Salmonella spp. in wild boar (Sus scrofa): a public ...

ISBN: 978-90-8686-165-1 e-ISBN: 978-90-8686-723-3 DOI: 10.3920/978-90-8686-723-3

First published, 2011

© Wageningen Academic Publishers The Netherlands, 2011

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Salmonella spp. in wild boar (Sus scrofa): a public and animal health concern Madalena Vieira-Pinto1, Luísa Morais1, Cristina Caleja1,2, Patrícia Themudo3, José Aranha4, Carmen Torres5, Gilberto Igrejas2,6, Patrícia Poeta1 and Conceição Martins1 1Departamento de Ciências Veterinárias, CECAV-UTAD, Universidade de Trás-os-Montes e

Alto Douro, Apartado 1013, 5001-801 Vila Real, Portugal; [email protected] 2Departamento de Genética e Biotecnologia, Universidade de Trás-os-Montes e Alto Douro, Apartado 1013, 5001-801 Vila Real, Portugal 3Laboratório Nacional de Investigação Veterinária, Estrada de Benfica, 701, 1549 Lisboa, Portugal 4Departamento Florestal, Lab SIG, Universidade de Trás-os-Montes e Alto Douro, Apartado 1013, 5001-801 Vila Real, Portugal 5Biochemistry and Molecular Biology Unit, University of La Rioja, Complejo Cientifico Tecnologico, C/Madre Dios, 51, 26006 Logroño, La Rioja, Spain 6Institute for Biotechnology and Bioengineering, Centre of Genetics and Biotechnology, University of Trás-os-Montes and Alto Douro, P.O. Box 202, 5001-801 Vila Real, Portugal

Summary Wild boars constitute a potential reservoir and may spread zoonotic agents, including Salmonella sp. and thus they represent a source of infection for (wild and domestic) animals and humans. During the 2006 hunting season, 77 rectal faecal samples from animals shot by hunters in Northern Portugal were collected and analysed to determine the prevalence and serovars of Salmonella sp. in wild boars (Sus scrofa). The results showed that 17 (22.1%) were positive for Salmonella sp. In these positive samples, the most prevalent serovar was Salmonella Typhimurium, identified in 11 (64.7%) isolates, followed by Salmonella Rissen in 6 (35.3%). These results confirm the importance of wild boar as a reservoir of pathogenic serovars of Salmonella and as a potential risk for humans and livestock and emphasise the importance of intervention procedures for improving surveillance. Keywords: wild boar, Salmonella, zoonoses, wildlife, food safety

1. Introduction Salmonella is defined, both at the European and national level, as being the main responsible pathogen for foodborne diseases, with approximately 170,000 annually notified human salmonellosis cases within the European Union (EFSA, 2007). Because of its importance as a zoonotic agent, extensive surveillance programmes exist in all Member States. However, in spite of sanitary campaigns, and according to recent literature reviews (Bengis, 2002; Gortázar et al., 2007), the possibility of persistent cycling of infection in wildlife is real and this could limit the success of domestic animals disease control programmes. In this context Salmonella

P. Paulsen et al. (eds.), Game meat hygiene in focus, DOI 10.3920/978-90-8686-723-3_10, © Wageningen Academic Publishers 2011

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may serve as a model for studying the role that wildlife plays as zoonotic agent reservoir and how this could compromise control programmes in use by veterinary authorities. Previous studies on the occurrence of Salmonella sp. in wildlife highlight the significance of game animals as carriers contributing to animal and human contamination, e.g. hedgehogs (Handeland et al., 2002), wild birds (Refsum et al., 2002), gulls (Wahlström et al., 2003), wild birds and mammals (Millan et al., 2004) and white-tailed deer (Renter et al., 2006). However, to date, data on the epidemiological distribution of Salmonella sp. in wild boars are very limited. In particular, bibliographic references for Portugal are lacking. Wild boar infected with Salmonella sp. may play an important role in the epidemiology of this zoonotic pathogen. Salmonella sp. shed in their faeces may be ingested by other wild animals or by domestic livestock animals, either through direct contact or when these resources are shared by food animals (specially pastured livestock) or through water cross contamination (Bengis et al., 2002; Vicente et al., 2002; Renter et al., 2006). This wildlife/domestic animal interface is observed in rural areas in Northern Portugal, where pasturage of domestic animals and backyard pig production is a tradition. Human health risks from wild boar infected with Salmonella sp. arise indirectly from agricultural areas and vegetable products contamination, through direct animal contact, during the hunting process and carcass manipulation, or directly from ingestion of contaminated meat or meat products, such as sausage (Renter et al., 2006). Considering the importance of wild boars as a major game species in Northern Portugal, as well as their potential role in transmission of Salmonella sp. to domestic and wild animal populations with the attendant risk for human health, assessing the prevalence and serotypes of Salmonella sp. in free-ranging wild boars harvested by hunters was the main objective of this study.

