Table_1_“Non-healing” claw horn lesions in dairy cows: Clinical, histopathological and molecular biological characterization of four cases.XLSX

The increasing prevalence of bovine digital dermatitis (BDD) contributes to a higher occurrence of secondary infections of exposed corium with Treponema 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; n = 3) or BDD-associated sole ulcer (BDD-SU; n = 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 Treponema spp., Fusobacterium (F.) necrophorum, and Porphyromonas (P.) levii by PCRs. BDD-HFA lesions contained Treponema pedis as revealed by genetic identities of 93, 99, and 100%. Treponemes in the BDD-SU lesion were 94% homologous to Treponema phylotype PT3. Fluorescent in situ hybridization (FISH) revealed extensive epidermal infiltration by treponemes that made up > 90% of the total bacterial population in all four lesions. FISH also tested positive for P. levii and negative for F. necrophorum in all four cases, whilst only one BDD-HFA contained Dichelobacter nodosus. Our data point to BDD-associated treponemes and P. levii constituting potential etiological agents in the development of “non-healing” claw horn lesions in cattle.

牛指（趾）间皮炎（bovine digital dermatitis, BDD）的发病率持续升高，导致牛蹄暴露真皮层继发密螺旋体属（Treponema spp.）感染的概率显著增加。“非愈合性”蹄角质病变（non-healing claw horn lesions, NHL）在临床表现上与BDD病变高度相似，该类病变病情严重，可引发慢性跛行且持续数月之久，对BDD标准治疗方案响应不佳，属于严重的动物福利问题。本研究纳入4例NHL病例，经临床分类为BDD相关轴侧蹄裂隙（BDD-associated axial horn fissures, BDD-HFA；n=3）与BDD相关足底溃疡（BDD-associated sole ulcer, BDD-SU；n=1）。所有4例病例均可见角质层多灶性显著角质溶解、溃疡形成，以及重度慢性淋巴浆细胞性血管周至间质性皮炎。经聚合酶链式反应（PCR）检测，所有病变样本均呈密螺旋体属、坏死梭杆菌（Fusobacterium necrophorum）和Levii卟啉单胞菌（Porphyromonas levii）阳性。其中BDD-HFA病变样本的基因同源性分别为93%、99%和100%，证实其携带足密螺旋体（Treponema pedis）；而BDD-SU病变中的密螺旋体与密螺旋体系统型PT3的同源性为94%。荧光原位杂交（FISH）结果显示，所有4例病变的表皮均被密螺旋体大量浸润，密螺旋体占病变内总细菌群落的比例超过90%。此外，FISH检测显示所有病例均呈P. levii阳性、F. necrophorum阴性，且仅1例BDD-HFA样本携带结节状杆菌（Dichelobacter nodosus）。本研究数据表明，BDD相关密螺旋体与P. levii可能是引发牛“非愈合性”蹄角质病变的潜在致病原。