Medicine

Validation of a New Stall-side Test for Serum Amyloid A in Horses (15-31)

Investigators:

Diana Schwartz, DVM (Resident)
Nicola Pusterla, DVM, Ph.D., DACVIM (Mentor)
Mary Christopher, DVM, Ph.D. (Mentor)

Serum amyloid A (SAA) is an acute phase protein that has been used in equine practice to assess and monitor horses for inflammation. Validation of a stall-side SAA test in horses provides an opportunity for equine practitioners to rapidly and accurately identify abnormalities in SAA concentrations that can facilitate disease diagnosis, evaluate response to therapy, and assess overall prognosis in horses with a variety of inflammatory diseases.

Benefits:

Based on the results of this study, the stall-side SAA test should be accurate for use by veterinarians to detect inflammation in horses, but with less precision at high concentrations, if performing serial measurements between batches. Interpretation of SAA results obtained using this stall-side test and other SAA laboratory tests should be undertaken with acknowledgment of differences in results between methods and between test kit batches.



Levels of a Heart Muscle Damage Marker (Cardiac Troponin) in Healthy Neonatal Thoroughbred Foals and Thoroughbred Foals with Rib Fractures (14-11)

Investigators:

Rana Bozorgmanesh, B.Sc., BVetMed, DACVIM, MRCVS, (Resident)
Gary Magdesian, DVM, DACVIM, DACVECC, DACVCP (Mentor)
Nathan M. Slovis DVM, DACVIM, CHT (Collaborator)
Jeanne Bowers-Lepore, DVM (Collaborator)

Rib fractures sustained during birth are not uncommon injuries in neonatal foals. In some foals, they can have severe effects including death from heart or lung damage. Prompt identification and assessment of rib fractures are necessary to determine if surgical management is warranted. Thoracic ultrasound is most commonly used to identify fractured ribs, but requires expertise and is time-consuming. Therefore, a quick and cost-effective method of identification of potentially fatal rib fractures would be a valuable clinical aid for the equine veterinarian.

Benefits:

In this study, cardiac troponin was determined to not be a specific indicator of rib fractures. This may be due to a low rate of direct damage to the heart muscle in foals in this study and the mortality rate for foals with rib fractures was lower than previously reported. Potential reasons for the low mortality include increased awareness, earlier identification, or improved management of rib fractures.

Temporal Variability in Serum Glucose and Insulin Concentrations in Neonatal Foals (14-13)

Investigators:

Emily Berryhill, DVM, DACVIM (Resident)
Gary Magdesian, DVM, DACVIM, DACVECC, DACVCP (Mentor)
Judy Edman, B.S. (Staff Research Associate)

Insulin dynamics are associated with metabolic diseases such as Equine Metabolic Syndrome and insulin resistance. It is well established that serum glucose and insulin concentrations in adult horses and foals are affected by many variables, including feed intake, stress, and metabolic phenotype. However, there are no studies that serially measure insulin and glucose concentrations in healthy foals of differing ages to establish normal daily variability, how insulin and glucose are associated with other metabolic parameters (i.e. serum triglycerides), and how they change with age. The researchers in this study hypothesized that newborn foals have highly variable serum glucose and insulin concentrations compared to adult horses.

Benefits:

The study confirmed the hypothesis that serum glucose and insulin concentrations in neonatal foals of different ages can have a high degree of variation when measured serially over several hours. For instance, the maximum serum insulin concentration over a 16-hour sampling period was almost double that of the lowest insulin concentration for individual foals at all ages analyzed.

Documenting and understanding insulin and glucose dynamics in healthy foals is imperative to understanding metabolic changes that occur with critical illness, including insulin resistance secondary to neonatal infection, and may influence treatment of sick foals.

Jaw Joint Arthritis in Horses: Comparison of Advanced Imaging with Gross and Microscopic Findings (15-35)

Investigators:

Jacqueline Tanner, DVM, MS, DACVR (Resident)
Derek Cissell, VMD, PhD, DACVR (Mentor)
Boaz Arzi, DVM, DAVDC, DEVDC (Mentor)

Temporomandibular joint (i.e., jaw joint or TMJ) arthritis in the horse is poorly understood and difficult to diagnose using conventional imaging techniques such as radiographs. Interest in advanced imaging to evaluate the TMJ has been growing; although up to 25% of horses are suspected to have evidence of TMJ arthritis on advanced imaging exams, very little has been published regarding the significance of these findings. Furthermore, there are no descriptions of abnormal advanced imaging findings in the TMJ and their relationship to TMJ arthritis.

Advanced imaging through computed tomography (CT), gross examination, and microscopic examination of the jaw joints of 18 deceased adult horses of varying ages were performed. CT images were scored for evidence of arthritis. These scores were compared to gross and microscopic evaluation of the jaw joints to confirm the presence of arthritis.

Benefits:

Advanced imaging through CT showed abnormalities that correlated strongly with evidence of arthritis in the postmortem examinations of adult horses of varying ages. Jaw joint arthritis has been proposed as a cause of reduced performance and behavior problems in horses. This study establishes advanced imaging findings through CT associated with jaw joint arthritis, providing a foundation for predicting clinically significant jaw joint arthritis. This will help identify patients that may benefit from treatment of the jaw joint to restore or improve performance.

