Fetal heart rate responses in chronic hypoxaemia with superimposed repeated hypoxaemia consistent with early labour: a controlled study in fetal sheep.

OBJECTIVE: Deceleration area (DA) and capacity (DC) of the fetal heart rate can help predict risk of intrapartum fetal compromise. However, their predictive value in higher risk pregnancies is unclear. We investigated whether they can predict the onset of hypotension during brief hypoxaemia repeated at a rate consistent with early labour in fetal sheep with pre-existing hypoxaemia. DESIGN: Prospective, controlled study. SETTING: Laboratory. SAMPLE: Chronically instrumented, unanaesthetised near-term fetal sheep. METHODS: One-minute complete umbilical cord occlusions (UCOs) were performed every 5 minutes in fetal sheep with baseline pa O2 <17 mmHg (hypoxaemic, n = 8) and >17 mmHg (normoxic, n = 11) for 4 hours or until arterial pressure fell <20 mmHg. MAIN OUTCOME MEASURES: DA, DC and arterial pressure. RESULTS: Normoxic fetuses showed effective cardiovascular adaptation without hypotension and mild acidaemia (lowest arterial pressure 40.7 ± 2.8 mmHg, pH 7.35 ± 0.03). Hypoxaemic fetuses developed hypotension (lowest arterial pressure 20.8 ± 1.9 mmHg, P < 0.001) and acidaemia (final pH 7.07 ± 0.05). In hypoxaemic fetuses, decelerations showed faster falls in FHR over the first 40 seconds of UCOs but the final deceleration depth was not different to normoxic fetuses. DC was modestly higher in hypoxaemic fetuses during the penultimate (P = 0.04) and final (P = 0.012) 20 minutes of UCOs. DA was not different between groups. CONCLUSION: Chronically hypoxaemic fetuses had early onset of cardiovascular compromise during labour-like brief repeated UCOs. DA was unable to identify developing hypotension in this setting, while DC only showed modest differences between groups. These findings highlight that DA and DC thresholds need to be adjusted for antenatal risk factors, potentially limiting their clinical utility.

The inter- and intra-observer reliability of a locomotion scoring scale for sheep.

A seven point locomotion scoring scale, ranging from 0=normal locomotion to 6=unable to stand or move, has been developed. To test the between and within observer reliability of the scale, 65 movie clips of sheep with normal and varying degrees of abnormal locomotion were made. Three observers familiar with sheep locomotion were trained to read the movie clips. Thirty clips were randomly selected and used to test between and within observer agreement. There was high inter-(intra-class correlation coefficient [ICC]=0.93, weighted kappa [kappa(w)]=0.93) and intra-(ICC=0.90, kappa(w)=0.91) observer reliability, with no evidence of observer bias. The main between score differences were for scores 0 (normal) and 1 (uneven posture and shortened stride but no head movement). The results indicate that the locomotion scoring scale using groups of defined observations for each point on the scale was reliable and may be a useful research tool to identify and monitor locomotion in individual sheep when used by trained observers.

Differential effects of slow rewarming after cerebral hypothermia on white matter recovery after global cerebral ischemia in near-term fetal sheep.

