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Durr S.,University of Bern | zu Dohna H.,University of California at Davis | Di Labio E.,Federal Veterinary Office | Carpenter T.E.,University of California at Davis | Doherr M.G.,University of Bern
Preventive Veterinary Medicine | Year: 2013

Classical swine fever (CSF) outbreaks can cause enormous losses in naïve pig populations. How to best minimize the economic damage and number of culled animals caused by CSF is therefore an important research area. The baseline CSF control strategy in the European Union and Switzerland consists of culling all animals in infected herds, movement restrictions for animals, material and people within a given distance to the infected herd and epidemiological tracing of transmission contacts. Additional disease control measures such as pre-emptive culling or vaccination have been recommended based on the results from several simulation models; however, these models were parameterized for areas with high animal densities. The objective of this study was to explore whether pre-emptive culling and emergency vaccination should also be recommended in low- to moderate-density areas such as Switzerland. Additionally, we studied the influence of initial outbreak conditions on outbreak severity to improve the efficiency of disease prevention and surveillance. A spatial, stochastic, individual-animal-based simulation model using all registered Swiss pig premises in 2009 (n= 9770) was implemented to quantify these relationships. The model simulates within-herd and between-herd transmission (direct and indirect contacts and local area spread). By varying the four parameters (a) control measures, (b) index herd type (breeding, fattening, weaning or mixed herd), (c) detection delay for secondary cases during an outbreak and (d) contact tracing probability, 112 distinct scenarios were simulated. To assess the impact of scenarios on outbreak severity, daily transmission rates were compared between scenarios. Compared with the baseline strategy (stamping out and movement restrictions) vaccination and pre-emptive culling neither reduced outbreak size nor duration. Outbreaks starting in a herd with weaning piglets or fattening pigs caused higher losses regarding to the number of culled premises and were longer lasting than those starting in the two other index herd types. Similarly, larger transmission rates were estimated for these index herd type outbreaks. A longer detection delay resulted in more culled premises and longer duration and better transmission tracing increased the number of short outbreaks. Based on the simulation results, baseline control strategies seem sufficient to control CSF in low-medium animal-dense areas. Early detection of outbreaks is crucial and risk-based surveillance should be focused on weaning piglet and fattening pig premises. © 2012 Elsevier B.V.


Durr S.,University of Bern | Fasel-Clemenz C.,Federal Veterinary Office | Thur B.,Institute of Virology and Immunoprophylaxis | Schwermer H.,Federal Veterinary Office | And 6 more authors.
Preventive Veterinary Medicine | Year: 2014

Foot-and-mouth disease (FMD) is highly contagious and one of the most economically devastating diseases of cloven-hoofed animals. Scientific-based preparedness about how to best control the disease in a previously FMD-free country is therefore essential for veterinary services. The present study used a spatial, stochastic epidemic simulation model to compare the effectiveness of emergency vaccination with conventional (non-vaccination) control measures in Switzerland, a low-livestock density country. Model results revealed that emergency vaccination with a radius of 3. km or 10. km around infected premises (IP) did not significantly reduce either the cumulative herd incidence or epidemic duration if started in a small epidemic situation where the number of IPs is still low. However, in a situation where the epidemic has become extensive, both the cumulative herd incidence and epidemic duration are reduced significantly if vaccination were implemented with a radius of 10. km around IPs. The effect of different levels of conventional strategy measures was also explored for the non-vaccination strategy. It was found that a lower compliance level of farmers for movement restrictions and delayed culling of IPs significantly increased both the cumulative IP incidence and epidemic duration. Contingency management should therefore focus mainly on improving conventional strategies, by increasing disease awareness and communication with stakeholders and preparedness of culling teams in countries with a livestock structure similar to Switzerland; however, emergency vaccination should be considered if there are reasons to believe that the epidemic may become extensive, such as when disease detection has been delayed and many IPs are discovered at the beginning of the epidemic. © 2013 Elsevier B.V.


