2012-2013 Projects

The effect of antimicrobials on the intestinal microbiome
Dr. J Scott Weese, Pathobiology

The intestinal tract of the horse is comprised of an incredibly complex and diverse population of bacteria; the bacterial microbiome. The intestinal microbiome is critical for health of the horse, and disruptions of this microbiome can result in various types of disease, including colitis (severe diarrhea).

One of the main recognized risk factors for colitis in horses is antibiotic use, as antibiotics are thought to be able to disrupt the normal balanced microbiome and result in proliferation of bacteria that can cause disease. Colitis is often fatal and survivors can have serious consequences such as laminitis.

Despite the importance of the intestinal microbiome and disease that is thought to occur because of its disruption, we are only now able to understand its composition and how it changes. Recently, we identified profound changes in the microbiome in horses with colitis, and further study of what drives those changes is required.

While antibiotics are known to be a major risk factor for colitis in horses, the actual reasons for this (beyond a vague assumption that ‘good’ bacteria get displaced) are not understood. With recent advances in technology, it is now possible to closely evaluate the intestinal microbiome and its response to stressors like antibiotics.

This study will evaluate changes in the composition of the intestinal microbiome in horses treated with different antibiotics. This will also us to better understand what antibiotics do to the intestinal microbiome, information that is critical for designing methods to reduce or prevent those changes, and corresponding disease.

Mechanisms of embryonic loss in mares

Dr. Keith Betteridge, Biomedical Science

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 and 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.

Prospective evaluation of MSC isolation from umbilical cord blood and jugular blood

Dr. Thomas Koch, Biomedical Science

Studies have shown that peripheral and cord blood stem cells are difficult to isolate. However cord blood-derived cells may be advantageous for a number of reasons. These cells may elicit minimal, if any, immune response if injected or transplanted into an unrelated individual. These cells may also be capable of giving raise to a wider array of cell types than stem cells from fat and bone marrow.

We have recently isolated stem cells from umbilical cord blood of foals and have demonstrated their potential to form bone, cartilage and fat in petri dishes. So far MSCs have only been attempted isolated from the peripheral blood of mature horses and with poor results.

The studies outlined in this application aim to evaluate equine cord blood and peripheral blood-derived mesenchymal stromal cells for the purpose of developing advanced cell-based therapies in the horse.

Equine induced pluripotent stem cells for treating cartilage defects and disease modelling

Dr. Thomas Koch, Biomedical Science

The long-term goal of the studies in this proposal is to initiate a research stream on equine induced pluripotent stem cells (eiPSCs) that will compliment our ongoing research efforts to solve the unmet clinical need for treating cartilage defects in horses.

The recent report on the production of eiPSCs by researchers in Montreal and Toronto has received widespread attention in the veterinary research community. These cells hold the promise of developing patient specific cells that can be used for both cell and tissue replacement strategies of that patient with reduced risk of immune rejection, or for evaluating efficacy and safety of new drugs at reduced costs through pharmacological screening platforms, or to treat inflammatory diseases.

A greater understanding of cellular reprogramming events may in the future also be utilized to help the body heal itself by directing resident cells of damaged tissue towards reparative processes. Our research group is part of newly formed international research consortium with the aim to advance our understanding of these cells biology and clinical potential much more rapidly than would be the case by individual research lab efforts. Exchange of graduate students between labs will also enhance the training of highly qualified personal.

We have just been awarded significant funds for a PhD student to explore canine iPS cells for the same purpose of cartilage repair and support of this grant application for another PhD student working on equine iPSCs would provide significant synergy in the lab for the rapid development of a robust research program in domestic animal iPS cells.

Molecular epidemiology of organisms potentially causing diarrhea in foals: A longitudinal study to identify pathogenic genotypes with emphasis on clostridial organisms.

Dr. Henry Staempfli, Department of Clinical Studies

Most foals experience an episode of diarrhea before 6 months of age. This past foaling season (2010/2012) at the Ontario Veterinary College we saw over 55 foals with severe diarrhea requiring hospital admission and intensive care. The cause was only established in a very few cases. The most recognized and understood infectious causes are rotavirus, Salmonella spp, and Clostridium perfringens. More recently Clostridium difficile (C.difficile) has been identified as an additional bacterium associated with acute diarrhea in horses.

Experimental infectious studies (sponsored by Equine Guelph) have shown that C.difficile causes infection and diarrhea in foals. In Sweden, C.difficile can be present in a third of normal young foals (<2wks old) but not in older foals. To date, in Ontario, there are no studies longitudinally addressing the dynamics of potential pathogens in foals at the farm level over time. Fecal samples from normal foals, from foals with diarrhea, their dams and from soil of the farms will be collected biweekly (for a total of 4 times) over the first 12 weeks of the foals’ life. Samples will be tested for presence of C.difficile and C. perfringens spores, as well as for Salmonella, Rotavirus and Cryptosporidia. We will use standard laboratory culture and molecular protocols to determine the virulence characteristics of isolated pathogens.

Results from this study will allow the identification of predominant pathogenic strains and would allow proposing intervention strategies (therapeutic and prophylactic) to reduce the risk of animal infection and disease development in foals.

Cardiac Troponin in the Standardbred Racehorse

Dr. Peter Physick-Sheard, Population Medicine

Cardiovascular problems, particularly rhythm disturbances and heart muscle damage, have been suggested as a cause of a range of exercise-associated conditions in racehorses, such as post-exercise pulmonary bleeding, poor performance and sudden death. Confirming this and identifying individual animals at risk has been problematic, as most tests that screen for cardiac problems are either expensive, time consuming or both. Tests are now available, however, that can efficiently and inexpensively detect markers of heart muscle damage, and in some cases are in frequent use. The problem is that these tests were designed for human patients and little is known about their ability to consistently detect cardiac damage in horses.

This study aims to determine how well selected tests perform when exposed to markers in equine cardiac tissue. The optimum time for blood sampling after presumed damage and the effect of racing on the level of the markers in normal horses will also be explored by carefully timed sampling of Standardbred horses before and after normally scheduled racing. The ultimate goal is to develop a procedure for screening racehorses for cardiac problems that is quick, inexpensive, accurate and humane. Such a test would improve the welfare and safety of racehorses and those who handle them.

Ex-vivo Pulmonary Arterial Perfusion System to model biomechanical and hemodynamic phenomena in equine pulmonary arteries

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.