested for disinfection of contaminated surfaces. Immobilized quaternary ammonium compound coatings were virucidal against the influenza virus within 2 min but no virucidal effect against poliovirus was found in 6 h. Thus the coating can be used against the influenza A virus to prevent the transmission through frequently touched sites but not for non-enveloped viruses. Our study demonstrated that a norovirus contaminated hand can transfer the viruses to different surfaces, including food, even after the virus is dried. As an intervention method to prevent the transmission of the virus, washing hands with soap and water (> 5 log10 PCRU reduction) is better than using alcohol based hand disinfectants in removing noroviruses from hands.

This research has delivered new insights in methods to reduce transmission of human norovirus and produced comparative quantitative data on intervention methods to control transmission of other enteric and respiratory viruses. The study has additionally contributed to a better understanding of human norovirus transmission intervention efficiency. The new insights allow for the development of science based guidelines to control norovirus and other enteric and respiratory viruses in outbreak settings and thus help to reduce the burden of illness caused by these viruses.

Field vaccinated chickens with low antibody titres show equally insufficient protection against matching and non-matching genotypesof virulent Newcastle disease virus
Dortmans, J.C.F.M. ; Venema-Kemper, S. ; Peeters, B.P.H. ; Koch, G. - \ 2014
Veterinary Microbiology 172 (2014)1-2. - ISSN 0378-1135 - p. 100 - 107.
shedding following vaccination - wild-type - outbreaks - strains - sequence - china - pathogenesis - challenge - genetics - poultry
Newcastle disease (ND) is a severe threat to the poultry industry and is caused by virulent strains of Newcastle disease virus (NDV). Many countries maintain a vaccination policy, but NDV is rapidly evolving as shown by the discovery of several new genotypes in the last decades. We tested the efficacy of the currently used classical commercial ND vaccine based on the genotype II strain VG/GA, applied under standard field conditions, against outbreak strains. Field vaccinated broilers were challenged with four different viruses belonging to genotype II, V or VII. A large proportion of field vaccinated broilers showed suboptimal immunity and the protection level against early and recent NDV isolates was dramatically low. Furthermore, there were no significant differences in protection afforded by a genotype II vaccine against a genotype II virus challenge compared to a challenge with viruses belonging to the other genotypes. This study suggests that the susceptibility of vaccinated poultry to NDV infection is not the result of vaccine mismatch, but rather of poor vaccination practices
Assessment of Food Safety Management Systems in the global fresh produce chain
Kirezieva, K.K. ; Jacxsens, L. ; Uyttendaele, M. ; Boekel, T. van; Luning, P.A. - \ 2013
Food Research International 52 (2013)1. - ISSN 0963-9969 - p. 230 - 242.
techno-managerial approach - irrigation water - public-health - microbiological quality - foodborne pathogens - enteric pathogens - escherichia-coli - cut lettuce - outbreaks - contamination
Foodborne outbreaks appear to increase with more incidences linked to fresh produce and derived food products. This indicates inadequacies in Food Safety Management Systems (FSMSs), which are currently implemented in companies along the fresh produce chain. However, the information related to these inadequacies is restricted and little is known about the status of the FSMS. This paper describes the development of a tool for assessment of FSMS implemented in the fresh produce chain. The tool consists of indicators and grids to assess activities that are important for fresh produce, and the system output in terms of microbiological and chemical food safety (that is, pesticide residues and emerging mycotoxins). Three sets of indicators, one for each stage of the production chain (primary production, processing and trade), have been validated by experts and tested in companies. The tool enables an integral and comprehensive assessment of FSMS across the entire supply chain. Users of the tool can identify improvement opportunities and learn how to develop towards more advanced levels of activities. For research purposes differences in FSMS can be identified and linked to type of commodity, production system, country, etc.