2. Material and methods 2.1 Study area The study area is located in Northern Portugal, where rural and hunting areas comprise numerous rural settlements (poorly fenced) that are used by local people to produce vegetables for sale in local markets. The domestic animal production system is characterised by outdoor production of ruminants and backyard pig production. Within this area, hunting activity (wild birds, rabbits and hares, wild boars) represents an important contribution to the development of the local economy, not only in terms of hunting fees but also from the viewpoint of complementary expenses spent by hunters for lodging, meals and purchases. 2.2 Sampling procedure During the hunting season of 2005/2006 (December 2005 to February 2006) several hunting associations from Northern Portugal were contacted with the request to indicate the calendar

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of their hunting activities so as to allow collecting a representative number of wild boar samples. After the hunting events, animals were transported to a site where the research team directly sampled rectal faeces from harvested wild boars (aseptically, i.e. using latex gloves). From a total of 253 wild boars (Sus scrofa), 77 hunted animals were sampled, whereupon samples were coded and transported under refrigerated conditions to the laboratory. All tested animals were subsequently marketed for human consumption. 2.3 Cultural microbiology All samples were analysed by means of standard culture methods, according to annex D of ISO standard 6579:2002 applied to Salmonella detection in animal faeces. Isolates of presumptive Salmonella (1 to 2 colonies from each sample) were confirmed by means of biochemical tests (Oxidase reaction, Triple Sugar Iron Agar (Oxoid® – CM277), Urea broth (Merck® – 1.08483), L-Lysine decarboxylation medium (Oxoid® – CM308S)) and serological agglutination with Poly A-I & Vi antiserum (Difco® – 222641). Salmonella isolates were serotyped from each positive sample according to the Kauffmann-White scheme (Popoff, 2001) in the LNIV – National Reference Laboratory for Salmonella.

3. Results and discussion This study is the first report of Salmonella sp. identification in wild boars´ faecal samples in Portugal, and demonstrates the presence of this microorganism in 17 (22.1%) faecal samples from 77 harvested wild boars. This prevalence highlights the importance of the wild boar as reservoir and as a faecal shedder of Salmonella sp., and indicates that faeces from apparently healthy wild boars can be a source of this pathogen and be potentially transferred, to livestock, other animals and humans. Vicente et al. (2002) reported a small seroprevalence of Salmonella in Spain, as based on antibodies against Salmonella serovar B in 4% and Salmonella serovar C in 3% of the cases. In contrast, Vengust et al. (2006) reported a seroprevalence of 47% of Salmonella sp. in wild boars in Slovenia. So far, no data on the prevalence of Salmonella sp. in faecal samples of wild boars have been published. In our study, only two serovars were identified: Salmonella Typhimurium (64.7%) and Salmonella Rissen (35.3%). This is partially explained by the small number (one or two) of Salmonella sp. colonies isolated and identified per sample, limiting identification of other possible serovars. Nevertheless, there is a clear dominance of Salmonella Typhimurium (identified in 64.7% of the positive samples), which suggests this is a predominant serovar in fecal sample of wild boars, as established in several national (Vieira-Pinto et al., 2005) and international studies (Davies et al., 2000; Giovannacci et al., 2001; Swanenburg et al., 2001; Botteldoorn et al., 2004; Castagna et al., 2004), and confirmed by the report on trends and sources of zoonoses, zoonotic agents, antimicrobial resistance and foodborne outbreaks in the European Union in 2006 (EFSA, 2007).


