Experimental infection of laying hens with Serpulina intermedia causes reduced egg production and increased faecal water content

Serpulina intermedia strain HB60, isolated from an Australian hen with diarrhoea, was used to infect 10 individually caged 14-week-old laying hens. Another 10 birds were sham inoculated with sterile broth. Birds were kept for 16 weeks, and faecal water content, egg production and body weights recorded. Strain HB60 was isolated from the faeces of nine of the infected birds at irregular intervals throughout the experiment, and from their caeca at slaughter. Infected birds tended to be lighter and their faeces, on average, were significantly wetter (by 2.85%; P < 0.002) than those of the controls. Significant reductions in mean number of eggs laid (1.4/week; P < 0.002) and mean egg weights (1.16 g; P < 0.05) were recorded in infected birds. Colonization did not induce any characteristic pathological changes. S. intermedia is potentially an economically significant cause of reduced egg production, and wet faeces in layer and broiler breeder flocks.