A wide variety of Clostridium perfringens type A food-borne isolates that carry a chromosomal cpe gene belong to one multilocus sequence typing cluster
Xiao, Y. ; Wagendorp, A. ; Moezelaar, R. ; Abee, T. ; Wells-Bennik, M.H.J. - \ 2012
Applied and Environmental Microbiology 78 (2012)19. - ISSN 0099-2240 - p. 7060 - 7068.
enterotoxin gene - multiplex pcr - sporulation - identification - strains - growth - locus - pathogens - outbreaks - genotype
Of 98 suspected food-borne Clostridium perfringens isolates obtained from a nationwide survey by the Food and Consumer Product Safety Authority in The Netherlands, 59 strains were identified as C. perfringens type A. Using PCR-based techniques, the cpe gene encoding enterotoxin was detected in eight isolates, showing a chromosomal location for seven isolates and a plasmid location for one isolate. Further characterization of these strains by using (GTG)5 fingerprint repetitive sequence-based PCR analysis distinguished C. perfringens from other sulfite-reducing clostridia but did not allow for differentiation between various types of C. perfringens strains. To characterize the C. perfringens strains further, multilocus sequence typing (MLST) analysis was performed on eight housekeeping genes of both enterotoxic and non-cpe isolates, and the data were combined with a previous global survey covering strains associated with food poisoning, gas gangrene, and isolates from food or healthy individuals. This revealed that the chromosomal cpe strains (food strains and isolates from food poisoning cases) belong to a distinct cluster that is significantly distant from all the other cpe plasmid-carrying and cpe-negative strains. These results suggest that different groups of C. perfringens have undergone niche specialization and that a distinct group of food isolates has specific core genome sequences. Such findings have epidemiological and evolutionary significance. Better understanding of the origin and reservoir of enterotoxic C. perfringens may allow for improved control of this organism in foods.
Estimating the per-contact probability of infection by highly pathogenic avian influenza (H7N7) virus during the 2003 epidemic in the Netherlands.
Ssematimba, A. ; Elbers, A.R.W. ; Hagenaars, T.H.J. ; Jong, M.C.M. de - \ 2012
PLoS One 7 (2012)7. - ISSN 1932-6203 - 1 p.
h5n1 infection - poultry farms - a virus - transmission - outbreaks - history
Estimates of the per-contact probability of transmission between farms of Highly Pathogenic Avian Influenza virus of H7N7 subtype during the 2003 epidemic in the Netherlands are important for the design of better control and biosecurity strategies. We used standardized data collected during the epidemic and a model to extract data for untraced contacts based on the daily number of infectious farms within a given distance of a susceptible farm. With these data, we used a maximum likelihood estimation approach to estimate the transmission probabilities by the individual contact types, both traced and untraced. The estimated conditional probabilities, conditional on the contact originating from an infectious farm, of virus transmission were: 0.000057 per infectious farm within 1 km per day, 0.000413 per infectious farm between 1 and 3 km per day, 0.0000895 per infectious farm between 3 and 10 km per day, 0.0011 per crisis organisation contact, 0.0414 per feed delivery contact, 0.308 per egg transport contact, 0.133 per other-professional contact and, 0.246 per rendering contact. We validate these outcomes against literature data on virus genetic sequences for outbreak farms. These estimates can be used to inform further studies on the role that improved biosecurity between contacts and/or contact frequency reduction can play in eliminating between-farm spread of the virus during future epidemics. The findings also highlight the need to; 1) understand the routes underlying the infections without traced contacts and, 2) to review whether the contact-tracing protocol is exhaustive in relation to all the farm’s day-to-day activities and practices.
The relation between farming practices, ecosystem, and white spot in syndrome virus (WSSV) disease outbreaks in penaeus monodon farms in the Philippines
Tendencia Alapide, E. - \ 2012
University. Promotor(en): Johan Verreth, co-promotor(en): Roel Bosma; J.H. Primavera. - S.l. : s.n. - ISBN 9789461733702 - 135
garnalen - witte-vlekken-syndroom-virus - garnalenteelt - uitbraken (ziekten) - epidemiologie - infectieziekten - dierziektepreventie - aquatische ecosystemen - fysicochemische eigenschappen - mangroves - filippijnen - shrimps - white spot syndrome virus - shrimp culture - outbreaks - epidemiology - infectious diseases - animal disease prevention - aquatic ecosystems - physicochemical properties - philippines

The white spot syndrome virus (WSSV) affecting shrimp aquaculture in most producing countries has caused huge economic losses resulting in bankruptcy to both large and small farmers. Studies done on WSSV epidemiology were mostly tank-based and on species other than Penaeus monodon. There is a need to investigate WSSV epidemiology in P. monodon in on-farm situations, thus including both risk and protective factors. This thesis aimed to generate knowledge that can improve prevention against WSSV in shrimp culture through better farm husbandry by studying the epidemiology of WSSV in on-farm situations. To achieve this goal data from cross-sectional and case studies were analysed to identify on-farm WSSV risk and protective factors, and longitudinal studies were done to assess factors affecting water quality and causing WSSV infection to result in an outbreak.

