Michael Laurence

Thiafentanil is a popular opioid agonist used for wildlife chemical immobilisation. Its effects are quickly and completely reversed by the antagonist naltrexone. Successful wildlife immobilisations using thiafentanil have been documented in a variety of wildlife species globally. The aim of this study was to describe the single‐dose intramuscular (IM) and intravenous (IV) pharmacokinetics of thiafentanil in goats at a dose of 90 μg/kg using a single cross‐over study. The IM dose was administered in the left Vastus lateralis. Plasma samples were collected up to 120 min after thiafentanil administration from two female and eight male adult goats. Samples were analysed by liquid chromatography–tandem mass spectrometry (LC–MS/MS). Pharmacokinetic parameters from one and two‐compartment models were estimated via a Bayesian approach. The two‐compartment model was preferred overall. The estimated bioavailability was 0.677 (90% Crl: 0.542–0.888), absorption rate constant ( k a ) was 0.058 1/min (90% Crl: 0.045–0.115) and clearance was 29.0 mL/min/kg (90% Crl: 23.7–36.3) from this model. This study provides key pharmacokinetic data on thiafentanil, supporting a two‐compartment model and offering insights into its absorption, bioavailability, and clearance when used for wildlife immobilisation.

Pinkeye (a generic term to describe infectious bovine keratoconjunctivitis) is a significant disease of cattle worldwide, impacting productivity and animal welfare. One commercial pinkeye vaccine, a systematically administered Moraxella bovis bacterin, has been available in Australia since 2007. This is the first field trial of the effectiveness of this vaccine for the prevention of naturally occurring disease in Australia. Extensively run beef herds in southwest Queensland that regularly experienced pinkeye were enrolled in the trial and animals were randomly allocated to vaccinated and control groups in different proportions in each herd. The subsequent incidence of clinical pinkeye between the two groups was compared for animals less than one-year-old. Data were analysed from 649 cattle from five herds over two pinkeye seasons: three herds of 390 calves from 1st November 2019 to 20th January 2020 and two herds of 259 calves from 23rd September 2020 to 21st April 2021. Pinkeye was common with 24% of all calves (156/649) contracting the disease during the trial. Univariable and multivariable binary logistic mixed-effect models were fitted to account for clustered data and potential residual confounding due to sex, weight, breed, coat colour, and periocular pigmentation. The incidence of pinkeye was not significantly different between vaccinated and control groups, both alone (p = 0.67) and after adjusting for sex and weight differences (p = 0.69). The vaccine was not protective against naturally occurring pinkeye under the field conditions.

Thiafentanil is a popular opioid agonist that is fully reversed by administering naltrexone. This agonist-antagonist combination is administered to a wide variety of wildlife species for chemical immobilisation, however plasma concentrations for thiafentanil remain unreported. This report describes a method that was developed and validated using human plasma and cross-validated for the analysis of goat plasma. Samples were extracted using a simple protein precipitation and analysed using LC-MS/MS. The assay was validated over the calibration range 4.38 - 1120 ng/mL for thiafentanil and 15.63 - 4000 ng/mL for naltrexone. The mean inter-day accuracies for QCs prepared in human plasma (n = 18) ranged from 94.8 - 103.8 % for thiafentanil and 94.8 - 95.9 % for naltrexone with corresponding precisions of 3.4 - 7.9 % and 2.8 - 11.4 %, respectively. The mean accuracies for QCs prepared in goat plasma (n = 6) ranged from 89.0 - 100.5 % for thiafentanil and 89.0 - 98.0 % for naltrexone with the associated precisions ranging from 7.1 - 11.6 % and 4.8 - 12.3 %, respectively. Both analytes were stable on bench for six hours and for three freeze-thaw cycles. The impact of heat-inactivation, necessary for the inactivation of potential foot-and-mouth disease, on analyte stability, matrix effect and recovery were evaluated, and a correction factor was established to determine the original analyte concentrations. The method was applied to pharmacokinetic samples collected from goats. The use of goats as a model species provides the first insight into the plasma concentrations of thiafentanil.

The study compared immobilisation of blesbok (Damaliscus pygargus phillipsi) with etorphine and azaperone vs etorphine and midazolam. Twelve female blesbok, weighing 59.4 ± 2.8 kg, were used. Each animal randomly received Treatment 1 (T1) (etorphine, 0.07 ± 0.003 mg/kg + azaperone, 0.36 ± 0.02 mg/kg) and Treatment 2 (T2) (etorphine, 0.07 ± 0.003 mg/kg + midazolam, 0.20 ± 0.01 mg/kg) with a one-week washout period between treatments. Induction times were recorded followed by physiological monitoring for 45 minutes of immobilisation. Immobilisation was reversed with naltrexone (20 mg per mg etorphine). Recovery times were also recorded. Induction, immobilisation and recovery were scored with subjective measures. Inductions and recoveries did not differ between combinations, but the quality of immobilisation was significantly better with T1. Rectal temperature and blood pressure were significantly lower during T1. Both treatments resulted in severe hypoxaemia and impaired gas exchange, although overall hypoxaemia was more pronounced for T1. Animals treated with T2, however, exhibited a deterioration in respiration as the monitoring period progressed, possibly as a result of impaired ventilatory muscle function due to the effects of midazolam. Both combinations are suitable for adequate immobilisation of blesbok and should be selected based on the specific capture situation. Supplementation with oxygen is highly recommended.