It is widely believed that rewarming slowly after therapeutic hypothermia for hypoxic-ischemic (HI) encephalopathy can improve outcomes, but its impact on white matter injury after HI is unclear. Fetal sheep (0.85 gestation) received 30 min ischemia-normothermia (n = 8), or hypothermia from 3-48 h with rapid spontaneous rewarming over 1 h (ischemia-48 h hypothermia, n = 8), or 48 h with slow rewarming over 24 h (ischemia-slow rewarming, n = 7) or 72 h with rapid rewarming (ischemia-72 h hypothermia, n = 8). Ischemia was associated with loss of total and mature oligodendrocytes and reduced area fraction of myelin basic protein (MBP) and 2',3'-cyclic nucleotide 3'-phosphodiesterase (CNPase; immature/mature oligodendrocytes) and increased microglia and astrocytes. Total numbers of oligodendrocytes were increased by all hypothermia protocols but only ischemia-72 h hypothermia attenuated loss of mature oligodendrocytes. All hypothermia protocols similarly increased the area fraction of MBP, whereas there was only an intermediate effect on the area fraction of CNPase. Microglia were suppressed by all hypothermia protocols, with the greatest reduction after ischemia-72 h hypothermia, and an intermediate effect after ischemia-slow rewarming. By contrast, induction of astrocytes was significantly reduced only after ischemia-slow rewarming. In conclusion, slow rewarming after hypothermia did not improve oligodendrocyte survival or myelination or suppression of microgliosis compared to fast rewarming, but modestly reduced astrocytosis.

Looking after the individual to reduce disease in the flock: a binomial mixed effects model investigating the impact of individual sheep management of footrot and interdigital dermatitis in a prospective longitudinal study on one farm.

A total of 160 ewes on one farm in England were studied for 18 months. The incidence of footrot and interdigital dermatitis in individually identified sheep and treatment and flock control measures were recorded. A binomial mixed effect model with the incidence of footrot or interdigital dermatitis as the outcome was used to investigate patterns of association between treatments, flock control measures and the incidence of footrot or interdigital dermatitis. In this one flock, the incidence of footrot and interdigital dermatitis was positively associated with the incidence of footrot and interdigital dermatitis and with trimming of feet and negatively associated with the use of parenteral antibiotics and topical antibiotic sprays in either the first and/or second 2-week period prior to the incidence of interest. These results provide two hypotheses: one that 'footrot and interdigital dermatitis are infectious diseases that can be controlled, in part, through the use of antibiotic therapy, which acts to reduce the infectious period of diseased sheep' and two, that 'routine trimming of diseased and healthy feet exacerbate disease, through environmental contamination and/or through increased susceptibility of sheep with recently trimmed feet'.

Endogenous alpha2-adrenergic receptor-mediated neuroprotection after severe hypoxia in preterm fetal sheep.

Central alpha-adrenergic receptor activity is important for fetal adaptation to hypoxia before birth. It is unclear whether it is also important during recovery. We therefore tested the hypothesis that an infusion of the specific alpha(2)-adrenergic receptor antagonist idazoxan (1 mg/kg/h i.v.) from 15 min to 4 h after profound hypoxia induced by 25 min umbilical cord occlusion in fetal sheep at 70% of gestation (equivalent to the 28-32 weeks in humans) would increase neural injury. After 3 days' recovery, idazoxan infusion was associated with a significant increase in neuronal loss in the hippocampus (P<0.05), expression of cleaved caspase-3 (P<0.05), and numbers of activated microglia (P<0.05). There was no significant effect on other neuronal regions or on loss of O4-positive premyelinating oligodendrocytes in the subcortical white matter. Idazoxan was associated with an increase in evolving epileptiform electroencephalographic (EEG) transient activity after occlusion (difference at peak 2.5+/-1.0 vs. 11.7+/-4.7 counts/min, P<0.05) and significantly reduced average spectral edge frequency, but not EEG intensity, from 54 until 72 h after occlusion (P<0.05). Hippocampal neuronal loss was correlated with total numbers of epileptiform transients during idazoxan infusion (P<0.01; r(2)=0.7). In conclusion, endogenous inhibitory alpha(2)-adrenergic receptor activation after severe hypoxia appears to significantly limit evolving hippocampal damage in the immature brain.

The detection and characterisation of Dichelobacter nodosus from cases of ovine footrot in England and Wales.

