AUTHOR=Alsaaod Maher , Weber Jim , Jensen Tim , Brandt Sabine , Gurtner Corinne , Devaux David , Studer Eveline , Steiner Adrian 

TITLE=“Non-healing” claw horn lesions in dairy cows: Clinical, histopathological and molecular biological characterization of four cases

JOURNAL=Frontiers in Veterinary Science

VOLUME=9

YEAR=2022

URL=https://www.frontiersin.org/journals/veterinary-science/articles/10.3389/fvets.2022.1041215

DOI=10.3389/fvets.2022.1041215

ISSN=2297-1769

ABSTRACT=<p>The increasing prevalence of bovine digital dermatitis (BDD) contributes to a higher occurrence of secondary infections of exposed corium with <italic>Treponema</italic> spp. in bovine claws. “Non-healing” claw horn lesions (NHL) clinically resemble BDD lesions. They are severe, cause chronic lameness, and may persist for several months. They poorly respond to standard treatments of BDD and represent a serious welfare issue. In this study, four cases of NHL were classified clinically either as BDD-associated axial horn fissures (BDD-HFA; <italic>n</italic> = 3) or BDD-associated sole ulcer (BDD-SU; <italic>n</italic> = 1). In all four cases, pronounced multifocal keratinolysis of the stratum corneum, ulceration, and severe chronic lymphoplasmacytic perivascular to interstitial dermatitis were observed. All lesional samples tested positive for <italic>Treponema</italic> spp., <italic>Fusobacterium</italic> (<italic>F</italic>.) <italic>necrophorum</italic>, and <italic>Porphyromonas</italic> (<italic>P</italic>.) <italic>levii</italic> by PCRs. BDD-HFA lesions contained <italic>Treponema pedis</italic> as revealed by genetic identities of 93, 99, and 100%. Treponemes in the BDD-SU lesion were 94% homologous to <italic>Treponema</italic> phylotype PT3. Fluorescent <italic>in situ</italic> hybridization (FISH) revealed extensive epidermal infiltration by treponemes that made up &gt; 90% of the total bacterial population in all four lesions. FISH also tested positive for <italic>P. levii</italic> and negative for <italic>F. necrophorum</italic> in all four cases, whilst only one BDD-HFA contained <italic>Dichelobacter nodosus</italic>. Our data point to BDD-associated treponemes and <italic>P. levii</italic> constituting potential etiological agents in the development of “non-healing” claw horn lesions in cattle.</p>