2020-2021 Projects

(EG2021-01) Investigation of Clostridium innocuum in horses with diarrhea
Dr. Luis G. Arroyo | Associate Professor | Lic. Med. Vet., DVSc, PhD, DACVIM

Typhlocolitis in horses is, by definition, inflammation of the cecum and colon, and diarrhea is the hallmark clinical sign of this intestinal disorder. Despite comprehensive microbiological investigative efforts to determine the cause of colitis, an etiological agent cannot be established for a large proportion (>60%) of these cases.

A recent study reported Clostridium innocuum as a potential causative agent of antibiotic associated (AAD) diarrhea in human patients. Clinically, in people it is characterized by diarrhea or severe colitis, including the most severe pseudomembranous colitis form. C. innocuum has been also associated with recurrent diarrhea in patients with prior C. difficile infection, and other forms of severe disease including bacteremia, endocarditis, and abscesses.

The isolation of C. innocuum from stool samples of human patients with suspected C. difficile infection led to the hypothesis that this organism may play a similar role as C. difficile in causing antibiotic associated diarrhea.

Therefore, the aim of this study to investigate whether C. innocuum is present in fecal or intestinal contents of horse with colitis.

(EG2021-08) Identification of putative exercise-induced pulmonary hemorrhage causing variants in Ontario’s Thoroughbred racehorses
Janet Beeler-Marfisi | Assistant Professor | BA, DVM, DVSc, Dipl. ACVP

Exercise-induced pulmonary hemorrhage (EIPH) is a common disease affecting up to 80% of training and racing Thoroughbreds (TBs). EIPH refers to bleeding within the lung during exercise and is diagnosed by visualizing blood in the trachea by endoscopic examination after work. The disease is caused by stress failure of the lung’s capillaries during intense exercise from increased capillary pressures in what should otherwise be a low-pressure organ. Additionally, for unknown reasons, severely affected horses can suffer fatal bleeding into the lungs during high-intensity work.

In 2001, the Alcohol and Gaming Commission of Ontario, developed the Equine Incidences in Ontario Racing program, and mandated that any horse dying during or within 60 days of a race must undergo postmortem examination. From 2003-2015, pulmonary hemorrhage and EIPH were determined as the cause of death in 76% of all sudden death cases, representing 37% of all sudden deaths in TB racehorses.

Therefore, the disease is important to the racing industry not only as a cause of poor performance but also for its negative impact on the health and welfare of the horse, and the distress it causes to the general public and the people involved with the affected animal. Genetics were shown to have a moderate to high role in determining whether a TB will develop EIPH. As such, there may be genetic markers, or variants, within the TB genome that are associated with the development of EIPH. These variants could be used to identify horses at high risk of developing EIPH or fatal EIPH; however, these variants have yet to be discovered. In this study, we will identify genetic markers of EIPH using whole-genome sequencing of DNA from TBs with fatal EIPH.

Our long-term goal is to identify and verify these EIPH-causing variants, with the aim of developing a genetic test, which could be used to inform breeding and training decisions in genetically predisposed TBs.

(EG2021-09) Microbiota of Surviving and Non-surviving Horses with Acute Diarrhea
Diego Gomez | Assistant Professor | DVM. MSc. MVSc. PhD. Dip. ACVIM

Acute diarrhea is a major cause of morbidity and mortality in horses worldwide. In Ontario, the mortality rate of diarrheic horses hospitalized at the Ontario Veterinary College is 35% (n = 75/216) from which Thoroughbred and Standardbred breeds represented approximately 50% of the cases.

Several pathogens are associated with acute diarrhea in horses, however the final cause of the diarrhea is commonly not identified. Some studies showed that the bacterial communities of the gut are distorted in horses with diarrhea, those studies included a small number of cases, and therefore the impact of gut bacteria changes on clinical outcomes such as mortality and the key bacteria associated with a healthy gut or diarrhea remains generally unidentified. Therefore, larger clinical studies using newly developed statistical methods are needed to address these knowledge gaps, and better understand the bacterial changes that occur during diarrhea in horses. This study aims to investigate the differences in the gut bacterial communities between healthy and horses with acute diarrhea. Additionally, this study will examine the gut bacterial communities of surviving and non-surviving diarrheic horses.

