Equine herpesvirus: Of the nine equine herpesviruses (EHV), 1, 3 and 4 pose the most serious risks. Of these, EHV-3 causes a venereal disease and EHV-4 causes a respiratory disease in foals. Equine herpesvirus 1 can cause respiratory infection, neonatal infection, abortion, or neurological signs. The neurologic form of EHV-1, equine herpesvirus myeloencephalopathy (EHM), attacks the spinal cord and brain and can be fatal.
While the term “asymptomatic carrier” has been making headlines recently with regard to the SARS-CoV2 virus that causes COVID-19, the concept is actually nothing new to epidemiologists and other researchers who study a variety of diseases in humans and animals. Asymptomatic carriers play critical roles in the transmission of infectious diseases in humans, horses, and other species, but they largely go undetected, thereby hampering control efforts.
Biosecurity is something that we at the Center for Equine Health and the UC Davis veterinary hospital think about all day, every day. With horses constantly coming and going, a significant amount of time, effort, and training go into making our facilities as safe as possible for horses and humans alike.
Thanks to advanced molecular tools, researchers are now able to understand the equine genome on a deeper level than ever before. In the future, genetic data and advanced diagnostics could be used to tailor medical treatments to an individual horse’s genetics, its environment, and the interactions between the two. The goal is to be able to evaluate, for example, how a particular patient is likely to respond to one drug versus another, making it possible to target treatments for the most successful outcomes.
DNA is found in the nucleus of cells. Samples submitted for genetic testing are usually hair, blood, or tissue. Hair samples must contain the “bulb”, which looks like a tiny ball at the root of the hair. This is where the DNA is located. When submitting hair samples, make sure to pull, not cut, the hairs so the bulb is present. Blood and tissue samples require additional steps, such as an anticoagulant (for blood) or freezing (for tissues).
The first equine genetic tests became available in the 1990’s, well before the equine genome sequence was completed in 2009. Technical advances have since led to a rapid expansion in available tests. Here are a few that can be utilized to inform breeding decisions and provide diagnostic information. (For more details, please visit our Equine Health Topics. For testing information, please visit the UC Davis Veterinary Genetics Laboratory.)
Genetic diseases can cause significant emotional and financial stress for owners and breeders. The American Quarter Horse Association (AQHA) is committed to educating owners and breeders about inherited conditions so they can make informed breeding decisions. The American Quarter Horse Foundation (AQHF) provides funding for a wide range of research projects, granting more than $12 million in support of equine research to date.
When a palomino Quarter Horse colt was born in May of 1994, the Smiths chose the name Sonnys Striking Gold to mark their good fortune. Immediately smitten, Tommy Smith, then 11 years old, fell asleep in the stall with his new best friend.
Most identified equine genetic diseases have autosomal dominant or recessive modes of inheritance. “Autosomal” means that males and females are equally affected. Here, “unaffected” and “affected” represent the phenotype, or presence of the disease. “Aa”, “aa”, "BB", "Bb", and "bb" represent the genotype, or genetic combination of alleles (one from each parent) that causes the phenotype.
As an equine genetics researcher, I am particularly excited to share this special issue of the Horse Report with you. Inside, you will find a roadmap to many of the currently available equine genetic tests, including the AQHA “five-panel” test, and more.
Rosie Pony is a valued member of the CEH teaching herd. At 25 years young, her current role is to teach horse handling to veterinary students. Rosie Pony is a textbook example of a horse with EMS, as evidenced by her “cresty” neck and fat deposits on her tail head. Fortunately, once diagnosed, Rosie Pony responded very well to dietary management. Horses like Rosie Pony present unique opportunities for veterinary students and residents to learn about this endocrine disease.
Equine nutrition is complex and it is easy to become overwhelmed when choosing what to feed your horse. We collaborated with Dr. Clair Thunes of Summit Equine Nutrition to share ten things you might not know about equine nutrition.