Footrot, caused by the strictly anaerobic bacterium Dichelobacter nodosus, is the most common cause of lameness in sheep in Great Britain but problems exist in association with its diagnosis and control. The fastidious nature of D. nodosus means that complex media and several weeks are required for characterisation. An alternative method to simplify and enhance the detection of D. nodosus in clinical samples is therefore highly desirable. In terms of control, anecdotal evidence from the farming community suggests that the commercially available vaccine, based on Australian isolates of D. nodosus, is not widely employed in this country due to its perceived inefficacy. Seven hundred and six isolates, collected from outbreaks in England and Wales, were therefore used to investigate these issues. A 16S rRNA PCR was adapted to detect D. nodosus in clinical material within 1 day of sampling; a 15% increase in detection compared with culture and less than 1% false negatives were achieved. This represents a major advance in the rapid diagnosis of footrot and will be of great value to practitioners and diagnostic laboratories. Bacterial virulence was tested using protease thermostability and zymogram assays, whilst serogrouping was performed by slide agglutination. All isolates demonstrated virulence patterns previously recorded in Australia and all nine serogroups of D. nodosus (A-I) were represented. Serogroup H was predominant. There was, therefore, no evidence for the presence of novel strains of D. nodosus compared with Australia suggesting the need for further investigation into farmers' views on the use of the commercial vaccine in Great Britain.

Footrot and interdigital dermatitis in sheep: farmers' practices, opinions and attitudes.

In 1999, a study was initiated to improve the treatment and control of footrot and interdigital dermatitis in sheep flocks in England and Wales. In November 2000, a retrospective cross-sectional study was conducted in which 392 sheep farmers were asked to estimate the prevalence of footrot and interdigital dermatitis in their flock in the previous 12 months, whether they considered these diseases to be a problem, how they treated and controlled them and their opinion on the success of the treatment and control measures that they used; 209 of them provided usable responses. The farmers tended to be more concerned as the prevalence of the diseases increased; 91 per cent of the farmers with a prevalence of footrot of less than 5 per cent considered it a small or very small problem on their farm, but 51 per cent of the farmers with a prevalence of 5 per cent or more also considered it to be a small or very small problem. Approximately 60 per cent of the farmers who used parenteral antibiotics considered that they were good or excellent at treating footrot, and this treatment was associated with a prevalence of less than 5 per cent. A similar proportion of farmers also considered topical foot sprays and footbathing to be good or excellent for controlling footrot or interdigital dermatitis, but these treatments were not associated with a lower prevalence of footrot or interdigital dermatitis. Of the 29 farmers who used a footrot vaccine, 20 (69 per cent) considered it good to excellent and this was associated with a prevalence of footrot of less than 5 per cent in their flock; however, vaccination was not associated with lower levels of footrot across the whole sample. Farmers spent approximately 34 minutes per sheep per year treating and controlling footrot; 31 per cent were prepared to spend more money and more time to manage footrot, 27 per cent were prepared to spend more time, 19 per cent were prepared to spend more money and 23 per cent were not prepared to do either. The farmers who were willing to invest more money or more money and time had a higher prevalence of footrot.

Specific leukotriene formation by purified human eosinophils and neutrophils.

Human granulocytes isolated from peripheral blood have been described to synthesize both LTB4 and LTC4 from arachidonic acid. We have observed that the amount of LTC4 produced by human granulocyte preparations is strongly dependent on the relative amount of eosinophils. To investigate a possibly significant difference in leukotriene synthesis of the eosinophilic and neutrophilic granulocytes, we developed a purification method to isolate both cell types from granulocytes obtained from the blood of healthy donors. Leukotrienes were generated by incubation of the purified cells with arachidonic acid, calcium ionophore A23187, calcium-chloride and reduced glutathione. Surprisingly, eosinophils were found to produce almost exclusively the spasmogenic LTC4. In contrast, neutrophils produce almost exclusively the chemotactic LTB4, its omega-hydroxylated metabolite 20-hydroxy-LTB4 and two non-enzymically formed LTB4 isomers.

Changes in the broncho-alveolar lavage fluid in smokers and patients with chronic obstructive lung disease.