We hypothesize that the gut bacterial communities are significantly different in horses with colitis compared to healthy control horses, and that the gut bacterial communities are particularly distinct in diarrheic non-surviving horses. Elucidating the importance of the gut microbiota in the development of diarrhea and subsequent mortality of horses have clinical implications

(EG2021-10) Hypotonic versus isotonic maintenance fluids in critically ill foals
Diego Gomez | Assistant Professor | DVM. MSc. MVSc. PhD. Dip. ACVIM

Critically ill foals often receive maintenance intravenous fluids (IVFs) to correct and maintain normal hydration once the initial fluid resuscitation therapy has finished. Historically, administration of low-sodium (hypotonic) fluids as opposed to fluids with sodium concentration similar to those in the blood (isotonic fluids) was recommended.

This practice was extrapolated from guidelines developed for healthy children in 1950s. However, this recommendation has recently been questioned in human medicine because some children can develop life-threating low blood sodium levels. Thus, the use of isotonic fluids has increased for maintenance of hydration in ill children while the use of hypotonic fluids declined.

Despite this, the current veterinary literature continues recommending hypotonic solution for maintenance IVFs in sick foals. This approach can be adequate in some cases because anecdotal reports suggest that administration of isotonic fluids to foals could lead to complications such as high levels of sodium in blood, fluid accumulation in the body, and increased blood pressure. However, these recommendations lack of evidence-based support.

The objective of this study is to compare the effect of isotonic versus hypotonic maintenance fluid therapy on blood sodium concentrations, cardiovascular variables, sodium-regulating hormones, and urine production in critically ill foals. Results of this study are expected to provide data to support evidence-based protocols and the development of guidelines for fluid therapy in critically ill foals.

(EG2021-11) Endothelial glycocalyx degradation in critically ill foals
Diego Gomez | Assistant Professor | DVM. MSc. MVSc. PhD. Dip. ACVIM

The endothelial glycocalyx (EG) is a thin gel-like layer covering the internal surface of blood vessels that regulates the transport of fluids, proteins oxygen and nutrients to the tissues. The EG also provides anticoagulant effects and protects the blood vessels from toxic insults.

Damage to the EG occurs when the blood supply to the tissue is compromised, in inflammation, and in patients with localized or blood-borne infections. In human medicine, there is increasing evidence that administration of large volume of fluids during resuscitation of critically ill patients damage the EG, even more than the disease itself. Increased blood levels of markers associated with EG damage are also associated with increased risk of death.

Administration of resuscitation intravenous fluid is one of the most important interventions in the management of critically ill foals presented to referring hospitals. However, no information is available regarding the blood levels of markers associated with EG damage in critically ill foals, their association with mortality and the impact of resuscitation fluid on the EG degradation.

Therefore, the objective of this study is to determine the blood levels of EG damage markers in critically ill foals, before and after fluid resuscitation to determine whether this practice can worsen the integrity of the blood vessels. We hypothesise that the blood levels EG degradation markers will be associated with disease severity, degree of inflammation, as well as volume and speed of intravenous fluids administered during early resuscitation.

(EG2021-12) Assessment of safety of encapsulated MSC and pooled MSC in fetlock joints Mesench
Thomas G. Koch | Associate Professor | DVM Copenhagen, PhD Guelph

Mesenchymal Stromal Cells (MSC) has been shown to alleviate pain in mild to moderate osteoarthritis (OA) of the fetlock joint. To date, these cells have been from single donor animals which makes the therapeutic response less standardized. Furthermore, the injected cells are often removed from the joint quickly, which likely limits their efficacy. We hypothesize that injection of pooled MSCs from multiple donors within a hydrogel formulation into normal fetlock joints is safe and comparable to injection of non-encapsulated single donor MSCs.

Our objectives are:

1) To compare and contrast the safety of single donor MSCs and pooled MSCs in normal fetlock joints;
  • 2) To compare and contrast the safety of encapsulated MSCs and non-encapsulated MSCs in normal fetlock joints.
  • These feasibility studies will be conducted in research horses, and the horses will be returned to the research herd upon completion of the study. Through our industry partner, we have access to a novel way to inject MSCs into joints and trap them there by first mixing them with a gelatin that hardens into microspheres small enough to go through a needle. The product is analogous to a slow-release capsule for medication but developed for cells.

    We expect that the tested cell formulation will not trigger significant adverse reactions following multiple injections. These results will set the stage for testing in horses with lameness due to fetlock OA.

