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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Managing a cluster outbreak of psittacosis in Belgium linked to a pet shop visit in The Netherlands
Boeck, C. De; DeHollogne, C. ; Dumont, A. ; Spierenburg, M. ; Heijne, M. ; Gyssens, I. ; Hilst, J. Van der; Vanrompay, D. - \ 2016
Epidemiology and Infection (2016). - ISSN 0950-2688 - p. 1710 - 1716.
Chlamydia psittaci - outbreak - psittacosis - zoonoses

In July 2013, a Belgian couple were admitted to hospital because of pneumonia. Medical history revealed contact with birds. Eleven days earlier, they had purchased a lovebird in a pet shop in The Netherlands. The bird became ill, with respiratory symptoms. The couple's daughter who accompanied them to the pet shop, reported similar symptoms, but was travelling abroad. On the suspicion of psittacosis, pharyngeal swabs from the couple were taken and sent to the Belgian reference laboratory for psittacosis. Culture and nested polymerase chain reaction (PCR) tests were positive for the presence of Chlamydia psittaci, and ompA genotyping indicated genotype A in both patients. The patients were treated with doxycycline and the daughter started quinolone therapy; all three recovered promptly. Psittacosis is a notifiable disease in Belgium and therefore local healthcare authorities were informed. They contacted their Dutch colleagues, who visited the pet shop. Seven pooled faecal samples were taken and analysed using PCR by the Dutch national reference laboratory for notifiable animal diseases for the presence of Chlamydia psittaci. Four (57%) samples tested positive, genotyping revealed genotype A. Enquiring about exposure to pet birds is essential when patients present with pneumonia. Reporting to health authorities, even across borders, is warranted to prevent further spread.

West Nile Virus: High Transmission Rate in North-Western European Mosquitoes Indicates Its Epidemic Potential and Warrants Increased Surveillance
Fros, J.J. ; Geertsema, C. ; Vogels, C.B.F. ; Roosjen, P.P.J. ; Failloux, A.B. ; Vlak, J.M. ; Koenraadt, C.J.M. ; Takken, W. ; Pijlman, G.P. - \ 2015
PLoS Neglected Tropical Diseases 9 (2015)7. - ISSN 1935-2727
united-states - differential virulence - experimental-infection - vector competence - lineage 1 - outbreak - circulation - strains - disease - encephalitis
West Nile virus (WNV) is on the rise in Europe, with increasing numbers of human cases of neurological disease and death since 2010. However, it is currently unknown whether or not WNV will continue to spread to north-western Europe (NWE), in a fashion similar to the WNV epidemic sweep in the United States (1999–2004). The presence of competent mosquitoes is a strict requirement for WNV transmission, but no laboratory studies have been conducted with the new European lineage 2 WNV outbreak strain. Our study is the first to investigate transmissibility in NWE Culex pipiens for lineage 2 WNV in a systematic, direct comparison with North American Culex pipiens and with the lineage 1 WNV strain. We demonstrate that European mosquitoes are highly competent for both WNV lineages, which underscores the epidemic potential ofWNV in Europe. However, the transmission rate for lineage 2 WNV was significantly lower in North American mosquitoes, which indicates different risk levels between both continents for lineage 2 but not lineage 1 WNV. Based on our result, we propose that WNV surveillance in mosquitoes and birds must be intensified in Europe to allow early detection, timely intervention strategies and prevent outbreaks of WNV neurological disease.
