Defining differential markers for symptomatic and asymptomatic Brachyspira hyodysenteriae isolates
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Research partner: Moredun Research Institute
Sponsors: BPEX
Project duration: 2009 – 2012
Swine dysentery (SD) is a disease affecting the gut of pigs which results in bloody diarrhoea. It is caused by the bacterium Brachyspira hyodysenteriae and is responsible for severe economic losses in the swine industry worldwide. Recently, strains of B. hyodysenteriae that cause no SD or very mild symptoms of SD (asymptomatic strains) have been reported in addition to those inducing severe diseases (symptomatic strains). To-date these two variants cannot be easily differentiated. Therefore a diagnostic test based on clear variations in genes and/or proteins between both types is needed to be able to distinguish between them so that unnecessary treatment, slaughter and/or loss of business can be avoided in the case of herd infection with no disease-causing strains.
During the last year a panel of B. hyodysenteriae isolates, including symptomatic and asymptomatic strains, has been assembled from different Scottish farms. Screening of this panel has shown that a gene involved in the process of iron binding (bitC gene) is more frequently present in symptomatic than asymptomatic strains. Importantly, iron is a key nutrient for the growth of bacteria. The iron binding system has only been detected in B. hyodysenteriae and seems to absent in related Brachyspira species which are unable to cause disease in animals. Therefore the iron binding system may be linked to the ability of the organism to cause SD and hence is a possible tool for differentiation.
Further comparison of various genes of symptomatic and asymptomatic strains of B. hyodysenteriae was carried out to investigate sets of genes that are either shared, variable or distinct to each other. Analysis to date has revealed high similarity between both types but also has led to the identification of 13 genes which are solely present in symptomatic strains. The results suggest that there are genetic differences between the two variants of B. hyodysenteriae. Further investigation of these distinguishing features are necessary to verify whether these findings are truly typical for each type and thus can be useful as a differential tool.
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04-Jan-2012