Pinkeye (infectious bovine keratoconjunctivitis, IBK) is an important disease of cattle worldwide. It has a substantial negative impact on farm productivity and is a major cost burden, but specific data on losses are lacking. This study was conducted to understand farmers’ perceptions of the impact of pinkeye on farm productivity and animal welfare, and factors influencing the money farmers estimated spending on pinkeye in 2018. Data were collected by the first Australia-wide online survey on pinkeye. There were 1035 suitable responses analysed for impact on farm productivity. From these 82% of respondents represented farms in southern Australia, 58% reported cattle breeding as their main enterprise, and 89% bred animals on farm. Farmers were more likely to rank the impact of pinkeye on farm productivity as high if they had younger cattle, treated cattle with pinkeye more frequently, and as their herd size increased. Fewer farmers chose pinkeye as an animal welfare concern than as an economic and farm management issue, but overall animal welfare was rated by the greatest number of farmers as a high severity concern (n = 691), followed by decreased sale value and farm profits (n = 561). This suggests a shift in the equipoise between the economics of food animal production and animal welfare expectations. The median amount reportedly spent on pinkeye in 2018 by Australian farmers (n = 779) was $250.00 per farm. Farmers reported spending more money on pinkeye as herd size and number of cattle affected by pinkeye increased, their perception of pinkeye impact on farm productivity and animal welfare increased, if they treated pinkeye more frequently, reported higher fly worry, if their herds contained Angus cattle, if they bred on farm, and if they were located in southern Australian regions. Study findings should be used to better understand pinkeye, target expenditure, and improve outcomes for cattle and farmers.

Identifying and quantifying the relative frequency of involuntary losses is an essential first step in developing fit-for-purpose herd health programmes. The objective of this study was to provide an estimate of the relative frequency of reasons for mortality among south-west Western Australian beef and dairy cattle, based on necropsy findings from a university-based veterinary pathology referral centre over 38 years. A total of 904 cattle were submitted for postmortem examination throughout the study period. Gastrointestinal, cardiopulmonary and reproductive conditions were the most common causes of mortality in cattle submitted for necropsy at Murdoch University for the period 1981–2018. In dairy cattle, the common problems were gastrointestinal (bloat, abomasal displacements) 18% (59/320), cardiovascular (traumatic reticulo-pericarditis) 9% (30/320) and respiratory conditions (pneumonia) 8% (27/320). In beef cattle, the most common conditions were gastrointestinal (bloat, rumen acidosis) 11% (39/358), reproductive (metritis) 11% (38/358), cardiovascular (traumatic reticulo-pericarditis) 7% (25/358), respiratory (pneumonia) 7% (24/358), lameness (fractures) 6%, (21/358) and hepatobiliary conditions (blue-green algae poisoning, hepatotoxicity) 6% (21/358). Selection bias and missing data were potential confounders in this study. Although necropsy investigations provide useful information on animal mortalities and avenues for future herd health programmes, there is a need to standardise data capture methods and disease definition criteria, and conduct more detailed recording of data both at the farm level and at necropsy diagnostic centres.

The increasing number of cases of acute encephalitis syndrome, a key presenting clinical sign of Japanese encephalitis infection in humans, along with increasing laboratory confirmed cases in Bali over recent years have led to the Indonesian government developing a national program of vaccination against Japanese encephalitis virus. In order to inform multidisciplinary management, a review was conducted to assess Japanese encephalitis virus-related cases in humans and animals including their determinants and detection in vectors. Along with published literature, key data from local authorized officers in Bali have been used to convey the recent situation of the disease. Related surveys detected up to 92% of the local children had antibodies against the virus with the annual incidence estimated to be 7.1 per 100,000 children. Additionally, reports on young and adult cases of infection within international travellers infected in Bali were documented with both non-fatal and fatal outcomes. Further seroprevalence surveys detected up to 90% with antibodies to the virus in animal reservoirs. The detection of the virus in certain Culex mosquito species and high levels of seropositivity may be associated with greater risk of the virus transmission to the human population. It was also highlighted that local sociocultural practices for agriculture and livestock were potentially associated with the high density of the vector and the reservoirs, which then may lead to the risk of the disease transmission in the ecology of Bali.