Social Pathways for Ebola Virus Disease in Rural Sierra Leone, and Some Implications for Containment
Richards, P. ; Amara, J. ; Ferme, M.C. ; Kamara, P. ; Mokuwa, E. ; Sheriff, A.I. ; Suluku, R. ; Voors, M.J. - \ 2015
PLoS Neglected Tropical Diseases 9 (2015)4. - ISSN 1935-2727
The current outbreak of Ebola Virus Disease in Upper West Africa is the largest ever recorded. Molecular evidence suggests spread has been almost exclusively through humanto- human contact. Social factors are thus clearly important to understand the epidemic and ways in which it might be stopped, but these factors have so far been little analyzed. The present paper focuses on Sierra Leone, and provides cross sectional data on the least understood part of the epidemic—the largely undocumented spread of Ebola in rural areas. Various forms of social networking in rural communities and their relevance for understanding pathways of transmission are described. Particular attention is paid to the relationship between marriage, funerals and land tenure. Funerals are known to be a high-risk factor for infection. It is suggested that more than a shift in awareness of risks will be needed to change local patterns of behavior, especially in regard to funerals, since these are central to the consolidation of community ties. A concluding discussion relates the information presented to plans for halting the disease. Local consultation and access are seen as major challenges to be addressed.
Evaluating vaccination strategies to control foot and mouth disease: a model comparison study
Roche, S.E. ; Garner, M.G. ; Sanson, R.L. ; Cook, C. ; Birch, C. ; Backer, J.A. ; Dube, C. ; Patyk, K.A. ; Stevenson, M.A. ; Yu, Z.D. - \ 2015
Epidemiology and Infection 143 (2015)6. - ISSN 0950-2688 - p. 1256 - 1275.
emergency vaccination - simulation-model - epidemic - spread - australia - outbreak
SUMMARY Simulation models can offer valuable insights into the effectiveness of different control strategies and act as important decision support tools when comparing and evaluating outbreak scenarios and control strategies. An international modelling study was performed to compare a range of vaccination strategies in the control of foot-and-mouth disease (FMD). Modelling groups from five countries (Australia, New Zealand, USA, UK, The Netherlands) participated in the study. Vaccination is increasingly being recognized as a potentially important tool in the control of FMD, although there is considerable uncertainty as to how and when it should be used. We sought to compare model outputs and assess the effectiveness of different vaccination strategies in the control of FMD. Using a standardized outbreak scenario based on data from an FMD exercise in the UK in 2010, the study showed general agreement between respective models in terms of the effectiveness of vaccination. Under the scenario assumptions, all models demonstrated that vaccination with 'stamping-out' of infected premises led to a significant reduction in predicted epidemic size and duration compared to the 'stamping-out' strategy alone. For all models there were advantages in vaccinating cattle-only rather than all species, using 3-km vaccination rings immediately around infected premises, and starting vaccination earlier in the control programme. This study has shown that certain vaccination strategies are robust even to substantial differences in model configurations. This result should increase end-user confidence in conclusions drawn from model outputs. These results can be used to support and develop effective policies for FMD control.
Land-Applied Goat Manure as a Source of Human QFever in the Netherlands, 2006–2010
Hermans, C.M.L. ; Jeurissen, L.J.J. ; Hackert, V. ; Hoebe, C. - \ 2014
PLoS ONE 9 (2014)5. - ISSN 1932-6203 - 9 p.
coxiella-burnetii - infection - epidemic - outbreak
Studies have shown a link between Q-fever positive farms (QFPFs) and community cases of human Q-fever. Our study is the first to investigate the potential role of contaminated land-applied manure in human Q-fever, based on a large set of nationwide notification and farm management data. Time between manure application and disease onset in geographically linked notified human cases coincided with the incubation period of Q-fever. Proximity of contaminated land parcels predicted human cases better than proximity of QFPFs (80% vs. 58%, 0–5 km in 2009). Incidence around QFPFs and contaminated land parcels decreased with distance, but not around non-contaminated land parcels. Incidence was higher around contaminated land parcels than non-contaminated land parcels (RR = [10],95%CI = [7], [1]–[14,2]). Our findings deliver evidence that, apart from QFPFs, land-applied contaminated manure may be another source of human Q-fever.
