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.

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.

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

OBJECTIVES: Bovine 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). METHODS: A 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. RESULTS: BDD 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. CONCLUSIONS: Treponeme 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.

Clinical and Pathological Features of Bovine Ischaemic Teat Necrosis.

Bovine ischaemic teat necrosis (ITN) is an emerging disease of unknown aetiology affecting mostly dairy cows in the early stages of first lactation and a substantial welfare concern frequently leading to premature culling and economic losses. Specific diagnostic criteria are lacking. The aims of this study were to develop an appropriate ITN grading system, describe the histopathological changes and investigate the potential aetiological role of several pathogens in 47 cows with 73 ITN lesions from 28 farms. ITN lesions were allocated to one of three broad macroscopic categories: presence of a non-proliferative lesion on the teat (type 1); proliferative teat lesion with crusting (type 2); severe purulent to eosinophilic, ulcerative and necrotising dermatitis and sloughing or total absence of the teat (type 3). Lesions were mostly observed on the medial aspect of the teat but there was no anatomical predisposition as to which teats were more frequently affected. In approximately 50% of the ITN teats reviewed, the lesions were continuous with the skin of the udder and 34.2% of cases had sloughed or partially sloughed teats. The main histological findings were: focally extensive severe purulent to eosinophilic, ulcerative and necrotizing dermatitis; serocellular crust formation; and epidermal hyperplasia with dyskeratosis. Some lesions also had leucocytoclastic to eosinophilic vasculitis and thrombosis with ischaemic necrosis. Macroscopic and histological analyses confirmed the suspected ischaemic nature of the lesions but the specific aetiopathogenesis was elusive with a wide range of bacteria present, probably as opportunistic infections. However, Treponema spp and Orthopox virus were excluded as major aetiological agents. This study establishes a foundation for further investigations of the pathogenesis of bovine ITN and a basis for consistency in diagnosis and classification of the stage of disease. The findings are also key to further understanding disease progression and prognosis.

An Observational Study Investigating Potential Risk Factors and Economic Impact for Bovine Ischaemic Teat Necrosis on Dairy Farms in Great Britain.

Bovine ischaemic teat necrosis (ITN) is an emerging disease of unknown aetiology that affects the teats of dairy cattle. It causes economic and animal welfare issues with many animals being culled. No effective treatments or epidemiological data to inform control strategies are currently available. The aim of this observational study was to investigate farmer-reported experiences and identify potential farm-level risk factors. In January 2018, a questionnaire was sent to a random sample of 1,855 Great Britain (GB) dairy farmers. A usable response rate of 12.3% was obtained. Fifty-one per cent [95% confidence interval (CI): 44.4-57.8%] of farmers reported having experienced ITN on their farm between 1985 and 2018. Rising numbers of farms indicated that ITN is an emerging disease with 46.3% of farmers reporting the first case in the 3 years up to 2018. At the animal level, 47.3% (95% CI: 38.7-55.9%) of the cases occurred during the first lactation and 78.9% (95% CI: 75.2-82.6%) within the first 90 days in milk. Only 20.8% (95% CI: 15.9-26.4%) of the cases were reported to recover, whereas 22.8% (95% CI: 17.8-28.5%) of the cases required culling. The remaining cases experienced complications such as loss of a teat and/or mastitis. From these data, the cost of ITN, through production losses and expenditure, was estimated to be £1,121 per farm per year. The costs were estimated at £720, £860 and £2,133 for recovered, complicated and culled cases, respectively. Univariable and multivariable logistic regression models were used to explore the associations between the presence of ITN on farm and various risk factors. The presence of udder cleft dermatitis (UCD) (odds ratio 2.80; 95% CI: 1.54-5.07; p < 0.01) and chapped teats (odds ratio 6.07; 95% CI: 1.96-18.76; p < 0.01) in the milking herd was associated with the presence of ITN at the farm level. This is the first national questionnaire of ITN within GB and highlights the association of UCD and chapped teats with ITN at the farm level. While there are many limitations and potential bias around farmer questionnaires, these findings highlight several key areas for further disease investigation and possible intervention.