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Analysis of the baseline survey on the prevalence of Salmonella in holdings with breeding pigs in the EU, 2008 - Part A: Salmonella prevalence estimates

EFSA Journal 2009; 7(12):1377 [93 pp.]. doi:10.2903/j.efsa.2009.1377
European Food Safety Authority Acknowledgment EFSA wishes to thank the members of the Task Force on Zoonoses Data Collection that endorsed this report: Andrea Ammon, Lisa Barco, Marta Bedriova, Susan Chircop, Georgi Chobanov, Ingrid Dan, Jürg Danuser, Noel Demicoli, Kris De Smet, Sylvie Francart, Matthias Hartung, Birgitte Helwigh, Merete Hofshagen, Patrícia Inácio, Sarolta Idei, Elina Lahti, Lesley Larkin, Peter Much, Edith Nagy, Lisa O’Connor, Rob Van Oosterom, Jacek Osek, Manca Pavšič, Antonio Petrini, Melanie Picherot, Christodoulos Pipis, Saara Raulo, Hanne Rosenquist, Jose Luis Saez Llorente, Petr Šatrán, Snieguole Sceponaviciene, Joseph Schon, Jelena Sõgel, Ana María Troncoso González, Kilian Unger, Luc Vanholme, Dimitris Vourvidis, Nicole Werner-Keišs. The contribution of the members of the working group that prepared this scientific report is gratefully acknowledged: Vojislava Bole-Hribovšek, Mariann Chriél, Rob Davies, June Fanning, Arjen W. van de Giessen, Laura Pérez Palancar, Antonia Ricci, Nicolas Rose, Lucy Snow; and that of EFSA’s contractors: Hendriek Boshuizen from National Institute for Public Health and Environment (RIVM); Tine Hald from Danish Technical University, National Food Institute, as well as EFSA’s staff members: Giusi Amore, Francesca Riolo and Frank Boelaert for the support provided to this EFSA scientific output. Contact zoonoses@efsa.europa.eu
Type: Scientific Report of EFSA On request from: European Commission, Question number: EFSA-Q-2006-043A Published: 17 December 2009 Affiliation: European Food Safety Authority (EFSA), Parma, Italy
Abstract

Salmonella is a major cause of food-borne illness in humans. Farm animals and foods of animal origin are important sources of human Salmonella infections. This European Union-wide Salmonella baseline survey was conducted in 2008 in holdings with breeding pigs. A total of 1,609 holdings housing and selling mainly breeding pigs (breeding holdings) and 3,508 holdings housing breeding pigs and selling mainly pigs for fattening or slaughter (production holdings) from 24 European Union Member States and two non-Member States, were randomly selected and included in the survey. In each selected breeding and production holding, fresh voidedpooled faecal samples were collected from 10 randomly chosen pens, yards or groups of breeding pigs over six months of age, representing the different stages of the breeding herd. The pooled faecal samples from each holding were tested for Salmonella and the isolates were serotyped. The overall European Union prevalence ofSalmonella-positive holdings with breeding pigs was 31.8% and all but one of the 24 participating Member States detected Salmonella in at least one holding. The European Union prevalence of Salmonella-positive breeding holdings was 28.7%, and prevalence varied from 0% to 64.0% among Member States. The European Union prevalence of Salmonella-positive production holdings was 33.3%, while the Member States’ prevalence varied from 0% to 55.7%. The number of different Salmonella serovars isolated in breeding holdings and production holdings in the European Union was 54 and 88, respectively. Salmonella Derby and Salmonella Typhimurium predominated in both types of holdings. Breeding pigs may be an important source of dissemination of Salmonella throughout the pig-production chain. The results of this survey provide valuable information for setting a Salmonella reduction target for breeding pigs and for assessing the impact of Salmonella transmission originating from holdings with breeding pigs

© European Food Safety Authority, 2009

Summary

Salmonella is a major cause of food-borne illness in humans. Farm animals and foods of animal origin are important sources of human Salmonella infections. Therefore, in order to reduce the incidence of human salmonellosis in the European Union, Community legislation foresees the setting of Salmonella reduction targets for food/animal populations, including breeding pigs. To underpin such targets, a series of baseline surveys have been conducted to ascertain the occurrence prior to the implementation of such Community legislation. This fifth European Union-wide baseline survey was carried out at farm level todetermine the prevalence of Salmonella in pig breeding holdings. The herds were randomly selected from holdings constituting at least 80% of the breeding pig population in a Member State.