An experimental Toxoplasma gondii dose response challenge model to study therapeutic or vaccine efficacy in cats
Cornelissen, J.B.W.J. ; Giessen, J.W.B. van der; Takumi, K. ; Teunis, P.F.M. ; Wisselink, H.J. - \ 2014
PLoS ONE 9 (2014)9. - ISSN 1932-6203 - 9 p.
crude rhoptry proteins - united-states - tissue cysts - oocysts - bradyzoites - infectivity - tachyzoites - outbreak - animals - humans
High numbers of Toxoplasma gondii oocysts in the environment are a risk factor to humans. The environmental contamination might be reduced by vaccinating the definitive host, cats. An experimental challenge model is necessary to quantitatively assess the efficacy of a vaccine or drug treatment. Previous studies have indicated that bradyzoites are highly infectious for cats. To infect cats, tissue cysts were isolated from the brains of mice infected with oocysts of T. gondii M4 strain, and bradyzoites were released by pepsin digestion. Free bradyzoites were counted and graded doses (1000, 100, 50, 10), and 250 intact tissue cysts were inoculated orally into three cats each. Oocysts shed by these five groups of cats were collected from faeces by flotation techniques, counted microscopically and estimated by real time PCR. Additionally, the number of T. gondii in heart, tongue and brains were estimated, and serology for anti T. gondii antibodies was performed. A Beta-Poisson dose-response model was used to estimate the infectivity of single bradyzoites and linear regression was used to determine the relation between inoculated dose and numbers of oocyst shed. We found that real time PCR was more sensitive than microscopic detection of oocysts, and oocysts were detected by PCR in faeces of cats fed 10 bradyzoites but by microscopic examination. Real time PCR may only detect fragments of T. gondii DNA without the presence of oocysts in low doses. Prevalence of tissue cysts of T. gondii in tongue, heart and brains, and anti T. gondii antibody concentrations were all found to depend on the inoculated bradyzoite dose. The combination of the experimental challenge model and the dose response analysis provides a suitable reference for quantifying the potential reduction in human health risk due to a treatment of domestic cats by vaccination or by therapeutic drug application.
Infection of great apes and a zoo keeper with the same Mycobacterium tuberculosis spoligotype
Akkerman, O.W. ; Werf, T.S. van de; Rietkerk, F. ; Eger, A. ; Soolingen, D. ; Loo, K. v.d.; Zanden, A.G.M. v.d. - \ 2014
Medical Microbiology and Immunology 203 (2014)2. - ISSN 0300-8584 - p. 141 - 144.
resistant tuberculosis - transmission - outbreak - epidemiology - school
An animal keeper was diagnosed with pulmonary tuberculosis (TB) after bi-annual screening for latent TB infection in zoo employees. In the same period, several bonobos of the zoo were suffering from TB as well. The Mycobacterium tuberculosis strains from both the animal keeper and the bonobos appeared identical. We provide evidence that the animals infected their keeper.
Economic assessment of Q fever in the Netherlands
Asseldonk, M.A.P.M. van; Prins, J. ; Bergevoet, R.H.M. - \ 2013
Preventive Veterinary Medicine 112 (2013)1-2. - ISSN 0167-5877 - p. 27 - 34.
vaccination - epidemics - zoonosis - benefits - outbreak - disease - burden
In this paper the economic impact of controlling the Q fever epidemic in 2007-2011 in the Netherlands is assessed. Whereas most of the long-term benefits of the implemented control programme stem from reduced disease burden and human health costs, the majority of short-term intervention costs were incurred in the dairy goat sector. The total intervention cost in agriculture amounted approximately 35,000 Euro per DALY occurred. By culling of infected animals, breeding prohibition and vaccination, the epidemic seems to be under control. As the dairy goat vaccination programme continues, future expenses in maintaining the current protected status are relatively low. (C) 2013 Elsevier B.V. All rights reserved.