Reist M.,University of Bern | Jemmi T.,Federal Veterinary Office | Stark K.D.C.,SAFOSO Inc. | Stark K.D.C.,Lane College
Preventive Veterinary Medicine | Year: 2012

Animal health and residue surveillance verifies the good health status of the animal population, thereby supporting international free trade of animals and animal products. However, active surveillance is costly and time-consuming. The development of cost-effective tools for animal health and food hazard surveillance is therefore a priority for decision-makers in the field of veterinary public health. The assumption of this paper is that outcome-based formulation of standards, legislation leaving room for risk-based approaches and close collaboration and a mutual understanding and exchange between scientists and policy makers are essential for cost-effective surveillance. We illustrate this using the following examples: (i) a risk-based sample size calculation for surveys to substantiate freedom from diseases/infection, (ii) a cost-effective national surveillance system for Bluetongue using scenario tree modelling and (iii) a framework for risk-based residue monitoring. Surveys to substantiate freedom from infectious bovine rhinotracheitis and enzootic bovine leucosis between 2002 and 2009 saved over 6 million € by applying a risk-based sample size calculation approach, and by taking into account prior information from repeated surveys. An open, progressive policy making process stimulates research and science to develop risk-based and cost-efficient survey methodologies. Early involvement of policy makers in scientific developments facilitates implementation of new findings and full exploitation of benefits for producers and consumers. © 2012 Elsevier B.V.


PubMed | University of Veterinary Medicine Hannover, Federal Veterinary Office, Ludwig Maximilians University of Munich, Institute for Virology and Immunology and 3 more.
Type: Journal Article | Journal: Transboundary and emerging diseases | Year: 2016

An outbreak of porcine reproductive and respiratory syndrome virus (PRRSV) occurred in November 2012 in Switzerland (CH), traditionally PRRSV-free. It was detected after a German boar stud informed a semen importer about the detection of PRRSV during routine monitoring. Tracing of semen deliveries revealed 26 Swiss sow herds that had used semen from this stud after its last negative routine monitoring and 62 further contact herds. All herds were put under movement restrictions and examined serologically and virologically. As a first measure, 59 sows from five herds that had previously been inseminated with suspicious semen were slaughtered and tested immediately. Investigations in the stud resulted in 8 positive boars with recent semen deliveries to CH (Seven with antibodies and virus, one with antibodies only). In one boar out of six tested, virus was detected in semen. Of the 59 slaughtered sows, five from three herds were virus-positive. In one herd, the virus had spread, and all pigs were slaughtered or non-marketable animals euthanized. In the remaining herds, no further infections were detected. After confirmatory testings in all herds 3 weeks after the first examination gave negative results, restrictions were lifted in January 2013, and Switzerland regained its PRRSV-free status. The events demonstrate that import of semen from non-PRRS-free countries--even from negative studs--poses a risk, because monitoring protocols in boar studs are often insufficient to timely detect an infection, and infections of sows/herds occur even with low numbers of semen doses. The outbreak was eradicated successfully mainly due to the high disease awareness of the importer and because immediate actions were taken before clinical or laboratory diagnosis of a single case in the country was made. To minimize the risk of an introduction of PRRSV in the future, stricter import guidelines for boar semen have been implemented.


Waters W.R.,U.S. Department of Agriculture | Thacker T.C.,U.S. Department of Agriculture | Nonnecke B.J.,U.S. Department of Agriculture | Palmer M.V.,U.S. Department of Agriculture | And 5 more authors.
Clinical and Vaccine Immunology | Year: 2012

Gamma interferon (IFN-γ)-induced protein 10 (IP-10) has recently shown promise as a diagnostic biomarker of Mycobacterium tuberculosis infection of humans. The aim of the current study was to compare IP-10 and IFN-γ responses upon Mycobacterium bovis infection in cattle by using archived samples from two aerosol inoculation studies. In the first study (10 4 CFU M. bovis by aerosol, n = 7), M. bovis purified protein derivative (PPDb)-specific IP-10 and IFN-γ gene expression was detected as early as 29 days after challenge. PPDb-specific IP-10 and IFN-γ mRNA responses followed a similar pattern of expression over the course of this study and were highly correlated (r = 0.87). In the second study (10 5 CFU M. bovis by aerosol, n = 5), IP-10 and IFN-γ (protein) responses to mycobacterial antigens were compared following challenge. IFN-γ responses to mycobacterial antigens were detected at 29 days after challenge and were sustained during the remainder of the study. IFN-γ responses to mycobacterial antigens exceeded corresponding responses in nonstimulated cultures. IP-10 responses to mycobacterial antigens exceeded preinfection responses at 7, 29, and 63 days after challenge. In contrast to IFN-γ responses, IP-10 responses to mycobacterial antigens generally did not exceed the respective responses in nonstimulated cultures. IP-10 responses to medium alone and to mycobacterial antigens followed a similar pattern of response. Correlations between IP-10 and IFN-γ (protein) responses were modest (r ≈ 0.50 to 0.65). Taken together, these findings do not support the use of IP-10 protein as a biomarker for bovine tuberculosis using the current testing protocol and reagents; however, mRNA-based assays may be considered for further analysis. Copyright © 2012, American Society for Microbiology. All Rights Reserved.


