Occurrence of Treponema spp. in porcine skin ulcers and gingiva

Porcine shoulder ulcers and ear necrosis are a significant animal welfare concern and impair efficient livestock production. Although spirochetes have been detected in both types of lesions the potential role of these bacteria in lesion propagation has received little attention. The objective of this study was to investigate the occurrence of spirochetes of the genus Treponema in shoulder ulcers or ear necrosis in pigs and compare these with treponemes from porcine gingiva. Samples were collected from gingiva and necrotic ulcers in 169 pigs. Presence of spirochetes was observed in silver stained histological sections and by phase contrast microscopy in scrapings from the necrotic lesions. Additionally, PCR of the 16SrRNA–tRNAIle intergenic spacer region (ISR2) was used to detect Treponema spp. in all samples. Combined analysis showed that 73% of the shoulder ulcers and 53% of the ear necroses were positive for spirochetes. Treponema spp. were detected in 9.7% of the gingival samples. Comparative DNA sequence analysis of the ISR2 sequences revealed the presence of three distinct genetic phylotypes of Treponema spp. corresponding to Treponema pedis, and as yet two unnamed phylotypes represented by GenBank sequences C1UD1 (Acc. No. AY342041) and C1BT2–8 (Acc. No. AY342046). Detection of identical ISR2 sequences from gingiva and ulcer samples indicates that oral Treponema spp. are spread from mouth to ulcer. We conclude that Treponema spp. frequently occur in shoulder ulcers and ear necrosis in pigs, and suggest a possible infection route through biting and licking.