Ranking the microbiological safety of foods: A new tool and its application to composite products
Stella, P. ; Cerf, O. ; Hugas, M. ; Koutsoumanis, K.P. ; Nguyen-The, C. ; Sofos, J.N. ; Valero, A. ; Zwietering, M.H. - \ 2013
Trends in Food Science and Technology 33 (2013)2. - ISSN 0924-2244 - p. 124 - 138.
quantitative risk-assessment - yersinia-enterocolitica - escherichia-coli - moisture transfer - water - infection - outbreak - storage - virus
A methodology based on the combination of two complementary approaches to rank microbiological risks in foods is presented. In the forward approach data on the pathogenicity of hazards and their behaviour in food during processing and following steps, up to consumption, are used in decision trees to qualitatively estimate the risk associated with foods. In the backward approach risks are evaluated based on the analysis of data available on the past occurrence of hazards and foodborne outbreaks. The categorisation of foods using the forward approach should prevail, and whenever it leads to a likely risk for a given food, the risk can be further qualified with the results from the backward approach. The methodology developed was applied to rank the public health risk posed by certain composite products, which contain both processed products of animal origin and products of plant origin (e.g., bread, cakes, chocolate). Despite limitations in the data available for these foods, valuable results were obtained. The method is therefore considered suitable for application with success to other types of food, and is proposed as a tool for risk managers to rank foods based on their potential food safety risks
Specific Interferon-¿ detection for the diagnosis of previous Q fever
Schoffelen, T. ; Joosten, L.A. ; Herremans, T. ; Haan, A.F.J. ; Ammerdorffer, A. ; Rumke, H.C. ; Wijkmans, C. ; Roest, H.I.J. ; Netea, M.G. ; Meer, J.W. van der; Sprong, T. ; Deuren, M. van - \ 2013
Clinical infectious diseases 56 (2013)12. - ISSN 1058-4838 - p. 1742 - 1751.
coxiella-burnetii infection - follow-up - tuberculosis infection - responses - vaccine - tests - outbreak - assays - cells - gold
BACKGROUND: Current practice for diagnosis of Q fever, caused by the intracellular pathogen Coxiella burnetii, relies mainly on serology and, in prevaccination assessment, on skin tests (STs), which both have drawbacks. In this study, C. burnetii-specific interferon ¿ (IFN-¿) production was used as a new diagnostic tool for previous Q fever, circumventing most of these drawbacks. Our aim was to compare this test to serology and ST. METHODS: One thousand five hundred twenty-five individuals from an endemic area with a risk for chronic Q fever were enrolled. IFN-¿ production was measured after in vitro stimulation of whole blood with C. burnetii antigens. Various formats using different C. burnetii antigens were tested. Serology and ST were performed in all individuals. RESULTS: In all assay formats, C. burnetii-specific IFN-¿ production was higher (P <.0001) in seropositive or ST-positive subjects than in seronegative and ST-negative subjects. Whole blood incubated for 24 hours with C. burnetii Nine Mile showed optimal performance. After excluding subjects with equivocal serology and/or borderline ST results, IFN-¿ production was 449 ± 82 pg/mL in the positive individuals (n = 219) but only 21 ± 3 pg/mL in negative subjects (n = 908). Using Bayesian analysis, sensitivity and specificity (87.0% and 90.2%, respectively) were similar to the combination of serology and ST (83.0% and 95.6%, respectively). Agreement with the combination of serology and ST was moderate (84% concordance; ¿ = 0.542). CONCLUSIONS: Specific IFN-¿ detection is a novel diagnostic assay for previous C. burnetii infection and shows similar performance and practical advantages over serology and ST. Future studies to investigate the clinical value in practice are warranted.
Q fever in humans and farm animals in four European countries, 1982 to 2010
Georgiev, M. ; Alfonso, A. ; Neubauer, H. ; Needham, H. ; Thiéry, R. ; Rodolakis, A. ; Roest, H.I.J. ; Stärk, K.D. ; Stegeman, J.A. ; Vellema, P. ; Hoek, W. van der; More, S.J. - \ 2013
Eurosurveillance 18 (2013)8. - ISSN 1025-496X - 13 p.
