Prevalence, Genetic Relationships and Pathogenicity of Intestinal Spirochaetes Infecting Australian Poultry

The prevalence of infection with intestinal spirochaetes in chickens in Western Australia was assessed by selective culture of faecal samples. Colonisation was common, with 35.1% of layer flocks and 53.3% of broiler breeder flocks being positive. Spirochaetes were recovered significantly more frequently from flocks with diarrhoea or reduced production than from clinically normal flocks. The genetic identity and diversity of 56 selected isolates from Australia, the USA and Europe were examined using multilocus enzyme electrophoresis: these were divided into six diverse genetic groups. Three groups contained isolates previously shown to be pathogenic for chickens: (i) "Serpulina intermedia ", (ii) an unnamed group (not identified in Australia), and (iii) Serpulina pilosicoli. Most pathogenic isolates from Australia were "S. intermedia ". Day-old broiler chicks were infected orally with Australian isolates either of "S. intermedia" (3), a commonly isolated but unnamed group (3), or S. pilosicoli (1). All spirochaetes induced diarrhoea, but this occurred earlier and more birds were colonised with "S. intermedia" and S. pilosicoli strains than with strains from the unnamed group. Infection of laying hens with an "S. intermedia " strain caused wet faeces and reduced egg production.