Topic:Airway Disease
Airway disease in horses is defined as a respiratory condition marked by inflammation and narrowing of the lower airways, leading to symptoms like coughing, increased mucus production, and reduced performance. This condition, which includes forms such as inflammatory airway disease (IAD) and recurrent airway obstruction (RAO), can significantly impact a horse’s respiratory efficiency and overall health.
This page compiles peer-reviewed research studies and clinical insights that explore the pathophysiology, diagnostic techniques, and effective treatment protocols to manage and improve equine respiratory health.
Association between cough and cytology of bronchoalveolar lavage fluid and pulmonary function in horses diagnosed with inflammatory airway disease. The objective of this study was to examine the relationship between chronic cough, pulmonary mechanical function, bronchial hyper-responsiveness, and peripheral airway inflammation in adult performance horses with nonseptic inflammatory airway disease (IAD). Objective: We hypothesized that horses with a presenting complaint of cough have a higher percentage of inflammatory cells on bronchoalveolar lavage (BAL), greater airway obstruction, and airway hyper-responsiveness (AHR) than do horses without cough. ANIMALS/SAMPLE POPULATION: Adult performance horses (n = 137) referred for evaluation of ...
The effect of adding oral dexamethasone to feed alterations on the airway cell inflammatory gene expression in stabled horses affected with recurrent airway obstruction. Chemokine expression in airway epithelium and bronchoalveolar lavage fluid (BALF) cells of horses with recurrent airway obstruction (RAO) is increased. Objective: For RAO-affected horses that are stabled and fed a pelleted ration, the addition of oral dexamethasone further improves pulmonary function and reduces inflammatory gene expression in pulmonary cells. Methods: Twelve RAO-affected horses. Methods: In a randomized cross-over experiment, the effect of feeding pellets in lieu of hay to stabled, RAO-affected horses was compared with the effect of feeding pellets and administering a 21-day ...
Effects of neuraminidase on equine isolated bronchi. It has been demonstrated in mammals that the airway hyper-responsiveness, which accompanies viral infections, is the result of increased reflex bronchoconstriction due to inhibition of muscarinic prejunctional receptors, which belong to M2 subtypes. Multiple mechanisms account for virus-induced M2 receptor dysfunction. Viral neuraminidase may deglycosylate the M2 receptor, decreasing acetylcholine affinity. Equine influenza remains a common viral respiratory disease of horses worldwide, which results in loss to the equine industry, by decreasing performance, convalescence time and loss of peak...
Development of equine upper airway fluid mechanics model for Thoroughbred racehorses. Computational fluid dynamics (CFD) models provide the means to evaluate airflow in the upper airways without requiring in vivo experiments. Objective: The physiological conditions of a Thoroughbred racehorse's upper airway during exercise could be simulated. Methods: Computed tomography scanned images of a 3-year-old intact male Thoroughbred racehorse cadaver were used to simulate in vivo geometry. Airway pressure traces from a live Thoroughbred horse, during exercise was used to set the boundary condition. Fluid-flow equations were solved for turbulent flow in the airway during inspiratory an...
A soluble secreted glycoprotein (eCLCA1) is overexpressed due to goblet cell hyperplasia and metaplasia in horses with recurrent airway obstruction. The equine putative chloride channel protein eCLCA1 is thought to be critically involved in the pathogenesis of recurrent airway obstruction (RAO) via modulation of the hydration of airway mucins. A recent study revealed a strong increase of eCLCA1 messenger ribonucleic acid (mRNA) in the lungs of horses with RAO. In this study, eCLCA1 protein and mRNA expression were quantified in airway goblet cells of 9 horses affected with RAO and 9 control horses by using immunohistochemistry and laser microdissection followed by real-time quantitative reverse transcription polymerase chain reaction, resp...
Equine recurrent airway obstruction and insect bite hypersensitivity: understanding the diseases and uncovering possible new therapeutic approaches. Recurrent airway obstruction (RAO) and insect bite hypersensitivity (IBH) are allergic conditions that are commonly encountered in the horse. Whilst complete allergen avoidance is an effective management strategy for both diseases, this may not be achievable in all cases and treatment options are therefore required. The inflammatory response is the main therapeutic target for glucocorticoids given to horses with RAO and severe cases of IBH, whilst the bronchodilators used in RAO primarily target airway smooth muscle. Such drugs are effective in most but not all individuals and there may be unw...
