Development of a risk based surveillance program for Trichinella spp. in domestic swine and wildlife in Switzerland

• Forschungsstelle: BLV
• Projektnummer: 1.06.03
• Projekttitel Englisch: Development of a risk based surveillance program for Trichinella spp. in domestic swine and wildlife in Switzerland

Schlüsselwörter (Englisch)

Trichinella spp., trichinellosis, risk based surveillance, digestion, ELISA

Kurzbeschreibung (Englisch)

Trichinellosis is a zoonotic disease caused by Trichinella spp. that is transmitted from animals to humans via the consumption of insufficiently cooked meat. Main sources of human infection are pork, horse meat, and meat of wild boar. There are strong indications that the prevalence in the Swiss domestic pig population is very low and the risk for consumers related to consumption of Swiss meat products is also very low. However, due to changes in the EU legislation, Switzerland will have to implement a full scale testing program for pigs and horses. Therefore, the Federal Veterinary Office would like to substantiate the status of freedom from trichinellosis with sound scientific evidence. In this project, a risk assessment will determine the main pathways through which pigs and humans can become infected with Trichinella spp. in Switzerland. Based on these results, a risk based surveillance program using both parasitological and serological detection methods will be developed and implemented for identified animal species. This combination of detection methods will enable statements both about the food safety situation and the occurrence of infections in animals.

Projektziele (Englisch)

Swiss pig husbandry systems largely exclude the possibility of Trichinella-free herds as defined in the draft legislation of the EC, because outdoor housing systems in pig production is a standard husbandry practice and the national trend for outdoor housing systems is increasing. As well, a national surveillance program to detect a prevalence exceeding 0.0001% (EU threshold level) would require a testing program covering almost all slaughtered pigs. The implementation of a meat inspection program for Trichinella spp. for the entire slaughter pig population will lead to an enormous increase in costs for the Swiss administration and will require an increased infrastructure in slaughterhouses and veterinary services. The expected benefits of such a meat control program in Switzerland, namely a reduction in human cases of trichinellosis and a cost reduction for medical treatments, are likely to be very limited. An additional benefit in international trade will also be limited, because exports of pig meat have steadily been decreasing from 506 tonnes in 2001 to 90 tonnes in 2003 (BLW, 2004).

 

The goal of this project is to contribute to the data needed for the demonstration of freedom from trichinellosis of the domestic pig population in Switzerland. Because this goal exceeds the goal of food safety, the most sensitive diagnostic test available needs to be used. In this respect, currently the ELISA test using E/S antigen is the most suitable test. As the specificity of the ELISA test is not 100%, false-positive test results are to be expected. Positive results in the ELISA test can be subjected to confirmatory tests, for which two tests will be used. One is represented by the digestion method using larger amounts of sample material (approximately 20 gram). The second is a Western Blot test that can be used to confirm the presence of antibody against specific antigen proteins, e.g. the p43 and others. The serological approach will comparatively go in line with the standard digestion tests using 1 gram of material and pooled samples. This will allow to compare the results of a food safety test with a more sensitive serological test, and to meet international obligations. With the support of sound scientific evidence, Switzerland may subsequently apply for the OIE status free from trichinellosis in domestic swine. This status may lead to a reduced size of the meat inspection program in comparison to the full scale testing program as prescribed by the EC. To achieve the goal of this project, the project is subdivided in four subprojects, with different objectives:

 

1)       In the first subproject, existing data will be analyzed to assess the prevalence of trichinellosis in different animal species and humans during the past years. These results will be used as input for subprojects 2 and 3.

2)       In the second subproject, a risk assessment will define the most likely pathways through which pigs can become infected with Trichinella spp. in Switzerland. The results of this risk assessment will be used as input for subproject 3. As well, the risk assessment will compare the likelihood of human infection with Trichinella spp. in Switzerland through the consumption of meat from Swiss origin with the likelihood of human infection with Trichinella spp. in Switzerland through illegal meat imports or international travel. After the surveillance program from subproject 3 has been completed, the outcomes of both risk assessments can be evaluated and possibly adapted using results from this program. These updated risk assessments may then lead to an improvement of new surveillance programs.