burnetii-inactivated vaccine - coxiella-burnetii - seroepidemiologic survey - hospitalized-patients - sheep flock - dairy herds - goat herds - netherlands - outbreak - germany
fever is a disease of humans, caused by Coxiella burnetii, and a large range of animals can be infected. This paper presents a review of the epidemiology of Q fever in humans and farm animals between 1982 and 2010, using case studies from four European countries (Bulgaria, France, Germany and the Netherlands). The Netherlands had a large outbreak between 2007 and 2010, and the other countries a history of Q fever and Q fever research. Within all four countries, the serological prevalence of C. burnetii infection and reported incidence of Q fever varies broadly in both farm animals and humans. Proximity to farm animals and contact with infected animals or their birth products have been identified as the most important risk factors for human disease. Intrinsic farm factors, such as production systems and management, influence the number of outbreaks in an area. A number of disease control options have been used in these four countries, including measures to increase diagnostic accuracy and general awareness, and actions to reduce spillover (of infection from farm animals to humans) and human exposure. This study highlights gaps in knowledge, and future research needs.
Genetic Data Provide Evidence for Wind-Mediated Transmission of Highly Pathogenic Avian Influenza
Ypma, R.J. ; Jonges, M. ; Bataille, A. ; Stegeman, A. ; Koch, G. ; Boven, M. van; Koopmans, M. ; Ballegooijen, W.M. ; Wallinga, J. - \ 2013
The Journal of Infectious Diseases 207 (2013)5. - ISSN 0022-1899 - p. 730 - 735.
outbreak - h5n1 - epidemic - poultry
Outbreaks of highly pathogenic avian influenza in poultry can cause severe economic damage and represent a public health threat. Development of efficient containment measures requires an understanding of how these influenza viruses are transmitted between farms. However, the actual mechanisms of interfarm transmission are largely unknown. Dispersal of infectious material by wind has been suggested, but never demonstrated, as a possible cause of transmission between farms. Here we provide statistical evidence that the direction of spread of avian influenza A(H7N7) is correlated with the direction of wind at date of infection. Using detailed genetic and epidemiological data, we found the direction of spread by reconstructing the transmission tree for a large outbreak in the Netherlands in 2003. We conservatively estimate the contribution of a possible wind-mediated mechanism to the total amount of spread during this outbreak to be around 18%.
Letter: Search for possible additional reservoirs for human Q fever, the Netherlands
Roest, H.I.J. ; Solt, C.B. van; Tilburg, J.J.H.C. ; Klaassen, C.H. ; Hovius, E.K. ; Roest, F.T.F. ; Vellema, P. ; Brom, R. van der; Zijderveld, F.G. van - \ 2013
Emerging Infectious Diseases 19 (2013)5. - ISSN 1080-6040 - p. 834 - 835.
coxiella-burnetii - epidemic - genotype - outbreak
Q fever in pregnant goats: humoral and cellular immune responses
Roest, H.I.J. ; Post, J. ; Gelderen, E. van; Zijderveld, F.G. van; Rebel, J.M.J. - \ 2013
Veterinary Research 44 (2013)1. - ISSN 0928-4249 - 9 p.
coxiella-burnetii infection - phase-i - t-cells - netherlands - outbreak - mice - lipopolysaccharide - progesterone - vaccination - history
Q fever is a zoonosis caused by the intracellular bacterium Coxiella burnetii. Both humoral and cellular immunity are important in the host defence against intracellular bacteria. Little is known about the immune response to C. burnetii infections in domestic ruminants even though these species are the major source of Q fever in humans. To investigate the goat’s immune response we inoculated groups of pregnant goats via inhalation with a Dutch outbreak isolate of C. burnetii. All animals were successfully infected. Phase 1 and Phase 2 IgM- and IgG-specific antibodies were measured. Cellular immune responses were investigated by interferon-gamma, enzyme-linked immunosorbent spot test (IFN-¿ Elispot), lymphocyte proliferation test (LPT) and systemic cytokines. After two weeks post inoculation (wpi), a strong anti-C. burnetii Phase 2 IgM and IgG antibody response was observed while the increase in IgM anti-Phase 1 antibodies was less pronounced. IgG anti-Phase 1 antibodies started to rise at 6 wpi. Cellular immune responses were observed after parturition. Our results demonstrated humoral and cellular immune responses to C. burnetii infection in pregnant goats. Cell-mediated immune responses did not differ enough to distinguish between Coxiella-infected and non-infected pregnant animals, whereas a strong-phase specific antibody response is detected after 2 wpi. This humoral immune response may be useful in the early detection of C. burnetii-infected pregnant goats.