Lung function and airway cytologic profiles in horses with recurrent airway obstruction maintained in low-dust environments. The effects of long-term environmental management on airway obstruction and inflammation in horses with recurrent airway obstruction (RAO) are unknown. Objective: Horses with RAO maintained in low-dust environments have persistent airway obstruction and neutrophilic inflammation. Methods: Study horses were treated for RAO and then maintained in low-dust environments with no medical management. Horses were classified into 3 groups by years after diagnosis: 1 year (time 1, n = 9), 2-3 years (time 2, n = 7), and 5-6 years (time 3, n = 8). The comparison groups were age-matched healthy horses. Met...
Adenosine receptor modulation: potential implications in veterinary medicine. Adenosine is a purine nucleoside whose concentration increases during inflammation and hypoxia and the many roles of this molecule are becoming better understood. Increased reactivity to adenosine of the airways of asthmatic but not of normal subjects underlines the role of adenosine in airway inflammation. The identification and pharmacological characterisation of different adenosine receptors have stimulated the search for subtype-specific ligands able to modulate the effects of this molecule in a directed way. Several compounds of different chemical classes have been identified as having po...
Equine recurrent airway obstruction does not alter airway muscarinic acetylcholine receptor expression and subtype distribution. In recurrent airway obstruction (RAO) or heaves, bronchospasm has been attributed to enhanced cholinergic activity. However, the expression and function of muscarinic acetylcholine receptors (mAChR) and their signaling components are not yet known. Thus, we examined the expression, subtype distribution and postreceptor signaling pathways of mAChR in the peripheral lung, bronchial and tracheal epithelia with the underlying smooth muscle from nine horses with RAO and 11 healthy control horses. In RAO horses, no significant segment-dependent alteration in mAChR density and subtype distribution (a...
Videoendoscopic evaluation of the upper respiratory tract in 93 sport horses during exercise testing on a high-speed treadmill. Videoendoscopy of the upper respiratory tract (URT) during high-speed treadmill exercise has proved to be invaluable in the assessment of URT dysfunction in racehorses. However, very little information exists regarding dynamic airway collapse in other sport horses used in nonracing equestrian disciplines. Objective: To evaluate the videoendoscopic findings at rest and during exercise in a mixed population of sport horses referred for investigation of poor athletic performance and/or abnormal respiratory noise. Methods: Videoendoscopy of the upper airway was performed at rest and during high-sp...
Endoscopic scoring of the tracheal septum in horses and its clinical relevance for the evaluation of lower airway health in horses. Although endoscopic scoring of the tracheal septum thickness is used as a diagnostic tool for evaluation of lower airway disease, its clinical relevance and reliability have never been critically assessed in the horse. Objective: To investigate if septum thickness scores (STS) are reliable and serve as a clinically useful indicator of lower airway disease status and/or inflammation. Methods: The variance of STS attributable to the horse, observer and changes over time was determined. The distribution of STS in a population of clinically normal horses and correlations of STS with age, gender, a...
Management of airway difficulties during induction of general anesthesia in an American miniature horse with dwarfism. This report describes previously unreported upper airway abnormalities encountered in a 5-month-old American miniature horse colt presented for elective surgery. Caution should be exercised when administering general anesthesia or heavy sedation to individuals of this breed that present with multiple congenital abnormalities. Conduite à tenir en présence de difficultés respiratoires pendant l’induction de l’anesthésie générale chez un cheval miniature américain atteint de nanisme. Ce rapport décrit des anomalies jamais rapportées des voies respiratoires supérieures d’un cheval ...
Reactivity of equine airways–a study on precision-cut lung slices. A study was performed to evaluate the use of precision-cut lung slices (PCLS) for studies on the contraction of equine airways. Lungs of 10 horses were taken to prepare PCLS of approximately 250 microm from equine lung tissue using a special microtome. The lung slices were cultured and the enclosed small airways were monitored using a microscope with coupled digital camera, which was used to determine the airway luminal area and diameter from digital images. As indicated by the beating of the ciliated epithelium and reactivity of airways on methacholine challenge, the tissue slices were found ...
Effect of tracheal mucus and tracheal cytology on racing performance in Thoroughbred racehorses. Accumulations of mucus within the trachea are often found during endoscopic examinations of the airways of poorly performing racehorses, but the clinical importance of this finding is unknown. Objective: To determine the effect of tracheal mucus, pharyngeal lymphoid hyperplasia (PLH) and cytological indices of tracheal aspirate on racing performance in Thoroughbred horses assessed by race place and whether the horse was raced. Methods: Endoscopic examination of the nasopharynx, larynx and trachea was performed, and a tracheal aspirate obtained monthly at Thistledown racetrack from April to Dec...
