Novel Hendra Virus Variant Detected by Sentinel Surveillance of Horses in Australia.

We identified and isolated a novel Hendra virus (HeV) variant not detected by routine testing from a horse in Queensland, Australia, that died from acute illness with signs consistent with HeV infection. Using whole-genome sequencing and phylogenetic analysis, we determined the variant had ≈83% nt identity with prototypic HeV. In silico and in vitro comparisons of the receptor-binding protein with prototypic HeV support that the human monoclonal antibody m102.4 used for postexposure prophylaxis and current equine vaccine will be effective against this variant. An updated quantitative PCR developed for routine surveillance resulted in subsequent case detection. Genetic sequence consistency with virus detected in grey-headed flying foxes suggests the variant circulates at least among this species. Studies are needed to determine infection kinetics, pathogenicity, reservoir-species associations, viral-host coevolution, and spillover dynamics for this virus. Surveillance and biosecurity practices should be updated to acknowledge HeV spillover risk across all regions frequented by flying foxes.

Validation of three-dimensional thoracic electrical impedance tomography of horses during normal and increased tidal volumes.

Objective. Data from two-plane electrical impedance tomography (EIT) can be reconstructed into various slices of functional lung images, allowing for more complete visualisation and assessment of lung physiology in health and disease. The aim of this study was to confirm the ability of 3D EIT to visualise normal lung anatomy and physiology at rest and during increased ventilation (represented by rebreathing).Approach. Two-plane EIT data, using two electrode planes 20 cm apart, were collected in 20 standing sedate horses at baseline (resting) conditions, and during rebreathing. EIT data were reconstructed into 3D EIT whereby tidal impedance variation (TIV), ventilated area, and right-left and ventral-dorsal centres of ventilation (CoVRLand CoVVD, respectively) were calculated in cranial, middle and caudal slices of lung, from data collected using the two planes of electrodes.Main results. There was a significant interaction of time and slice for TIV (p< 0.0001) with TIV increasing during rebreathing in both caudal and middle slices. The ratio of right to left ventilated area was higher in the cranial slice, in comparison to the caudal slice (p= 0.0002). There were significant effects of time and slice on CoVVDwhereby the cranial slice was more ventrally distributed than the caudal slice (p< 0.0009 for the interaction).Significance. The distribution of ventilation in the three slices corresponds with topographical anatomy of the equine lung. This study confirms that 3D EIT can accurately represent lung anatomy and changes in ventilation distribution during rebreathing in standing sedate horses.

Thoracic Electrical Impedance Tomography-The 2022 Veterinary Consensus Statement.

Electrical impedance tomography (EIT) is a non-invasive real-time non-ionising imaging modality that has many applications. Since the first recorded use in 1978, the technology has become more widely used especially in human adult and neonatal critical care monitoring. Recently, there has been an increase in research on thoracic EIT in veterinary medicine. Real-time imaging of the thorax allows evaluation of ventilation distribution in anesthetised and conscious animals. As the technology becomes recognised in the veterinary community there is a need to standardize approaches to data collection, analysis, interpretation and nomenclature, ensuring comparison and repeatability between researchers and studies. A group of nineteen veterinarians and two biomedical engineers experienced in veterinary EIT were consulted and contributed to the preparation of this statement. The aim of this consensus is to provide an introduction to this imaging modality, to highlight clinical relevance and to include recommendations on how to effectively use thoracic EIT in veterinary species. Based on this, the consensus statement aims to address the need for a streamlined approach to veterinary thoracic EIT and includes: an introduction to the use of EIT in veterinary species, the technical background to creation of the functional images, a consensus from all contributing authors on the practical application and use of the technology, descriptions and interpretation of current available variables including appropriate statistical analysis, nomenclature recommended for consistency and future developments in thoracic EIT. The information provided in this consensus statement may benefit researchers and clinicians working within the field of veterinary thoracic EIT. We endeavor to inform future users of the benefits of this imaging modality and provide opportunities to further explore applications of this technology with regards to perfusion imaging and pathology diagnosis.

Preanalytical variables affecting the measurement of serum paraoxonase-1 activity in horses.

