Comparative Genome Sequence Analysis of Actinobacillus pleuropneumoniae Serovar 8 Isolates From Norway, Denmark, and the United Kingdom Indicates Distinct Phylogenetic Lineages and Differences in Distribution of Antimicrobial Resistance Genes

Actinobacillus pleuropneumoniae is the etiological agent of porcine pleuropneumonia, a disease of major impact on pig health, welfare, and productivity globally. Serovar 8 (APP) is the predominant clinical serovar in Norway and the United Kingdom (UK), and has been isolated from clinical cases in Denmark. The primary objective of this study was to characterize the genetic variability of isolates of A. pleuropneumoniae APP8 in the Norwegian population. The secondary objectives were to determine the within-host variability of APP8; to compare the APP8 bacterial populations in Norway, Denmark, and the UK, including antimicrobial resistance (AMR) gene profiles and to assess the effect of national differences in antimicrobial drug use and restricted animal movement on the occurrence of resistance. Isolates of APP8 from the UK (n=67), Denmark (n=22), and Norway (n=123) collected between 1983 and 2020 were compared using whole genome sequencing. To investigate genetic variability within individual hosts, an additional 104 APP8 isolates from the lungs of six Norwegian pigs were compared. Very low within-host variation was observed (≤ 2 single nucleotide polymorphisms). The phylogeny of 123 Norwegian APP8 isolates from 76 herds revealed some within-herd genetic variation, but substantial geographical clustering. When inferring the relatedness of the three international APP8 collections, the topology highlighted the existence of two distinct monophyletic branches characterized by the Norwegian and UK isolates, respectively. Three Danish isolates were scattered across the UK branch, whereas the remaining 19 Danish isolates clustered in two monophyletic groups nested in the Norwegian branch. Coalescence analysis, performed to estimate the divergences from a common ancestor, indicated a last common ancestor several centuries ago. The phylogenetic analyses also revealed striking differences in occurrence of AMR genes, as these were 23-times more prevalent among the UK isolates than among the Norwegian isolates. An increased understanding of the effects of population strategies is helpful in surveillance and control of infectious diseases.

The use of social network analysis to describe the effect of immune activation on group dynamics in pigs

The immune system can influence social motivation with potentially dire consequences for group-housed production animals, such as pigs. The aim of this study was to test the effect of a controlled immune activation in group-housed pigs, through an injection with lipopolysaccharide (LPS) and an intervention with ketoprofen on centrality parameters at the individual level. In addition, we wanted to test the effect of time relative to the injection on general network parameters in order to get a better understanding of changes in social network structures at the group level. 52 female pigs (11-12 weeks) were allocated to four treatments, comprising two injections: ketoprofen-LPS (KL), ketoprofen-saline (KS), saline-LPS (SL) and saline-saline (SS). Social behaviour with a focus on damaging behaviour was observed continuously in 10 × 15 min bouts between 0800 am and 1700 pm 1 day before (baseline) and two subsequent days after injection. Activity was scan-sampled every 5 min for 6 h after the last injection in the pen. Saliva samples were taken for cortisol analysis at baseline and at 4, 24, 48, 72 h after the injections. A controlled immune activation affected centrality parameters for ear manipulation networks at the individual level. Lipopolysaccharide-injected pigs had a lower in-degree centrality, thus, received less interactions, 2 days after the challenge. Treatment effects on tail manipulation and fighting networks were not observed at the individual level. For networks of manipulation of other body parts, in-degree centrality was positively correlated with cortisol response at 4 h and lying behaviour in the first 6 h after the challenge in LPS-injected pigs. Thus, the stronger the pigs reacted to the LPS, the more interactions they received in the subsequent days. The time in relation to injection affected general network parameters for ear manipulation and fighting networks at the group level. For ear manipulation networks, in-degree centralisation was higher on the days following injection, thus, certain individuals in the pen received more interactions than the rest of the group compared to baseline. For fighting networks, betweenness decreased on the first day after injection compared to baseline, indicating that network connectivity increased after the challenge. Networks of tail manipulation and manipulation of other body parts did not change on the days after injection at the group level. Social network analysis is a method that can potentially provide important insights into the effects of sickness on social behaviour in group-housed pigs.

