Salmonellosis in Finishing Pigs in Spain

Salmonella spp. were isolated from 31 per cent of the animals and 94 per cent of the herds sampled, and resistance to at least one antimicrobial agent was detected in 73 per cent of the Salmonella strains, according to recent research from Spain.

13 September 2011

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A herd-based survey of Salmonella in pigs was carried in a major pig-producing region of Spain, explain J.P. Vico of the Centre for Research and Food Technology of Aragon in Zarazoza and co-authors there and at the Public University of Navarra in Pamplona, Spain. Their paper was published recently in Journal of Food Protection.

Mesenteric lymph nodes were collected from the carcasses of 25 pigs from each of 80 herds at time of slaughter.

Salmonella spp. were isolated from 31 per cent of animals and 94 per cent of herds. Within-herd prevalence ranged from 4 to 88 per cent, with the prevalence in most herds being greater than 10 per cent.

A large diversity of Salmonella serotypes was found, with Typhimurium, 4,[5],12:i:-, and Rissen being the most prevalent. Two or more serotypes coexisted in 73 per cent of the herds. Salmonella Typhimurium was present in 68 per cent of the herds. Most (82 per cent) of the Salmonella isolates belonged to serogroups targeted by enzyme-linked immunosorbent assay tests for pig salmonellosis.

Resistance to at least one antimicrobial agent was detected in 73 per cent of the strains, and one or more resistant strains were recovered from pigs in 93 per cent of the herds. Antimicrobial agent resistance (AR) was more frequent among the most prevalent than it was among the rarer serotypes. Twenty-five multi-AR patterns were found. Resistance to three or more families of antimicrobial agents was found in 75 per cent of AR strains.

The finding that many of the herds yielded isolates of several multi-AR patterns indicates that Salmonella infections were acquired from multiple sources.

A high prevalence of Salmonella in herds was associated with lack of rodent control programmes, herds from farms with only finishing pigs, herds managed by more than one full-time worker, herds for which the source of drinking water was not a city supply, and relatively long fattening times.

Reference

Vico, J.P., Rol, I., Garrido, V., San Román, B., Grilló, M.J. and Mainar-Jaime, R.C. 2011. Salmonellosis in finishing pigs in Spain: prevalence, antimicrobial agent susceptibilities, and risk factor analysis. Journal of Food Protection, 74 (7):1070-1078. DOI: 10.4315/0362-028X.JFP-10-515