'Brachyspira hampsonii', discovered in North America in 2010 associated with dysentery-like illness, is an economically relevant swine pathogen resulting in decreased feed efficiency and increased morbidity, mortality and medication usage, report first-named author, Matheus O. Costa of the University of Saskatchewan in a paper in BMC Veterinary Research.

He and colleagues explain that 'B. hampsonii' clade II strain 30446 has been shown to be causally associated with mucohaemorrhagic diarrhoea and colitis.

Their objectives were to determine if 'B. hampsonii' clade I strain 30599 is pathogenic to pigs, and to evaluate the relative diagnostic performance of three ante mortem sampling methodologies, i.e. direct PCR on faeces, PCR on rectal GenoTube Livestock swabs and Brachyspira culture from rectal swabs.

Five-week old pigs were intragastrically inoculated thrice with 10⁸ genomic equivalents 'B. hampsonii' (n=12), or served as sham controls (n= 6). Faeces were sampled and consistency assessed daily. Necropsies were performed 24 hours after peak clinical signs.

One pig died due to an unrelated illness. Nine of 11 inoculated pigs, but no controls, developed mucoid or mucohaemorrhagic diarrhoea (MHD). Characteristic lesions of swine dysentery were observed in large intestine.

'B. hampsonii' strain 30599 DNA was detected by qPCR in faeces of all inoculated pigs for up to six days prior to the onset of MHD. The organism was isolated from the faeces and colons of pigs demonstrating MHD but not from controls.

B. intermedia was isolated from inoculated pigs without MHD, and from five of the six controls.

Costa and colleagues concluded that 'B. hampsonii' clade I strain 30599 is pathogenic and causes mucohaemorrhagic diarrhoea and colitis in susceptible pigs.

Moreover, the three sampling methodologies performed similarly. GenoTube Livestock, a forensic swab designed to preserve DNA during shipping is a useful tool especially in settings where timely transport of diagnostic samples is challenging, the Saskatoon-based group added.

Reference

Costa M.O., J.E. Hill, C. Fernando, H.D. Lemieux, S.E. Detmer, J.E. Rubin and J.C.S. Harding. 2014. Confirmation that “Brachyspira hampsonii” clade I (Canadian strain 30599) causes mucohemorrhagic diarrhea and colitis in experimentally infected pigs. BMC Veterinary Research. 10:129. doi:10.1186/1746-6148-10-129

July 2014