The Effect of LPS and Ketoprofen on Cytokines, Brain Monoamines, and Social Behavior in Group-Housed Pigs

Poor health is a risk factor for damaging behaviors, but the mechanisms behind this link are unknown. Injection of pigs with lipopolysaccharide (LPS) can be used to model aspects of poor health. Recent studies have shown that LPS-injected pigs perform more tail- and ear-directed behavior compared to saline-injected pigs and suggest that pro-inflammatory cytokines may play a role in these behaviors. The aims of this study were to test the effect of LPS on the social behavior of pigs and the neurotransmitters and modulators in their brains and to test the effect of a nonsteroidal anti-inflammatory drug on the effects of LPS. Fifty-two female pigs (11-12 weeks) were allocated to four treatments comprising two injections: saline-saline (SS), saline-LPS (SL), ketoprofen-saline (KS), and ketoprofen-LPS (KL). Activity was scan-sampled every 5 min for 6 h after the last injection in the pen. Social behavior was observed continuously in 10 × 15-min bouts between 8 a.m. and 5 p.m. 1 day before (baseline) and 1 and 2 days after the injection. Saliva was analyzed for cortisol and plasma for tryptophan and kynurenine. The frontal cortex, hippocampus, hypothalamus, and brain stem were sampled 72 h after the injection and analyzed for cytokines and monoamines. LPS activated the HPA axis and decreased the activity within 6 h after the injection. Ketoprofen lowered the effect of LPS on cortisol release and attenuated the behavioral signs of sickness in challenged pigs. SL pigs manipulated the ears of their pen mates significantly longer than SS pigs 2 days after the injection. LPS had no observed effect on IFN-γ, TNF-α, and IL-18. At 72 h after the injection, plasma tryptophan was depleted in SL pigs, and tryptophan and kynurenine concentrations in the frontal cortex and brain stem of SL pigs were significantly lower compared to those in SS pigs. Dopamine concentrations in the hypothalamus of SL pigs were significantly lower compared to those in SS pigs. Serotonin concentrations in the hypothalamus and noradrenaline concentrations in the hippocampus of SL pigs were significantly lower compared to those in KL pigs. In conclusion, LPS influenced the different neurotransmitters and modulators in the brain that are hypothesized to play an important role in the regulation of mood and behavior.

Demyelinating polyneuropathy in goats lacking prion protein

Studies in mice with ablation of Prnp, the gene that encodes the cellular prion protein (PrP^C ), have led to the hypothesis that PrP^C is important for peripheral nerve myelin maintenance. Here, we have used a nontransgenic animal model to put this idea to the test; namely, goats that, due to a naturally occurring nonsense mutation, lack PrP^C . Teased nerve fiber preparation revealed a demyelinating pathology in goats without PrP^C . Affected nerves were invaded by macrophages and T cells and displayed vacuolated fibers, shrunken axons, and onion bulbs. Peripheral nerve lipid composition was similar in young goats with or without PrP^C , but markedly different between corresponding groups of adult goats, reflecting the progressive nature of the neuropathy. This is the first report of a subclinical demyelinating polyneuropathy caused by loss of PrP^C function in a nontransgenic mammal.

Disposition and effect of intra-articularly administered dexamethasone on lipopolysaccharide induced equine synovitis

Background

Dexamethasone is used for the intra-articular route of administration in management of aseptic arthritis in horses. Despite its widespread use there is very little quantitative data of the disposition and response to dexamethasone. The aim of this study was to investigate and describe the synovial fluid and plasma dexamethasone concentration over time and to explore the relation between synovial fluid concentration and response using clinical endpoints as response biomarkers after IA injection of dexamethasone disodium salt solution in an equine model of synovitis.

Results

Inflammation was induced in the radiocarpal joint of six horses by injection of 2 ng lipopolysaccharide (LPS). Two hours later either saline or dexamethasone was injected in the same joint in a two treatment cross over design. Each horse was treated once with one of the six doses dexamethasone used (0.01, 0.03, 0.1, 0.3, 1 or 3 mg) and once with saline. Dexamethasone was quantified by means of UHPLC–MS/MS. Dexamethasone disposition was characterised by means of a non-linear mixed effects model. Lameness was evaluated both objectively with an inertial sensor based system and subjectively scored using a numerical scale (0–5). Joint circumference, skin temperature over the joint and rectal temperature were also recorded. The LPS-challenge induced lameness in all horses with high inter-individual variability. Dexamethasone significantly decreased lameness compared with saline. Other variables were not statistically significant different between treatments. Objective lameness scoring was the most sensitive method used in this study to evaluate the lameness response. A pharmacokinetic/pharmacodynamic model was successfully fitted to experimental dexamethasone and lameness data. The model allowed characterization of the dexamethasone synovial fluid concentration–time course, the systemic exposure to dexamethasone after intra-articular administration and the concentration–response relation in an experimental model of synovitis.

Conclusions

The quantitative data improve the understanding of the pharmacology of dexamethasone and might serve as input for future experiments and possibly contribute to maintain integrity of equine sports.