Rift Valley Fever Risk Map Model and Seroprevalence in Selected Wild Ungulates and Camels from Kenya
Britch, S.C. ; Binepal, Y.S. ; Ruder, M.G. ; Kariithi, H.M. ; Linthicum, K.J. ; Anyamba, A. ; Small, J.L. ; Tucker, C.J. ; Ateya, L.O. ; Oriko, A.A. ; Gacheru, S. ; Wilson, W.C. - \ 2013
PLoS ONE 8 (2013)6. - ISSN 1932-6203 - 16 p.
saudi-arabia - vertical transmission - vegetation index - african buffalo - virus - outbreak - antibody - humans - prevalence - prevention
Since the first isolation of Rift Valley fever virus (RVFV) in the 1930s, there have been multiple epizootics and epidemics in animals and humans in sub-Saharan Africa. Prospective climate-based models have recently been developed that flag areas at risk of RVFV transmission in endemic regions based on key environmental indicators that precede Rift Valley fever (RVF) epizootics and epidemics. Although the timing and locations of human case data from the 2006–2007 RVF outbreak in Kenya have been compared to risk zones flagged by the model, seroprevalence of RVF antibodies in wildlife has not yet been analyzed in light of temporal and spatial predictions of RVF activity. Primarily wild ungulate serum samples from periods before, during, and after the 2006–2007 RVF epizootic were analyzed for the presence of RVFV IgM and/or IgG antibody. Results show an increase in RVF seropositivity from samples collected in 2007 (31.8%), compared to antibody prevalence observed from 2000–2006 (3.3%). After the epizootic, average RVF seropositivity diminished to 5% in samples collected from 2008–2009. Overlaying maps of modeled RVF risk assessments with sampling locations indicated positive RVF serology in several species of wild ungulate in or near areas flagged as being at risk for RVF. Our results establish the need to continue and expand sero-surveillance of wildlife species Kenya and elsewhere in the Horn of Africa to further calibrate and improve the RVF risk model, and better understand the dynamics of RVFV transmission.
Q fever in pregnant Goats: PAthogenesis and excretion of Coxiella burnetii
Roest, H.I.J. ; Gelderen, E. van; Dinkla, A. ; Frangoulidis, D. ; Zijderveld, F.G. van; Rebel, J.M.J. ; Keulen, L.J.M. van - \ 2012
PLoS ONE 7 (2012)11. - ISSN 1932-6203
brucella-abortus - natural-history - netherlands - infection - outbreak - placentitis - agent
Coxiella burnetii is an intracellular bacterial pathogen that causes Q fever. Infected pregnant goats are a major source of human infection. However, the tissue dissemination and excretion pathway of the pathogen in goats are still poorly understood. To better understand Q fever pathogenesis, we inoculated groups of pregnant goats via the intranasal route with a recent Dutch outbreak C. burnetii isolate. Tissue dissemination and excretion of the pathogen were followed for up to 95 days after parturition. Goats were successfully infected via the intranasal route. PCR and immunohistochemistry showed strong tropism of C. burnetii towards the placenta at two to four weeks after inoculation. Bacterial replication seemed to occur predominantly in the trophoblasts of the placenta and not in other organs of goats and kids. The amount of C. burnetii DNA in the organs of goats and kids increased towards parturition. After parturition it decreased to undetectable levels: after 81 days post-parturition in goats and after 28 days post-parturition in kids. Infected goats gave birth to live or dead kids. High numbers of C. burnetii were excreted during abortion, but also during parturition of liveborn kids. C. burnetii was not detected in faeces or vaginal mucus before parturition. Our results are the first to demonstrate that pregnant goats can be infected via the intranasal route. C. burnetii has a strong tropism for the trophoblasts of the placenta and is not excreted before parturition; pathogen excretion occurs during birth of dead as well as healthy animals. Besides abortions, normal deliveries in C. burnetii-infected goats should be considered as a major zoonotic risk for Q fever in humans.
