2013 - 2014 Projects

Characterization of the respiratory microbiome of healthy horses
Weese JS

The horse’s body consists of a vast, diverse and critically important bacterial population. It plays a crucial role in prevention of disease in many body sites, may influence inflammation and metabolism and is a prime source of bacteria that cause infections. The upper respiratory tract is home to an abundant bacterial population and the reservoir of many important bacteria that can cause disease. The lower airways have been traditionally considered to be sterile or only transiently contaminated with bacteria, but evidence from humans indicates that the lower airways also have a diverse bacterial population that might play a critical role in both development and prevention of disease.

An understanding of the composition of the bacterial population in different parts of the respiratory tract is crucial for understanding the body’s normal protective mechanisms, for evaluating how the bacterial populations change in response to disease and how they can be manipulated to prevent and treat disease. This study will use advanced molecular methods to characterize the complex bacterial population of the equine respiratory tract in healthy horses. It will describe and compare the bacterial compositions of different locations in the respiratory tract, as well as 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, future studies investigating the role of this population in various diseases, as well as studies regarding treatment and prevention of disease, will be possible.

The effect of a newly designed probiotic on prevention of diarrhea and fecal pathogen shedding of foals during the first two months of life
Staempfli H

Acute diarrhea in foals is an important disease that affects up to 80% of foals during their first 6 months of life and causes large financial losses as well as concern for the well-being of the foals. The diarrhea is often caused by infection with gastrointestinal pathogens such as Clostridium difficile and C. perfringens. Methods for prevention of diarrhea in foals are currently limited and rely on standard infection control protocols, therefore further preventative measures are sought after.

Probiotics are bacterial strains of human or animal origin (e.g. Lactobacillus) that have been reported to exert a positive health effect when administered. Probiotics have been shown to prevent some types of diarrhea in animals and humans; however, only few studies have been conducted in horses and further research is needed. Currently available over the counter products are often mislabelled and do not contain the label described concentration of bacteria, and there are no published studies providing evidence for the claimed health effects of such products. Several fermenting bacterial strains, produced for the food industry have recently been shown to inhibit the growth of pathogens such as C. difficile and C. perfringens, and these strains also had growth characteristics which would make them suitable as probiotics for horses. These strains need to be evaluated in in-vivo animal clinical trials for their ability to prevent neonatal foal diarrhea.

Immuno-histochemical staining of adrenergic and cholinergic fibers in the equine sympathetic and parasympathetic nerves of the lower and upper airways in 6 horses
Viel L & Gallastegui A

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 36 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.

Effectiveness of a paravertebral block compared with local anesthetic infiltration of portal sites in horses undergoing laparoscopic surgery for closure of the nephrosplenic space understanding sedation.
Cribb N & Valverde A

Standing laparoscopy is minimally invasive and few complications are reported following surgery. Laparoscopic closure of the nephrosplenic space in standing horses successfully prevents dorsal displacement of the large colon in the nephrosplenic space. Reliable immobilization of the standing horse requires sedative drugs, and local anesthesia that desensitize it to nociceptive stimulation. The most common technique for laparoscopic surgery is infiltration of local anesthetics using a line block. A paravertebral technique is also described but is rarely used despite the described effectiveness and ease of administration. Standing laparoscopy has been performed on 44 horses at the OVC. In one horse, a paravertebral block was subjectively assessed to provide better analgesia enabling better immobilization, facilitating easier and more effective laparoscopic suturing, and faster surgery time. There was a reduction in the overall amount of sedation used, reducing side effects such as colic.

Our objective is to determine and compare the effectiveness of a paravertebral block with local infiltration of the portal entry sites for horses undergoing laparoscopic surgery for closure of the nephrosplenic space. Twelve horses will be randomly assigned to each local anesthetic protocol. The degree of sedation and ataxia during the procedure will be evaluated. Following surgery the overall quality of sedation, analgesia and behaviour will be scored.

An improved anesthetic protocol would benefit horses undergoing any type of laparoscopic surgery. Of the common types of standing laparoscopic surgery, closure of the nephrosplenic space is the most technically demanding and therefore will allow us to draw the most valid conclusions.

Calibration and assessment of capsule-endoscopy technology as a diagnostic tool for imaging the small intestine of the horse 37
Thomason J

Co-investigators: Dr. Judith Koenig, Dr. Heather Chalmers, Diane Gibbard, Grad Student, Dr. Laura Frost, Dr. Ken Armstrong, Warren Armstrong, Technical Support at Halton Equine Veterinary Services.

