Brachyspira-associated diarrhoea is a re-emerging concern for Canadian swine producers, according to Janet Hill and colleagues at the University of Saskatchewan. To identify critical control points for reducing the impact of Brachyspira on production, improved diagnostic tools and a better understanding of the on-farm epidemiology of these pathogens are required, they say.

In BMC Veterinary Research, they recently reported a cross-sectional study conducted for the detection of Brachyspira on a commercial, two-site, farrow-to-finish pork production unit in Saskatchewan, Canada with a clinical history of mucohaemorrhagic colitis associated with “B. hampsonii”.

Previous investigation of similar cases has led to the recognition of novel, strongly beta-haemolytic Brachyspira isolates, for which the name “Brachyspira hampsonii” has been proposed, the researchers explain.

Rectal swabs from pigs at all production stages were collected over 13 weeks (n=866). Two swabs were collected per pig for culture and Gram stain, and for PCR.

Ninety-one culture positive samples were detected, with the highest prevalence of Brachyspira shedding in grower pigs (21 per cent). No Brachyspira were detected in pre-weaned piglets.

PCR and Gram stain of rectal swabs detected fewer positive samples than culture.

The most prevalent species detected was B. murdochii; other species detected included B. pilosicoli, B. innocens and “Brachyspira hampsonii”.

Phylogenetic analysis revealed that several of the isolates, including some strongly beta-haemolytic isolates, might represent novel taxa.

Hill and colleagues highlight that their results indicate apparently healthy pigs can be colonised with diverse Brachyspira species, including some potential pathogens, and that frequency of shedding peaks in the grower stage.

They add that difference in the detection rates of Brachyspira amongst culture, Gram stain or PCR on rectal swabs have implications for choice of detection methods and surveillance approaches that may be most effective in Brachyspira control strategies.

The detection of established species, atypical and unclassified isolates on a two-site farm with a clinical history of mucohaemorrhagic diarrhoea associated with “Brachyspira hampsonii” infection is an indication of the complexities of Brachyspira ecology and an indication that there is much work to be done in determining the potential role of these diverse organisms, alone or in combination, in causing diarrhea and colitis, the researchers commented.

Reference

^{Patterson A.H., J.E. Rubin, C. Fernando, M.O. Costa, J.C.S. Harding and J.E. Hill. 2013. Fecal shedding of Brachyspira spp. on a farrow-to-finish swine farm with a clinical history of “Brachyspira hampsonii”-associated colitis. BMC Veterinary Research, 9:137. doi:10.1186/1746-6148-9-137}

July 2013