Survival of bovine digital dermatitis treponemes in conditions relevant to the host and farm environment

Objectives: Bovine digital dermatitis (BDD), a painful infectious foot disease in dairy cattle, endemic in many countries worldwide, causes substantial economic and welfare impacts. Treponema spp. are considered key to BDD pathogenesis. To aid infection reservoir identification and control measure development, survival of BDD treponemes was investigated in different temperatures (4, 12, 20, 37, 45 and 60 degrees C), pH values (5-9.0), dairy cattle faeces and bedding types: straw shavings, sand, sand containing 5% lime (w/w) and recycled manure solids (RMS).Methods: A turbidity microplate methodology was adapted to measure pH impact on growth. Survival of BDD treponemes for the different conditions were assessed by sub-cultures of microcosms over different time points.Results: BDD treponemes remained viable between 4 and 37 degrees C and pH 5.5 and 9.0 under anaerobic conditions. In sterile faecal microcosms, incubated aerobically at 12 degrees C, BDD treponemes remained viable for a median of 1 day (15 min -6 day range). Variation in duration of survival and ability to grow was observed between phylogroups and strains. In aerobic microcosms, T. phagedenis T320A remained viable for the full 7 days in sand, 6 days in sawdust, 5 days in RMS, but was not viable after 15 min in straw or sand containing 5% (w/w) lime.Conclusions: Treponeme survival conditions identified here should enhance future BDD infection reservoir sur-veys and enable control measures. Of note, straw or sand containing 5% (w/w) lime should be assessed in BDD field trials. Finally, these data indicate BDD treponemes exhibit characteristics of facultative anaerobes.