The effect of lipopolysaccharide (LPS) on inflammatory markers in blood and brain and on behavior in individually-housed pigs

Most of us have experienced deterioration of mood while ill. In humans, immune activation is associated with lethargy and social withdrawal, irritability and aggression; changes in social motivation could, in theory, lead to less functional interactions. This might also be the case for animals housed in close confinement. Tail biting in pigs is an example of damaging social behavior, and sickness is thought to be a risk factor for tail biting outbreaks. One possible mechanism whereby sickness may influence behavior is through cytokines. To identify possible mediators between immune activation and behavioral change, we injected 16 gilts with lipopolysaccharide (LPS; O111:B4; 1.5 μg kg^-1 IV through a permanent catheter). In LPS-treated pigs, a significant increase in cortisol, TNF-α, IL-1 receptor antagonist, IL-6, and IL-8 was observed alongside decreased activity within the first 6 h after the injection. CRP was elevated at 12 and 24 h after injection, and food intake was reduced for the first 24 h after injection. Three days post-injection, LPS pigs had lower levels of noradrenaline in their hypothalamus, hippocampus and frontal cortex compared to saline-injected pigs. Pigs injected with LPS also had higher levels of the pro-inflammatory cytokine IFN-γ in their frontal cortex compared to saline-injected pigs. Thus, a low dose of LPS can induce changes in brain cytokine levels and neurotransmitter levels that persist after inflammatory and stress markers in the periphery have returned to baseline levels.

PK/PD modeling of flunixin meglumine in a kaolin-induced inflammation model in piglets

Flunixin is marketed in several countries for analgesia in adult swine but little is known about its efficacy in piglets. Thirty-two piglets (6-8 days old) were randomized to receive placebo saline (n = 11, group CONTROL) or flunixin meglumine intravenously at 2.2 (n = 11, group MEDIUM) or 4.4 (n = 10, group HIGH) mg/kg, 10 hr after subcutaneous injection of kaolin in the left metacarpal area. A hand-held algometer was used to determine each piglet's mechanical nociceptive threshold (MNT) from both front feet up to 50 hr after treatment (cut-off value of 24.5 newton). Serial venous blood samples were obtained to quantify flunixin in plasma using LC-MS/MS. A PKPD model describing the effect of flunixin on the mechanical nociceptive threshold was obtained based on an inhibitory indirect response model. A two-compartmental PK model was used. A significant effect of flunixin was observed for both doses compared to control group, with 4.4 mg/kg showing the most relevant (6-10 newton) and long-lasting effect (34 hr). The median IC50 was 6.78 and 2.63 mg/ml in groups MEDIUM and HIGH, respectively. The ED50 in this model was 6.6 mg/kg. Flunixin exhibited marked antinociceptive effect on kaolin-induced inflammatory hyperalgesia in piglets.

The pharmacokinetics of dexmedetomidine administered as a constant rate infusion in horses

Dexmedetomidine, the most selective α2-adrenoceptor agonist in clinical use, is increasingly being used in both conscious and anaesthetized horses; however, the pharmacokinetics and sedative effects of this drug administered alone as an infusion are not previously described in horses. Seven horses received an infusion of 8 μg dexmedetomidine/kg/h for 150 min, venous blood samples were collected, and dexmedetomidine concentrations were assayed using liquid chromatography-mass spectrometry (LC/MS) and analyzed using noncompartmental pharmacokinetic analysis. Sedation was scored as the distance from the lower lip of the horse to the ground measured in centimetre. The harmonic mean (SD) plasma elimination half-life (Lambda z half-life) for dexmedetomidine was 20.9 (5.1) min, clearance (Cl) was 0.3 (0.20) L/min/kg, and volume of distribution at steady-state (Vdss ) was 13.7 (7.9) L/kg. There was a considerable individual variation in the concentration of dexmedetomidine vs. time profile. The level of sedation covaried with the plasma concentration of dexmedetomidine. This implies that for clinical use of dexmedetomidine constant rate infusion in conscious horses, infusion rates can be easily adjusted to effect, and this is preferable to an infusion at a predetermined value.