Residual viral and bacterial contamination of surfaces after cleaning and disinfection
Tuladhar, E. ; Hazeleger, W.C. ; Koopmans, M. ; Zwietering, M.H. ; Beumer, R.R. ; Duizer, E. - \ 2012
Applied and Environmental Microbiology 78 (2012)21. - ISSN 0099-2240 - p. 7769 - 7775.
round structured viruses - hepatitis-a virus - real-time pcr - murine norovirus - feline calicivirus - enteric viruses - environmental contamination - inanimate surfaces - human hands - outbreak
Environmental surfaces contaminated with pathogens can be sources of indirect transmission, and cleaning and disinfection are common interventions focused on reducing contamination levels. We determined the efficacy of cleaning and disinfection procedures for reducing contamination by noroviruses, rotavirus, poliovirus, parechovirus, adenovirus, influenza virus, Staphylococcus aureus, and Salmonella enterica from artificially contaminated stainless steel surfaces. After a single wipe with water, liquid soap, or 250-ppm free chlorine solution, the numbers of infective viruses and bacteria were reduced by 1 log10 for poliovirus and close to 4 log10 for influenza virus. There was no significant difference in residual contamination levels after wiping with water, liquid soap, or 250-ppm chlorine solution. When a single wipe with liquid soap was followed by a second wipe using 250- or 1,000-ppm chlorine, an extra 1- to 3-log10 reduction was achieved, and except for rotavirus and norovirus genogroup I, no significant additional effect of 1,000 ppm compared to 250 ppm was found. A reduced correlation between reduction in PCR units (PCRU) and reduction in infectious particles suggests that at least part of the reduction achieved in the second step is due to inactivation instead of removal alone. We used data on infectious doses and transfer efficiencies to estimate a target level to which the residual contamination should be reduced and 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.
Unravelling transmission trees of infectious diseases by combining genetic and epidemiological data
Ypma, R.J.F. ; Bataille, A. ; Stegeman, A. ; Koch, G. ; Wallinga, J. ; Ballegooijen, W.M. - \ 2012
Proceedings of the Royal Society. B: Biological Sciences 279 (2012)1728. - ISSN 0962-8452 - p. 444 - 450.
influenza-a virus - mouth-disease - h7n7 - netherlands - outbreak - foot
Knowledge on the transmission tree of an epidemic can provide valuable insights into disease dynamics. The transmission tree can be reconstructed by analysing either detailed epidemiological data (e.g. contact tracing) or, if sufficient genetic diversity accumulates over the course of the epidemic, genetic data of the pathogen. We present a likelihood-based framework to integrate these two data types, estimating probabilities of infection by taking weighted averages over the set of possible transmission trees. We test the approach by applying it to temporal, geographical and genetic data on the 241 poultry farms infected in an epidemic of avian influenza A (H7N7) in The Netherlands in 2003. We show that the combined approach estimates the transmission tree with higher correctness and resolution than analyses based on genetic or epidemiological data alone. Furthermore, the estimated tree reveals the relative infectiousness of farms of different types and sizes.
