Effect of parenteral selenium administration to sheep on prevalence and recovery from footrot.

BACKGROUND: Insufficient intake of selenium (Se) is common in many regions, and can contribute to increased susceptibility to and prolonged recovery from infectious diseases. OBJECTIVE: To determine the effect of Se administration in decreasing the severity and prevalence of footrot in sheep. ANIMALS: Thirty-eight footrot-affected and 19 nonaffected sheep from a commercial flock of known high incidence of footrot. METHODS: Placebo-controlled, prospective, 15-month clinical trial. Footrot-affected sheep were randomly assigned into 2 groups (n = 19) and injected with either 5 mg Se (footrot [FR]-Se) or saline (FR-Sal) at 1-month intervals for the duration of the study. Unaffected sheep (controls) received no treatment. Sheep feet were examined, trimmed, and scored for footrot with a scale of 0 (no footrot) to 4 (extensive) at 0, 3, 6, 9, and 15 months. Sheep were also bled at time 0 and then at 3, 6, and 15 months to assess whole blood Se concentrations. RESULTS: At time 0, control sheep (255 +/- 11 ng/mL) had higher (P < .05) whole blood Se concentrations compared with FR-Se (205 +/- 12 ng/mL) and FR-Sal (211 +/- 14 ng/mL) sheep. By 6 months, FR-Se sheep (317 +/- 9 ng/mL) had whole blood Se concentrations greater (P < .05) than both control (281 +/- 14 ng/mL) and FR-Sal (277 +/- 16 ng/mL) sheep. FR-Se ewes showed a faster decline in highest lesion score at 3 (P= .012) and 6 (P= .0036) months, and a greater decrease in the number of feet with foot score >0 at 6 (P= .020) months compared with FR-Sal ewes. Sheep with blood Se concentrations <300 ng/mL were at 3.5 times greater risk (1.1-12.1 confidence interval, odds ratio) for FR, although this relationship was only significant (P= .04) at 6 months of the study. CONCLUSIONS AND CLINICAL IMPORTANCE: In sheep with footrot, improved Se status in conjunction with routine control practices result in more rapid improvement of foot lesions.

Nuclear magnetic resonance-based serum metabolic profiling of dairy cows with footrot.

Footrot is a debilitating and contagious disease in dairy cows, caused by the Gram-negative anaerobe Dichelobacter nodosus. 1H-NMR (nuclear magnetic resonance)-based metabolomics has been previously used to understand the pathology and etiology of several diseases. The objective of this study was to characterize serum from dairy cows with footrot (n=10) using 1H-NMR-based metabolomics and chemometric analyses. 1H-NMR spectroscopy with multivariate pattern recognition (principal component analysis and orthogonal partial least-squares discriminant analysis) was performed to identify biomarkers in cows with footrot (F) and healthy controls (C). 1H-NMR analysis facilitated the identification of 21 metabolites. Among these metabolites, 4 metabolites were higher and 17 metabolites were lower in the F group than in the C group. The serum levels of 5 metabolites were significantly different (P<0.05) between the two groups. The results revealed that cows with footrot have altered carbohydrate, amino acid, lipid and energy metabolic pathways. Metabolomic approaches are a clinically useful diagnostic tool for understanding the biochemical alterations and mechanisms of several diseases.

Bovine digital dermatitis and severe virulent ovine foot rot: a common spirochaetal pathogenesis.

A potential pathological role for spirochaetes in bovine digital dermatitis (bovine DD) and severe virulent ovine foot rot (SVOFR) has been considered and a treponeme isolate obtained from each disease in the UK. In this work, we have investigated the hypothesis that the two diseases may have a shared (common) spirochaetal aetiology. Experiments were designed to identify serological similarities and differences between the two spirochaetes; an enzyme-linked immunosorbent assay (ELISA) was developed to detect anti-treponeme antibodies in the sera of cows and sheep against the two-treponeme isolates. Sera were further tested for antigen reactivity by Western blotting. Cattle and sheep with bovine DD and SVOFR, respectively, had increased seropositivity rates to both treponeme isolates, with different patterns of reactivity between farms. In some cattle herds, significant correlations were shown between antibodies to bovine DD treponemes and SVOFR treponemes (P<0.001). In other herds, there was no apparent cross reaction, suggesting the presence of more than one treponeme in bovine DD on some farms. There was no significant correlation between the two treponeme isolates when ELISA-tested against 58 sheep sera from SVOFR cases (P>0.05); sheep showed strong evidence of reactivity to one or the other treponeme antigens, but never to both. Western blotting against both treponeme antigens showed that they frequently displayed different antigen epitopes, although some minor bands were common to both organisms. The data suggest that there are a number of spirochaetes in UK farms, which could be involved in the pathogenesis of either bovine DD or SVOFR.

Antigens for serological diagnosis of ovine footrot.

An antigen extracted from Dichelobacter nodosus with potassium thiocyanate (KSCN) is currently used in enzyme-linked immunosorbent assay (ELISA) for serological diagnosis of ovine footrot, but the test lacks specificity in mature sheep. Other antigens were therefore evaluated for use in this test. Structural components of the cell envelope of D. nodosus including outer membrane, cytoplasmic membrane, lipopolysaccharide and pilus and extracellular proteases were purified from cultured D. nodosus while recombinant membrane proteins, protease and pilus antigens were also evaluated. Many antigenic components of D. nodosus participated in reactions in ELISA that were not specific for infection with D. nodosus and apart from pilus, none of the antigens resulted in improved specificity of the ELISA. Using a positive-negative cut-off to yield sensitivity of 70%, ELISA using pili from cultured D. nodosus serogroup A had a specificity of 98.3% compared with 89.7% for the ELISA with KSCN-extract as antigen (P < 0.001). Recombinant pili morphogenetically expressed in Pseudomonas aeruginosa were unsuitable for use in ELISA due to copurification of Pseudomonas antigens to which apparently healthy sheep directed antibodies. The application of ELISA with D. nodosus pilus as antigen in footrot control programs is discussed.