Antinociceptive effects of three escalating dexmedetomidine and lignocaine constant rate infusions in conscious horses

Dexmedetomidine and lignocaine IV are used clinically to provide analgesia in horses. The aims of this study were to investigate the antinociceptive effects, plasma concentrations and sedative effects of 2, 4 and 6 µg/kg/h dexmedetomidine IV, with a bolus of 0.96 µg/kg preceding each continuous rate infusion (CRI), and 20, 40 and 60 µg/kg/min lignocaine IV, with a bolus of 550 µg/kg preceding each CRI, in 10 Swiss Warmblood horses. Electrically elicited nociceptive withdrawal reflexes were evaluated by deltoid muscle electromyography. Nociceptive threshold and tolerance were determined by electromyography and behaviour following single and repeated stimulation. Plasma concentrations of drugs were determined by liquid chromatography and mass spectrometry. Sedation was scored on a visual analogue scale. Dexmedetomidine increased nociceptive threshold to single and repeated stimulation for all CRIs, except at 2 µg/kg/h, where no increase in single stimulation nociceptive threshold was observed. Dexmedetomidine increased nociceptive tolerance to single and repeated stimulation at all CRIs. There was large individual variability in dexmedetomidine plasma concentrations and levels of sedation; the median plasma concentration providing antinociceptive effects to all recorded parameters was 0.15 ng/mL, with a range from <0.02 ng/mL (below the lower limit of quantification) to 0.25 ng/mL. Lignocaine increased nociceptive threshold and tolerance to single and repeated stimulation at CRIs of 40 and 60 µg/kg/min, corresponding to plasma lignocaine concentrations >600 ng/mL. Only nociceptive tolerance to repeated stimulation increased at 20 µg/kg/min lignocaine. Lignocaine at 40 µg/kg/min and dexmedetomidine at 4 µg/kg/h were the lowest CRIs resulting in consistent antinociception. Lignocaine did not induce significant sedation.

Factors affecting mechanical (nociceptive) thresholds in piglets

Objective

To evaluate the stability and repeatability of measures of mechanical (nociceptive) thresholds in piglets and to examine potentially confounding factors when using a hand held algometer.

Study design

Descriptive, prospective cohort.

Animals

Forty-four piglets from four litters, weighing 4.6 ± 1.0 kg (mean ± SD) at 2 weeks of age.

Methods

Mechanical thresholds were measured twice on each of 2 days during the first and second week of life. Data were analyzed using a repeated measures design to test the effects of behavior prior to testing, sex, week, day within week, and repetition within day. The effect of body weight and the interaction between piglet weight and behaviour were also tested. Piglet was entered into the model as a random effect as an additional test of repeatability. The effect of repeated testing was used to test the stability of measures. Pearson correlations between repeated measures were used to test the repeatability of measures. Variance component analysis was used to describe the variability in the data.

Results

Variance component analysis indicated that piglet explained only 17% of the variance in the data. All variables in the model (behaviour prior to testing, sex, week, day within week, repetition within day, body weight, the interaction between body weight and behaviour, piglet identity) except sex had a significant effect (p < 0.04 for all). Correlations between repeated measures increased from the first to the second week.

Conclusions and Clinical relevance

Repeatability was acceptable only during the second week of testing and measures changed with repeated testing and increased with increasing piglet weight, indicating that time (age) and animal body weight should be taken into account when measuring mechanical (nociceptive) thresholds in piglets. Mechanical (nociceptive) thresholds can be used both for testing the efficacy of anaesthetics and analgesics, and for assessing hyperalgesia in chronic pain states in research and clinical settings.

The influence of a continuous rate infusion of dexmedetomidine on the nociceptive withdrawal reflex and temporal summation during isoflurane anaesthesia in dogs

OBJECTIVE

To examine the influence of a low dose dexmedetomidine infusion on the nociceptive withdrawal reflex and temporal summation in dogs during isoflurane anaesthesia.

STUDY DESIGN

Prospective experimental blinded cross-over study.

ANIMALS

Eight healthy mixed breed dogs, body weight Mean ± SD 26.5 ± 8.4 kg and age 25 ± 16 months.

METHODS

Anaesthesia was induced with propofol and maintained with isoflurane (Fe'ISO 1.3%) delivered in oxygen and air. After stabilization, baseline recordings (time 0) were obtained, then a dexmedetomidine bolus (1 μg kg(-1) IV) followed by a continuous rate infusion (1 μg kg(-1) hour(-1)) or saline placebo were administered. At times 10, 30 and 60 minutes after the initial bolus, electrical stimulations of increasing intensity were applied over the lateral plantar digital nerve, and administered both as single and as repeated stimuli. The resulting reflex responses were recorded using electromyography. Data were analysed using a multivariable linear regression model and a Kruskal Wallis test for single stimulation data, and repeated measures anova and paired t-test for repeated stimulation data.

RESULTS

The AUC for the stimulus-response curves after single stimulation were similar for both treatments at time 0. At times 10, 30 and 60 the AUCs for the stimulus-response curves were significantly lower with dexmedetomidine treatment than with placebo. Temporal summation was evident in both treatments at times 0, 10, 30 and 60 starting from a stimulation intensity of 10 mA. The magnitude of temporal summation was smaller in dexmedetomidine than in placebo treated dogs at time 10, 30 and 60, but not at time 0.