Airway inflammation in Michigan pleasure horses: prevalence and risk factors. Although subclinical airway inflammation is thought to be common in horses, there is little information on its prevalence and none on risk factors. Objective: To determine the prevalence and risk factors for an increased number of inflammatory cells and for mucus accumulation in the trachea of pleasure horses. Methods: Horses (n = 266) in stables (n = 21) in Michigan were examined endoscopically, once in winter and once in summer 2004. Visible tracheal mucoid secretions were graded 0-5 and inflammatory cell numbers counted in a tracheal lavage sample. Information collected about each horse inc...
DNA binding activity of transcription factors in bronchial cells of horses with recurrent airway obstruction. Horses with recurrent airway obstruction (RAO) present many similarities with human asthmatics including airway inflammation, hyperresponsiveness, reversible obstruction, and increased NF-kappaB expression. Studies in experimental asthma models have shown that transcriptions factors such as activator protein-1 (AP-1), GATA-3, cyclic AMP response element binding protein (CREB) and CAAT/enhancer binding protein (C/EBP) may also play an important role in airway inflammation. The purpose of this study was to measure DNA binding activity of these transcription factors in the airways of horses with ...
Heaves, an asthma-like equine disease, involves airway smooth muscle remodeling. Increased airway smooth muscle mass is a prominent feature of asthmatic airway remodeling. Airway smooth muscle hyperplasia occurs in rodent models of experimental asthma, but the relevance of such finding to spontaneously occurring disease in large mammals is unknown. Objective: We examined horses with heaves, a naturally occurring equine asthma related to sensitization and exposure to moldy hay. We hypothesized that airway remodeling occurs in heaves and shares disease mechanisms with asthma. Methods: We quantified the airway smooth muscle mass and the numbers of proliferating and apoptotic ...
Effect of beclomethasone dipropionate and dexamethasone isonicotinate on lung function, bronchoalveolar lavage fluid cytology, and transcription factor expression in airways of horses with recurrent airway obstruction. Glucocorticoid (GC) therapy is recognized to be effective for the treatment of recurrent airway obstruction (RAO) in horses. Anti-inflammatory properties of GC are thought to be mediated by suppression of inflammatory gene expression via inhibition of transcription factors such as nuclear factor-kappaB (NF-kappaB) and activator protein-1 (AP-1). The purpose of this study was to evaluate the effect of low-dose inhaled beclomethasone dipropionate and injectable dexamethasone 21-isonicotinate on clinical signs, pulmonary function, airway cytology, and activity of NF-kappaB and AP-1 in bronchial c...
Endothelin receptor alterations in equine airway hyperreactivity. The purpose of this study was to evaluate the role of endothelin-1 (ET-1) and its receptors in the airway hyperreactivity of horses with obstructive pulmonary disease associated with summer pasture (SPAOPD). The right diaphragmatic lobe of the lung of 8 clinically healthy (unaffected) and 8 SPAOPD-affected horses was collected immediately after euthanasia. Bronchial rings (4 mm wide) were prepared and mounted in organ baths and attached to force transducers interfaced with a polygraph. Four rings were used to study each ET-1 receptor; 1 ring served as the control, and the other 3 were incubate...
Radiographic scoring lacks predictive value in inflammatory airway disease. Diagnosis of inflammatory airway disease (IAD) currently rests upon the results of bronchoalveolar lavage (BAL) cytology, lung function testing and histamine bronchoprovocation (HBP), none of which provides direct information about structural change in the lung. Objective: That thoracic radiography might better portray structural change in the lungs and therefore offer a good clinical assessment of IAD. Methods: A radiographic scoring system was developed to assess the extent of bronchial and interstitial pattern on thoracic radiographs in the dorsocaudal, dorsocranial and caudoventral regions...
Effect of acute airway inflammation on the pulmonary antioxidant status. Effects of acute airway inflammation induced by organic dust inhalation on pulmonary antioxidant status were investigated in healthy horses and horses affected by recurrent airway obstruction. Exposure to organic dust induced acute airway neutrophilia, which was associated with increases in elastase and decreases in ascorbic acid concentrations in bronchoalveolar lavage fluid. However, markers of oxidative stress were unaffected, as was hydrogen peroxide in breath condensate. Decreases in ascorbic acid correlated with increased respiratory resistance (P = .001) when both groups were combined. ...
