Background: The husbandry systems for laying hens were changed in Sweden during the years 2001 -2004, and an increase in the number of submissions for necropsy from laying hen farms was noted. Hence, this study was initiated to compare causes of mortality in different housing systems for commercial laying hens during this change.

Erysipelas is a bacterial disease caused by Erysipelothrix rhusiopathiae, which may infect swine as well as several other species of mammals and birds, including domestic fowl. In poultry, erysipelas may cause sudden high mortality due to septicemia. This communication describes the first isolation of E. rhusiopathiae from the haematophagous poultry red mite, Dermanyssus gallinae DeGeer (Acari: Dermanyssidae), that was collected on three farms where hen erysipelas was diagnosed. The bacteria were isolated from the integument as well as from the interior of the mites. Serotypes 1a and 1b of E. rhusiopathiae found in the mites corresponded with those isolated from the diseased birds. These findings imply that D. gallinae is a potential vector of E. rhusiopathiae. The current lack of effective measures to control D. gallinae causes recurring mite problems in poultry facilities once afflicted by this parasite. Consequently, mites containing E. rhusiopathiae may act as reservoir hosts of this bacterium, allowing it to persist in the poultry house between flock cycles as a source of infection for the replacement pullets. The zoonotic potentials of both E. rhusiopathiae and D. gallinae should also be considered.

Atypical, strongly haemolytic porcine isolates of intestinal spirochaetes differing genetically from Brachyspira hyodysenteriae were identified and characterized. The isolates were subjected to culture and biochemical tests, antimicrobial susceptibility testing and molecular analyses. None of four species-specific polymerase chain reaction systems targeting genes of B. hyodysenteriae gave a positive reaction. All the atypical porcine isolates were identical in their partial 16S rRNA and nox gene sequences with a previously described isolate from a mallard (Anas platyrhynchos), and differed only slightly from another mallard isolate. All these isolates were distinctly different from all currently recognized Brachyspira species. A challenge study was carried out using recently weaned pigs. Clinical signs and macroscopic changes consistent with swine dysentery were seen both in pigs given the atypical porcine isolate and in control pigs given the reference strain of B. hyodysenteriae (B204(R)). Pigs given the genetically similar isolate from a mallard became colonized and diarrhoea was observed. This is the first study indicating that Brachyspira isolates from mallard can infect pigs and induce diarrhoea. We propose that this atypical spirochaete genotype should be regarded as a new species within the genus Brachyspira, and be provisionally designated 'Brachyspira suanatina' sp. nov.

The purpose of this study was to evaluate a multilocus sequence typing (MLST) scheme for intestinal spirochaetes of the genus Brachyspira. Eight loci mainly coding for enzymes previously used in multilocus enzyme electrophoresis analysis of Brachyspira species were examined in 66 Brachyspira field isolates and type/reference strains. The isolates and strains were recovered from pigs, birds, dogs and a mouse and originated from seven European countries, the USA and Canada. Forty-six isolates represented recognized Brachyspira species and 20 represented provisionally designated species or isolates that have not been classified. Only two loci gave PCR products for all 66 strains and isolates, but amplicons for seven loci were obtained for 44 of the isolates. Sequences for each locus had a DNA allelic variation of 30-47 and an amino acid allelic variation of 14-47 that gave rise to the same number of sequence and amino acid types (58) for the strains and isolates studied. A population snapshot based on sequence and amino acid types showed a close phylogenetic relationship amongst the porcine isolates from the same geographical regions, and indicated a close evolutionary relationship between isolates recovered from pigs and mallards. A general concordance was obtained between the MLST groupings and classifications based on culture and biochemical tests, 16S rDNA sequence analysis and random amplified polymorphic DNA analysis. This is a first step towards establishing an MLST system for use in identifying Brachyspira species and determining relationships between individual strains and species in the genus.