Ex-vivo Pulmonary Arterial Perfusion System to model biomechanical and hemodynamic phenomena in equine pulmonary arteries - 2014-2015 Projects
Dr Luis Arroyo, Department of Clinical Studies

Co-investigator: Bruce Guest

The behavior of catheters within the pulmonary artery was investigated using equine en bloc heart and lung preparations. An equine ex vivo heart and lung perfusion system (EVHLPS) was built and utilized to develop a blind technique for catheter placement into the distal main stem of the pulmonary artery utilizing balloon tipped catheters. A 7Fr, 200cm pancreatic sphincteroplasty catheter with a 16mm balloon was found to be an effective device to facilitate placement of a pressure measurement catheter within the pulmonary artery at the location where EIPH occurs in the horse.

The EVHLPS replicated basic aspects of equine pulmonary artery hemodynamics and mechanics. The navigation technique developed in the EVHLPS is currently being used to collect hemodynamic and mechanical data from the pulmonary arteries of live horses. Increased knowledge of the properties of the equine pulmonary may shed light on the causes of EIPH in horses. The EVHLPS will allow development of this knowledge without the use of live animal testing

Characterization of the respiratory microbiome of healthy horses - 2014-2015 Projects
Dr Scott Weese, Department of Pathobiology

With advancement in testing methods, it has become abundantly clear that the body’s microbiota (microbial populations) and microbiome (genetic composition of those populations) are incredibly large, diverse and critical for health. While focus has mainly been in the intestinal tract, other body sites also harbour important bacterial microbiomes.

The upper respiratory tract microbiome is a potential reservoir of various pathogens (e.g. Streptococcus equi) that can cause disease in the host or be spread to other horses. Its composition may play a key role in determination of whether an animal becomes infected or a carrier. Further, while the lower airways are often considered to be sterile or only transiently contaminated, evidence from humans indicates the presence of a diverse microbiome that plays a critical role in both development and prevention of disease. Understanding the respiratory microbiome is crucial for understanding the airway’s normal protective mechanisms, how bacterial populations change in response to disease, how microbiome changes may cause disease and how microbiomes can be altered to prevent and treat disease.

This study will use advanced molecular and bioinformatics methods to characterize the equine respiratory microbiome, describe and compare the bacterial compositions of different locations in the respiratory tract, and determine the variability between different sites and between horses that are in active training versus those that are on pasture. With a better understanding of the respiratory bacterial population, studies investigating the role of this population in various diseases, as well as studies regarding treatment and prevention of disease, will be possible.

A Immuno-histochemical staining of adrenergic and cholinergic fibers in the equine sympathetic and parasympathetic nerves of the lower and upper airways in 6 horses - 2014-2015 Projects
Dr Laurent Viel, Clinical Studies and Aitor Gallastegui

The current understanding of the role of innervation in upper and lower equine airway disease in horses is limited even though there is a significant impact of respiratory disease upon equine athletic performance. Attempt to correct surgically recurrent laryngeal neuropathy (roarer) in horses has some short-term benefit but has also a high relapse rate.

Recently Vanschandevij et al. (2011) demonstrated the benefit of using electro stimulation of some nerve branches of the recurrent nerve with some very promising results. Nevertheless one of the difficulties of those studies in the horse has been convincing identification of the nerve branches as to whether the branches are totally sympathetic and parasympathetic autonomic innervation. A recent anatomical study in our lab intended to accurately describe the cervical and thoracic autonomic neural networks that supply the airways in horses. The autonomic network innervating the airways was dissected in 10 horses. In this group of horses studied, it was identified that sympathetic and parasympathetic nerves intermingled mainly at the thoracic region.

In addition, the autonomic nervous supply was provided to the lower airways principally by branches from the vagus nerve (a parasympathetic nerve). The latter finding questioned the anatomic presence of sympathetic nerve branches needed to maintain bronchodilation of the airways. However the precise fibre type causing bronchodilation or constriction within the respiratory tract of horses has not been determined. We hypothesize that adrenergic fibers frequently reach the airways within the vagus nerve branches, and that some cholinergic fibers also travel within sympathetic nerves.

The proposed study will selectively identify these fibers at different levels of the autonomic neural network that supply the airways in horses. Describing the physical pathways of these fibers in horses will improve the understanding on equine airway physiology, and establish a basic knowledge necessary for the development of new diagnostic and therapeutic tools in the field of the equine neuro stimulation.

Ex-vivo Pulmonary Arterial Perfusion System to model biomechanical and hemodynamic phenomena in equine pulmonary arteries
- 2012-2013 Projects
Dr. Luis Arroyo, Department of Clinical Studies

Exercise-Induced Pulmonary Haemorrhage (EIPH) is a condition affecting virtually all horses during intensive exercise worldwide. The management and treatment of EIPH have a substantial economic impact to the equine industry, with the cost of treating EIPH estimated to exceed $100 million annually in the United States alone.

Vascular diseases in domestic animals and particularly in horses are clinically poorly defined and have previously been thought to be uncommon. Interestingly, the most accepted cause for EIPH is exercise-induced pulmonary hypertension, resulting in pulmonary vascular failure (capillary rupture).