Horses are at a high risk of developing gastrointestinal tract (GIT) diseases such as ulcers and colic that are often undiagnosed given the limitations of available diagnostic tools (i.e. gastroscopy and rectal examinations). The horse has a very large GIT and it is a physical challenge to reach and view sections of the GIT without the use surgery. Capsule endoscopy (CE) is a new diagnostic tool that has been successfully used in human medicine to help diagnose gastrointestinal disease by collecting images of the GIT as the capsule is traveling through it. The first two objectives of this study are to develop modifications to the human CE device and a procedure for tracking it in, order to image the small intestine of the horse. The third objective is to perform a pilot study comparing images from the GIT of healthy and diseased horses. The results will determine whether CE will be a useful diagnostic tool for the horse.

Molecular mechanisms of prostaglandin-induced embryonic loss in mares
Betteridge K

Co-investigators: M. Anthony Hayes (Co-PI) and Brandon Lillie, Pathobiology; James I. Raeside, Biomedical Sciences

We study how the horse embryo attaches to the endometrium (lining of the uterus) during the critical third week of pregnancy. At this stage the embryo is still enclosed in a ‘capsule’ and is known as a conceptus. We collect conceptuses of defined ages, as well as small pieces of the uterine lining (endometrium), through the cervix from normal pregnancies, and also from pregnancies that have been ‘compromised’ by injection of the mare with a hormone to induce pregnancy failure. We then characterize important changes in proteins, steroid hormones and other molecules that change in the conceptus and uterus to identify those that best explain success and failure of pregnancy. We have already found several molecules that help us understand how the embryo exchanges signals with the mare and becomes attached.

Recent availability of the horse genome and various new discovery tools such as gene expression arrays mean that we can now examine these events in a more comprehensive manner. Having developed methods for sampling tissues and fluids in both the conceptus and its uterine environment, we can now analyze them for the presence and absence of our target molecules in normal and failing pregnancies and assess the significance of differences that are recognized.

The work will help explain interactions between the conceptus and endometrium that are essential to pregnancy maintenance and which, when disrupted, result in pregnancy failure. This will be key to the development of diagnostic tests of reproductive health and, possibly, to new treatments for infertility.

Electro arthrography for non-invasive on-farm assessment of fetlock joint cartilage health
Hurtig M

Co-investigators: Dr. Adele Changoor, Dr. Mohamed Hoba, MSc candidate, Dr. Karen Gordon, Dr. Don Trout, Dr. Lance Bassage.

Horses intended for competition and racing endure rigorous training, thereby increasing their susceptibility to joint disease. Veterinarians mainly use physical exam, diagnostic injections, x-ray images 38 and ultrasound to evaluate joint health, yet these methods provide no information about the quantity or health of the articular cartilage. Cartilage damage and erosions are associated with pain and lead to chronic lameness. Some therapies are available to stop or slow cartilage damage, but there are no practical methods for monitoring progress or making a long-term prognosis. Electro arthrography (EAG) is a novel method for measuring electrical signals produced by cartilage through electrodes placed on skin and is similar in principle to electrocardiography (ECG) for the heart.

Pilot studies in people have been successful at distinguishing between normal and osteoarthritic knees. The EAG assessment is simple and completely non-invasive since it requires only surface electrodes the size of a dime. In this study we will focus on the fetlock since it is the most common joint injured, particularly in the racehorse. Our pilot data in cadaveric forelimbs of horses under simulated weight bearing have shown that EAG signals can be easily recorded from the fetlock and are altered by damaged or osteoarthritic cartilage.

The purpose of the first phase of the proposal is to strengthen the diagnostic value of EAG by performing correlative studies on cadaveric fetlock joints before and after inducing controlled cartilage damage. During the second phase of the study, EAG will be applied clinically to normal and lame horses.

Effect of allogeneic umbilical cord blood mesenchymal stromal cells on induced synovitis in horses
Koenig J

Co-investigator: Thomas Koch, DVM, PhD, Dept. of Biomedical Sciences

Currently the focus of systemic and intra-articular therapies involves slowing the progression of osteoarthritis since reversal of established osteoarthritis has yet to be demonstrated. In equine joints with naturally occurring disease intraarticular administration of stem cells were reported to improve lameness in horses unresponsive to conventional treatment. Recently, frozen stem cells obtained from unrelated horses were used by injection into joints successfully with only a mild transient inflammation. This suggests there may be potential for developing frozen allogeneic stem cell products that could be available for treatment of the equine athlete at the time of diagnosis of injury. Further study is needed to determine if intra-articular allogeneic stem cells modulate inflammation during acute joint inflammation in horses.