Direct contact of the cells normally present in the bronchial lumen, such as alveolar macrophages, with air pollutants (e.g. cigarette smoke) can lead to the activation of these cells. This activation is beneficial for the cleaning task these cells have in the bronchial tree, but also leads to the release of chemotactic substances, toxic oxygen radicals, enzymes and mediators responsible for bronchial obstruction. As a first step in these processes, an enhanced chemotactic activity can attract neutrophils to the bronchial lumen, where they help by cleaning the lungs from possible dangerous intruders, but can also cause damage to the normal lung architecture. In the present study concerned with the pathogenesis of chronic obstructive lung disease (COLD), broncho-alveolar lavage (BAL) was performed in 35 individuals, who could be divided on he basis of their history and lung function into normal/nonsmokers, normal/smokers, COLD-patients/nonsmokers and COLD-patients/smokers. Neutrophilic chemotactic activity was assayed using Boyden chambers where the patients' own neutrophils were tested. More neutrophils and more neutrophilic chemotactic activity were found in the BAL-fluid of the smokers and COLD-patients. A correlation was demonstrated between the amount of chemotactic activity released during the incubation of cells obtained by BAL and the airway resistance or the airway conductance. These data suggest an enhanced chemotactic activity as one of the initiating factors in the pathogenesis of chronic obstructive lung disease.

Changes in alveolar macrophage enzyme content and activity in smokers and patients with chronic obstructive lung disease.

An influx of polymorphonuclear and mononuclear cells into the lungs of smokers and patients with chronic obstructive lung disease (COLD) is thought to be an important factor in the development of pulmonary emphysema. Next to the synthesis and release of toxic oxygen radicals and mediators, an enhanced production and activity of proteolytic enzymes could play an important role in the pathogenesis of emphysema. In the present study changes were investigated in the broncho-alveolar lavage (BAL) fluid and BAL-cells, especially in alveolar macrophages. Pulmonary lavages were performed in the middle lobe with sterile saline of 37 degrees C in individuals, who could be divided on the basis of their history and lung function into normal/nonsmokers, normal/smokers, COLD-patients/nonsmokers and COLD-patients/smokers. Alveolar macrophages obtained by BAL were stained for different lysosomal enzymes. Isolated BAL-fluid and BAL-cells were assayed for elastolytic activity. In alveolar macrophages of smoking COLD-patients significantly more beta-glucuronidase could be demonstrated. Elastolytic activity changed with smoking habits, suggesting an enhanced release of elastolytic enzymes. No correlation was found between elastolytic activity and the amount of polymorphonuclear cells in the BAL-fluid. From these results it may be concluded that enzymes from alveolar macrophages play a more important role in the pathogenesis of emphysema than those from polymorphonuclear cells.

The relationship between decrease in feed intake and infection with Trypanosoma congolense and T. vivax in west African dwarf goats.

Twenty-three mature dwarf goats were used to study whether there is a relationship between the decrease in feed intake for individual goats and infection with T.congolense and T. vivax. Furthermore, it was investigated how rectal temperatures and blood parameters were affected by the T. congolense infection and how changes in these parameters can be used to predict the effect of a T. vivax infection on feed intake. For individual goats a ranking correlation was found between relative dry matter intake and infection (r = 0.59; p < .05). Animals with the most marked decrease in dry matter intake during the T. congolense infection showed a smaller increase in urea and a higher increase in non esterified fatty acids and beta-hydroxy butyrate levels in their blood. Evidence was obtained that the relative decrease in dry matter intake for individual goats during a T. vivax infection can be predicted on the basis of urea and creatinine responses measured in the blood during a previous infection with T. congolense infection.

Risk factors associated with the prevalence of interdigital dermatitis in sheep from 1999 to 2000.

