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Topic:Respiratory Health
Respiratory health in horses encompasses the study of the equine respiratory system, its function, and the various conditions that can affect it. The respiratory system in horses includes the upper airways, lungs, and associated structures, which facilitate gas exchange and are vital for maintaining physiological homeostasis during rest and exercise. Common respiratory conditions in horses include equine asthma, infectious diseases like strangles, and exercise-induced pulmonary hemorrhage (EIPH). These conditions can impact a horse's performance and overall health. This page compiles peer-reviewed research studies and scholarly articles that explore the anatomy, physiology, pathophysiology, and management of respiratory health in horses.
Effect of ionization, bedding, and feeding on air quality in a horse stable. Organic dust is associated with Equine asthma. Ionization should reduce airborne dust levels. Objective: To determine the effect of ionization of air, type of bedding, and feed on the levels of airborne dust, endotoxin, and fungal colonies in horse stables. Methods: 24 healthy University-owned horses occupied the stables. Methods: A randomized controlled cross-over study. Four units with 6 stables were equipped with an ionization installation (25 VA, 5000 Volt Direct Current). Horses were kept either on wood shavings and fed haylage (2 units), or on straw and fed dry hay (2 units). Measurement...
Clinical effect of corticosteroids in asthma-affected horses: A quantitative synthesis. There are limited findings from low-powered studies based on few number of subjects with equine asthma. Furthermore, no studies have been performed to assess a meaningful clinically detectable impact of corticosteroids in equine asthma. Objective: To assess and compare the clinical effect of inhaled and systemic corticosteroids in equine asthma and identify a quantitative clinical score suitable to assess the Minimal Important Difference (MID), expressed as the Minimally Clinically Detectable Difference (MCDD). Methods: Pair-wise and network meta-analysis. Methods: Literature searches for stud...
Histologic investigation of airway inflammation in postmortem lung samples from racehorses. OBJECTIVE To describe histologic findings in the small airways during postmortem examination of actively racing horses and to quantify the degree of airway inflammation by use of a semiquantitative scoring system. SAMPLE Lung tissues obtained from 95 horses (Thoroughbreds, Standardbreds, and Quarter Horses) that had been actively racing or training. PROCEDURES 10 standardized lung sections were obtained during postmortem examination of 37 horses that had been actively racing or training, and 2 histologic sections of the caudodorsal lung lobes previously collected from each of 58 horses that di...
Use of quantitative real-time PCR to determine viability of Streptococcus equi subspecies equi in respiratory secretions from horses with strangles. In recent years, molecular approaches have been able to characterise the viability of equine upper respiratory tract pathogens using absolute molecular quantitation as well as detection of transcripts for virulence genes. Objective: The objective of this study was to investigate molecular surrogates for S. equi subspecies equi (S. equi) viability in biological samples from horses with strangles. Methods: Retrospective cross-sectional study. Methods: S. equi culture-positive and culture-negative upper airway secretions were assessed by qPCR at the genomic (gDNA) and complimentary DNA (cDNA) ...
Maintenance of equine anaesthesia over the last 50 years: Controlled inhalation of volatile anaesthetics and pulmonary ventilation. In the first edition of this journal, Barbara Weaver wrote a review titled 'Equine Anaesthesia', stating that, at that time, it was quickly becoming accepted practice that many horses were being anaesthetised 'by essentially similar procedures, i.e. premedication, induction and then maintenance by controlled inhalation'. To celebrate the 50th anniversary of the first edition of this journal, this review covers the development of understanding and practice of inhalational anaesthesia and controlled ventilation in horses over the last 50 years. We review how the perceived benefits of halothane ...
Tamoxifen induces apoptotic neutrophil efferocytosis in horses. Macrophages and neutrophils are important cellular components in the process of acute inflammation and its subsequent resolution, and evidence increasingly suggests that they play important functions during the resolution of chronic, adaptive inflammatory processes. Exacerbated neutrophil activity can be harmful to surrounding tissues; this is important in a range of diseases, including allergic asthma and chronic obstructive pulmonary disease in humans, and equine asthma (also known as recurrent airway obstruction (RAO). Tamoxifen (TX) is a non-steroidal estrogen receptor modulator with effec...
Hold your horses: A comparison of human laryngomalacia with analogous equine airway pathology. Laryngomalacia is the most common cause of stridor in infants. Dynamic airway collapse is also a well-recognised entity in horses and an important cause of surgical veterinary intervention. We compare the aetiology, clinical features and management of human laryngomalacia with equine dynamic airway collapse. Methods: A structured review of the PubMed, the Ovid Medline and the Cochrane Collaboration databases (Cochrane Central Register of Controlled Trials, Cochrane Database of Systemic Reviews). Results: There are numerous equine conditions that cause dynamic airway collapse defined specifical...
