Challenge of Bovine Foot Skin Fibroblasts With Digital Dermatitis Treponemes Identifies Distinct Pathogenic Mechanisms

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.</jats:p

Fatal complications associated with caesarean section in the bitch: post-mortem investigation of 17 cases.

This case series describes the post-mortem findings in 17 bitches (Canis lupus familiaris) with a recent (<7 days) history of caesarean section, most (94%) of which had undergone conservative caesarean section with preservation of the uterus. Brachycephalic breeds accounted for 71% of all cases, with the French Bulldog (35%, n = 6), English Bulldog (18%, n = 3) and Boston Terrier (12%, n = 2) overrepresented. Eleven animals (65%) died between 4 and 48 h after surgery, whereas six (35%) died during the procedure. The most common cause of death was septicaemia (41%, n = 7) associated with Streptococcus canis (29%, n = 5) and/or Escherichia coli (24%, n = 4). Other causes of death included brachycephalic obstructive airway syndrome (BOAS)-associated respiratory failure (24%, n = 4), haemorrhagic shock (18%, n = 3), inconclusive (12%, n = 2) and gastric dilatation and volvulus (6%, n = 1). Histopathological changes were seen in the uterus of 10 cases and included marked inflammation (60%, n = 6), marked haemorrhage (20%, n = 2) or both (20%, n = 2). Metritis was often characterized by fibrinonecrotic, neutrophilic to mixed inflammation, consistent with acute infection. However, prominent lymphohistiocytic infiltrates in two cases suggested that infection had been present prior to surgery. Peritonitis, myositis and panniculitis commonly (35%, n = 6) surrounded the incision sites. The presence of inflammation and bacterial colonies within multiple surgical sites suggested iatrogenic implantation of bacteria, potentially from the uterine lumen. Bacterial culture and isolation, as well as tape measurements for evaluation of conformational BOAS risk factors where applicable, are recommended as part of the routine post-mortem work-up for bitches that die shortly after caesarean section

Bilateral ulnar retained cartilage cores causing thoracic angular limb deformities in a cat

AbstractA 6‐month‐old, female, neutered, Bengal‐cross cat presented for bilateral thoracic angular limb deformity. Radiographs and computed tomography revealed well‐defined, flame‐shaped radiolucent and hypoattenuating defects within the medullary cavity of the distal ulnar metaphyses, surrounded by a thin rim of sclerosis. Surgical correction of initially the right angular limb deformity involved radial and ulnar ostectomies, and a bone biopsy of the distal ulnar metaphysis was submitted for histopathology. The morphological diagnosis was consistent with retained cartilage core, never previously reported in a cat.</jats:p

Primary retropharyngeal leiomyosarcoma in a young cat

Case summaryAn Oriental Shorthair cat, aged 1 year and 6 months, developed progressive stridor and a palpable right ventral cervical mass. Fine-needle aspiration of the mass was inconclusive, while thoracic radiography and CT showed no evidence of metastasis. There was initial improvement in stridor with oral doxycycline and prednisolone treatment, but it recurred 4 weeks later and excisional biopsy was performed. Histopathology with immunohistochemistry diagnosed leiomyosarcoma with incomplete surgical margins. Adjunctive radiation therapy was declined. Repeated physical examination and CT 7 months postoperatively documented no evidence of mass recurrence.Relevance and novel informationThis is the first reported case of retropharyngeal leiomyosarcoma in a young cat with no evidence of local reoccurrence 7 months following an excisional biopsy

Molecular Screening for Digital Dermatitis-Associated Treponemes in Bovine Ischaemic Teat Necrosis Lesions and Milk in Dairy Cattle

Bovine ischaemic teat necrosis (ITN) is a disease affecting the skin of the teats of dairy cows with an unknown aetiopathogenesis. Digital dermatitis (DD)-associated treponemes have previously been suggested as a potential aetiological agent in ITN, although the sample size was small. The current study, using established PCR techniques, aimed to examine the association with the presence of DD-associated treponemes in a large number of ITN samples from a wider geographical area, and surveyed the potential of milk as an infection reservoir. From 95 ITN lesions, 35.8% (n = 34) were positive for at least one DD-associated treponeme compared with only 5.6% (n = 1) of 18 non-lesioned teats from cows with ITN lesions on a different teat using a nested PCR approach. All 10 age- and production-matched control cows were negative for DD-associated treponemes via PCR. No DD-associated treponemes could be detected from foremilk of cows with (n = 19) and without (n = 31) a DD lesion on the hind feet. DD-associated treponemes could be detected via PCR after incubation in milk for up to 2 h. Therefore, milk does not appear to be a competent reservoir for transmission of DD-associated treponemes. Moreover, in the current study DD-associated treponemes were only detected in a subset of ITN samples, so it is unlikely these opportunistic skin-associated pathogens are the major or sole agent of ITN.</jats:p

Survival of bovine digital dermatitis treponemes in conditions relevant to the host and farm environment.

ObjectivesBovine digital dermatitis (BDD), a painful infectious foot disease in dairy cattle, endemic in many countries worldwide, causes substantial economic and welfare impacts. Treponema spp. are considered key to BDD pathogenesis. To aid infection reservoir identification and control measure development, survival of BDD treponemes was investigated in different temperatures (4, 12, 20, 37, 45 and 60 °C), pH values (5-9.0), dairy cattle faeces and bedding types: straw shavings, sand, sand containing 5% lime (w/w) and recycled manure solids (RMS).MethodsA turbidity microplate methodology was adapted to measure pH impact on growth. Survival of BDD treponemes for the different conditions were assessed by sub-cultures of microcosms over different time points.ResultsBDD treponemes remained viable between 4 and 37 °C and pH 5.5 and 9.0 under anaerobic conditions. In sterile faecal microcosms, incubated aerobically at 12 °C, BDD treponemes remained viable for a median of 1 day (15 min - 6 day range). Variation in duration of survival and ability to grow was observed between phylogroups and strains. In aerobic microcosms, T. phagedenis T320A remained viable for the full 7 days in sand, 6 days in sawdust, 5 days in RMS, but was not viable after 15 min in straw or sand containing 5% (w/w) lime.ConclusionsTreponeme survival conditions identified here should enhance future BDD infection reservoir surveys and enable control measures. Of note, straw or sand containing 5% (w/w) lime should be assessed in BDD field trials. Finally, these data indicate BDD treponemes exhibit characteristics of facultative anaerobes