The output from the heart into the pulmonary artery occurs as a brief but intense wave of flow and pressure. The elastic nature of the pulmonary arterial system allows it to expand during heart contraction, which reduces arterial pressure and provides a reservoir to store blood. In between contractions, the elastic recoil of the stretched pulmonary artery allows it to gently squeeze blood into the capillaries. Recently we observed the presence of calcification and fibrosis of the pulmonary arterial walls in a large proportion of racehorses. These lesions stiffen the arteries and have been shown to result in hypertension in humans, and it is suspected to occur in horses also.

The aim of the study is to design and develop an ex-vivo model that could accurately reproduce pulmonary artery dynamic flow and pressure characteristics prior to testing in live animals. Further, a high fidelity ex-vivo model may also significantly reduce the number of live horses required for future studies in this area.

Etiologic agents and their interaction with macrophages in heaves - 2011-2012 Projects
Dr. Dorothee Bienzle, Department of Pathobiology

Inflammatory airway disease (IAD) and recurrent airway obstruction (RAO, or heaves) affect horses of different ages. Both conditions lead to inability to function as performance or pleasure horse, and result in loss of revenue. The cause of both conditions is thought to be chronic exposure to dusty environments, and the disease may be worsened by concurrent viral infections.

The role of other infectious agents in IAD and RAO is unknown. Exposure to dusty environments is inevitable for horses stabled indoors, and results in inhalation of fungal spores and bacterial components. Spores from molds that reach the lower airway of horses are taken up by macrophage cells, which starts inflammation. Previously, we showed that horses with RAO had exacerbation of disease if they inhaled a combination of dust and molds. We therefore know that experimentally, inhalation of molds can cause lung inflammation, but whether molds or bacterial components are present in the lungs of naturally affected or healthy horses is unknown. Further, the effect of mold spores and bacteria on macrophages is not understood.

Therefore, the goals of this study are 1) to collect lung washes form horses with naturally occurring RAO, and from horses with no lung disease; 2) to identify the molds by culture and PCR assays; 3) to measure a key bacterial component’ and 4) to culture lung wash fluid with macrophages to determine whether these interactions initiate inflammatory responses.

Results from these studies will define whether presence of fungal spores in the lung is associated with RAO, and whether fungal spores can initiate inflammation.

Learn more about: respiratory research.

Assessing post-operative outcomes in horses treated for dorsal displacement of the soft palate - 2011-2012 Projects
Dr. Heather Chalmers, Clinical Studies

Affecting between 10-20% of 2 -3 year-old racehorses, dorsal displacement of the soft palate (DDSP) is a condition resulting in upper airway obstruction, noise, and inability to perform at peak exercise1. Towards the end of a race, a palatial displacement can cause a horse to pull up suddenly and be unable to complete the race.

There are many treatments for DDSP, characterized as non-surgical (eg. tack modifications) and surgical. The two most common surgical treatments are 1) the laryngeal tie forward and 2) the myectomy (Llewellyn) procedure. 1 The choice of surgery depends on factors both intrinsic (age, breed, value) and extrinsic (availability, clinician preference) to the horse. Importantly, the efficacy of these surgeries has never been assessed in clinical patients and the relative outcomes have never been compared. This gap in knowledge is likely because traditionally DDSP is only accurately diagnosed by endoscopic exam during treadmill exercise, which limits its practicality.

Recently, two additional tools have become available to diagnose DDSP in horses – 1) ultrasound of the upper airway2, performed stall side and 2) over-ground wireless endoscopy, performed at the race track. We propose to assess horses following surgery for DDSP at the trackside using both ultrasound and the new dynamic respiratory endoscopy system.

The goal of this study is to evaluate the post-operative outcomes of horses that underwent surgery for DDSP, to establish if these treatments reduce the incidence of DDSP during exercise, and to compare the relative success of the two surgeries. We anticipate that this novel information will greatly improve our ability to make treatment and prognostic recommendations for affected horses.

Intravascular Assessment of the Pulmonary Artery Haemodynamics: A pilot study. - 2010-2011 Projects
Dr. R John Runciman, School of Engineering; Luis Arroyo, Department Clinical Studies, Co-investigators: Laurent Viel, Department of Clinical Studies; Alexander Valverde, Department of Clinical Studies

Approximately 80% of racehorses can be expected to develop Exercise-Induced Pulmonary Haemorrhage (EIPH) during their career. The management and treatment of EIPH have a substantial economic impact to the equine industry, with the cost of treating EIPH estimated to exceed $100 million annually in the United States alone.

There is currently a poor understanding regarding the cause of EIPH and potential mechanisms include capillary stress failure, pulmonary fibrosis, and small airway disease. Currently, the most accepted cause for EIPH is exercise-induced pulmonary hypertension, resulting in pulmonary capillary rupture.

