TEHRF research grants: 2021-22

The Townsend Equine Health Research Fund (TEHRF) has allocated over $82,000 to support three equine health research projects at the Western College of Veterinary Medicine (WCVM). Read the summaries below for more details on each study.

How can we use ACE inhibitors to better manage heart failure in horses?
Drs. Tiago Afonso and Nicole van der Vossen, WCVM

Congestive heart failure is a serious condition in horses that can cause the animal to deteriorate quickly and may lead to euthanasia or death. Treatment options are limited because of the lack of research in this area of equine health, which has compelled veterinarians to directly apply data from studies on dogs and people to their equine cases.

Angiotensin-converting enzyme (ACE) inhibitors are a well-recognized method of treatment for heart failure in dogs and humans. These drugs have helped to extend survival time in both species and improve overall quality of life. Based on recent reports, one particular ACE inhibitor called benazepril has also been effective for managing congestive heart failure in horses. However, while effective, benazepril is expensive for horse owners who reside outside of the United States. Ramipril, another ACE inhibitor, is more affordable but requires further testing to confirm its efficacy in treating cases of equine congestive heart failure.

In this pilot study, WCVM will compare the two ACE inhibitors and their effects to inhibit serum ACE activity in a group of horses. The team will administer benazepril, ramipril (in higher doses than in previous studies) and a placebo to six healthy horses in a randomized order and then compare the drugs’ efficacy by evaluating blood and urine samples from the horses. Results of this study may help to identify a more affordable option for treating congestive heart failure in horses.

What roles do certain hormones play in a mare’s pregnancy recognition?
Dr. Claire Card, WCVM; and Dr. Mariana Diel de Amorim, Cornell University College of Veterinary Medicine

The events associated with maternal recognition of pregnancy (MRP) in mares are still unknown. In this study, the WCVM scientists will focus on two hormones – prostaglandin F2 alpha (PGF) and prostaglandin E (PGE) – and their role in pregnancy recognition. Previous studies have shown that pulsatile PGF secretion causes the demise of the corpus luteum (endocrine tissue that secretes progesterone necessary for pregnancy maintenance) in the absence of a pregnancy and a return to a state of heat. PGE supports the production of the hormone progesterone during the luteal phase, which either ends in pregnancy or the return to heat. The pattern of PGE secretion is unknown during the critical window of pregnancy recognition.

The WCVM research team will study six mares over two cycles – both pregnant and non-pregnant – and evaluate whether PGE is secreted in the uterus in a similar pulsatile manner to PGF. The research team will also compare levels of PGF, PGE and progesterone hormone levels of the mares at the times of pregnancy recognition and luteolysis (the demise of the endocrine tissue in the absence of pregnancy).

Mares in the pregnant cycle will be bred. Researchers will use ultrasonography to observe the mares for signs of ovulation and to look for signs of pregnancy. The WCVM team will take hourly blood samples for 72 hours to monitor PGF, PGE and progesterone levels during the critical window of pregnancy recognition.

Results of this study will contribute valuable information to the knowledge gap about early pregnancy recognition. They will also contribute to future therapies aimed at supporting early pregnancy and decreasing pregnancy loss rates in mares.

How can we better diagnose intestinal parasites in horses and which ones are becoming resistant?
Drs. Emily Jenkins and Chris Clark, and Toni-Anne Saworski, WCVM; Dr. Phil McLoughlin, USask College of Arts and Science; Jocelyn Poissant and John Gilleard, University of Calgary Faculty of Veterinary Medicine

The current method for diagnosing intestinal parasites is to look for parasite eggs in a horse’s feces. However, the appearance of eggs only indicates the presence of intestinal parasites – not the species. Over 50 species of small strongyles (the most common intestinal roundworms) and three species of large strongyles lay eggs that are virtually identical in appearance. To identify a species is time consuming and requires hatching larvae out of the eggs and identification by a trained expert. Species identification is important because some parasites, like the “equine bloodworm,” are more likely to cause problems in horses.

Many parasites that affect horses are becoming increasingly difficult to treat as they have developed a resistance to anthelmintic (deworming) products. In this study, WCVM researchers will use DNA of parasites in fecal samples to identify parasite species shed by horses before and after treatment with deworming medication. Study results will help determine which parasites are most common in horses in western Canada, how herds differ in their “parasite profiles” and which parasite species are most resistant to commonly used treatments.

These methods will help equine veterinarians and owners make better informed choices about parasite control, which is urgently needed as resistance to many deworming products is now well established in almost all horse populations – including those in Western Canada.