CONCLUSIONS

During isoflurane anaesthesia, low dose dexmedetomidine suppresses the nociceptive reflex responses after single and repeated electrical stimulation.

CLINICAL RELEVANCE

This experimental study confirms previous reports on its peri-operative efficacy under clinical conditions, and further indicates that dexmedetomidine might reduce the risk of post-operative chronic pain development.

Enantioselective pharmacokinetics of ketoprofen in piglets: the significance of neonatal age

Following intravenous dose of 6mg/kg racemic ketoprofen, the chiral pharmacokinetics of ketoprofen was investigated in eight piglets aged 6 and 21days old. S-ketoprofen predominated over R-ketoprofen in plasma of the piglets in both age groups. The volumes of distribution of S-ketoprofen for the 6- and 21-day-old piglets were 241.7 (211.3-276.5) mL/kg and 155.0 (138.7-173.1) mL/kg, respectively, while the corresponding parameters for R-ketoprofen were 289.2 (250.3-334.2) mL/kg and 193.0 (168.7-220.8) mL/kg. The clearances of R-ketoprofen [948.4 (768.0-1171.2) mL/h/kg and 425 (319.1-566.0) mL/h/kg for the 6- and 21-day-old piglets, respectively] were significantly higher compared to the clearances of S-ketoprofen [57.3 (46.6-70.4) mL/h/kg and 33.8 (27.0-42.2) mL/h/kg for 6- and 21-day-old piglets, respectively]. The elimination half-life of S-ketoprofen was 3.4h for both age groups, while the elimination half-life of R-ketoprofen was 0.2h for the 6-day-old and 0.4h for the 21-day-old piglets. The clearances of both R- and S-ketoprofen were significantly higher in the 6-day-old piglets compared to when they were 21 days old. Furthermore, the volumes of distribution were larger in the youngest age group.

Ketoprofen in piglets: enantioselective pharmacokinetics, pharmacodynamics and PK/PD modelling

The chiral pharmacokinetics and pharmacodynamics of ketoprofen were investigated in a placebo-controlled study in piglets after intramuscular administration of 6 mg/kg racemic ketoprofen. The absorption half-lives of both enantiomers were short, and S-ketoprofen predominated over R-ketoprofen in plasma. A kaolin-induced inflammation model was used to evaluate the anti-inflammatory, antipyretic and analgesic effects of ketoprofen. Skin temperatures increased after the kaolin injection, but the effect of ketoprofen was small. No significant antipyretic effects could be detected, but body temperatures tended to be lower in the ketoprofen-treated piglets. Mechanical nociceptive threshold testing was used to evaluate the analgesic effects. The piglets in the ketoprofen-treated group had significantly higher mechanical nociceptive thresholds compared to the piglets in the placebo group for 12-24 h following the treatment. Pharmacokinetic/pharmacodynamic modelling of the results from the mechanical nociceptive threshold testing gave a median IC(50) for S-ketoprofen of 26.7 μg/mL and an IC(50) for R-ketoprofen of 1.6 μg/mL. This indicates that R-ketoprofen is a more potent analgesic than S-ketoprofen in piglets. Estimated ED(50) for racemic ketoprofen was 2.5 mg/kg.

Pharmacokinetics of morphine after intramuscular injection in common goldfish Carassius auratus and Atlantic salmon Salmo salar

Teleost fish have a nociceptive system and likely perceive pain. This warrants the development of analgesic protocols both for experimental surgery and for various husbandry procedures. Morphine is the standard analgesic against which the efficacy of other analgesics is assessed, and is the analgesic that has been most used in fish. The aims of this study were to describe the pharmacokinetics of morphine after an intramuscular (i.m.) injection in common goldfish and Atlantic salmon, and to illustrate the whole-body distribution of morphine in salmon following i.m. injection of tritiated morphine. In the kinetic experiment, goldfish and salmon were respectively i.m. injected with 40 and 100 mg morphine kg(-1) in the right dorsal epaxial musculature. Blood was drawn at predetermined time points. Plasma was analysed for morphine and metabolites using liquid chromatography-mass spectrometry (LC-MS/MS). Morphine had a Tmax (time at which the maximum plasma concentration was measured) of 0.5 h in both species. The Cmax (maximum plasma concentration) showed substantial inter-individual variation, with a mean (90% CI) of 187 (167 to 199) mg l(-1) in salmon and 37 (29 to 43) mg l(-1) in goldfish, as determined by bootstrap analysis. The mean elimination half-lives were 12.5 and 13.5 h in goldfish and in salmon, respectively. The degree of metabolism to morphine-3-glucuronide (M3G) and morphine-6-glucuronide (M6G) was low, with levels of M3G exceeding those of M6G. The distribution study demonstrated that the levels of tritiated morphine in the anterior kidney surpassed those in the other organs. A substantial amount seemed to be excreted through the gastrointestinal tract, while little tritium activity could be detected in the central nervous system.