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The similarity of the Salmonella serovar prevalence pattern of pig and wild boar populations indicates a possible bidirectional circulation of Salmonella sp. through both animal ecosystems. This is not unlikely to occur in Northern Portuguese rural areas, as physical contact between wild boars and backyard raising pigs is frequently reported. Yet, at the present time, this hypothesis cannot be substantiated since the sanitary status of the northern Portuguese pig population with respect to Salmonella sp. is not known. According to Vicente et al. (2002), Salmonella Typhimurium is pathogenic for animals, and could affect the dynamics of European wild boar populations as well as interfere with the health of other wild animals, such as birds. In addition, this serovar deserves special attention in view of its virulence in humans (Botteldoorn et al., 2004) and because it is highly resistant to antibiotics (Fedorka-Cray et al., 1999; Nielsen et al., 1999; Cruchaga et al., 2001; Botteldoorn et al., 2004). Currently, Salmonella Typhimurium, is the second most prevalent Salmonella identified in the European Human Salmonellosis cases in 2006 (EFSA, 2007). In respect to the second most prevalent serovar, Salmonella Rissen, no references were found on its prevalence in wildlife. Wild boars may indirectly represent a reservoir and source of infection for humans, by uncooked contaminated vegetables (lettuce, cress), water (streams, stagnant pools) or domestic animals, or directly through contact with infected carcasses, by consuming meat or meat products (Everard et al., 1979; Kruse et al., 2004; Vengust et al., 2006). Salmonella sp. occurrence in wild boar meat and carcass was also demonstrated in studies by Decastelli et al. (1995) in Italy, Kanai et al. (1997) in Japan and Wisniewski (2001) in Poland. For example, Wisniewski (2001) reported the presence of Salmonella spp. in 11 animals (7%), in carcasses and internal organs of 156 hunted wild boars. Since hunted wild boars are marketed for human consumption, they are a potential source of infection to man, if they harbour Salmonella sp. in their edible tissues, or if meat is contaminated by intestinal content during evisceration or processing of the carcass (Lillehaug et al., 2005). Faecal contamination of wild boar carcasses can be expected when hunted animals are poorly bled, eviscerated and skinned under precarious hygienic conditions (Decastelli et al., 1995; Lillehaug et al., 2005). In Portugal, this scenario is of particular concern, since the majority of the hunted animals are used for human consumption, in almost all cases after a deficient transportation of the hunted animals, and technically and hygienically undesirable evisceration and dressing procedures.

4. Conclusions The results presented in this study show that wild boar can represent a vehicle of pathogenic serovars of Salmonella to humans and animals, suggesting that more attention should be paid to game meat hygiene. Our study also indicates that systematic serological and bacteriological surveillance of wild boar populations should be improved with a view to better understand and minimise the impact of such diseases on wild and domestic animals as well as humans.

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References Bengis, R.G., 2002. Infectious diseases of wildlife: detection, diagnosis and management. Rev. Tech. Off. Int. Epiz. 21(1), 11-12. Bengis, R.G., Kock, R.A. and Fischer, J., 2002. Infectious animal diseases: the wildlife/livestock interface. Rev. Tech. Off, Int. Epiz. 21(1), 53-65. Botteldoorn, N., Herman, L., Rijpens, N. and Heyndrickx, M., 2004. Phenotypic and molecular typing of Salmonella strains reveals different contamination sources in two commercial pig slaughterhouses. Appl. Environ. Microb. 70(9), 5305-5314. Castagna, S.M.F., Schwartz, P., Canal, C.W. and Cardoso, M., 2004. Presence of Salmonella sp. in the intestinal tract in tonsils/submandibular lymph nodes of slaughter pigs. Arq. Brás. Med. Vet. Zootec. 56(3), 300-306. Cruchaga, S., Echeita, A., Aladuena, A., Garcia-Pena, J., Frias, N. and Usera, M.A., 2001. Antimicrobial resistance in Salmonellae from humans, food and animals in Spain in 1998. J. Antimicrob. Chemoth. 47, 315-321. Davies, R., Paiba, G.A., Evans S.J. and Dalziel, R., 2000. Surveys for Salmonella in pigs, cattle and sheep at slaughter in Great Britain. Vet. Rec. 147, 695. Decastelli, L., Giaccone, V. and Mignone, W., 1995. Bacteriological examination of meat of wild boars shot down in Piedmont and Liguria, Italy. IBEX J.M.E. 3, 88-89. EFSA (European Food Safety Authority), 2007. The Community summary report on trends and sources of zoonoses, zoonotic agents, antimicrobial resistance and foodborne outbreaks in the European Union in 2006. The EFSA Journal 130, 2-352. Everard, C.O.R., Tota, B., Basset, D. and Cameille, A.L. 1979. Salmonella in wildlife from Trinidad and Grenada, W.I.J. Wildl. Dis. 15, 213-217. Fedorka-Cray, P.J., Bailey, J.S., Stern, N.J., Cox, N.A., Ladely, S.R. and Musgrove, M., 1999. Mucosal competitive exclusion to reduce Salmonella in swine. J. Food Protect. 62(12), 1376-1380. Giovannacci, I., Queguiner, S., Ragimbeau, C., Salvat, G., Vendeuvre, J.L., Carlier, V. and Ermel, G., 2001. Tracing of Salmonella spp. in two porks slaughter and cutting plants using serotyping and macrorestriction genotyping. J. Appl. Microbiol. 90, 131-147. Gortázar, C., Ferroglio, E., Höfle, U., Frölich, K. and Vicente, J., 2007. Diseases shared between wildlife and livestock: a European perspective. Eur. J. Wildl. Res. 53, 241-256. Handeland, K., Refsum, T., Johansen, B.S., Holstad, G., Knutsen, G., Solberg, I., Schulze, J. and Kapperud, G., 2002. Prevalence of Salmonella Typhimurium infection in Norwegian hedgehog population associated with two human disease outbreaks. Epidemiol. Infect. 128, 523-527. Kanai, Y., Hayashidani, K., Kancko, M., Ogawa, M., Takahashi, T. and Nakamura, M., 1997. Occurrence of zoonotic bacteria in retail game meat in Japan with special reference to Erysipelothrix. J. Food Protect. 60, 328-331. Kruse, H., Kirkemo, A.-M. and Handeland, K., 2004. Wildlife as source of zoonotic infections. Emerg. Infect. Dis. 10(12), 2067-2071. Lillehaug, A., Bergsjø, B., Schar, J., Bruheim, T., Vikoren, T. and Handeland, K., 2005. Campylobacter spp., Salmonella spp., verocytotoxic Escherichia coli, and antibiotic resistance in indicator organisms in wild cervids. Acta Vet. Scand. 46, 23-32. Millán, J., Aduriz, G., Moreno, B., Juste, R.A. and Barral, M., 2004. Salmonella isolates from wild birds and mammals in the Basque Country (Spain). Rev. Sci. Tech. 23(3), 905-911. Nielsen, B., Mogelmose, V. and Sorensen, L.L., 1999. Tracing back multiresistant Salmonella Typhimurium DT104 from pork at the slaughterhouse to a specific swine herd by strategical use of serology and culture. Proceedings of the 3rd International Symposium On the Epidemiology and Control of Salmonella in Pork. Washington, DC, USA, pp. 261-263.