Recently we observed the presence of calcification and fibrosis of the pulmonary artery wall in a large proportion of racehorses. Such lesions are known to interfere with elasticity that the vessel needs in order to accommodate the cardiovascular pumping action of the heart during strenuous exercise. Indeed, arterial calcification is the most important cause of vascular stiffness in humans and is considered a predictive factor for cardiovascular mortality, coronary morbidity and fatal stroke.

Similarly, we suspect that the compliance of the pulmonary arterial wall of horses with artery calcification is affected. This impaired compliance will directly affect the capacity of the vessel to deal with large fluctuations in blood pressure, which may in turn cause the downstream microvasculature damage seen with EIPH.

We hypothesize that the pulmonary artery compliance of horses with calcified arteries is impaired. This study will establish a protocol on how to catheterize the pulmonary artery and measure the relative stiffness of the pulmonary arterial tree.

Histopathological pulmonary lesions in actively racing horses submitted for Post-Mortem examination in the Ontario Death Registry; an investigation into Inflammatory Airway Disease prevalence. - 2010-2011 Projects
Dr. Laurent Viel, Clinical Studies, Co-investigators: Dr. Federica ter Woort, Dr. Luis Arroyo– Department of Clinical Studies

Inflammatory Airway Disease (IAD) in horses results from an inflammatory response of the lungs to an unknown stimuli, although it is commonly referred to as an allergic airway disorder.

Many studies document the exaggerated response to inhaled particulate, including dust and mold spores from feed and bedding as a major component of IAD. IAD has been recognised as a different condition from heaves or Recurrent Airway Obstruction, since it primarily affects young athletic horses in training and racing. At the present time, it is speculated in both the scientific literature and lay press that IAD may contribute to as much as 50-60% of coughing horses and subsequently poor athletic performance.

The Ontario Racing Commission Death Registry program examines between 110-125 horses per year which have been euthanized based upon humane grounds or which have died suddenly.

Hence, this study proposes to examine a total of 150-200 horses for the prevalence of airway pathology and to describe semi-quantitatively the observed pathology lesions. The study results should provide a relatively accurate indication of the disease prevalence as well as the severity of the lesions associated with IAD. This knowledge may contribute to future recommendations and regulatory changes for treatment options for airway disease in racing horses.

The role of Clara cells in the pathogenesis of equine airway disease. - Projects 2005-2006
Dr. Dorothee Bienzle

Comparison of continuous infusion with intermittent bolusing of cefotaxime in neonatal foals. - Projects 2005-2006
Dr. Joanne Hewson
Septicemia is the most significant cause of foal illness and death in the neonatal period (< 14 days of age). This study will continue to advance intensive care of the septicemic neonate, with the hope to improve short-term and long-term survivability of these foals by optimizing medical therapy and minimizing potential sequelae. To this end, the information provided by this study will allow veterinarians to determine the optimal method of administration of cefotaxime in critically ill neonates to treat various complications of septicemia, including peritonitis, septic arthritis, and pneumonia.

Blood neutrophil and pulmonary leukocyte function in horses with heaves and the effect of inhaled fluticasone propionate therapy. - Projects 2004-2005
Dr. J. Hewson
Impaired lung function due persistent airway inflammation is seen clinically as exercise intolerance or prolonged recovery from exercise. The key inflammatory cells, neutrophils, found in the airways of affected young horses, are poorly understood. Neutrophil activity in the lung will be related to clinical signs, pulmonary function, airway hyper-reactivity, adrenal suppression, and airway inflammation over time in non-treated and treated horses with inhaled corticosteroids.

The role of Clara cells in the pathogenesis of equine allergic airway disease. - Projects 2004-2005
Dr. D. Bienzle
Clara cells are specialized epithelial cells present in the terminal small airways of the horse. The cells have the property to secrete a surfactant like substance to keep the non-cartilagenous small airways open during expiration and have the ability to secrete protective substances against bacterial/viral infections. A protein called CC10, produced by those specialized lining cells is important in the regulation of lung inflammation. The cells producing this protein are destroyed in horses with "heaves". A diagnostic test for CC10 in blood and lung fluid is presently being developed.

Immunoquantification of collagen fibre type in the pulmonary airways of horses with heaves. - Projects 2004-2005
Dr. L. Viel
Equine Respiratory disease manifested as inflammatory allergic airway disease has the potential to severely limit the athletic capacity of performance in racing horses. The study is designed to first recognise and identify airway injury such as scaring of the airways caused by the continuous exposures to environmental pollutants (track / stable environment) and second to assist the veterinarian in establishing long term effective therapy to minimize permanent airway damage of those athletic horses.

Surveillance of equine influenza virus prevalence and antigenic drift in young performance horses in Ontario. - Projects 2004-2005
Drs. J. Hewson and L. Viel
One of the most common causes of viral respiratory infection in the young horse is influenza. As a result of virus membrane changes, previously vaccinated animals may develop the infection. Accurate identification of viruses during outbreaks is essential in order to monitor variants and thus explain vaccination failures. This study aims to develop a surveillance program in Ontario that will provide assistance to veterinarians in evaluating influenza risk as well as contributing to international surveillance and providing pharmaceutical companies with information that helps them produce suitable vaccines.