The thesis identified the following WSSV risk factors related to the physico-chemical parameters of the water: low and fluctuating temperature, low and fluctuating salinity, and pH fluctuation. The risk of high temperature and high salinity for an outbreak of WSV disease may be related to fluctuations in these two parameters. Risk factors related to farm husbandry techniques were feeding with molluscs, sludge removal and its deposition on the dike, sharing water source with other farms and having the same receiving and intake water. Identified WSSV protective factors were high mangrove to pond area ratio, feeding with natural food or phytoplankton, and higher percentage of beneficial bacteria like the yellow colonies that grow on thiosulphate citrate bilesalt sucrose agar, a Vibrio selective medium.

Results of the longitudinal studies demonstrated that WSSV infection may not result in outbreaks in greenwater pond and in ponds with mangroves in the receiving environment. Our results did not provide explanations why the WSSV infection did not result in an outbreak in farms with mangroves in the receiving environment. In greenwater ponds, this was attributed to the better water and soil quality, higher plankton count, and higher heterotrophic bacterial count.

Classical Swine Fever and Avian Influenza epidemcis: Lessons learned
Elbers, A.R. ; Loeffen, W.L.A. ; Koch, G. - \ 2012
Berliner und Münchener Tierärztliche Wochenschrift 125 (2012)1/2. - ISSN 0005-9366 - p. 21 - 26.
clinical signs - h7n7 epidemic - wild boar - decision-support - outbreaks - netherlands - virus - diagnosis - europe - performance
This publication is based on a talk which was held in the course of the spring symposium „Impfen statt Keulen“ of the Akademie für Tiergesundheit (AfT) 2011 in Wiesbaden-Naurod. Experience with recent large-scale epidemics of Classical Swine Fever and Avian Influenza – among others in the Netherlands – have teached us several lessons that should prepare us better for future outbreaks. Among others, improving early detection of outbreaks – by using syndrome surveillance systems – is a key factor, in which farmers and veterinary practitioners have an imminent role. A major step in this respect is facilitation of the use of exclusion diagnostics without closing down the farm in clinical situations with non-specific clinical signs observed in sick animals. The hesitance of farmers and veterinary practitioners to report a suspect clinical situation on a livestock farm and how to facilitate that process is another major issue. Furthermore, the importance of communication between the field and the laboratory with respect to post mortem examination will be highlighted, and the need for outbreak simulation exercises with neighbouring countries in order to be better prepared, will be discussed.
Unspecified gastroenteritis illness and deaths in the elderly associated with norovirus epidemics
Asten, L. van; Siebenga, J. ; Wijngaard, C. van den; Verheij, R. ; Vliet, H. van; Kretzschmar, M. ; Boshuizen, H.C. ; Pelt, W. van; Koopmans, M. - \ 2011
Epidemiology 22 (2011)3. - ISSN 1044-3983 - p. 336 - 343.
hospital admissions - united-states - rotavirus infection - nursing-homes - outbreaks - netherlands - disease - england - europe - virus
Background: New variant strains of norovirus have emerged worldwide in recent years, evolving by mutation much like influenza viruses. These strains have been associated with a notable increase in the number of annual norovirus outbreaks. However, the impact of such increased norovirus activity on morbidity and mortality is not clear because norovirus infection is rarely specifically registered. Methods: We studied trends of gastroenteritis with unspecified cause in medical registrations (ie, general practitioner [GP] visits, hospitalizations, and deaths) and their association with known temporal trends in norovirus outbreaks in the Netherlands. Using weekly counts in the elderly (aged 65+ years) from 1999 through 2006, we applied Poisson regression analyses adjusted for additional pathogens and seasonal trends (linear, sine, and cosine terms). Results: In the elderly, each notified norovirus outbreak was associated with an estimated 26 unspecified gastroenteritis GP visits (95% confidence interval = 17-34), 2.2 unspecified gastroenteritis hospitalizations (1.6-2.7), and 0.14 unspecified gastroenteritis deaths (0.08-0.21). For the heaviest norovirus season (2004-2005), these models attributed up to 3804 unspecified gastroenteritis GP visits, 318 unspecified gastroenteritis hospitalizations, and 21 unspecified gastroenteritis deaths to norovirus outbreaks among a total elderly population of 2.3 million. Discussion: The recent increase in norovirus outbreak activity is associated with increases of unspecified gastroenteritis morbidity and even deaths in the elderly. Norovirus should not be regarded as an infection with trivial health risks.
