A fim de pesquisar a presença de yersinia pseudotuberculosis em quadro de diarreia bovina, foram analisadas 220 amostras de fezes, 60 conteudos de intestino delgado e 56 conteudos de intestino grosso. Obteve-se isolamento positivo em 46 (21%), 9 (15%) e 5 (9%) das amostras respectivamente, totalizando 60 cepas do microrganismo. As 60 cepas de yersinia pseudotuberculosis pertenciam ao sorogrupo o iii., Apresentando identica sensibilidade aos antibioticos e quimioterapicos quando testados in vitro. Estatisticamente comprovou-se haver relação entre os isolamentos das cepas de yersinia pseudotuberculosis e os meses mais frios do ano. A cepa y. Pseudotuberculosis mostrou-se patogenica aos cobaios, quando administrada via oral. Apesar dos resultados bacteriologicos negativos, não se descartou a possibilidade do envolvimento de roedores silvestres e comensais na transmissão do microrganismo aos bovinos, podendo os proprios bovinos ou o solo, servirem como reservatorios do microrganismo. A metodologia utilizada no isolamento das cepas de y. Pseudotuberculosis possibilitou que 73,3% das mesmas fossem isoladas no cultivo primario e 26,66% apos o crioenriquecimento na temperatura de 4 GRAUS c por 7, 14 e 21 dias.

The main purposes of this research was to search for Yersinia pseudotuberculosis in faecal samples from bovine with diarrhea, from farms in the State of Paraná. We have analyzed 220 faecal samples, 60 samples from small intestine contents and 56 samples from large intestine contents. Yersinia pseudotuberculosis isolation was positive in 46 (21%), 9 (15%) and 5 (9%), respectively, totalizing 60 strains of the microrganism. The 60 strains of Yersinia pseudotuberculosis belong to serogroup 0 III, and they shown identical sensibility to antibiotics and other drugs, when tested in vitro. Through the statistical methods, X² test, we found a positive correlation between Yersinia pseudotuberculosis isolation and the winter season. To establish the morbidity and mortality rates, cattle population was separated into three age related categories, wich are: calfs, yearlings and adults. In 1987 and 1988, the morbidity rates were 0%, 10,3% and 6,7%; 0%, 13,4% and 11,7%, respectively. In relation to mortality rates, they were 0%, 1,0% and 2,6% in 1987, and 0%, 2,1% and 2,6% in 1988. The strains of Yersinia pseudotuberculosis placed on serogroup 0 III, were pathogenic to guinea pigs, when giver per-os. We didn't get any isolation of Yersinia pseudotuberculosis from wild rodents and others, but we still think that may be incriminated in the transmission of the microrganism to bovines, although the bovines as well as the soil, may function as reservoires of the bacteria. Isolation of Yersinia pseudotuberculosis in primary cultures was possible in 73,33% although 26,66% of the isolations were successfull only after cold-temperature enrichment, with incubation at 4 C for 7, 14 an 21 days.