Direct activation of gelatinase B (MMP-9) by hay dust suspension and different components of organic dust. Matrix metalloproteinases (MMPs) are involved in tissue destruction in allergic airway diseases. We studied the ability of various allergenic substances to directly activate recombinant 92kDa proMMP-9. The substances included hay dust suspension (HDS) and its components (supernatant, particulate matter and wash fluid of particulate matter), storage mite extract and two Aspergillus fumigatus extracts. The allergen suspensions were incubated in vitro with proMMP-9. After incubation the conversion of proMMP-9 to 10kDa lower active forms were studied using gelatin zymography and Western immunoblot...
Respiratory mechanics in Standardbred horses with sub-clinical inflammatory airway disease and poor athletic performance. The aim of this study was to investigate and quantify respiratory mechanical dysfunctions in Standardbred horses with both poor performance and bronchoalveolar lavage fluid cytology characteristic of inflammatory airway disease (IAD). A control group of healthy Standardbred horses was compared. Respiratory mechanics and breathing pattern were examined at rest and during hyperventilation induced using a rebreathing method. At rest, respiratory mechanics and breathing pattern were superimposable in both groups. In IAD horses, rebreathing increased ventilation, with larger tidal volumes and lower...
Laser vocal cordectomy fails to effectively reduce respiratory noise in horses with laryngeal hemiplegia. To report the effect of unilateral laser vocal cordectomy on respiratory noise and airway function in horses with experimentally induced laryngeal hemiplegia (LH). Methods: Experimental study. Methods: Six Standardbred horses without upper airway abnormalities at rest or during high-speed treadmill exercise. Methods: Respiratory sounds and inspiratory trans-upper airway pressure (P(Ui)) were measured before (baseline) and 14 days after induction of LH by left recurrent laryngeal neurectomy, and again 30, 60, 90, and 120 days after endoscopically assisted laser cordectomy of the left vocal cord...
Ventilatory support of the critically ill foal. Critically ill foals often have respiratory failure and benefit from respiratory support. Conventional mechanical ventilation using modem mechanical ventilators is easily adapted to foals. Establish-ing ventilator settings is a dynamic process aided by constant monitoring of blood gas values, end-tidal carbon dioxide, airway pressures, respiratory volumes, airway resistance, and respiratory compliance. Early weaning is as important as timely initiation of ventilation.
Kinetics of pulmonary neutrophil recruitment and clearance in a natural and spontaneously resolving model of airway inflammation. Neutrophil apoptosis and phagocytic clearance have been proposed as key determinants affecting the resolution of airway inflammation. Objective To determine the kinetics of neutrophil priming, recruitment, activation and subsequent clearance in a naturally occurring equine disease model of neutrophilic pulmonary inflammation. Results: A 5 h mouldy hay/straw challenge in hypersensitive horses induced transient pulmonary dysfunction lasting 4 days. At 24 h circulating neutrophils were primed and displayed delayed rates of spontaneous apoptosis in vitro. Neutrophil numbers in the airspaces peaked...
Airway inflammation is associated with mucous cell metaplasia and increased intraepithelial stored mucosubstances in horses. This study was performed to determine if a peripheral sample of lung from the site where biopsy is conducted is representative of the rest of the lung and to investigate the relationship between airway inflammation and intraepithelial mucous production in the peripheral airways. Lung parenchyma samples were collected from five different regions of the lung in five control and five heaves-affected horses. Horse groups were defined by clinical response to stabling. Tissue sections were used for semi-quantitative scoring of lesions, to count the number of airways, to quantify the amount of stored...
Overexpression of eCLCA1 in small airways of horses with recurrent airway obstruction. The human hCLCA1 and murine mCLCA3 (chloride channels, calcium-activated) have recently been identified as promising therapeutic targets in asthma. Recurrent airway obstruction in horses is an important animal model of human asthma. Here, we have cloned and characterized the first equine CLCA family member, eCLCA1. The 913 amino acids eCLCA1 polypeptide forms a 120-kDa transmembrane glycoprotein that is processed to an 80-kDa protein in vivo. Three single nucleotide polymorphisms were detected in the eCLCA1 coding region in 14 horses, resulting in two amino acid changes (485H/R and 490V/L). Ho...
Effect of airway disease on blood gas exchange in racehorses. Inflammatory Airway Disease (IAD), exercise-induced pulmonary hemorrhage (EIPH), and upper airway obstruction (UAO) are common respiratory tract diseases that can decrease performance. The purpose of this retrospective study was to compare bronchoalveolar lavage fluid cytology and arterial blood gas analysis during a treadmill test by poorly performing racehorses presented to Purdue University. One hundred thirty-two horses with a history of poor performance were included in this study. Ten horses with no history or diagnosis of EIPH, IAD, or UAO served as controls. Horses were evaluated by rh...