Effect of intratesticular injection of lidocaine on cardiovascular responses to castration in isoflurane-anesthetized stallions

OBJECTIVE

To evaluate the effect of intratesticular administration of lidocaine on cardiovascular responses and cremaster muscle tension during castration of isoflurane-anesthetized stallions.

ANIMALS

28 healthy stallions (mean +/- SD age, 4.2 +/- 2.8 years) with no testicular abnormalities that were scheduled for castration.

PROCEDURE

Each horse was given acepromazine (20 microg/kg, IM), romifidine (50 microg/kg, IV), and butorphanol (20 microg/kg, IV). Anesthesia was induced with ketamine (2.5 mg/kg, IV) and midazolam (50 microg/kg, IV) and maintained with isoflurane (1.7% end-tidal concentration). After 10 minutes at a stable anesthetic plane, a needle was placed in each testicle and either no fluid or 15 mL of 2% lidocaine was injected; 10 minutes after needle placement, surgery was commenced. Pulse rate and arterial blood pressures were measured invasively at intervals from 5 minutes prior to castration (baseline) until 5 minutes after the left spermatic cord was clamped. The surgeon subjectively scored the degree of cremaster muscle tension. In 2 horses, lidocaine labeled with radioactive carbon (C(14)) was used and testicular autoradiograms were obtained.

RESULTS

Compared with baseline values, castration significantly increased blood pressure measurements; intratesticular injection of lidocaine decreased this blood pressure response and cremaster muscle tension. In 2 horses, autoradiography revealed diffuse distribution of lidocaine into the spermatic cord but poor distribution into the cremaster muscle.

CONCLUSIONS AND CLINICAL RELEVANCE

In isoflurane-anesthetized stallions, intratesticular injection of lidocaine prior to castration appeared to decrease intraoperative blood pressure responses and cremaster muscle tension and may be a beneficial supplement to isoflurane anesthesia.

Castration of piglets: the analgesic effects of intratesticular and intrafunicular lidocaine injection

OBJECTIVE

The aim of this study was to evaluate the analgesic effect of intratesticular and intrafunicular lidocaine for the surgical castration of piglets and to investigate the degree of nociception induced by lidocaine injection.

STUDY DESIGN

Prospective controlled experimental study.

ANIMALS

Forty-seven male Norwegian landrace piglets with normal testicular anatomy, aged 22 (+/-2.6 SD) days and weighing 7.4 +/- 1.4 kg.

MATERIALS AND METHODS

Anaesthesia was induced and maintained using halothane delivered in oxygen. End-tidal halothane was stabilized at 1.3% for 20 minutes before mean arterial blood pressure (MAP) pulse rate and electroencephalography (EEG) monitoring began. After 5 minutes of data collection, scrotal skin was desensitized with lidocaine before either an intrafunicular (IF) (n = 15) or an intratesticular (IT) (n = 16) lidocaine injection was made. Pigs in the control group (n = 16) did not receive lidocaine. Ten minutes later, a scalpel and an emasculator were used to cut the funiculus spermaticus. The MAP, pulse rate and EEG were monitored continuously for 5 minutes after castration.

RESULTS

During castration, MAP increased significantly, while pulse rate and EEG theta power fell significantly more in control, compared with the IT or IF groups. EEG alpha power fell more in the control group than in the IF group. No significant differences were found between the IF and IT groups. EEG, MAP and pulse rate responses to castration in the control group were significantly larger than the response to lidocaine injection.

CONCLUSION/CLINICAL RELEVANCE

Injecting lidocaine into the funiculus spermaticus or into the testes is effective in reducing signs of nociception caused by castration. Lidocaine injection is less noxious than castration without local anaesthetic.

Benzathine penicillin G and procaine penicillin G in piglets: comparison of intramuscular and subcutaneous injection

The disposition of penicillin G in piglets is described after intramuscular or subcutaneous injection of depot preparations. The piglets were injected with 33,000 IU/kg or 100,000 IU/kg benzathine + procaine penicillin G intramuscularly or subcutaneously, or 100,000 IU/kg procaine penicillin G intramuscularly or subcutaneously. Intramuscular injection of benzathine + procaine penicillin resulted in higher maximum concentrations in plasma (Cmax) than did subcutaneous injection. The mean residence time (MRT) of penicillin G was longer when the drugs were injected subcutaneously rather than intramuscularly. The plasma concentration versus time profiles of the subcutaneous injections of benzathine + procaine penicillin revealed secondary peaks, possibly reflecting a certain degree of inflammation at the injection site.