Paraoxonase-1 (PON-1) activity is a new inflammatory and oxidative marker. Technical effects and biological factors could affect the accuracy of PON-1 activity measurement. We investigated the effects of storage at different temperatures, repeated freeze-thaw cycles, interferences from hemolytic, lipemic, and icteric samples, and seasonal effects on PON-1 activity in horses. We evaluated 2 substrates with an automated spectrophotometer. Ten equine serum samples were stored under different conditions. Although storage at room (21°C) or refrigeration (4°C) temperature induced a statistically significant decrease (p < 0.05) in PON-1 activity, this is not diagnostically relevant. PON-1 activity in frozen samples (-20°C) was stable for short-term storage; diagnostically significant (p < 0.01) fluctuations were observed after 1 mo. Four repeated freeze-thaw cycles were assessed, and all cycles affected PON-1 activity (p < 0.01); however, this was diagnostically significant only after the 4th cycle. Hemolysis induced an overestimation of PON-1 activity; lipemia and hyperbilirubinemia did not change PON-1 activity. Thirty-four horses were sampled monthly for 1 y, and PON-1 activity was higher in autumn (p < 0.05) and winter (p < 0.05) than in spring and summer.

Can bronchoconstriction and bronchodilatation in horses be detected using electrical impedance tomography?

BACKGROUND: Electrical impedance tomography (EIT) generates images of the lungs based on impedance change and was able to detect changes in airflow after histamine challenge in horses. OBJECTIVES: To confirm that EIT can detect histamine-provoked changes in airflow and subsequent drug-induced bronchodilatation. Novel EIT flow variables were developed and examined for changes in airflow. METHODS: Bronchoconstriction was induced using stepwise histamine bronchoprovocation in 17 healthy sedated horses. The EIT variables were recorded at baseline, after saline nebulization (control), at the histamine concentration causing bronchoconstriction (Cmax ) and 2 and 10 minutes after albuterol (salbutamol) administration. Peak global inspiratory (PIFEIT ) and peak expiratory EIT (PEFEIT ) flow, slope of the global expiratory flow-volume curve (FVslope ), steepest FVslope over all pixels in the lung field, total impedance change (surrogate for tidal volume; VTEIT ) and intercept on the expiratory FV curve normalized to VTEIT (FVintercept /VTEIT ) were indexed to baseline and analyzed for a difference from the control, at Cmax , 2 and 10 minutes after albuterol. Multiple linear regression explored the explanation of the variance of Δflow, a validated variable to evaluate bronchoconstriction using all EIT variables. RESULTS: At Cmax , PIFEIT , PEFEIT , and FVslope significantly increased whereas FVintercept /VT decreased. All variables returned to baseline 10 minutes after albuterol. The VTEIT did not change. Multivariable investigation suggested 51% of Δflow variance was explained by a combination of PIFEIT and PEFEIT . CONCLUSIONS AND CLINICAL IMPORTANCE: Changes in airflow during histamine challenge and subsequent albuterol administration could be detected by various EIT flow volume variables.

Electrical impedance tomography to measure lung ventilation distribution in healthy horses and horses with left-sided cardiac volume overload.

BACKGROUND: Left-sided cardiac volume overload (LCVO) can cause fluid accumulation in lung tissue changing the distribution of ventilation, which can be evaluated by electrical impedance tomography (EIT). OBJECTIVES: To describe and compare EIT variables in horses with naturally occurring compensated and decompensated LCVO and compare them to a healthy cohort. ANIMALS: Fourteen adult horses, including university teaching horses and clinical cases (healthy: 8; LCVO: 4 compensated, 2 decompensated). METHODS: In this prospective cohort study, EIT was used in standing, unsedated horses and analyzed for conventional variables, ventilated right (VAR) and left (VAL) lung area, linear-plane distribution variables (avg-max VΔZLine , VΔZLine ), global peak flows, inhomogeneity factor, and estimated tidal volume. Horses with decompensated LCVO were assessed before and after administration of furosemide. Variables for healthy and LCVO-affected horses were compared using a Mann-Whitney test or unpaired t-test and observations from compensated and decompensated horses are reported. RESULTS: Compared to the healthy horses, the LCVO cohort had significantly less VAL (mean difference 3.02; 95% confidence interval .77-5.2; P = .02), more VAR (-1.13; -2.18 to -.08; P = .04), smaller avg-max VΔZLLine (2.54; 1.07-4.00; P = .003) and VΔZLLine (median difference 5.40; 1.71-9.09; P = .01). Observation of EIT alterations were reflected by clinical signs in horses with decompensated LCVO and after administration of furosemide. CONCLUSIONS AND CLINICAL IMPORTANCE: EIT measurements of ventilation distribution showed less ventilation in the left lung of horses with LCVO and might be useful as an objective assessment of the ventilation effects of cardiogenic pulmonary disease in horses.