Effect of reducing inspired oxygen concentration on oxygenation parameters during general anaesthesia in horses in lateral or dorsal recumbency. To compare the effects of two concentrations of oxygen delivered to the anaesthetic breathing circuit on oxygenation in mechanically ventilated horses anaesthetised with isoflurane and positioned in dorsal or lateral recumbency. Methods: Selected respiratory parameters and blood lactate were measured and oxygenation indices calculated, before and during general anaesthesia, in 24 laterally or dorsally recumbent horses. Horses were randomly assigned to receive 100% or 60% oxygen during anaesthesia. All horses were anaesthetised using the same protocol and intermittent positive pressure ventilat...
Differential Expression of Serum MicroRNAs Supports CD4⁺ T Cell Differentiation into Th2/Th17 Cells in Severe Equine Asthma. MicroRNAs (miRNAs) regulate post-transcriptional gene expression and may be exported from cells via exosomes or in partnership with RNA-binding proteins. MiRNAs in body fluids can act in a hormone-like manner and play important roles in disease initiation and progression. Hence, miRNAs are promising candidates as biomarkers. To identify serum miRNA biomarkers in the equine model of asthma we investigated small RNA derived from the serum of 34 control and 37 asthmatic horses. These samples were used for next generation sequencing, novel miRNA identification and differential miRNA expression ana...
The Contribution of Oxidative Stress and Inflamm-Aging in Human and Equine Asthma. Aging is associated with a dysregulation of the immune system, leading to a general pro-inflammatory state of the organism, a process that has been named inflamm-aging. Oxidative stress has an important role in aging and in the regulation of immune responses, probably playing a role in the development of age-related diseases. The respiratory system function physiologically declines with the advancement of age. In elderly asthmatic patients, this may contribute to disease expression. In this review, we will focus on age-related changes affecting the immune system and in respiratory structure an...
Access to a main alphaherpesvirus receptor, located basolaterally in the respiratory epithelium, is masked by intercellular junctions. The respiratory epithelium of humans and animals is frequently exposed to alphaherpesviruses, originating from either external exposure or reactivation from latency. To date, the polarity of alphaherpesvirus infection in the respiratory epithelium and the role of respiratory epithelial integrity herein has not been studied. Equine herpesvirus type 1 (EHV1), a well-known member of the alphaherpesvirus family, was used to infect equine respiratory mucosal explants and primary equine respiratory epithelial cells (EREC), grown at the air-liquid interface. EHV1 binding to and infection of mucosal e...
Workload of horses on a water treadmill: effect of speed and water height on oxygen consumption and cardiorespiratory parameters. Despite the use of water treadmills (WT) in conditioning horses, the intensity of WT exercise has not been well documented. The workload on a WT is a function of water height and treadmill speed. Therefore, the purpose of this study was to determine the effects of these factors on workload during WT exercise. Fifteen client-owned Quarter Horses were used in a randomized, controlled study. Three belt speeds and three water heights (mid cannon, carpus and stifle), along with the control condition (dry treadmill, all three speeds), were tested. Measured outcomes were oxygen consumption (V̇O2), v...
Effects of selective α2 -adrenergic receptor agonists on electrical field-stimulated contractions of isolated bronchi in horses. We investigated the effects of different selective α -adrenergic receptor (AR) agonists (detomidine, medetomidine, xylazine, and brimonidine) on the contractions of horse-isolated bronchi induced by electrical field stimulation (EFS) and by carbachol. No effects were observed on the contraction induced by carbachol, while α -AR agonists reduced EFS-evoked contractions in a concentration-related fashion. The rank order of potency (pD ) was brimonidine (7.40 ± 0.20) >medetomidine (7.09 ± 0.24) >detomidine (6.13 ± 0.55) >xylazine (4.59 ± 0.16). The maximal effects (E ) were...
Effectiveness of furosemide in attenuating exercise-induced pulmonary haemorrhage in horses when administered at 4- and 24-h prior to high-speed training. Due to the high prevalence of EIPH in racehorses and its potential impact on the horse's health, furosemide administration is permitted up to 4-h prior to post time in most North American racing jurisdictions. Anecdotal reports suggest that administration of furosemide 24-h prior to strenuous exercise may be equally effective in decreasing the severity of EIPH. Objective: To 1) compare the efficacy of furosemide in reducing the presence and severity of EIPH when administered 4- or 24-h prior to strenuous exercise 2) characterise electrolyte and blood parameters following administration of furo...
