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Studies on the epidemiology of the intestinal spirochaete Brachyspira pilosicoli

Oxberry, Sophy Louise (2002) Studies on the epidemiology of the intestinal spirochaete Brachyspira pilosicoli. PhD thesis, Murdoch University.

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Brachyspira pilosicoli is an anaerobic intestinal spirochaete which colonises the large intestine of a number of species of animals and birds, as well as human beings. Colonisation can result in a diarrhoea disease known as "intestinal spirochaetosis", a feature of which can be the presence of large numbers of the spirochaete attached by one cell end to the colorectl epithelium. Studies have shown that infection with B. pilosicoli is widespread, especially amongst intensively-reared production animals such as pigs and poultry. Economic losses in the pig and poultry industries caused by this spirochaetes are thought to be significant, however knowledge of effective control measures are currently limited. The major aims of this thesis were to expand understanding of the epidemiology and cycles of transmission of B. pilosicoli, and to examine the in-vitro efficacy of various therapeutic agents available to control the infection.

Pigs of all ages in Australian pig herds were shown to be colonised with B. pilosicoli, and the presence of the organism was associated with diarrhoea. Although multiple strains of the species were identified on individual piggeries, in a detailed study on two farms in Western Australia, one strajn of B. pilosicoli was shown to be predominant, and was probably transferred between the piggeries by infected stock. Similarly, studies of B. pilosicoli in chjckens showed that certain strains of B. pilosicoli predominated in individual flocks.

Brachyspira pilosicoli was shown to occur in natural and artificial water bodies, and to survive for a prolonged period in water at 4 °C. Wild waterbirds were shown to have a high prevalence of colonisation, and might represent a public health risk due to contamination of water sources with bird faeces. As such, transmission of the organism via contaminated water represents a newly-described route of transmission. In an experimental infection of a human volunteer, the strain of B. pilosicoli used was shown to colonise the individual and to cause gastrointestinal problems. Isolates of 8. pilosicoli were also obtained from puppies that were for sale in pet shops, and these dogs represent a potential source of zoonotic spread of B. pilosicoli. A subgroup of 108 isolates of B. pilosicoli obtained from the various host species in this study were examined by multilocus enzyme electrophoresis, and were generally found to be genetically diverse, without any obvious species-specific clustering of strains. This lack of clustering supports the concept that there is potential cross species transmission of strains. A total of 186 B. pilosicoli isolates obtained from the various animal species and humans in this study were also examined for their in vitro antimicrobial susceptibility. Metronidazole was found to be an effective agent for inhibiting in-vitro growth of B. pilosicoli isolates from humans and various animal species. Tiamulin was also effective against porcine isolates of B. pilosicoli, as was tetracycline for isolates of B. pilosicoli from chickens. Human strains from some but not all sources examined tended to be resistant to ampicillin.

This study adds to the body of knowledge concerning the prevalence, transmission and antimicrobial susceptibility of B. pilosicoli. It has shown that the organism is widespread, and has more than one route of potential transmission. The susceptibility of the organism to antimicrobials varies with the host species affected, as well as with the geographical origin of the isolate.

Item Type: Thesis (PhD)
Murdoch Affiliation(s): School of Veterinary and Biomedical Sciences
Notes: Note to the author: If you would like to make your thesis openly available on Murdoch University Library's Research Repository, please contact: Thank you.
Supervisor(s): Hampson, David
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