On the ecology of Yersinia enterocolitica O 3. Yersinia in synanthropic animals.

Rats (Rattus rattus) and sewer rats (R. norvegicus) trapped outside in piggeries, small mouse-like rodents trapped in human habitations and swine from piggeries and slaughterhouses were examined. In rats, sewer rats and mouse-like rodents other serotypes of Y. enterocolitica than O3 were isolated. However, two out of five sewer rats caught at a slaughterhous yielded Y. pseudotuberculosis I; this finding corresponded with some findings made in swine. Swine positivity rates in piggeries corresponded to the hygienic conditions found there. In a hygienically backward farm six out of 14 piglets were positive, whereas in a piggery with a high standard of hygiene only one out of 44 piglets yielded Y. pseudotuberculosis. Specimens of colon contents from 318 slaughtered pigs yielded Y. enterocolitica O3 three times (0.94%), Y. pseudotuberculosis four times (1.26%) and Y. Enterocolitica serotypes other than O3 18 times; a total of 19 swine (5.9%) were positive, some for two serotypes simultaneously, one for a combination of Y. enterocolitica O3 and Y. pseudotuberculosis I. Apart from this, Plesiomonas shigelloides was isolated from several slaughtered pigs and from one slaughterhouse rat; salmonellae were isolated from some slaughtered pigs, and a common finding was H2S-positive E. coli.