Clinical evaluation of established optimal immobilizing doses of medetomidine-ketamine in captive reindeer (Rangifer tarandus tarandus)

OBJECTIVE

To evaluate clinical effects and repeatability of clinical effects for an optimal immobilizing dose of a combination of medetomidine hydrochloride (MED) and ketamine hydrochloride (KET) in reindeer (Rangifer tarandus tarandus).

ANIMALS

12 healthy 6- to 8-month old reindeer.

PROCEDURE

Each reindeer was immobilized once with an initial dose (combination of 0.06 mg of MED/kg of body weight and 0.3 mg KET/kg) and twice with an optimal dose of MED-KET. Reversal was achieved with 5 mg of atipamezole/mg of MED injected 45 minutes after MED-KET administration. Observational variables were recorded. Oxygen saturation of arterial hemoglobin measured by pulse oximetry (Spo2), respiratory rate (RR), heart rate (HR), and rectal temperature (RT) were recorded 10, 25, and 40 minutes after immobilization.

RESULTS

Mean time to first sign of sedation and time until a recumbent animal lifted its head were significantly reduced for reindeer given the optimal dose, compared with the initial dose. Mean Spo2 remained > 90% during initial immobilization; this value was significantly lower for the optimal dose, but increased during immobilization from 85 to 89%. At all doses, RR increased significantly throughout the recorded period; however, RT and HR were constant. Except for time until reindeer stood, all time variables, Spo2, RR, RT, and HR were repeatable.

CONCLUSION AND CLINICAL RELEVANCE

mmobilization of captive reindeer achieved by use of the optimal dose established here is clinically acceptable, although Spo2 should be carefully monitored. Administration of the optimal dose produced the same clinical effect during repeated immobilization of the same reindeer.

The effects of medetomidine and its reversal with atipamezole on plasma glucose, cortisol and noradrenaline in cattle and sheep

In the present study, we report the effect of medetomidine followed by atipamezole on plasma glucose, cortisol and noradrenaline in calves, cows and sheep. Eight calves, eight lactating dairy cows and eight adult female sheep were included in a crossover trial. The animals were injected i.v. with medetomidine (40 microg/kg), followed 60 min later by atipamezole i.v. (200 microg/kg) or saline. The wash-out period between experiments was 1 or 2 weeks. In every animal, medetomidine induced a marked hyperglycaemia, which was reversed by atipamezole. Cortisol levels increased significantly in cows and sheep, reaching levels 4-8-fold higher than the baseline levels 25-45 min after injection of medetomidine. Atipamezole did not affect the cortisol levels, except in sheep where an increase was observed. Plasma levels of noradrenaline decreased in cows and sheep after medetomidine injection, reflecting the inhibition of sympathetic activity by the drug. After injection of the antagonist, there was a large increase in noradrenaline levels. In conclusion, a high dose of medetomidine does not seem to reduce the overall endocrine stress response in cattle and sheep, which has previously been reported in other species.

A pharmacokinetic study including some relevant clinical effect of medetomidine and atipamezole in lactating dairy cows

Medetomidine is the most potent and selective alpha2-agonist used in veterinary medicine and its effects can be antagonized by the alpha2-antagonist atipamezole. The pharmacokinetics of medetomidine and atipamezole were studied in a cross-over trial in eight lactating dairy cows. The animals were injected intravenously (i.v.) with medetomidine (40 microg/kg) followed by atipamezole i.v. (200 microg/kg) or saline i.v. after 60 min. Drug concentrations in plasma were measured by HPLC. After the injection of atipamezole, the concentration of medetomidine in plasma increased slightly, the mean increment being 2.7 ng/mL and the mean duration 12.1 min. However, atipamezole did not alter the pharmacokinetics of medetomidine. It is likely that the increase in medetomidine concentration is caused by displacement of medetomidine by atipamezole in highly perfused tissues. The volume of distribution at steady state (Vss) for medetomidine followed by saline and medetomidine followed by atipamezole was 1.21 and 1.32 L/kg, respectively, whereas the total clearance (Cl) values were 24.2 and 25.8 mL/min x kg. Vss and Cl values for atipamezole were 1.77 mL/kg and 48.1 mL/min x kg, respectively. Clinically, medetomidine significantly reduced heart rate and increased rectal temperature for 45 min. Atipamezole reversed the sedative effects of medetomidine. However, all the animals, except one, relapsed into sedation at an average of 80 min after injection of the antagonist.

