Contagious ovine digital dermatitis (CODD) is a cause of severe lameness in sheep and the three Treponema phylogroups Treponema medium/Treponema vincentii-like, Treponema phagedenis-like and Treponema pedis have been associated with clinical disease. The aims of this study were: (1) to describe the histopathological changes associated with each previously established grade of clinical lesion, and (2) to investigate immunohistochemically the association of the Treponema-like organisms with the observed histopathological changes. Early lesions were characterized by lymphoplasmacytic infiltration of the distal digital skin, with suppurative coronitis and intracorneal pustules. In more advanced stages of the disease there was complete separation of the dorsal wall of the hoof with a necrotizing and fibrinosuppurative exudate and dermatitis. The later lesions were mostly resolved, but with milder suppurative changes remaining within the cornified layer and periosteal reaction of the dorsal aspect of the distal phalanx. Large numbers of Treponema-like organisms were identified within early grade lesions (as well as later, more advanced grade lesions) and were specifically associated with the observed histopathological changes. The results of this study provide some evidence in support of the hypothesis that the three CODD-associated Treponema phylogroups are involved in the aetiopathogenesis of this disease.

Treponeme-associated foot disease has been described in cattle with digital dermatitis and sheep with contagious ovine digital dermatitis. In this study, severe foot lesions in dairy goats associated with digital dermatitis treponemes (i.e. Treponema medium, Treponema phagedenis and Treponema pedis) were characterized macroscopically, radiographically and histologically. The main macroscopic foot lesion was of extensive solar ulceration with or without exophytic papilliform hyperkeratosis. Radiographically, the distal phalanx and distal sesamoid bones were severely damaged and remodelled. Histologically, the lesion was categorized as a chronic lymphoplasmacytic, suppurative and ulcerative pododermatitis. Immunohistochemistry identified the spirochaetal microorganisms located extracellularly in the superficial horn. Study limitations mean that the treponeme bacteria could not be considered the sole or causal agents in the cases described.

Pressure sores cause severe pain and discomfort in hospitalized people and in farmed cattle and are often infected with unknown bacteria. Pressure sores occur on the upper legs of 6-10% of recumbent cattle and are generally considered to be caused by constant pressure, commonly on bony areas of the limbs. This study analyzed pressure sores taken from the upper limbs of 14 cattle using isolation in culture and nested polymerase chain reaction (PCR) to detect treponemes associated with digital dermatitis (DD). A 100% association of DD treponemes with the pressure sores was demonstrated, but treponemes were shown not to be part of the normal skin microbiota. Immunohistochemistry showed an association of DD treponemes with lesions and particularly with the hair follicles in lesions, identifying the bacteria deep within wounds, thereby suggesting that they could contribute to lesion pathogenesis. The bacteria isolated from the pressure sore lesions were similar or identical on analysis of the 16S rRNA gene to those found in DD foot lesions in cattle, suggesting the same bacteria can infect multiple lesions. Indeed, the results of this study suggest that these spirochaetal bacteria may be expanding in host range and in their ability to colonize different tissues and contribute to a range of disease manifestations in farm animals.

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Summary A descriptive case report of the management of a miniature pony presenting to a UK equine veterinary hospital with marked trismus and increased masseter muscle size. Diagnosis of masseter myodegeneration (MM) was aided by the use of computed tomography and excisional biopsy. Hyperlipaemia was diagnosed as a sequelae of MM. Treatment included nonsteroidal anti‐inflammatories, parenteral nutrition and fluid therapy in addition to supportive care. The gelding was discharged from the hospital 30 days after admission, having made a full recovery. MM in the horse is a rare condition that appears to be physiologically distinct from canine masticatory muscle myositis which is primarily immune mediated.

Bovine digital dermatitis (BDD) is a common infectious disease of digital skin in cattle and an important cause of lameness worldwide, with limited treatment options. It is of increasing global concern for both animal welfare and food security, imposing a large economic burden on cattle farming industries each year. A polytreponemal etiology has been consistently identified, with three key phylogroups implicated globally: Treponema medium, Treponema phagedenis, and Treponema pedis. Pathogenic mechanisms which might enable targeted treatment/therapeutic development are poorly defined. This study used RNA sequencing to determine global differential mRNA expression in primary bovine foot skin fibroblasts following challenge with three representative BDD treponemes and a commensal treponeme, Treponema ruminis. A pro-inflammatory response was elicited by the BDD treponemes, mediated through IL-8/IL-17 signaling. Unexpectedly, the three BDD treponemes elicited distinct mechanisms of pathogenesis. T. phagedenis and T. pedis increased abundance of mRNA transcripts associated with apoptosis, while T. medium and T. pedis increased transcripts involved in actin rearrangement and loss of cell adhesion, likely promoting tissue invasion. The upregulation of antimicrobial peptide precursor, DEFB123, by T. phagedenis spirochaetes may present a microbial ecological advantage to all treponemes within BDD infected tissue, explaining their dominance within lesions. A commensal, T. ruminis, significantly dysregulated over three times the number of host mRNA transcripts compared to BDD treponemes, implying BDD treponemes, akin to the syphilis pathogen (Treponema pallidum), have evolved as “stealth pathogens” which avoid triggering substantial host immune/inflammatory responses to enable persistence and tissue invasion. Immunohistochemistry demonstrated increased IL-6, IL-8, RND1, and CFB protein expression in BDD lesions, confirming in vitro fibroblast observations and highlighting the system’s value in modeling BDD pathogenesis. Several unique shared gene targets were identified, particularly RGS16, GRO1, MAFF, and ZC3H12A. The three key BDD Treponema phylogroups elicited both distinct and shared pathogenic mechanisms in bovine foot skin; upregulating inflammation whilst simultaneously suppressing adaptive immunity. The novel gene targets identified here should enable future vaccine/therapeutic approaches.

A first lactation dairy cow (in late gestation) presented with a hard round swelling of the right olecranon and slight lameness. A lateromedial radiograph of the right olecranon had a mottled appearance with indistinct borders.Bone biopsy was performed post calving. Histology showed fibrosis and reactive changes, however this sample was considered too superficial and not representative of the whole lesion.Based on the differential diagnoses treatment was not possible and the cow was culled at the end of her lactation. At slaughter the forelimb was retained for further analysis. Grossly, the olecranon was severely enlarged, irregular with multiple yellow granulomas in the cortex and medulla of the bone. Histology showed multifocal pyogranulomas containing bacteria, Splendore-Hoeppli material and surrounded by remodelled bone and fibrosis.Despite displaying biochemical properties characteristic of Actinomycesspecies this could not be confirmed by partial 16s rRNA sequencing and the organism could not be definitively speciated.

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