As part of an investigation into improving the treatment and control of lameness in sheep flocks in England and Wales, a postal survey was conducted in November 2000. Farmers were asked to estimate the prevalence of footrot and interdigital dermatitis in their flocks. In the ewes the prevalence of interdigital dermatitis remained relatively stable throughout the year, but there was a large increase in lambs during late spring and early summer. Logistic regression models were used to assess statistically significant risk factors associated with prevalences of the condition of 5 per cent or more in ewes and 10 per cent or more in lambs. Factors that increased the risk in ewes were 'sometimes/never' catching lame sheep compared with 'always' farm land 100 m or less above sea level and renting-in winter grazing; factors that increased the risk in lambs were a prevalence of 5 per cent or more of footrot in ewes, 'sometimes/never' catching lame ewes compared with 'always', 'sometimes/never' treating ewes with footrot with parenteral antibiotics compared with 'always', showing sheep at agricultural events, farm land 100 m or less above sea level, and a prevalence of 5 per cent or more of interdigital dermatitis in ewes. Turning sheep on to a field which had been free from livestock for at least two weeks after footbathing decreased the risk of interdigital dermatitis in lambs. Footbathing without the use of a clean field compared with not footbathing did not significantly affect the prevalence of the interdigital dermatitis.

Risk factors associated with the prevalence of footrot in sheep from 1999 to 2000.

A postal survey of the techniques being used for the treatment and control of footrot in sheep flocks between November 1999 and October 2000 was conducted in England and Wales in November 2000. Of the 392 questionnaires circulated, 251 (64 per cent) were returned, and 209 of these were usable. Negative binomial regression analysis indicated that the isolation of bought-in sheep, and the separation and individual treatment of diseased sheep with parenteral antibiotics, foot trimming and topical foot sprays were associated with a significantly lower prevalence of footrot in a flock. In contrast, ewe flocks which were routinely foot trimmed more than once a year had a significantly higher prevalence of footrot. No evidence was found that footbathing a flock reduced the level of footrot, except on the 14 per cent of farms where the penning and race facilities for footbathing were reported by the farmer to be excellent. Vaccination had no significant beneficial effect on the level of footrot in a flock

Footrot and interdigital dermatitis in sheep: farmer satisfaction with current management, their ideal management and sources used to adopt new strategies.

The aims of this research were to identify management practices that sheep farmers currently use to treat and prevent footrot in sheep and whether they consider that these are successful management tools and to find out how sheep farmers would ideally like to manage footrot in their flock. Over 90% of lameness in sheep in the UK is caused by Dichelobacter nodosus, which presents clinically as interdigital dermatitis (ID) alone or with separation of hoof horn (FR). A questionnaire was sent to 265 farmers to investigate their current management and their satisfaction with current management of the spectrum of clinical presentations of footrot. Farmers were also asked their ideal management of footrot and their interest in, and sources of information for, change. Approximately 160 farmers responded. Farmers satisfied with current management reported a prevalence of lameness < or = 5%. These farmers caught and treated lame sheep within 3 days of first seeing them lame, and treated sheep with FR and ID with parenteral antibacterials. Farmers dissatisfied with their management reported a prevalence of lameness >5%. These farmers practised routine foot trimming, footbathing and vaccination against footrot. Whilst 89% of farmers said they were satisfied with their management of FR over 34% were interested in changing management. Farmers identified veterinarians as the most influential source for new information. Farmers reported that ideally they would control FR by culling/isolating lame sheep, sourcing replacements from non-lame parents, trimming feet less, using antibacterial treatments less and using vaccination more. Footbathing was a commonly used management that was linked with dissatisfaction and that also was listed highly as an ideal management. Consequently, some of the ideal managements are in agreement with our understanding of disease control (culling and isolation, sourcing healthy replacements) but others are in contrast with our current knowledge of management and farmers self-reporting of satisfaction of management of footrot (less use of antibacterial treatment, more footbathing and vaccination). One explanation for this is the theory of cognitive dissonance where belief follows behaviour, i.e. farmers report that they believe an ideal which is what they are currently doing, even if the management is sub-optimal.