135


Popoff, M.Y., 2001. Antigenic formulas of the Salmonella serovars. Report of the WHO Collaborating Centre for reference and Research on Salmonella. 8th Edition. Institute Pasteur, Paris, France. Refsum, T., Handeland, K., Baggesen, D.L., Holstad, G. and Kapperud, G., 2002. Salmonellae in Avian Wildlife in Norway from 1969 to 2000. Appl. Environ. Microbiol. 68(11), 5595-5599. Renter, D.G., Gnad, D.P., Sargeant, J.M. and Hygnstrom, S.E., 2006. Prevalence and Serovars of Salmonella in feces of free-ranging White-Tailed Deer (Odocoileus virginianus) in Nebraska. J. Wildl. Dis. 42(3), 699-703. Swanenburg, M., Urlings, H.A.P., Snijders, J.M.A., Keuzenkamp, D.A. and Van Knapen, F., 2001. Salmonella in slaughter pigs: prevalence, serovars and critical control points during slaughter in two slaughterhouses. Int. J. Food Microbiol. 70, 243-254. Vengust, G., Valencak, Z. and Bidovec, A., 2006. A serological survey of selected pathogens in wild boar in Slovenia. J. Vet. Med. B 53, 24-27. Vicente, J., Léon-Vizcaíno, L., Gortázar, C., Cubero, M.J., González, M. and Martín-Antace, P., 2002. Antibodies to selected viral and bacterial pathogens in European Wild Boars from Southcentral Spain. J. Wildl. Dis. 38(3), 619-652. Vieira-Pinto, M.M., Themudo, P. and Martins, C., 2005. Occurrence of Salmonella in the ileum, ileocolic lymph nodes, tonsils, mandibular lymph nodes and carcasses of pigs slaughtered for consumption. J. Vet. Med. B. 52, 476-481. Wahlström, H., Olsson, E., Engvall, E., Brändström, B., Vågsholm, I., Eriksson, E. and Mörner, T., 2003. Survey of Campylobacter species, VTEC 0157 and Salmonella species in Swedish wildlife. Vet. Rec. 153(3), 74-80. Wisniewski, J., 2001. The incidence of Salmonella spp. in wild boars in Poland. Medycyny Wet. 57(6), 399-401. Available at: http://www.medwet.lublin.pl/Year%202001/vol01-06/art224-00htm.htm.

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