3)       In the third subproject, the information provided by subprojects 1 and 2 will be used to develop and implement a risk based surveillance program for domestic pigs and defined other animal species. Data collected during this surveillance program will provide information with regard to the occurrence of trichinellosis in various animal species, and may be able to contribute to the claim of freedom from disease. The results of the surveillance program will also be used to improve the risk assessments as mentioned in subproject 2.

4)       In the fourth subproject, a benefit-cost analysis will be made in order to compare the cost and benefits of various monitoring and surveillance program options. Costs for logistics and labour will also be included in the analysis in order to make a proper comparison between a full scale testing program and a risk based surveillance program. This benefit-cost analysis will support the Swiss Federal Veterinary Office to determine its future strategy towards Trichinella testing program.

Umsetzung und Anwendungen (Deutsch)

UMS 2009:

Umsetzung ist genügend erfolgt. Resultate wurden verwendet.

Gesuch an EU um die Ausnahmeregelung zu verlängern.

Ist momentan die kostengünstigste Variante. In einigen

Jahren haben wir mehr Daten, so dass für risikobasierte

Untersuchung vielleicht weniger untersucht werden müssen.

Dafür müsste Haltungsform registriert sein. Ist bereits geplant.

Status: erledigt (mvo)

Publikationen / Ergebnisse (Deutsch)

29.10.2009: Umsetzungssitzung 2009: Umsetzung ist genügend erfolgt. Resultate wurden verwendet. Gesuch an EU um die Ausnahmeregelung zu verlängern. Ist momentan die kostengünstigste Variante. In einigen Jahren haben wir mehr Daten, so dass für risikobasierte Untersuchung vielleicht weniger untersucht werden müssen. Dafür müsste Haltungsform registriert sein. Ist bereits geplant. Neuer Status: „erledigt“ (mvo).

Publikationen / Ergebnisse (Englisch)

Schuppers, M.; Frey, C.; Kihm, U.; Gottstein, B.(2009) Development of a risk based surveillance program for Trichinella spp. in domestic swine and wildlife in Switzerland. SAFOSO Bern, Institute for Parasitology University Bern, VetSuisse Faculty University Bern

Frey, C.F.; Schuppers, M.E.; Müller, N,; Ryser-Degiorgis, M.P.; Gottstein, B. (2009) Assessment of the prevalence of Trichinella spp. in red foxes and Eurasian lynxes from Switzerland. Veterinary Parasitology 159: 295 - 299.

Frey, C.F.; Schuppers, M.E.; Nöckler, K.; Marinculic, A.; Pozio, E.; Kihm, U.; Gottstein, B. (2008) Validation of a Western Blot for the detection of anti-Trichinella spp. antibodies in domestic pigs. Parasitology Research 104: 1269-1277.

Schuppers, M.E.; Frey, C.F.; Gottstein, B.; Stärk, K.D.C.; Kihm, U.; Regula, G. (2010) Comparing the demonstration of freedom from Trichinella infection of domestic pigs by traditional and risk-based surveillance. Epidemiology and Infection, doi: 10.1017/S0950268809991518, published online ahead of print 13 January 2010

Schuppers, M. E.; Rosenberg G.; Graf R.; Eidam V.; Wittwer C.; Zimmermann W.; Gottstein B.; C. F. Frey (2009) A Study to Demonstrate Freedom from Trichinella spp. in Domestic Pigs in Switzerland. Zoonoses and Public Health, doi: 10.1111/j.1863-2378.2009.01299.x, published online ahead of print 8 December 2009

Frey, C. F.; Schuppers, M. E.; Eidam, V.; Boujon, P.; Waldvogel, A.; Gottstein B. (2009) Vorkommen von Trichinella spp. beim Wildschwein in der Schweiz. Schweiz Arch Tierheilk 151(10): 485-489.

Gottstein, B.; Pozio, E.; Nöckler, K. (2009) Epidemiology, Diagnosis, Treatment, and Control of Trichinellosis. Clin Microbiological Rev 22: 127-145.

Müller, N.; Sager, H.; Schuppers, M.; Gottstein, B. (2006) Methoden zur Untersuchung von Trichinella-Infektionen bei Haus- und Wildtieren. Schweiz Arch Tierheilk 148(9): 463-471.

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