No Listeria Found in Spanish Pig Herds

SPAIN - Researchers were unable to find Listeria monocytogenes in faecal samples from 17 pig herds in the Basque country although the bacteria were isolated widely in sheep and cattle.
calendar icon 21 January 2009
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Listeria monocytogenes is among the most important foodborne bacterial pathogens due to the high mortality rate and severity of the infection. It is a ubiquitous organism occasionally present in the intestinal tract of various animal species and faecal shedding by asymptomatically infected livestock poses a risk for contamination of farm environments and raw food at the pre-harvest stages.

The aim of this study was to determine the prevalence and strain diversity of L. monocytogenes in healthy ruminants and swine herds.

Faecal samples from 30 animals per herd were collected from 343 herds (120 sheep, 124 beef cattle, 82 dairy cattle and 17 swine) in the Basque Country and screened in pools by an automated enzyme-linked fluorescent immunoassay (VIDAS®) to estimate the prevalence of positive herds. Positive samples were subcultured onto the selective and differential agar ALOA and biochemically confirmed.

L. monocytogenes was isolated from 46.3 per cent of dairy cattle, 30.6 per cent beef cattle and 14.2 per cent sheep herds, but not from swine.

Within-herd prevalence investigated by individually analysing 197 sheep and 221 cattle detected in 1.5 per cent of faecal shedders in sheep and 21.3 per cent in cattle. Serotyping of 114 isolates identified complex 4b as the most prevalent (84.2 per cent), followed by 1/2a (13.2 per cent), and PFGE analysis of 68 isolates showed a highly diverse L. monocytogenes population in ruminant herds.

The results suggested that cattle represent a potentially important reservoir for L. monocytogenes in the Basque Country, and highlighted the complexity of pathogen control at the farm level.


Esteban J.I., B. Oporto, G. Aduriz, R.A. Juste and A. Hurtado. 2009. Faecal shedding and strain diversity of Listeria monocytogenes in healthy ruminants and swine in Northern Spain. BMC Veterinary Research 2009, 5:2

Further Reading

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