Spread and Control of Rift Valley Fever virus after accidental introduction in the Netherlands: a modelling study.
Fischer, E.A.J. ; Boender, G.J. ; Koeijer, A.A. de; Nodelijk, G. ; Roermund, H.J.W. van - \ 2011
Lelystad : CVI - 59
veehouderij - riftvalleykoortsvirus - virusziekten - rundveeziekten - schapenziekten - geitenziekten - wiskundige modellen - uitbraken (ziekten) - waarschijnlijkheidsanalyse - livestock farming - rift valley fever virus - viral diseases - cattle diseases - sheep diseases - goat diseases - mathematical models - outbreaks - probability analysis
Rift Valley Fever (RVF) is a zoonotic vector-borne infection and causes a potentially severe disease in both humans and young animals. The Ministry of Economic Affairs, Agriculture and Innovation (EL&I) is interested in the risk of an outbreak of Rift Valley Fever virus (RVFV) for the Netherlands, and more knowledge is needed about the risk of introduction of the virus, the risk of spread (transmission) of the virus in the country once introduced, and the methods for control and surveillance. For this purpose, a mathematical model was developed to study (1) the probability of a RVF outbreak at different days of introduction during the year, (2) the probability of persistence of the infection during the entire year, and (3) outbreak size and duration at different days of introduction during the year.
Quantitative analysis of transmission parameters for bluetongue virus serotype 8 in Western Europe in 2006.
Koeijer, A.A. de; Boender, G.J. ; Nodelijk, G. ; Staubach, C. ; Meroc, E. ; Elbers, A.R. - \ 2011
Veterinary Research 42 (2011). - ISSN 0928-4249 - 9 p.
mouth-disease epidemic - northern europe - great-britain - netherlands - spread - vaccination - outbreaks - belgium - vector - farms
The recent bluetongue virus serotype 8 (BTV-8) epidemic in Western Europe struck hard. Controlling the infection was difficult and a good and safe vaccine was not available until the spring of 2008. Little was known regarding BTV transmission in Western Europe or the efficacy of control measures. Quantitative details on transmission are essential to assess the potential and efficacy of such measures. To quantify virus transmission between herds, a temporal and a spatio-temporal analysis were applied to data on reported infected herds in 2006. We calculated the basic reproduction number between herds (Rh: expected number of new infections, generated by one initial infected herd in a susceptible environment). It was found to be of the same order of magnitude as that of an infection with Foot and Mouth Disease (FMD) in The Netherlands, e.g. around 4. We concluded that an average day temperature of at least 15°C is required for BTV-8 transmission between herds in Western Europe. A few degrees increase in temperature is found to lead to a major increase in BTV-8 transmission. We also found that the applied disease control (spatial zones based on 20 km radius restricting animal transport to outside regions) led to a spatial transmission pattern of BTV-8, with 85% of transmission restricted to a 20 km range. This 20 km equals the scale of the protection zones. We concluded that free animal movement led to substantial faster spread of the BTV-8 epidemic over space as compared to a situation with animal movement restrictions.
Diagnosing foodborne illness: A behavioral analysis of barriers to testing
Kaptan, G. ; Fischhoff, B. - \ 2011
Journal of Public Health Policy 32 (2011). - ISSN 0197-5897 - p. 60 - 72.
population-based estimate - united-states - foodborne disease - infectious diarrhea - surveillance - burden - outbreaks - guidelines - etiology - workers
Public health authorities rely on the timely flow of laboratory results to detect and control food-borne illnesses. At times, social and economic barriers limit individuals’ ability to get needed tests. We demonstrate a simple behavioral approach to assess the cost-effectiveness of interventions designed to remove three social and economic barriers to testing individuals with acute diarrheal illness: testing costs, income loss, and inconvenience. We use readily available statistics to rank programs by their cost effectiveness to identify those most worthy of studying in greater detail.
