Doctoral thesis, 2009
Genus Brachyspira in birdsJansson, Désirée S.
AbstractSpirochaetes of genus Brachyspira colonize the large intestine of some mammals and birds, and cause intestinal disease and production losses in pigs and chickens. The precise significance of Brachyspira spp. colonization in birds, the bacterial species involved, and the epidemiology are incompletely understood. Possible transmission between birds and mammals, and the role of wildlife have previously received little attention. In this thesis intestinal spirochaetes were isolated from commercial laying hens and free-living wild mallards (Anas platyrhynchos), jackdaws (Corvus monedula), rooks (C. frugilegus) and hooded crows (C. corone cornix). The isolates were investigated by phenotypic tests, molecular methods (PCR, RAPD, PFGE, sequencing of 16S rRNA and nox genes) and phylogenetic analysis. Experimental animal models were applied in pigs and mallards to study colonization rates and enteropathogenicity. The results showed that Brachyspira spp. were commonly isolated from the investigated species. Phenotypic and molecular analyses showed considerable diversity, and simultaneous colonization by two or more species or genetic variants of the same species was commonly found. In laying hens, pathogenic species (B. intermedia and B. alvinipulli), presumed non-pathogenic species (B. innocens, murdochii, ‘B. pulli’), and isolates that could not be assigned to any presently known species were isolated. No association with disease or production losses was identified. The etiologic agent of swine dysentery, B. hyodysenteriae, was isolated from mallards, which is the first time from wild birds. A putative novel species, ‘B. suanatina’, was isolated from mallards and Swedish and Danish pig herds. Isolates from both a pig and a mallard were shown to cause diarrhoea in pigs by experimental challenge. In mallards, focal epithelial changes were observed with B. hyodysenteriae and ‘B. suanatina’. Another novel and presumed non-pathogenic species, ‘B. corvi’, from corvid birds, was characterized and provisionally described. The results of the thesis highlight the diagnostic difficulties, the genetic diversity, and suggest that birds may be important reservoirs of Brachyspira spp.
Keywordsbirds; swine; crows; layer chickens; spirochaetales; phenotypes; phylogeny; swine dysentery; intestinal diseases; epidemiology
Published inActa Universitatis Agriculturae Sueciae
2009, number: 2009:14
Publisher: Dept. of Clinical Sciences, Swedish University of Agricultural Sciences