Avian Intestinal Spirochaetosis

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Avian Intestinal Spirochaetosis (AIS) is a disease affecting commercial laying and meat breeding hens resulting from the colonisation of the caeca and rectum by one or more species of anaerobic spirochaetal bacteria. AIS was first described a decade ago in commercial chickens from the United Kingdom, The Netherlands and the United States. Seven species of the bacterium are capable of colonising poultry hosts, but only three are considered to be pathogenic. Of these, Brachyspira intermedia is considered the most common and significant species.

AIS is characterised by chronic diarrhoea in diseased birds, resulting in the faecal staining of eggs and wet litter. The resultant wet litter is an industrial problem necessitating the mechanical cleaning of cages. A delay and (or) reduction of egg laying capacity is also observed, with hatched broiler chicks from eggs of infected parents showing reduced performance compared to those of healthy parents. The significance of AIS is often unappreciated due to the variable clinical signs of the disease. In addition, the isolation of the bacterium can only be achieved using specialised media and techniques.

Treatment

Currently there are no chemotherapeutic compounds that are registered for treatment or prevention of AIS. Nevertheless compounds that have been used to treat or prevent spirochaetosis in pigs have also been used in laying chickens with limited success; and importantly have not provided any long term control with recurrence of infection and reduction in performance occurring within 3 weeks to 3 months.

Research is currently in progress to develop a diagnostic immunological test method and a recombinant vaccine to detect antibodies and provide sufficient protection against AIS in chickens.