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.
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.
Zweifel C.,University of Zurich |
Giezendanner N.,University of Zurich |
Corti S.,University of Zurich |
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.
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.
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.