Zweifel C.,University of Zürich | Giezendanner N.,University of Zürich | Corti S.,University of Zürich | Krause G.,Federal Institute for Risk Assessment BfR | And 3 more authors.
Journal of Food Protection | Year: 2010

Food is an important vehicle for transmission of Shiga toxin-producing Escherichia coli (STEC). To assess the potential public health impact of STEC in Swiss raw milk cheese produced from cow's, goat's, and ewe's milk, 1,422 samples from semihard or hard cheese and 80 samples from soft cheese were examined for STEC, and isolated strains were further characterized. By PCR, STEC was detected after enrichment in 5.7% of the 1,502 raw milk cheese samples collected at the producer level. STEC-positive samples comprised 76 semihard, 8 soft, and 1 hard cheese. By colony hybridization, 29 STEC strains were isolated from 24 semihard and 5 soft cheeses. Thirteen of the 24 strains typeable with O antisera belonged to the serogroups 02, 022, and 091. More than half (58.6%) of the 29 strains belonged to 0:H serotypes previously isolated from humans, and STEC 022:H8, O91:H10, 091:H21, and 0174:H21 have also been identified as agents of hemolytic uremic syndrome. Typing of Shiga toxin genes showed that stx 1 was only found in 2 strains, whereas 27 strains carried genes encoding for the StX2 group, mainly, stx2 and stX 2Vh-a/b Production of StX2 and StX2vh-a/b subtypes might be an indicator for a severe outcome in patients. Nine strains harbored hlyA (enterohemorrhagic E. coli hemolysin), whereas none tested positive for eae (intimin). Consequently, semihard and hard raw milk cheese may be a potential source of STEC, and a notable proportion of the isolated non-0157 STEC strains belonged to serotypes or harbored Shiga toxin gene variants associated with human infections. Copyright ©, International Association for Food Protection.


Kittl S.,University of Bern | Korczak B.M.,University of Bern | Niederer L.,University of Bern | Baumgartner A.,Federal office of Public Health of Fribourg | And 3 more authors.
Applied and Environmental Microbiology | Year: 2013

Multilocus sequence typing (MLST) and antibiotic resistance patterns of Campylobacter jejuni and Campylobacter coli from retail chicken meat showed high overlap with isolates collected at slaughterhouses, indicating little selection along the production chain. They also showed significant common sequence types with human clinical isolates, revealing chicken meat as a likely source for human infection. © 2013, American Society for Microbiology.


Buettner S.,Federal Veterinary Office | Wieland B.,Royal Veterinary College University of London | Staerk K.D.C.,Royal Veterinary College University of London | Regula G.,University of Bern
Epidemiology and Infection | Year: 2010

Knowledge on the relative importance of alternative sources of human campylobacteriosis is important in order to implement effective disease prevention measures. The objective of this study was to assess the relative importance of three key exposure pathways (travelling abroad, poultry meat, pet contact) for different patient age groups in Switzerland. With a stochastic exposure model data on Campylobacter incidence for the years 2002-2007 were linked with data for the three exposure pathways and the results of a case-control study. Mean values for the population attributable fractions (PAF) over all age groups and years were 27% (95% CI 17-39) for poultry consumption, 27% (95% CI 22-32) for travelling abroad, 8% (95% CI 6-9) for pet contact and 39% (95% CI 25-50) for other risk factors. This model provided robust results when using data available for Switzerland, but the uncertainties remained high. The output of the model could be improved if more accurate input data are available to estimate the infection rate per exposure. In particular, the relatively high proportion of cases attributed to other risk factors requires further attention. © 2010 Cambridge University Press.