Fifty years of recurring struggles with recurrent laryngeal neuropathy. Recurrent laryngeal neuropathy appears to be a simple problem that should have a simple solution, yet the complexity and dynamic nature of laryngeal function is underappreciated. This review highlights the challenges and accomplishments that work towards that greater understanding of what is necessary to find a successful solution.
A comparison of unheated loose housing with stables on the respiratory health of weaned-foals in cold winter conditions: an observational field-study. Newly weaned horses in Finland are often moved to unheated loose housing systems in which the weanlings have free access to a paddock and a shelter. This practice is considered to be good for the development of young horses. The daily temperatures can stay below - 20 °C in Finland for several consecutive weeks during the winter season. However, the effect of unheated housing in a cold climatic environment on the respiratory health of weanlings under field conditions has not been studied before. This investigation was an observational field-study comprising 60 weanlings among 11 different vo...
Evaluation of total intravenous anesthesia with propofol-guaifenesin-medetomidine and alfaxalone-guaifenesin-medetomidine in Thoroughbred horses undergoing castration. Anesthetic and cardiorespiratory effects of total intravenous anesthesia (TIVA) technique using propofol-guaifenesin-medetomidine (PGM) and alfaxalone-guaifenesin-medetomidine (AGM) were preliminarily evaluated in Thoroughbred horses undergoing castration. Twelve male Thoroughbred horses were assigned randomly into two groups. After premedication with intravenous (IV) administrations of medetomidine (5.0 µg/kg) and butorphanol (0.02 mg/kg), anesthesia was induced with guaifenesin (10 mg/kg IV), followed by either propofol (2.0 mg/kg IV) (group PGM: n=6) or alfaxalone (1.0 mg/kg IV) (group AGM...
The Modification and Performance of a Large Animal Anesthesia Machine (Tafonius®) in Order to Deliver Xenon to a Horse. Xenon, due to its interesting anesthetic properties, could improve the quality of anesthesia protocols in horses despite its high price. This study aimed to modify and test an anesthesia machine capable of delivering xenon to a horse. Methods: An equine anesthesia machine (Tafonius, Vetronic Services Ltd., UK) was modified by including a T-connector in the valve block to introduce xenon, so that the xenon was pushed into the machine cylinder by the expired gases. A xenon analyzer was connected to the expiratory limb of the patient circuit. The operation of the machine was modeled and experimen...
The effect of stable bedding materials on dust levels, microbial air contamination and equine respiratory health. The choice of bedding material affects the quality of air in a stable and, consequently, the respiratory health of horses and humans. The risk of respiratory problems can be mitigated by improving the quality of air in the stable. The choice of bedding material is particularly important in cold climate conditions where horses are kept indoors throughout the year. This study examined the impact of three bedding materials: straw (S), peat with shavings (PS), and crushed wood pellets (CWP). The investigated factors were air contamination, including dust contamination and microbial (bacterial and ...
Overground endoscopy in 311 Thoroughbred racehorses: findings and correlation to resting laryngeal function. To review a large number of equine overground endoscopy (OGE) examinations to determine the incidence of dynamic upper airway obstructions (DUAO); correlations were explored with laryngeal endoscopy findings at rest and abnormal exercising respiratory noise. Methods: Retrospective analysis of horses presenting for OGE because of perceived poor performance and/or history of abnormal exercising respiratory noise between 2010 and 2014. Signalment, history and examination findings during resting laryngeal endoscopy and OGE were reviewed. Results: Of the total examinations, 311 were reviewed. One o...
Upper and lower respiratory tract microbiota in horses: bacterial communities associated with health and mild asthma (inflammatory airway disease) and effects of dexamethasone. The microbial composition of the equine respiratory tract, and differences due to mild equine asthma (also called Inflammatory Airway Disease (IAD)) have not been reported. The primary treatment for control of IAD in horses are corticosteroids. The objectives were to characterize the upper and lower respiratory tract microbiota associated with respiratory health and IAD, and to investigate the effects of dexamethasone on these bacterial communities using high throughput sequencing. Results: The respiratory microbiota of horses was dominated by four major phyla, Proteobacteria (43.85%), Actinob...
