Isolation of spirochetes of genus Treponema from pigs with ear necrosis

Various ear lesions, often caused by ear biting, are common in pigs. Some herds have a high frequency of ear necrosis, a syndrome characterized by necrotic lesions along the rim of the pinna, often bilateral and sometimes resulting in loss of the entire ear. In samples from such lesions spirochetes have been observed microscopically but never isolated or identified. In this study two herds with periodic outbreaks of ear necrosis among weaners were investigated. Samples were collected from ear lesions and from the gingiva of the pigs. Spirochetes were observed in silver stained histological sections and by phase contrast microscope in scrapings from the necrotic lesions. From an ear lesion a pure spirochete isolate was obtained and identified as a yet unnamed species of genus Treponema, closely related to spirochetes found in digital dermatitis in cattle. From the oral samples two pure isolates were obtained. One of these isolates was identified as the same species as in the ear lesion and one as Treponema socranskii. Species identification was based on 16S rRNA gene sequences.