Visceral lesions caused by Yersinia pseudotuberculosis, serotype II, in different species of bird

The size and distribution of histological lesions was studied in 14 cases o f avian pseudotuberculosis using a combination of serotype-specific immunoh istochemistry and image analysis. The material was derived from recent and archival cases in six canaries (Serinus canaria), two zebra finches (Poephi la guttata), three psittaciformes (a kaka, Nestor meriondalis, one rainbow lorikeet, Trichoglossus mollucanus, and one budgerigar, Melopsittacus undul atus), and three New Zealand wood pigeons (Hemiphaga novaeseelandiae), The disease observed in the passerine species appeared to have an acute clinica l course and the bacterial lesions were predominately enteric, In the pigeo ns and the psittaciformes examined, the clinical course of the disease was more chronic in nature and involved the liver and spleen. A correlation was found between the amount of stainable iron in the liver of affected birds and the area of bacterial lesions, All of the 11 strains of Yersinia pseudo tuberculosis isolated from fresh necropsy material were serotype II, as det ermined using a standard serum agglutination test. Immunohistochemistry ind icated the presence of antigen(s) common to serotype II in histological mat erial from confirmed cases and in another three cases where the organism ha d been cultured but the serotype not specified. The in vitro virulence char acteristics and plasmid profiles of Y, pseudotuberculosis isolates were als o determined.