Evaluation of histamine-provoked changes in airflow using electrical impedance tomography in horses.

BACKGROUND: Electrical impedance tomography (EIT) generates thoracic impedance images of the lungs and has been used to assess ventilation in horses. This technique may have application in the detection of changes in airflow associated with equine asthma. OBJECTIVES: The objective was to determine if histamine-induced airflow changes observed with flowmetric plethysmography (Δflow) could also be explained using global and regional respiratory gas flow signals calculated from EIT signals. STUDY DESIGN: Experimental in vivo study. METHODS: Six horses, sedated using detomidine were fitted with a thoracic EIT belt and flowmetric plethysmography hardware. Saline (baseline = BL) and increasing concentrations of histamine (C1-4) were nebulised into the face mask until a change in breathing pattern was clinically confirmed and Δflow increased greater or equal to 50%. After nebulisation Δflow and EIT images were recorded over 3 minutes and peak global inspiratory (InFglobal ) and expiratory (ExFglobal ) flow as well as peak regional expiratory and inspiratory flow for the dorsal and the ventral area of the right and left lungs were evaluated. Delta flow, InFglobal and ExFglobal at subsequent concentrations were indexed to baseline (yi  = Ci /BL-1). Indexed and nonindexed variables were evaluated for a difference from baseline at sequential histamine doses (time). Multiple linear regression assessment of variance in delta flow was also investigated. RESULTS: Consistent with histamine-provoked increases in Δflow, the global flow indices increased significantly. A significant increase in regional inspiratory flow was seen in the right and left ventral lung and dorsal right lung. Multiple regression revealed that the variance in ExFglobal , and right and left ventral expiratory flow best explained the variance in Δflow (r2  = .82). MAIN LIMITATIONS: Low number of horses and horses were healthy. CONCLUSIONS: Standardised changes in airflow during histamine challenge could be detected using EIT gas flow variables.

Effects of dobutamine hydrochloride on cardiovascular function in horses anesthetized with isoflurane with or without acepromazine maleate premedication.

OBJECTIVE To determine the effects of acepromazine maleate premedication on cardiovascular function before and after infusion of dobutamine hydrochloride for 30 minutes in isoflurane-anesthetized horses. ANIMALS 6 healthy adult horses. PROCEDURES Each horse was anesthetized once following premedication with acepromazine (0.02 mg/kg, IV) administered 30 minutes prior to anesthetic induction (ACP+ treatment) and once without premedication (ACP- treatment). Anesthesia was induced with IV administration of xylazine hydrochloride (0.8 mg/kg), ketamine hydrochloride (2.2 mg/kg), and diazepam (0.08 mg/kg). Horses were positioned in right lateral recumbency, and anesthesia was maintained via inhalation of isoflurane delivered in oxygen. End-tidal isoflurane concentration was adjusted to achieve a target mean arterial blood pressure of 60 mm Hg (interquartile range [25th to 75th percentile], 57 to 63 mm Hg) for at least 15 minutes. Cardiac index, oxygen delivery index, and femoral arterial blood flow indices were determined 60 minutes after anesthetic induction (baseline). Dobutamine was then infused to achieve a target mean arterial blood pressure of 80 mm Hg (interquartile range, 76 to 80 mm Hg). Data collection was repeated 30 minutes after the start of dobutamine infusion for comparison with baseline values. RESULTS Complete data sets were available from 5 of the 6 horses. Dobutamine administration resulted in significant increases in oxygen delivery and femoral arterial blood flow indices but no significant change in cardiac index for each treatment. However, at baseline or 30 minutes after the start of dobutamine infusion, findings for the ACP+ and ACP- treatments did not differ. CONCLUSIONS AND CLINICAL RELEVANCE In isoflurane-anesthetized horses, dobutamine administration increased oxygen delivery and femoral arterial blood flow indices, but these changes were unaffected by premedication with acepromazine.