Low-pathogenic notifiable avian influenza serosurveillance and the risk of infection in poultry - a critical review of the European Union active surveillance programme (2005-2007)
Gonzales, J.L. ; Elbers, A.R.W. ; Bouma, A. ; Koch, G. ; Wit, J.J. de; Stegeman, J.A. - \ 2010
Influenza and Other Respiratory Viruses 4 (2010)2. - ISSN 1750-2640 - p. 91 - 99.
h7n7 epidemic - virus h7n7 - netherlands - outbreaks - performance - farms
Background Since 2003, Member States (MS) of the European Union (EU) have implemented serosurveillance programmes for low pathogenic notifiable avian influenza (LPNAI) in poultry. To date, there is the need to evaluate the surveillance activity in order to optimize the programme's surveillance design. Objectives To evaluate MS sampling operations [sample size and targeted poultry types (PTs)] and its relation with the probability of detection and to estimate the PTs relative risk (RR) of being infected. Methods Reported data of the surveillance carried out from 2005 to 2007 were analyzed using: (i) descriptive indicators to characterize both MS sampling operations and its relation with the probability of detection and the LPNAI epidemiological situation, and (ii) multivariable methods to estimate each PTs RR of being infected. Results Member States sampling a higher sample size than that recommended by the EU had a significantly higher probability of detection. Poultry types with ducks & geese, game-birds, ratites and "others" had a significant higher RR of being seropositive than chicken categories. The seroprevalence in duck & geese and game-bird holdings appears to be higher than 5%, which is the EU-recommended design prevalence (DP), while in chicken and turkey categories the seroprevalence was considerably lower than 5% and with that there is the risk of missing LPNAI seropositive holdings. Conclusion It is recommended that the European Commission discusses with its MS whether the results of our evaluation calls for refinement of the surveillance characteristics such as sampling frequency, the between-holding DP and MS sampling operation strategies.
Quantitative Microbial Risk Assessment for Escherichia coli O157:H7, Salmonella enterica, and Listeria monocytogenes in Leafy Green Vegetables Consumed at Salad Bars, Based on Modeling Supply Chain Logistics
Tromp, S.O. ; Rijgersberg, H. ; Franz, E. - \ 2010
Journal of Food Protection 73 (2010)10. - ISSN 0362-028X - p. 1830 - 1840.
iceberg lettuce - dose-response - fresh produce - growth - outbreaks - foodborne - o157h7 - temperatures - restaurant - infection
Quantitative microbial risk assessments do not usually account for the planning and ordering mechanisms (logistics) of a food supply chain. These mechanisms and consumer demand determine the storage and delay times of products. The aim of this study was to quantitatively assess the difference between simulating supply chain logistics (MOD) and assuming fixed storage times (FIX) in microbial risk estimation for the supply chain of fresh-cut leafy green vegetables destined for working-canteen salad bars. The results of the FIX model were previously published (E. Franz, S. O. Tromp, H. Rijgersberg, and H. J. van der Fels-Klerx, J. Food Prot. 73:274-285, 2010). Pathogen growth was modeled using stochastic discrete-event simulation of the applied logistics concept. The public health effects were assessed by conducting an exposure assessment and risk characterization. The relative growths of Escherichia coli O157 (17%) and Salmonella enterica (15%) were identical in the MOD and FIX models. In contrast, the relative growth of Listeria monocytogenes was considerably higher in the MOD model (1,156%) than in the FIX model (194%). The probability of L. monocytogenes infection in The Netherlands was higher in the MOD model (5.18 × 10-8) than in the FIX model (1.23 × 10-8). The risk of listeriosis-induced fetal mortality in the perinatal population increased from 1.24 × 10-4 (FIX) to 1.66 × 10-4 (MOD). Modeling the probabilistic nature of supply chain logistics is of additional value for microbial risk assessments regarding psychrotrophic pathogens in food products for which time and temperature are the postharvest preventive measures in guaranteeing food safety.