Neurotoxin gene profiling of Clostridium botulinum types C and D gathered from different countries within Europe
Woudstra, C. ; Skarin, A. ; Anniballi, F. ; Fenicia, F. ; Bano, L. ; Drigo, I. ; Koene, M.G.J. ; Bäyon-Auboyer, M.H. ; Buffereau, J.P. ; Medici, D. ; Fach, P. - \ 2012
Applied and Environmental Microbiology 78 (2012)9. - ISSN 0099-2240 - p. 3120 - 3127.
real-time pcr - polymerase-chain-reaction - wound botulism - quantitative detection - bovine samples - cattle herds - alpha-toxin - outbreak - identification - diagnostics
Clostridium botulinum types C and D, as well as their mosaic variants C-D and D-C, are associated with avian and mammalian botulism. This study reports on the development of low-density macroarrays based on the GeneDisc cycler platform (Pall-GeneDisc Technologies) applied to the simultaneous detection of the C. botulinum subtypes C, C-D, D, and D-C. The limit of detection of the PCR assays was 38 fg of total DNA, corresponding to 15 genome copies. Artificially contaminated samples of cecum showed a limit of detection below 50 spores/g. The tests were performed with a large variety of bacterial strains, including C. botulinum types C (n = 12), C-D (n = 29), D (n = 5), and D-C (n = 10), other botulinum neurotoxin (BoNT)-producing Clostridium strains (n = 20), non-BoNT-producing clostridia (n = 20), and other bacterial species (n = 23), and showed a high specificity. These PCR assays were compared to previously published real-time PCRs for the detection of C. botulinum in 292 samples collected from cases of botulism events in four European regions. The majority of the samples originated from wild birds (n = 108), poultry (n = 60), and bovines (n = 56). Among the 292 samples, 144 were positive for either the bont/C-D or the bont/D-C gene by using the GeneDisc arrays. The reliability of the results tallied to 97.94%. Interestingly, only BoNT mosaics, types C-D and D-C, were found in naturally contaminated samples whatever their animal origin and their geographical location. Further investigations should now be performed in order to check that mosaic types dominate in Europe and that acquisition of mosaic types helps in survival or adaptation to particular niche
Vaccination against foot-and-mouth disease I: Epidemiological consequences
Backer, J.A. ; Hagenaars, T.H.J. ; Nodelijk, G. ; Roermund, H.J.W. van - \ 2012
Preventive Veterinary Medicine 107 (2012)1-2. - ISSN 0167-5877 - p. 27 - 40.
great-britain - virus transmission - emergency vaccination - contact transmission - clinical variation - fmd epidemic - dairy-cows - pigs - outbreak - strategies
An epidemic of foot-and-mouth disease (FMD) can have devastating effects on animal welfare, economic revenues, the export position and society as a whole, as occurred during the 2001 FMD epidemic in the Netherlands. Following the preemptive culling of 260,000 animals during this outbreak, the Dutch government adopted emergency vaccination as preferred control policy. However, a vaccination-to-live strategy has not been applied before, posing unprecedented challenges for effectively controlling the epidemic, regaining FMD-free status and minimizing economic losses. These three topics are covered in an interdisciplinary model analysis. In this first part we evaluate whether and how emergency vaccination can be effectively applied to control FMD epidemics in the Netherlands. For this purpose we develop a stochastic individual-based model that describes FMD virus transmission between animals and between herds, taking heterogeneity between host species (cattle, sheep and pigs) into account. Our results in a densely populated livestock area with >4 farms/km2 show that emergency ring vaccination can halt the epidemic as rapidly as preemptive ring culling, while the total number of farms to be culled is reduced by a factor of four. To achieve this reduction a larger control radius around detected farms and a corresponding adequate vaccination capacity is needed. Although sufficient for the majority of simulated epidemics with a 2 km vaccination zone, the vaccination capacity available in the Netherlands can be exhausted by pig farms that are on average ten times larger than cattle herds. Excluding pig farms from vaccination slightly increases the epidemic, but more than halves the number of animals to be vaccinated. Hobby flocks – modelled as small-sized sheep flocks – do not play a significant role in propagating the epidemic, and need not be targeted during the control phase. In a more sparsely populated livestock area in the Netherlands with about 2 farms/km2 the minimal control strategy of culling only detected farms seems sufficient to control an epidemic
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