Yersinia pseudotuberculosis infection: study of an epizootic in squirrel monkeys

An epizootic of an acutely fatal enteric disease in a colony of squirrel monkeys (Saimiri sciureus) was attributed to infection by Yersinia pseudotuberculosis serotype III. Of a total adult population of 96 animals at risk, there were six fatal cases of yersiniosis. Serological evaluation of the colony just after the outbreak ended revealed that 22 of 60 monkeys tested (37%) had significant antibody to Y. pseudotuberculosis (microagglutination titer of greater than or equal to 1:80) but did not have clinical disease. The outstanding pathological lesions noted in dying monkeys were acute, purulent, necrotic and focal enteritis primarily affecting the jejunum and ileum and focal hepatic necrosis and abscessation. Y. pseudotuberculosis was isolated from the organs of two of the dying monkeys. Using cold enrichment techniques, Yersinia was also isolated from the feces of two apparently healthy monkeys (both seropositive), from the spleen of a monkey dying of other causes, and from the colon contents of a stillborn squirrel monkey baby. All isolates had the same biotype and serotype. An episode of abortions was associated both temporally and spatially with the fatal cases of yersiniosis, and Y. pseudotuberculosis was cultured from the uterus of two of the dying monkeys, suggesting that yersinia infection may be associated with abortion, as well as with enteric infection, in these animals.