PAIN MANAGEMENT IN THE EQUINE ATHLETE
Britt Conklin is an equine veterinarian who is employed by Boehringer-Ingelheim (the largest equine animal health provider in the world) and owns a Sports Medicine and Podiatry practice near Amarillo, Texas. This is the third installment of his TR-- exclu
Part 3: Diagnosing the problem area—Internal Issues. By Britt Conklin, DVM
The first article in this series began the discussion of pain in the performing horse. Last month, we highlighted common sources of musculoskeletal pain causing lameness, and identified ways to diagnose where those problems occur. While soundness issues are the most common limiting factor in our equine athletes, insidious internal problems often play a compromising role, reducing the full potential of our horse’s performance. The three areas of primary internal focus are the respiratory system, the gastrointestinal system, and the endocrine system.
The capabilities and scale of the respiratory tract in a horse, though often underappreciated, is truly remarkable. The end goal for this system, in any creature, is the elimination of carbon dioxide in exchange for oxygen, which is necessary for energy production in the body’s cells. At rest, an average horse may take 12 breaths per minute, equaling 60 liters (think 30 two-liter bottles of soda) of total volume of air inhaled in that minute. In comparison, at maximal exercise, the horse may take 120 breaths per minute, and because the lungs expand, have a total volume of 1,800 liters of air inhaled—the equivalent to six normal-sized bathtubs of air exchanged each minute your horse is running at full speed.
While our roping horses don’t run for multiple minutes, any compromise to the demand of the system can affect the overall performance of your horse. Disease and inflammation significantly reduce the exchange of air and, therefore, compromise energy to the cells of the body, especially large oxygen-utilizing cells, like muscle. Viruses like influenza, herpes, or rhinitis can damage lung tissue, and bacteria like streptococcus can compromise lung function by thickening mucous and producing exudate that clogs the airway. Allergens, for some horses, can cause asthma-like symptoms and are categorized by veterinarians based on their severity: inflammatory airway disease (IAD), or recurrent airway obstruction (RAO). Long-term inflammation may not cause your horse to gasp for air like the human asthmatic, but may cause your horse to cough when warming up, or fatigue at the end of multiple runs, and seemingly have the inability to “catch their air,” as if they are out of shape.
To diagnose respiratory problems, veterinarians often sample or look at different parts of the airway for laboratory evaluation. Endoscopy, or “scoping,” involves putting a camera down the horse’s nose to visualize the anatomy of the upper airway, and can be used to differentiate potential mechanical problems in breathing from abnormal structures. Vets may also culture parts of the airway, looking for viruses, bacteria, or fungus. A transtracheal wash is a technique that allows sterile access to the lung for culture, while a bronchoalveolar lavage, or “lung-wash,” collects fluid from the lung to look for diseases like IAD and RAO.
The gastrointestinal tract (GI) can also be an under recognized source of pain. The most common issue is gastric ulceration. Multiple studies show that two-thirds of all non-racing performance horses have ulcers, and racehorses, in particular, have up to a 90-percent prevalence rate. One reason for this high incidence is that the horse’s stomach is prone to ulceration because sensitive cells from the esophagus extend down into the stomach and are easily “burned” by stomach acid. Additionally, our feeding and management practices compound the problem. Horses were designed to graze small amounts of grasses, forages, and legumes continuously throughout the day, while moving, which keeps their stomachs full and buffered, limiting the splashing of acid onto those sensitive cells. In general, though, horses are fed twice a day, leaving large gaps of time for the stomach to be
empty and exposed to acid, which, unlike in people, horses produce continuously. Additionally, grain diets tend to evoke a strong acid response and are digested quickly, once again leaving the stomach vulnerable over time to acid irritation.
Diagnosing ulcers is done by gastroscopy, or “scoping,” the stomach. Veterinarians will look for compromised tissues that range from focal minor irritation to diffuse full thickness erosions, which can occur in multiple areas of the stomach. They are very similar to blisters or burns on your skin, and can manifest in horses in many ways. Horses can be “cinchy,” have box issues, back soreness, bucking fits, weight loss, or appear to be poor-doing. Like respiratory disease, accurately diagnosing and treating ulcers appropriately can have a significant impact on your horse’s health and performance.
Another area of internal focus that we may not realize is inhibiting our horses is the endocrine system. This system reg- ulates almost every activity in the body. That regulation is managed by hormones. In addition to being reproductive molecules, hormones are molecules that tell the body to do many different essential functions. When hormones are disrupted or diseased, the result can be detrimental.
For example, insulin is a hormone that regulates sugar in the body. If this hormone is missing in a person, that person becomes diabetic. Diabetics deal with an enhanced risk of many detrimental issues, from heart disease to diabetic neuropathy, all because one hormone is in short supply. In horses, the most common endocrine disease is Pituitary Pars Intermedia Dysfunction, or PPID. It is often referred to as Cushing’s disease and originates from a problem in the horse’s brain. This abnormality causes a host of hormones to be disrupted.
The incidence for PPID in horses is high and increases with age. About 20–25 percent of horses over the age of 15 have some form of PPID. Some early issues we see in horses with the disease are increased rates of infections (skin, dental, feet), abnormal sweating, increased tendon or ligament injuries, mild retention of hair coat in the spring and summer, infertility, and laminitis. To diagnose the issue, veterinarians may draw blood for a screening sample, or they may give a drug to stimulate the pituitary gland and then sample the blood for analysis. Early diagnosis is key in preventing some of the more life-threatening issues that can occur with endocrine diseases.
Thinking about all the issues that can affect our performing horse can be overwhelming. Mostly, our concerns revolve around the mobility of our athlete, but careful consideration should be given to internal issues that may impact the peak performance of our equine partners. Next month, I will discuss the treatments that are available for many of the problems we have been learning about.