    (EG2021-13) Assessment of safety and potential of antisense miRNA-181 to treat fetlock OA
    Thomas G. Koch | Associate Professor | DVM Copenhagen, PhD Guelph

    Osteoarthritis (OA) of the fetlock joint is a major equine welfare problem across breeds and disciplines leading to loss of training days, pre-mature retirement, or reduced performance. No therapies exist that delay progression of fetlock OA. MicroRNAs are small molecules that control gene expression; increased microRNA levels reduce expression of selected proteins. MicroRNA number 181 has been shown to be overexpressed in human facet joint OA. Injection of microRNA 181 into lab animal joints resulted in joint disease suggesting a critical role of microRNA 181 in joint health. Moreover, injection of antisense miR-181, which binds to and inactivates the effect of microRNA 181 in mice and rat models of joint disease, prevented the expected joint damage. This suggests that antisense miR-181 may be a useful therapy to treat OA.

    We hypothesize that injection of antisense miR-181 into equine fetlock joints is safe and associated with reduced joint inflammation and pain. Our objectives are: 1) To determine the safety of antisensemiR-181 in normal equine fetlock joints 2) To determine the safety, anti-inflammatory properties and analgesic effects of antisense-miR-181 in fetlock joints with documented OA and pain. 3) To determine if antisense miR-181 injected into the fetlock joint is detectable in the bloodstream.

    We expect that multiple injections of antisense miR-181 will not be associated with significant adverse reactions in normal or OA fetlock joints. We expect that multiple injections of antisense miR-181 will lead to a reduction of miR-181 concentrations within the fetlock joint, reduced lameness, and reduced joint inflammation.

    (EG2021-14) Cone beam CT technique development to image the standing horse cervical spine
    Judith Koenig | Associate Professor | Mag Med vet, Dr Med Vet, DVSc, DACVS, DACVSMR

    Using computed tomography (CT) to diagnose diseases of vertebra and associated structures of the neck in people and other species is common. In horses we rely largely on radiographs to diagnose diseases of the neck.

    In a recently published study we showed that diagnosing osteoarthritis in neck joints on radiographs is not reliable and not repeatable. Misdiagnosis of compressive lesions with survey radiography alone occurs in 61% of cases compared with necropsy. CT evaluation of the neck in horses enables more accurate identification of bone and soft tissue lesions than traditional laterolateral radiography. Currently, to perform CT general anesthesia is required and complete cervical vertebral column examination has been limited by horse size and CT scanner gantry size. Development of a standing CT technique will avoid the expense and risk of general anesthesia and the cone beam CT is better able to image the caudal cervical spine. Development of this technique may also allow for CT myelography of the standing horse as the soft tissue differentiation with cone beam CT is limited, but excellent for bone.

    We hypothesize that cone beam CT will allow evaluation of the cervical spine in standing horses that is comparable to that of a standard helical CT scanner for bones, and the procedure can be safely performed with reproducible results, and will identify boney abnormalities in clinical horses that are not fully characterized or seen with radiographs.

    (EG2021-17) Molecular epidemiology of Streptococcus equi subsp equi in Ontario horses
    Scott Weese | Professor | DVM, DVSc Guelph; Dipl ACVIM

    Streptococcus equi is the cause of ‘strangles’, an important and highly contagious equine disease. In addition to the impact on individual horses, identification of S. equi in a horse may lead to voluntary quarantine of entire facilities or restriction of horses from affected facilities from competition. The costs of disruptions in training and competition can be substantial, as can the healthcare costs for affected horses and testing costs required for disease control.

    Despite its importance in Ontario, little is known about the epidemiology of disease, such as reservoirs and transmission patterns. Molecular typing involves evaluation of part of the bacterium’s gene sequence (in this case, the SeM gene) to identify different strains, and is a key component of studying disease spread. However, there has been limited typing performed internationally, and none reported in Canada.

    Development of a typing database will facilitate future research and infection control efforts. As a database of strains grows, more refined information about the role of different strains in disease and spread, and better understanding of how this bacterium circulates in the horse population will be obtained. The objectives are to molecularly characterize S. equi from horses in Ontario, from sporadic disease and outbreaks, and to develop an Ontario S. equi typing database for future study and surveillance.

    For this study, S. equi will be isolated from horses in Ontario through collaboration with the Animal Health Laboratory, OMAFRA and the Ontario Racing Commission. Information about the clinical disease, herd-level disease, transmission on farm and presumed source will be collected. Isolates will be typed by sequence analysis of the SeM gene.

    Strangles is an important equine disease and can be severely disruptive to farms or facilities. Greater understanding of the transmission of this bacterium will be useful for infection prevention and control, on facilities and more broadly.