Effects of clinically occurring chronic lameness in sheep on the concentrations of plasma noradrenaline and adrenaline.

Plasma adrenaline (AD) and noradrenaline (NA) concentrations were measured by high performance liquid chromatography with electrochemical detection in blood samples from control and lame sheep. The lame sheep suffered from naturally occurring foot rot and showed behavioural characteristics normally associated with chronic pain. The lame sheep were scored both for impairment of gait and pathology of the foot and divided into mild and severely affected groups. Both the mildly and severely lame group showed a significant increase in plasma AD and plasma NA which tended to persist even after clinical resolution of the condition. The measurement of plasma AD and NA may provide information which can be used to assess animals experiencing chronic pain, when taken in conjunction with other parameters, such as nociceptive thresholds and plasma hormone levels.

Effect of chronic pain associated with lameness on plasma cortisol concentrations in sheep: a field study.

Plasma cortisol concentrations were measured in two groups of sheep taken from 29 flocks in north Devon. The first group were healthy adult females and the second group were adult females suffering from footrot in one forefoot. These sheep were assessed for the severity of the lesion and the level of lameness and assigned a score. The plasma cortisol concentration was significantly higher in the lame sheep than in the healthy sheep and remained so for up to three months after the apparent resolution of the clinical lesion. There was no correlation between the severity of the footrot and the concentration of plasma cortisol.

Chemotaxis, phagocytosis, and oxidative metabolism in bovine macrophages exposed to a novel interdigital phlegmon (foot rot) lesion isolate, Porphyromonas levii.

OBJECTIVE: To examine the host response toward Porphyromonas levii, by evaluating chemotaxis, phagocytosis, and oxidative burst of bovine macrophages in vitro. SAMPLE POPULATION: Cultured bovine macrophages obtained from monocytes harvested from blood samples of 15 Holstein steers. Porphyromonas levii was isolated from the foot rot lesion of an acutely affected feedlot steer. PROCEDURE: Monocytes were cultured for macrophage differentiation over 7 days. Porphyromonas levii was cultured in strict anaerobic conditions for experimentation. Chemotaxis was evaluated by quantifying macrophage migration toward P. levii in Boyden chambers. Phagocytosis was assessed by quantification of macrophages engulfing P. levii following incubation with or without anti-P. levii serum or purified IgG. Oxidative burst was measured by use of the nitroblue tetrazolium reduction assay. RESULTS: Chemotaxis toward P. levii was not significantly different from control values at any of the tested bacterial concentrations. Phagocytosis of P. levii was approximately 10% at a 10:1 bacterium to macrophage ratio and did not change significantly over time. When higher proportions of P. levii were tested for phagocytosis, the 1,000:1 bacterium to macrophage ratio had a significant increase, compared with the 10:1 test group. Opsonization of P. levii with high-titeranti-P. levii serum or anti-P. levii IgG produced a significant increase in macrophage phagocytosis. Oxidative production significantly increased compared with control in the 1,000:1 test group only. CONCLUSIONS AND CLINICAL RELEVANCE: Porphyromonas levii may evade host detection by decreased chemotaxis, phagocytosis, and oxidative burst by macrophages. Acquired immunity may be beneficial for clearance of P. levii in foot rot lesions in cattle.

Effects of chronic lameness on the concentrations of cortisol, prolactin and vasopressin in the plasma of sheep.

Plasma cortisol, prolactin and vasopressin concentrations were measured by radioimmunoassay in blood samples from control and lame sheep. The lame sheep were all suffering from naturally occurring clinical cases of footrot and showed all the behavioural characteristics of chronic pain; they were scored for impairment of gait and pathology of the foot and divided into mild and severely lame groups. The severely lame sheep had increased plasma prolactin and decreased plasma cortisol concentrations. Plasma vasopressin was variable and showed no consistent changes with lameness. The relationships between plasma cortisol, prolactin and vasopressin may be a useful index in the assessment of animals experiencing chronic pain, when taken in conjunction with other measurements.

The effects of opioid and alpha 2 adrenergic blockade on non-steroidal anti-inflammatory drug analgesia in sheep.

The analgesic effects of the non-steroidal anti-inflammatory drugs (NSAIDs) flunixin and dipyrone were assessed in healthy sheep with no pre-existing inflammation, and in sheep with a chronic inflammatory lesion, using a mechanical noxious stimulus. Saline and dexamethasone were given as controls. Blood taken from healthy sheep after NSAID administration was assayed for thromboxane B2 (TxB2) to compare the ability of these drugs to inhibit cyclo-oxygenase. Both flunixin and dipyrone produced a small but statistically significant rise in pain thresholds (18% and 21% of maximum possible effect respectively) in the healthy sheep which peaked at 30 min and had returned to pre-drug values by 2-3 h. In the lame sheep a similar effect occurred but the response was smaller, much more variable and tended to be prolonged. Saline and dexamethasone had no effect on thresholds over 6 h in either group of sheep. The rise in thresholds was prevented by pre-treatment with naloxone (an opioid antagonist) or atipamezole (an alpha 2-adrenergic antagonist) in the healthy sheep. Naloxone and atipamezole had no effect on thresholds when given alone to healthy sheep. Both NSAIDs inhibited the production of TxB2 to a similar extent. These results indicate that central mechanisms may be involved in NSAID analgesia.