Characterizing Equine Odontoclastic Tooth Resorption and Hypercementosis (EOTRH) Lesions through Radiographic and Histological Methods. (15-29)

Investigators:

Amanda L. Johnson, DVM, MPH (Resident)
Travis J, Henry, DVM (Mentor)
Brian G. Murphy, DVM, Ph.D., DACVP (Mentor)
Verena K. Affolter, DVM, Ph.D., DECVP (Mentor)

Equine odontoclastic tooth resorption and hypercementosis (EOTRH) is a commonly recognized, but poorly characterized disease in middle-aged and older horses. The underlying cause remains elusive, and at present, the only therapeutic option is surgical extraction of affected teeth. Loss of incisor teeth can have a negative impact on athletic performance as well as the ability to grasp food material. The goal of this study was to identify microscopic changes in teeth and paradental tissues characteristic of EOTRH that relate to specific radiographic changes. An improved understanding of the pathogenesis of EOTRH may aid in the development of future treatments.

The study evaluated tissues and radiographic evidence of equine odontoclastic tooth resorption and hypercementosis as well as the affected tooth, adjacent teeth and surrounding bone and soft tissue structures.

Benefits:

The data collected demonstrated the histopathologic features of EOTRH and information was gained in how to process tissues to avoid loss of cellular detail.  To avoid loss of cellular detail associated with decalcification of tissue, future studies should focus on acrylic embedding of tissues, which allows processing and staining of hard tissues without decalcification. This study additionally provided preliminary data for a larger scale project on EOTRH. A greater understanding of the underlying mechanisms of EOTRH could provide the ability to sustain a full complement of incisor teeth in the older horse, and may provide a path forward to novel treatment strategies.

Comparison of Duration of Target Intra-Articular Concentrations Following Intravenous Regional Limb Perfusion with Two Doses of Amikacin Sulfate in Horses (14-10)

Investigators:

Alison Harvey, BVSc, MRCVS
Isabelle Kilcoyne, MVB DACVS
Barbara A. Byrne, DVM, Ph.D., DACVIM, DACVM
Jorge Nieto, MVZ, Ph.D., DACVS, DACVSMR

Traumatic wounds in the limbs of horses are common and frequently involve synovial (joint) structures that can affect the life and athletic career of the horse. Intravenous regional limb perfusion (IVRLP) with antibiotics is a simple procedure, which allows effective levels of antibiotics to be administered locally with minimal systemic effects.

To date, there is limited information available on the duration of targeted antibiotic concentrations within joints following IVRLP with amikacin, and how this is affected by the dose used. Determining the length of time that antibiotic concentrations remain above adequate protective levels based on hospital-established minimum inhibitory concentrations (MICs) would guide clinical decisions on the appropriate dosage and frequency of treatment for horses with synovial sepsis, and potentially reducing the frequency of treatment and incidence of unwanted side effects. Study results showed that a 2-gram dose of amikacin, administered through IVRLP, is likely appropriate for most injuries. A 3-gram dose is feasible but may not be justified in the majority of distal limb injuries and should be reserved for cases where culture and sensitivity of the bacterial infections reveals MICs above those achievable with a routine dose range

Benefits:

The study results will guide veterinary decisions on use of the antibiotic amikacin for treatment of wound infections in joints and reduce the use of more antibiotic than is productive. For most infectious conditions, a daily IVRLP 2 gram dose will be sufficient. There were no adverse effects noted using either dose.

Evaluation of 10 Minute vs. 30 Minute Tourniquet Time for Intravenous Regional Limb Perfusion (IVRLP) with Amikacin Sulfate in Standing Sedated Horses (13-16)

Investigators:

Isabelle Kilcoyne, MVB, DACVS
Julie E. Dechant, DVM, M.S., DACVS, DACVECC
Jorge E. Nieto, MVZ, Ph.D., DACVS, DACVSMR

To address traumatic wounds in the limbs of horses involving synovial structures in a joint, veterinarians often administer 2 grams of amikacin in 60 mL of 0.9% Saline, which allows effective levels of antibiotics to be administered locally with minimal systemic effects. Tourniquets have been used on the distal limb of horses undergoing surgery to maintain a bloodless surgical field for up to 1-2 hours with minimal adverse effects being reported. When performing IVRLP to deliver antibiotics locally, tourniquet times of up to 25-30 minutes have been reported in previous studies. Use of a shorter tourniquet time could greatly reduce the discomfort experienced by the horse and the level of sedation required to perform the procedure in the standing animal.

Benefits:

The study showed that there was no significant difference between the synovial amikacin concentrations noted between 10 minute and 30 minute IVRLP. Based on these results, 10 minute tourniquet time may be sufficient to achieve peak synovial amikacin concentrations when performing IVRLP.

To further investigate the actual time required to reach peak synovial concentrations of antibiotics during intravenous regional limb perfusion the group performed a second study in which samples of joint fluid were taken every five minutes after the IVRLP was performed. This study demonstrated the time to reach peak concentrations within the joint was 15 minutes, thereby only necessitating tourniquet application for 15 minutes.

This study was reported in Veterinary Record.