EHRF Research Grants, 2012-13

Can an antihistamine prevent morphine’s side effects?
Drs. T. Duke, J. Bracamonte, J. and J. Carmalt

Although morphine infusions are becoming the standard, pain-relieving analgesic for horses undergoing invasive surgery, the drug frequently causes negative side effects, particularly low blood pressure (hypotension).

Because these problems may result from morphine triggering a histamine release, researchers want to investigate the effectiveness of giving equine patients an antihistamine drug called dephenhydramine before surgery.

In this study, researchers will divide 45 client-owned or research horses into three groups. The research team will use standard procedures to anesthetize the horses and will regularly monitor several factors including arterial blood pressure. Researchers will also take baseline blood samples before administering any analgesic, but one group of horses (DM) will receive diphenhydramine before the initial sample.

The control group (B) will receive butorphanol, an analgesic drug that doesn’t trigger histamine release. Groups M (morphine only) and DM will receive morphine infusions, with group DM receiving diphenhydramine 15 minutes before the infusion is started. Researchers will compare the histamine concentrations of baseline blood samples as well as eight more samples taken at regular intervals for four hours after the analgesic is given.

Using the monitoring data and blood sample results, researchers will confirm whether morphine infusions cause histamine release leading to low blood pressure. They will also determine if an antihistamine dose before surgery can prevent this negative side effect.

Can targeted gene therapy treat night vision in CSNB-affected mice and Appaloosa horses?
Drs. B. Grahn, V. Misra, L. Sandmeyer, B. Bauer and N. Denk

Researchers have established that a defect in the TRPM1 gene is linked to congenital stationary night blindness (CSNB) in Appaloosa horses. In previous studies, scientists have successfully treated inherited retinal conditions through gene therapy that uses a viral vector for transferring genetic material. This four-part study will evaluate the effectiveness and safety of using gene therapy to restore the gene affecting night vision in mice and horses with CSNB.

In part one, researchers will confirm that TRPM1 can 
be transduced (genetic material can be transferred) by introducing tissue culture cells containing TRPM1 to retinal explants of wild mice and genetically-engineered mice as well as horses.

The second part, a comparative study, will use 30 wild mice to evaluate the effectiveness of transducing TRPM1 using a viral vector administered through intravitreal injections. The third part will repeat the TRPM1 transduction using 30 genetically-engineered mice.

In the fourth part, the scientists will use the same viral vector to transduce TRPM1 into 10 night-blind Appaloosa horses. The team will evaluate the results by comparing pre- and post-treatment electroretinography (ERG) and scotopic (low light) maze testing. The study results could confirm gene therapy as a permanent solution for restoring deficient night vision in affected horses.

What causes reactivation of latent EHV-1?
Drs. K. Lohmann, V. Misra and A. Di Marzo

Equine herpesvirus type 1 (EHV-1) is a worldwide threat to equine health that causes a potentially fatal neurologic disorder, equine herpesvirus myeloencephalopathy (EHM). When latently infected horses, the main reservoir of EHV-1, experience virus reactivation, they shed the virus and infect other horses.

Previous investigations have indicated that a cellular stress response, unfolded protein response (UPR), is linked to the latency and reactivation of the human herpes simplex virus (HSV). This study will investigate whether the UPR also influences EHV-1 latency and reactivation in horses.

Using blood samples from at least six latently infected horses, investigators will study the sensitivity of a genetic analysis technique, polymerase chain reaction (PCR), for detecting latent EHV-1 and will establish protocols for differentiating latent and active virus infection. Once a modified PCR (RT-PCR) has been successfully developed for analyzing UPR genes in equine cells, the researchers will establish protocols for UPR activation by inducing and then measuring UPR expression in blood samples collected from six healthy horses. Finally they will induce UPR in latently infected blood samples in order to detect and observe EHV-1 activation using PCR and RT-PCR.