Financial consequences of the Dutch bluetongue serotype 8 epidemics of 2006 and 2007
Velthuis, A.G.J. ; Saatkamp, H.W. ; Mourits, M.C.M. ; Koeijer, A.A. de; Elbers, A.R.W. - \ 2010
Preventive Veterinary Medicine 93 (2010)4. - ISSN 0167-5877 - p. 294 - 304.
field observations - clinical signs - netherlands - cattle - sheep - outbreaks
This study calculates the financial consequences of the bluetongue serotype 8 (BTV8) epidemics of 2006 and 2007 in the Netherlands. We constructed a deterministic economic model that is compatible with the Dutch livestock production systems for cattle, sheep and goats. Two hundred cattle farms and 270 sheep farms were infected with BTV8 in the epidemic of 2006, whereas 30,417 cattle farms, 45,022 sheep farms and 35,278 goat farms were estimated to be infected in the epidemic of 2007. The net costs (costs minus benefits) of the BTV8 epidemic of 2006 (BT2006) was estimated at 32.4 million Euros. The net costs of the BTV8 epidemic of 2007 (BT2007) was valued at 164–175 million Euros, depending on the mortality and morbidity rates for cattle used. The losses account for 2%, 10% and 11% of the gross value of the primary production within Dutch pasture-based livestock farming that equals 1.6 billion Euros. Control measures accounted for 91% of the net costs of the BT2006, while diagnostic costs represented 7%. By contrast, for the BT2007 92% of the net costs were in the form of production losses and veterinary treatment fees, while only 6% were related to control measures. Furthermore, the control costs dropped from 29,630 in BT2006 to 10,990 in BT2007 mainly due to the costly indoor housing that was not obligatory during the BT2007 epidemic. The cattle sector suffered 88% and 85% of the net costs for the BT2006 and BT2007, respectively; the highest of all sectors.
De invloed van houderijaspecten op het risico van ziekte-uitbraak op varkensbedrijven en de sterke en zwakke punten in gangbare en high health systemen
Bokma-Bakker, M.H. ; Bergevoet, R.H.M. ; Napel, J. ten; Swanenburg, M. - \ 2009
Lelystad : Animal Sciences Group (Rapport / Wageningen UR Livestock Research 242) - 33
varkens - varkenshouderij - dierhouderij - infectieziekten - uitbraken (ziekten) - ziekteresistentie - diergezondheid - bedrijfssystemen - intensieve veehouderij - biologische landbouw - nederland - dierziektepreventie - pigs - pig farming - animal husbandry - infectious diseases - outbreaks - disease resistance - animal health - farming systems - intensive livestock farming - organic farming - netherlands - animal disease prevention
Methods for the enormous killing of poultry by animal illnesses a challenge: acceptable in certain concerns for nuisance and efficiency = Methoden voor het grootschalig doden van pluimvee voor dierziekte bestrijding: aanvaardbaar wat betreft ongerief en efficiëntie
Gerritzen, M.A. - \ 2007
Tijdschrift voor Diergeneeskunde 132 (2007)4. - ISSN 0040-7453 - p. 129 - 131.
bio-ethiek - vernietiging van dieren - pluimveehouderij - ziektebestrijding - aviaire influenzavirussen - fumigatie - dierenwelzijn - aviaire influenza A-virussen - uitbraken (ziekten) - bezettingsdichtheid - pluimveebedrijf - pluimveeproducten - pluimveeziekten - ziektedistributie - aviciden - dierfysiologie - bioethics - destruction of animals - poultry farming - disease control - avian influenza viruses - fumigation - animal welfare - avian influenza A viruses - outbreaks - stocking density - poultry industry - poultry products - poultry diseases - disease distribution - avicides - animal physiology
De productie van pluimveeproducten is in Nederland een belangrijke economische activiteit. Allen al in Nederland worden voor de productie van eieren en vlees jaarlijks driehonderd miljoen kippen gefokt en geslacht. De productie van deze pluimveeproducten is voornamelijk geconcentreerd op grote bedrijven die dicht bij elkaar liggen met veel dieren per vierkante meter, met als gevolg gebieden met een hoge pluimveedichtheid. Door deze hoge concentratie dieren in een beperkt gebied hebben uitbraken van besmettelijke dierziekten, zoals hoog pathogene aviaire influenza (HPAI), ernstige consequenties voor pluimvee, de pluimveehouders, en de gemeenschap
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