Sampling took place between January 2008 and December 2008. A total of 1,609 holdings housing and selling mainly breeding pigs (sows or boars of at least six months of age kept for breeding purposes) (breeding holdings) and 3,508 holdings housing breeding pigs and selling mainly pigs for fattening or slaughter (production holdings) from 24 European Union Member States, plus Norway and Switzerland were included in the survey. In each selected breeding and production holding, fresh voided pooled faecal samples were collected from 10 randomly chosen pens, yards or groups of breeding pigs over six months of age, representing the different stages of production of the breeding herd (maiden gilts, pregnant pigs, farrowing and lactating pigs, pigs in the service area, or mixed). The pooled samples from each holding were tested for the presence of Salmonella and the isolates were serotyped. The country level and European Union level prevalence presented in the report are apparent prevalence, meaning that the prevalence estimates do not account for imperfect sampling and test characteristics.

The overall European Union prevalence of Salmonella-positive holdings with breeding pigs was 31.8% and all but one participating Member State detected Salmonella in at least one holding. Twenty of the 24 Member States isolated Salmonella in breeding holdings and at European Union level 28.7% of the holdings was estimated to be positive for Salmonella. This prevalence varied from 0% to 64.0% among the Member States.  The estimated European Union prevalence of breeding holdings positive to Salmonella Typhimuriumand to Salmonella Derby was 7.8% and 8.9%, respectively.

Twenty-one of the 24 Member States isolated Salmonella in production holdings and at the European Union level 33.3% of the production holdings was estimated to be positive for Salmonella. This prevalence varied from 0% to 55.7% among the Member States. The estimated European Union prevalence of production holdings positive for Salmonella Typhimurium and Salmonella Derby was 6.6% and 9.0%, respectively. For the two non-Member States, Switzerland detected Salmonella in both breeding and production holdings while Norway did not detect any Salmonella in its surveyed holdings.

The number of different Salmonella serovars isolated in breeding holdings and production holdings across the European Union was 54 and 88, respectively. Salmonella Derby was the most frequently isolated serovar in both breeding and production holdings, detected in 29.6% and 28.5% of the Salmonella-positive holdings, respectively. The next most commonly isolated serovar wasSalmonella Typhimurium accounting for 25.4% and 20.1% of Salmonella-positive breeding holdings and production holdings, respectively. These serovars were also commonly found in the EU-wide baseline survey of fattening pigs at slaughter in 2006-2007. The next most frequently reported serovars were Salmonella London,Salmonella Infantis and Salmonella Rissen both in breeding and production holdings and each accounted for approximately 7% of the positive holdings, in each type of holding. Also Salmonella isolates with the incomplete antigenic formula 4,[5],12:i:-, which are likely to be related to the recent emergence of monophasic Salmonella Typhimurium, were reported by several Member States.

Salmonella infection in breeding pigs may be transmitted to slaughter pigs through trade and movement of live animals and contamination of holding, transport, lairage and slaughter facilities. This may lead to Salmonella-contamination of pig meat and consequently to human disease. Further studies in surveillance and control methods for Salmonella in breeding pigs as well as in the public health importance of consumption of meat from culled breeding pigs are recommended. Also investigations on the epidemiology of monophasic Salmonella Typhimurium would be welcome. The results of this survey provide valuable information for the assessment of the impact of Salmonella transmission originating from holdings with breeding pigs as a source of Salmonella in the food chain. These baseline prevalence figures may be used for the setting of targets for the reduction of Salmonella in breeding pigs, to follow trends and to evaluate the impact of control programmes.

Keywords

Salmonella, pigs, breeding pigs, survey, prevalence, EU.