Serosurveillance of Schmallenberg virus in Switzerland using bulk tank milk samples.

Infections with Schmallenberg virus (SBV), a novel Orthobunyavirus transmitted by biting midges, can cause abortions and malformations of newborns and severe symptoms in adults of domestic and wild ruminants. Understanding the temporal and spatial distribution of the virus in a certain territory is important for the control and prevention of the disease. In this study, seroprevalence of antibodies against SBV and the spatial spread of the virus was investigated in Swiss dairy cattle applying a milk serology technique on bulk milk samples. The seroprevalence in cattle herds was significantly higher in December 2012 (99.5%) compared to July 2012 (19.7%). This high between-herd seroprevalence in cattle herds was observed shortly after the first detection of viral infections. Milk samples originating from farms with seropositive animals taken in December 2012 (n=209; mean 160%) revealed significantly higher S/P% ratios than samples collected in July 2012 (n=48; mean 103.6%). This finding suggests a high within-herd seroprevalence in infected herds which makes testing of bulk tank milk samples for the identification farms with past exposures to SBV a sensitive method. It suggests also that within-herd transmission followed by seroconversion still occurred between July and December. In July 2012, positive bulk tank milk samples were mainly restricted to the western part of Switzerland whereas in December 2012, all samples except one were positive. A spatial analysis revealed a separation of regions with and without positive farms in July 2012 and no spatial clustering within the regions with positive farms. In contrast to the spatial dispersion of bluetongue virus, a virus that is also transmitted by Culicoides midges, in 2008 in Switzerland, the spread of SBV occurred from the western to the eastern part of the country. The dispersed incursion of SBV took place in the western part of Switzerland and the virus spread rapidly to the remaining territory. This spatial pattern is consistent with the hypothesis that transmission by Culicoides midges was the main way of spreading.

[Development of a monitoring program for antibiotic resistance in bacteria from Swiss food-producing animals]. / Aufbau eines Monitoringprogramms zur Bestimmung der Antibiotikaresistenz bei Bakterien von Schweizer Nutztieren.

Resistant bacteria from food-producing animals may compromise the success of antibiotic treatment in animals and in humans. Therefore, the level of antibiotic resistance in bacteria from farm animals and its development over time needs to be monitored. In Switzerland, a monitoring program for antibiotic resistance is currently being developed. Pilot-monitoring programs were conducted in selected animal species in order to obtain current data on antibiotic resistance. The data on the prevalence of bacteria and antibiotic resistance in poultry were used to optimize the sampling plan. The influence of sampling more farms compared to sampling more animals per farm on the prevalence estimate for antibiotic resistance was analyzed by a Monte Carlo simulation model. Accounting for the costs for sample collection, transportation and laboratory analysis of the samples, the number of samples to be taken at the respective step in the production line was optimized. Optimization was defined as maximizing the precision of the prevalence estimate while minimizing the costs. The model will be expanded to other bacterial and animal species in the future.

Risk factors for antibiotic resistance in Campylobacter spp. isolated from raw poultry meat in Switzerland.

BACKGROUND: The world-wide increase of foodborne infections with antibiotic resistant pathogens is of growing concern and is designated by the World Health Organization as an emerging public health problem. Thermophilic Campylobacter have been recognised as a major cause of foodborne bacterial gastrointestinal human infections in Switzerland and in many other countries throughout the world. Poultry meat is the most common source for foodborne cases caused by Campylobacter. Because all classes of antibiotics recommended for treatment of human campylobacteriosis are also used in veterinary medicine, in view of food safety, the resistance status of Campylobacter isolated from poultry meat is of special interest. METHODS: Raw poultry meat samples were collected throughout Switzerland and Liechtenstein at retail level and examined for Campylobacter spp. One strain from each Campylobacter-positive sample was selected for susceptibility testing with the disc diffusion and the E-test method. Risk factors associated with resistance to the tested antibiotics were analysed by multiple logistic regression. RESULTS: In total, 91 Campylobacter spp. strains were isolated from 415 raw poultry meat samples. Fifty-one strains (59%) were sensitive to all tested antibiotics. Nineteen strains (22%) were resistant to a single, nine strains to two antibiotics, and eight strains showed at least three antibiotic resistances. Resistance was observed most frequently to ciprofloxacin (28.7%), tetracycline (12.6%), sulphonamide (11.8%), and ampicillin (10.3%). One multiple resistant strain exhibited resistance to five antibiotics including ciprofloxacin, tetracycline, and erythromycin. These are the most important antibiotics for treatment of human campylobacteriosis. A significant risk factor associated with multiple resistance in Campylobacter was foreign meat production compared to Swiss meat production (odds ratio = 5.7). CONCLUSION: Compared to the situation in other countries, the data of this study show a favourable resistance situation for Campylobacter strains isolated from raw poultry meat produced in Switzerland. Nevertheless, the prevalence of 19% ciprofloxacin resistant strains is of concern and has to be monitored. "Foreign production vs. Swiss production" was a significant risk factor for multiple resistance in the logistic regression model. Therefore, an adequate resistance-monitoring programme should include meat produced in Switzerland as well as imported meat samples.