This novel approach to understanding the mechanisms leading to EHV-1 reactivation may ultimately open new avenues to treatment and control of EHV-1 related disease.

What’s the prevalence of tick-borne diseases?
Drs. K. Lohmann, G. Schvartz, H. Burgess, T. Epp, N. Chilton and D. Pearl

Although tick-borne granulocytic anaplasmosis and Lyme disease are becoming more common in Canada, the current risk of exposure is poorly understood.

This one-year pilot study will provide valuable information for horse owners and veterinarians by estimating the prevalence of tick-borne diseases in Saskatchewan, Manitoba and Ontario. The researchers will also evaluate the accuracy of a portable screening test (SNAP ELISA) for determining disease exposure, and they will study the prevalence of blacklegged ticks in Saskatchewan.

Using archived serum and whole blood samples collected in the three provincial laboratories during high-risk months (October to December), investigators will use the SNAP ELISA to test 100 samples per province for antibodies against Anaplasma phagocytophilum and Borrelia burgdorferi (causative agent of Lyme disease).

All positive samples will then be re-evaluated using laboratory-based tests: IFA (immunofluorescent assay), Western Blot and PCR (polymerase chain reaction). Twenty-five per cent of the samples testing negative will be retested using the IFA. In addition, the researchers will solicit tick samples from Saskatchewan horse owners and veterinarians and will use PCR to test any blacklegged ticks for A. phagocytophilum and B. burgdorferi.

This study will provide a baseline for future research and will be particularly significant as climate change continues to affect tick populations throughout Canada.

Does the facial venous sinus work for blood samples?
Drs. F. Marqués, I. Roquet, H. Sparks and T. Epp

Horses suffering from gastrointestinal disease often require continuous blood work monitoring. But intravenous catheterization and repeated catheterization increase their risk of developing jugular vein thrombophlebitis. Since the transverse facial venous sinus has been reported as an alternative site that would spare the jugular veins, this study will verify the accuracy of blood samples taken from this site.

After securing horse owners’ permission, researchers will analyze and compare blood samples from 25 horses admitted to the WCVM for gastrointestinal disease to 25 healthy animals admitted for elective procedures not attributed to the gastrointestinal tract.

Before treating the animals with gastrointestinal disease, the scientists will collect paired blood samples from the transverse facial venous sinus and the jugular vein and will follow a standardized procedure for submitting and analyzing packed cell volume (PCV), total solids (TS), venous blood gas (VBG) analysis and complete blood count (CBC). This procedure will be repeated for a healthy horse admitted on the same day.

After 24 hours, paired samples from both animals will again be taken and analyzed. Researchers will then perform statistical analysis to determine whether the facial venous sinus is a consistent, safe sampling site for horses that are at an increased risk of developing jugular vein thrombo-phlebitis.

Do papillomaviruses have a role in equine skin tumours?
Drs. B. Wobeser and C. Duncan

Equine skin tumours, which are relatively common in western North America, are often costly to treat and can be disfiguring, invasive and potentially fatal.

However, little is known about their causes or how they develop. Papillomaviruses have been associated with the development of cancer in several species, and their relationship to equine skin tumours needs to be investigated.

Researchers will randomly select 750 samples from an existing data base of surgical biopsies identified as equine cutaneous squamous cell carcinomas (SCC), SCC in situ, squamous papillomas and soft tissue sarcomas. Using polymerase chain reaction (PCR), they will analyze the samples as well as 100 non-malignant skin biopsies (control group) to determine the presence of papillomaviruses.

Any positive samples will receive additional testing (nucleotide sequencing) to determine their specific papillomavirus type, and scientists will correlate that information with their geographic locations to determine any geographic variation in the types.

Study results will be significant to further research aimed at developing a vaccine and tailoring vaccination strategies to specific regions. The findings can also be used to identify risk factors for papillomaviruses – vital information that veterinarians can share with their clients while developing procedures for prevention, diagnosis and therapy.

Download a research journal article that reports on the results of this study.