YERSINIOSIS, PSEUDOTUBERCULOSIS

Yersiniosis, also called pseudotuberculosis, is an infectious bacterial disease which is worldwide in distribution.  The disease has seldom been reported from wild birds but has been reported from more than 50 species of mammals including beaver, muskrat, white-tailed deer and cottontail rabbits.  In Ontario, yersiniosis has been the most common bacterial disease of beaver during the past decade.

Two closely related species of bacteria, Yersinia pseudotuberculosis and Yersinia enterocolitica cause yersiniosis.  The name pseudotuberculosis is sometimes used to refer only to disease caused by Y. pseudotuberculosis and enterocolitis to refer to disease caused by Y. enterocolitica.  More frequently the disease arising from infection with either species of bacteria is called yersiniosis or pseudotuberculosis.

Diarrhea, fever, inflammation of the mesenteric lymph system, headaches, vomiting and abdominal pain may accompany disease caused by either species of bacterium.

Unlike tularemia, transmission of yersiniosis appears to be restricted to faecal-oral routes.  The most common source of infection is probably consumption of contaminated food or water.  The majority of bacteria released from an infected animal are thought to be excreted with faeces.  Widespread epizootics of yersiniosis are uncommon in wildlife occupying natural habitat.

Post-mortem examination of beaver with yersiniosis reveals focal necrosis in liver and spleen and hypertrophy of mesenteric lymph nodes, liver and spleen.  This gross pathology is also observed in beaver with tularemia and some other bacterial diseases.  Yersiniosis, like tularemia, can only be diagnosed using laboratory techniques.  Specimens should be submitted to the diagnostic lab in a fresh (refrigerated) or freshly frozen state.

Selected References:

Benenson, A.S. (ed.). 1975.  Control of communicable diseases in man. 12th ed.  Rep. Am.  Public Health Association.

Wetzier, T.F. 1970.  Pseudotuberculosis, pp. 224-235.  In: Davis, J.W., L.H. Karstad and D.O. Trainer (eds.), Infectious diseases of wild mammals.  The Iowa State University Press, Ames.