A within farm clinical trial to compare two treatments (parenteral antibacterials and hoof trimming) for sheep lame with footrot.

From observational studies, farmers who use parenteral antibacterials to promptly treat all sheep with footrot (FR) or interdigital dermatitis (ID) have a prevalence of lameness of < 2% compared with a prevalence of 9% lameness reported by farmers who treat lame sheep by trimming affected feet. We tested the hypothesis that prompt treatment of sheep lame with naturally developing FR or ID with parenteral and topical antibacterials reduces the prevalence and incidence of lameness with these conditions compared with less frequent treatment with trimming of hoof horn and applying topical antibacterials.A further hypothesis was that reduction of ID and FR would improve productivity. A lowland sheep flock with 700 ewes was used to test these hypotheses in an 18-month within farm clinical trial with four groups of ewes: two intervention and two control. The duration and severity of lameness was used to categorise sheep into three weighted scores of lameness (WLS): never lame (WLS0), mildly lame/lame for < 6 days (WLS1) and severely or chronically lame (WLS2). The intervention reduced the prevalence of lameness due to FR and ID in ewes and lambs and the incidence of lameness in ewes. The WLS was also significantly lower in sheep in the intervention groups. Ewes with a higher WLS were subsequently significantly more likely to have a body condition score < 2.5 and to have lame lambs. Significantly more ewes lambed and successfully reared more lambs that were ready for slaughter at a younger age in the intervention versus control groups. There was an increase in the gross margin of Pound630/100 ewes mated in the intervention group, including the cost of treatment of Pound150/100 ewes mated. We conclude that prompt parenteral and topical antibacterial treatment of sheep lame with ID and FR reduced the prevalence and incidence of these infectious conditions and led to improved health, welfare and productivity.

Factors associated with changes of state of foot conformation and lameness in a flock of sheep.

The aim of this research was to investigate transitions between foot conformation, lameness and footrot in sheep. Data came from one lowland flock of approximately 700 ewes studied for 18 months. Multilevel multistate analyses of transitions between good and poor foot conformation states in ewes, and lame and non-lame states in ewes and lambs were conducted. Key results were that the longer sheep had feet in good conformation, the more likely they were to stay in this state; similarly, the longer a ewe was not lame the more likely she was not to become lame. Ewes with poor foot conformation were more likely to become lame (OR: 1.83 (1.24-2.67)) and to be >4 years (OR: 1.50 (1.09-2.05)). Ewes with footrot were less likely to move to good foot conformation (OR: 0.48 (0.31-0.75)) and were more likely to become lame (OR: 3.81 (2.60-5.59)). Ewes lame for >4 days and not treated with parenteral antibacterials had a higher risk of developing (OR: 2.00 (1-3.61)), or remaining in (OR: 0.49 (0.29-0.95)), poor foot conformation compared with ewes never lame. Treatment of ewes lame with footrot with parenteral antibacterials increased the probability of transition from a lame to a non-lame state (OR: 1.46 (1.05-2.02)) and these ewes, even if lame for >4 days, were not more likely to develop poor foot conformation. The risk of a ewe becoming lame increased when at least one of her offspring was lame (OR: 2.03 (1.42-2.92)) and when the prevalence of lameness in the group was ≥5% (OR: 1.42 (1.06-1.92)). Lambs were at increased risk of becoming lame when they were male (OR: 1.42 (1.01-2.01)), single (OR: 1.86 (1.34-2.59)) or had a lame dam or sibling (OR: 3.10 (1.81-5.32)). There were no explanatory variables associated with lambs recovering from lameness. We conclude that poor foot conformation in ewes increases the susceptibility of ewes to become lame and that this can arise from untreated footrot. Treatment of ewes lame with footrot with parenteral antibacterials leads to recovery from lameness and prevents or resolves poor foot conformation which then reduces the susceptibility to further lameness with footrot.