Comprehensive Analyses of the Bacterial Population in Non-Healing Claw Lesions of Dairy Cattle

SIMPLE SUMMARY: Non-healing claw lesions (NHCLs) are a newly characterized disorder affecting the deep dermis of the hoof in dairy cattle. Although NHCLs have been associated with bovine digital dermatitis (BDD), their precise etiology is not yet understood. To investigate the bacterial populations of NHCLs, 16S rRNA-based metagenomic analysis with next-generation sequencing (NGS) was employed. As reported in BDD, Treponema species and Fusobacterium necrophorum were detected frequently in NHCLs by PCR and immunohistochemistry, but NGS showed that both bacterial genera were not predominant in NHCLs. The predominant bacterial genera in NHCLs differed among the lesions examined, suggesting that the Treponema species present predominantly in BDD were not predominant in NHCLs and that the constituent bacterial population in NHCLs may vary among individual cattle and/or farms. ABSTRACT: Non-healing claw lesions (NHCLs) are a newly characterized disorder affecting the deep dermis of the hoof in dairy cattle. Although NHCLs are thought to be associated with bovine digital dermatitis (BDD), their precise etiology is not yet understood. To investigate the bacterial populations present in each type of NHCL (toe necrosis: TN, non-healing white line disease: nhWLD, and a non-healing sole ulcer: nhSU), and the newly added entity non-healing verrucous-like lesions (nhVLL), 16S rRNA-based metagenomic analysis with next-generation sequencing (NGS) was employed. Twelve cases of NHCLs (3 TN, 3 nhWLD, 4 nhSU, and 2 nhVLL) were collected from five dairy farms in two prefectures in Japan. Three samples of healthy hoof dermis collected from two farms and a slaughterhouse were used as controls. Furthermore, culture-dependent and -independent approaches were conducted for detecting Treponema species and Fusobacterium necrophorum. As reported in BDD, Treponema species and F. necrophorum were detected frequently from NHCLs by PCR and immunohistochemistry, but NGS showed that these bacterial genera were not predominant in NHCLs. The predominant bacterial genera in NHCLs differed among the lesions examined, suggesting that Treponema species present predominantly in BDD were not predominant in NHCLs and that the bacterial population in NHCLs may vary among individual cattle and/or farms.