Effects of medetomidine and atipamezole on serum glucose and cortisol levels in captive reindeer (Rangifer tarandus tarandus)

<p>Serum concentrations of glucose and Cortisol were measured in five adult captive reindeer (Rangifer tarandus tarandus) at 24 h and 10 min before, and at 0.5, 1,2,4, 8, 12 and 24 h after, treatment with 60 p.g/kg of medetomidine i.v. followed by 300 jig/kg of atipamezole i.v. 60 min later. The experiments were performed in January and repeated in July-August. The animals were used as their own controls and treated with saline in July-August. The wash-out period between experiments in summer was 2 weeks or more. No obvious seasonal differences were observed. Mederomidine induced a 2.5-fold increase in glucose (mean &plusmn; standard error of the mean being 15.4 &plusmn; 0.6 mmol/1 at 1 h) and a 3.5-fold increase Cortisol (349 &plusmn; 28 nmol/1 at 0.5 h). Serum glucose reached control levels within 12 h, and Cortisol declined to baseline levels within 4 h after injection og medetomidine. The use of blood concentrations of glucose and Cortisol to assess nutritonal status, body condition and stress may be significantly biased in animals chemically immobilized with medetomidine or other alpha-2 adrenoceptor agonists.</p>

Pharmacokinetics of medetomidine and atipamezole in dairy calves: an agonist-antagonist interaction

Medetomidine and atipamezole are licensed for use in dogs and cats in several countries and are highly selective and specific alpha2-adrenoceptor agents. The pharmacokinetics of the agonist medetomidine and the antagonist atipamezole were studied in a cross-over trial in eight dairy calves. The animals were injected intravenously (i.v.) with medetomidine (40 microg/kg i.v.), followed by atipamezole (200 microg/kg i.v.) or saline after 60 min. The wash-out period between experiments was 1 week. Drug concentrations in plasma were determined using HPLC. Atipamezole significantly (P < 0.05) increased the AUMC and MRT of medetomidine due to an increase in the medetomidine concentration when atipamezole was injected i.v. The mean increment in medetomidine concentration was 6.4 ng/mL, increased levels having a mean duration of 39.4 min. Other pharmacokinetic parameters of medetomidine were not significantly altered by atipamezole. Sedative effects of the agonist, and the effectiveness of the antagonist were recorded. All the animals relapsed into sedation on average 80 min after reversal with atipamezole. It is likely that the increase in medetomidine concentration after the injection of atipamezole i.v. results from displacement of medetomidine from alpha2-adrenoceptors in highly perfused tissues.

[Bjørnstjerne Bjørnson, a wife of a cotter and a physician. The lawsuit against physicians 1907]

The Norwegian poet and Nobel Prize laureate in literature Bjørnstjerne Bjørnson (1832-1910) lived for the last 35 years of his life on his estate Aulestad, near Lillehammer. The wife of a cottar at a nearby farm, a servant to his wife Karoline, fell ill in November 1906 with an incarcerated hernia and was sent to the local hospital by Bjørnson's physician. On arrival at the hospital the doctor in charge found her too ill to operate on. She died a few hours after an operation the next day of peritonitis and a gangrenous intestine. Bjørnson found this inexcusable. Because of a session with the Nobel Peace Prize Committee, he left his son Erling to attack the hospital in a press article. This led to a lawsuit in which the doctor was accused of irresponsibility and incompetence. After several court sessions the case was dropped on 7 July 1907. This was probably the first case in Norway raised against doctors for irresponsible and incompetent treatment of a patient with death as the result.

Reversal of medetomidine-induced sedation in reindeer (Rangifer tarandus tarandus) with atipamezole increases the medetomidine concentration in plasma

The pharmacokinetics of two potent alpha 2-adrenoceptor agents that can be used for immobilization (medetomidine) and reversal (atipamezole) of the sedation in mammals, were studied in three reindeer (Rangifer tarandus tarandus) in winter and again in summer. Medetomidine (60 micrograms/kg) was injected intravenously (i.v.), followed by atipamezole (300 micrograms/kg) intravenously 60 min later. Drug concentrations in plasma were measured by HPLC. The administration of atipamezole resulted in an immediate 2.5-3.5 fold increase in the medetomidine concentration in plasma. Clearance for medetomidine (median 19.3 mL/min.kg) was lower than clearance for atipamezole (median 31.0 mL/min.kg). The median elimination half-lives of medetomidine and atipamezole in plasma were 76.1 and 59.9 min, respectively. The animals became resedated 0.5-1 h after the reversal with atipamezole. Resedation may be explained by the longer elimination half-life of medetomidine compared to atipamezole.