Hasler B.,Lane College | Howe K.S.,University of Exeter | Di Labio E.,Federal Veterinary Office | Schwermer H.,Federal Veterinary Office | Stark K.D.C.,Lane College
Preventive Veterinary Medicine | Year: 2012

Empirical analyses founded on sound economic principles are essential in advising policy makers on the efficiency of resource use for disease mitigation. Surveillance and intervention are resource-using activities directed at mitigation. Surveillance helps to offset negative disease effects by promoting successful intervention. Intervention is the process of implementing measures (e.g. vaccination or medication) to reduce or remove a hazard in a population. The scale and ratios in which the two are combined affect the efficiency of mitigation, its costs, benefits, and thus net effect on society's well-being. The Swiss national mitigation programme for bluetongue virus serotype 8 was used as case study to investigate the economic efficiency of mitigation. In 2008, Switzerland implemented a vaccination programme to avoid and reduce disease and infection in its ruminant population. To monitor the vaccination programme and the vector dynamics, a surveillance system consisting of serological and entomological surveillance was established. Retrospective analyses for the years 2008-2009 and prospective analyses for the years 2010-2012 were conducted to investigate if the mitigation programme was economically beneficial. In the retrospective analysis, the implemented programme (=comparative scenario) was compared to a hypothesised baseline scenario of voluntary vaccination and surveillance. In the prospective analysis, the comparative scenario assumed to continue was compared to two baseline scenarios: one of voluntary vaccination combined with surveillance and one of no vaccination combined with surveillance. For each scenario, monetary surveillance, intervention and disease costs were calculated. The comparison of baseline and comparative scenarios yielded estimates for the total benefit (=disease costs avoided), margin over intervention cost and the net value of the programme. For 2008-2009, in aggregate, the mean biannual total benefit was 17.46. m Swiss francs (CHF) (1CHF = 0.66€ at the time of analysis) and the mean net benefit after subtraction of the intervention and surveillance cost was 3.95. m CHF. For the three years 2010-2012, overall net costs were estimated at 12.93. m and 8.11. m CHF, respectively, for comparison of the implemented mitigation programme with the two baseline scenarios. It was concluded that the surveillance and intervention programme implemented in 2008-2009 was economically beneficial, while its continuation in the same form in 2010-2012 would produce net costs. These costs were due to the mean intervention cost remaining constant at a level of approximately 11. m CHF per year while the mean total benefit would be gradually reduced in 2010-2012 due to the reduced occurrence of disease in a fully vaccinated population. © 2011 Elsevier B.V.


Hasler B.,Lane College | Howe K.S.,University of Exeter | Hauser R.,Federal Veterinary Office | Stark K.D.C.,Lane College
Preventive Veterinary Medicine | Year: 2012

The aim of the project was to apply cost-effectiveness analysis to the economic appraisal of avian influenza virus (AIV) surveillance, using the implemented surveillance programme in Switzerland as a case study. First a qualitative risk assessment approach was used to assess the expected impact of surveillance on the transmission and spread of AIV. The effectiveness of surveillance was expressed as the difference in defined probabilities between a scenario with surveillance and a scenario without surveillance. The following probabilities were modelled (i) transmission of highly pathogenic AIV (HPAIV) from wild birds to poultry, (ii) mutation from low pathogenic AIV (LPAIV) into HPAIV in poultry, and (iii) transmission of HPAIV to other poultry holdings given a primary outbreak.The cost-effectiveness ratio was defined conventionally as the difference in surveillance costs (Δ. C) divided by the change in probability (Δ. P), the technical objective, on the presumption that surveillance diminishes the respective probabilities. However, results indicated that surveillance in both wild birds and poultry was not expected to change the probabilities of primary and secondary AIV outbreaks in Switzerland. The overall surveillance costs incurred were estimated at 31,000 €/year, which, to be a rational investment of resources, must still reflect the value policy makers attribute to other benefits from having surveillance (e.g. peace of mind). The advantage of the approach adopted is that it is practical, transparent, and thus able to clarify for policy makers the key variables to be taken into account when evaluating the economic efficiency of resources invested in surveillance, prevention and intervention to exclude AIV. © 2012 Elsevier B.V.

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