Electrical impedance tomography (EIT) is used in lung physiology monitoring. There is evidence that EIT is linearly associated with global tidal volume (VT) in clinically healthy patients where no positive end-expiratory pressure (PEEP) is applied. This linearity has not been challenged by altering lung conditions. The aim of this study was to determine the effect of PEEP on VT estimation, using EIT technology and spirometry, and observe the stability of the relationship under changing lung conditions. Twelve male castrated cattle (Steer), mean age 7.8 months (SD ± 1.7) were premedicated with xylazine followed by anaesthesia induction with ketamine and maintenance with halothane in oxygen via an endotracheal tube. An EIT belt was applied around the thorax at the level of the fifth intercostal space. Volume controlled ventilation was used. PEEP was increased in a stepwise manner from 0 to 5, 10 and 15 cmH2O. At each PEEP, the VT was increased stepwise from 5 to 10 and 15 mL kg−1. After a minute of stabilisation, total impedance change (VTEIT), using EIT and VT measured by a spirometer connected to a flow-partitioning device (VTSpiro) was recorded for the following minute before changing ventilator settings. Data was analysed using linear regression and multi variable analysis. There was a linear relationship between VTEIT and VTSpiro at all levels of PEEP with an R2 of 0.71, 0.68, 0.63 and 0.63 at 0, 5, 10 and 15 cmH2O, respectively. The variance in VTEIT was best described by peak inspiratory pressure (PIP) and PEEP (adjusted R2 0.82) while variance in VTSpiro was best described by PIP and airway deadspace (adjusted R2 0.76). The relationship between VTEIT and VTSpiro remains linear with changes in tidal volume, and stable across altered lung conditions. This may have application for monitoring and assessment in vivo.

Objective To compare the cardiopulmonary effects of the opioids etorphine and thiafentanil for immobilization of impala. Study design Two-way crossover, randomized study. Animals A group of eight adult female impala. Methods Impala were given two treatments: 0.09 mg kg–1 etorphine or 0.09 mg kg–1 thiafentanil via remote dart injection. Time to recumbency, quality of immobilization and recovery were assessed. Respiratory rate, heart rate (HR), mean arterial blood pressure (MAP) and arterial blood gases were measured. A linear mixed model was used to analyse the effects of treatments, treatments over time and interactions of treatment and time (p < 0.05). Results Time to recumbency was significantly faster with thiafentanil (2.0 ± 0.8 minutes) than with etorphine (3.9 ± 1.6 minutes; p = 0.007). Both treatments produced bradypnoea, which was more severe at 5 minutes with thiafentanil (7 ± 4 breaths minute–1) than with etorphine (13 ± 12 breaths minute–1; p = 0.004). HR increased with both treatments but significantly decreased over time when etorphine (132 ± 17 to 82 ± 11 beats minute–1) was compared with thiafentanil (113 ± 22 to 107 ± 36 beats minute–1; p < 0.001). Both treatments caused hypertension which was more profound with thiafentanil (mean overall MAP = 140 ± 14 mmHg; p < 0.001). Hypoxaemia occurred with both treatments but was greater with thiafentanil [PaO2 37 ± 13 mmHg (4.9 kPa)] than with etorphine [45 ± 16 mmHg (6.0 kPa)] 5 minutes after recumbency (p < 0.001). After 30 minutes, PaO2 increased to 59 ± 10 mmHg (7.9 kPa) with both treatments (p < 0.001). Conclusions and clinical relevance The shorter time to recumbency with thiafentanil may allow easier and faster retrieval in the field. However, thiafentanil caused greater hypertension, and ventilatory effects during the first 10 minutes, after administration.

Repeatable measures of pain in ruminants following husbandry procedures are required to validate responses to pain relief. This study tested the hypotheses that facial action units, activity and time spent with dam can be used to assess the efficacy of pain relief in lambs following mulesing. Merino lambs (n = 120) were allocated to one of six treatments implemented at mulesing: (1) lambs that were not mulesed or lambs that were mulesed and administered (2) no pain relief, (3) meloxicam 15 min before mulesing, (4) Tri‐Solfen®, (5) a combination of meloxicam 15 min before mulesing and Tri‐Solfen after mulesing and (6) meloxicam at mulesing. Facial action units detected a difference in pain between mulesed and non‐mulesed lambs at 1 and 5 h post‐mulesing (P = 0.005 and <0.001) but not at 26 h post‐mulesing. Lambs that were not mulesed were more active and spent more time with their dams than mulesed lambs (P < 0.001). No differences were observed between lambs that were mulesed with or without pain relief. Therefore, facial action units, activity of the lamb and time spent with dam can detect pain in response to mulesing in Merino lambs but cannot detect any changes associated with pain relief.