Fluticasone/salmeterol reduces remodelling and neutrophilic inflammation in severe equine asthma. Asthmatic airways are inflamed and undergo remodelling. Inhaled corticosteroids and long-acting β2-agonist combinations are more effective than inhaled corticosteroid monotherapy in controlling disease exacerbations, but their effect on airway remodelling and inflammation remains ill-defined. This study evaluates the contribution of inhaled fluticasone and salmeterol, alone or combined, to the reversal of bronchial remodelling and inflammation. Severely asthmatic horses (6 horses/group) were treated with fluticasone, salmeterol, fluticasone/salmeterol, or with antigen avoidance for 12 weeks. ...
Epidemiology of Musculoskeletal Injury during Racing on New Zealand Racetracks 2005-2011. The objective of the study was to determine the incidence of veterinary events that resulted in a horse failing to finish a race and identify risk factors for musculoskeletal injury (MSI) during a race. Data were obtained on Thoroughbred flat race starts in New Zealand between 1 August 2005 and 31 July 2011 (six racing seasons). Stipendiary Steward's reports were key-word searched to identify veterinary events that prevented a horse from finishing a race. Race data were used calculate the incidence of veterinary events per 1000 horse starts and Poisson regression was used to investigate risk f...
Age associated changes in peripheral airway smooth muscle mass of healthy horses. Peripheral airway smooth muscle (ASM) mass is increased in severe equine asthma, but no information is available on age related changes in ASM. In this study, peripheral ASM dimensions were determined in healthy horses of different ages. The thickness of the peripheral ASM layer was constant in horses of different ages, but ASM occupied a greater proportion of the inner wall area in young horses compared to older horses. This finding suggests that equine airways experience a decrease in the relative abundance of ASM with age.
Influence of the Respiratory Cycle on Caudal Vena Cava Diameter Measured by Sonography in Healthy Foals: A Pilot Study. Intravascular volume assessment in foals is challenging. In humans, intravascular volume status is estimated by the caudal vena cava (CVC) collapsibility index (CVC-CI) defined as (CVC diameter at maximum expiration [CVC ] - CVC diameter at minimal inspiration [CVC ])/CVC × 100%. Objective: To determine whether the CVC could be sonographically measured in healthy foals, determine differences in CVC and CVC , and calculate inter- and intrarater variability between 2 examiners. We hypothesized that the CVC could be measured sonographically at the subxiphoid view and that there would be a differ...
Maxillary unicystic ameloblastoma in a 6-week-old filly evaluated with computed tomography. A 6-week-old Thoroughbred filly was presented for evaluation of an expansile mass overlying the right nasal passage and causing respiratory stertor. On skull radiographs, there was a loculated, soft tissue-opaque mass identified dorsal to the right upper premolars and effacing the right nasal cavity. Computed tomography (CT) revealed a locally extensive mass with relatively benign characteristics located centrally on the tooth root apices of the deciduous second premolar (506). The mass extended axially into the right nasal cavity, occluding the meatuses and causing displacement of the nasal s...
Pharmacological characterization of the interaction between tiotropium and olodaterol administered at 5:5 concentration-ratio in equine bronchi. Equine airways represent a suitable ex vivo model to study the functional impact of pharmacological treatments on human chronic obstructive pulmonary disorders, such as asthma and chronic obstructive pulmonary disease (COPD). We aimed to characterize the pharmacological interaction between the long-acting muscarinic antagonist (LAMA) tiotropium and the long-acting β-agonist (LABA) olodaterol in equine airways. The effect of tiotropium and olodaterol, administered alone and in combination at the ratio of concentrations reproducing ex vivo the concentration-ratio delivered by the currently avai...
A genome-wide association study for equine recurrent airway obstruction in European Warmblood horses reveals a suggestive new quantitative trait locus on chromosome 13. Recurrent airway obstruction (RAO), also known as heaves, is an asthma-like respiratory disease. Its development is strongly influenced by environmental risk factors such as sensitization and exposure to moldy hay, straw bedding and stabling indoors. A hereditary component has been documented in previous studies; however, so far no causative genetic variant that influences the risk of developing RAO has been identified. In this study, we revised an existing dataset and selected 384 horses for genotyping on the Affymetrix high-density equine SNP array. We performed an allelic case-control genom...
Validation of masks for determination of V̇O2 max in horses exercising at high intensity. The need for a horse to be ridden while wearing a measurement device that allows unrestricted ventilation and gas exchange has hampered accurate measurement of its maximal oxygen consumption (V̇O max) under field conditions. Objective: Design and validate a facemask with the potential to measure V̇O max accurately in the field. Methods: Experiment with 6 × 6 Latin square design. Methods: Two variations of a mask and associated electronic control module (ECM) were designed to enable breath-by-breath measurement of airflows through two 7.8 cm diameter pneumotachometers located 7.5 cm in front...
