Prevalence of bovine papillomavirus and Treponema DNA in bovine digital dermatitis lesions.

Bovine digital dermatitis (BDD) is a common infectious foot disease whose aetiology is not fully understood. Its origin is thought to be multifactorial, with treponemes being involved. Using PCR-based techniques, BDD samples from 45 affected cows and intact skin from 8 BDD-affected and 33 healthy cows were assessed for the presence of bovine papillomavirus and Treponema DNA. BPV DNA (mainly BPV-1/2) was detected in 22% of lesions and one skin sample from affected animals, and in 15% (BPV-1/-2) and 23% (BPV-3/4/6/9/10) of skin samples from healthy cows. Using quantitative PCR, Treponema DNA was demonstrated in 38/45 BDD lesions, with bacterial DNA loads ranging between 2 × 10(3) and 2.78 × 10(5) copies/40 ng of total DNA. Qualitative PCR confirmed this result and revealed Treponema DNA in 4 additional BDD samples, thus leading to an overall infection rate of 93.3%. Sequence analysis of amplified Treponema DNA revealed T. pedis sp. nov. in 51%, T. medium ssp. bovis in 37.7%, and T. phagedenis ssp. vaccae in 4.4% of lesions. T. brennaborense was not detected in any of the samples. Six BDD samples contained type IV oral Treponema strains, 6 other harboured so far unpublished Treponema sequences. To our knowledge, this is the first report providing information on BPV infection in BDD-affected cattle, and the Treponema DNA load and occurrence of type IV treponemes in BDD samples. Our findings further support an etiologic association of treponemes, particularly T. pedis sp. nov., with BDD disease, yet indicate that BPVs do not directly contribute to BDD development.