DVM Sonja Virtanen has discovered that piglets are a major source of Yersinia enterocolitica on fattening-pig farms. Contaminated piglets from certain breeding farms bring the infection to fattening farms and the infection subsequently spreads through the whole unit. The study was done in research group of professor Hannu Korkeala. Results were recently published in Applied and Environmental Microbiology.

Appl Environ Microbiol. 2012, published online ahead of print on 3 February 2012

Virtanen S., Salonen L., Laukkanen-Ninios R., Fredriksson-Ahomaa M. and Korkeala H.

Department of Food Hygiene and Environmental Health, University of Helsinki

Piglets are a source of pathogenic Yersinia  enterocolitica on fattening-pig farms

Piglets (n=76) from 16 farrowing farms were monitored in a fattening farm in two separate units through the whole fattening time. Fecal samples were collected in two-week intervals and blood samples were taken both in the beginning and at the end of the study. Feces were cultured on CIN-agars after cold enrichment in PMB-broth. Y. enterocolitica isolates were genotyped using an MLVA method. Blood samples were tested for the presence of Yersinia antibodies with an ELISA test.

Certain piglets were found to be infected with Y. enterocolitica already in their original farm. Antibodies against Yersinia were found in their blood samples and farm-specific genotypes of the pathogen were isolated from their feces next day after arrival into the fattening farm.

Only a minority of piglets seemed to bring Y. enterocolitica into the fattening farm but these piglets soon transmitted the infection to the rest of the pigs. During the fattening time the infection was spreading through the whole herd. Each pig was shedding the pathogen in feces at some point.

Dominant Y. enterocolitica genotypes were detected within the pens.  Same genotypes circulated within each unit and were present through the whole fattening time. No additional genotypes emerged after the beginning of the follow-up.

The same genotype (type A) was found in both units. This genotype originated from a certain farm who delivered piglets into the two units. This farm seemed to be a reservoir of this genotype and apparently the piglets from this farm continuously transmit the contamination when delivered into different fattening farms.

Piglets from certain farms bring Y. enterocolitica into a fattening farm and the infections spreads through the whole unit. In order to prevent this pathogen in pig production, mixing Y. enterocolitica positive and negative piglets should be avoided and preventive methods should be targeted into contaminated farrowing farms.

The project is funded by the Ministry of Agriculture and Forestry.