Diagnosing PPID
Q: Pituitary pars intermedia dysfunction (PPID, or Cushing’s disease) develops when a part of the horse’s pituitary gland becomes enlarged and produces excessive amounts of hormones. The resulting hormonal imbalances affect organs and tissues throughout the body. Although PPID can often be identified by its typical clinical signs, which include a persistent shaggy coat and muscle wasting, a diagnosis can be made using laboratory tests and treatment initiated well before the worst of these effects develops. Three tests may be used to diagnose PPID. Which one is always considered the best choice?
a. dexamethasone suppression test b. adrenocorticotrophic hormone (ACTH) test c. thyrotropin-releasing hormone (TRH) stimulation test
d. none of the above
A: d. None of the above. Although the dexamethasone suppression test is reliable, veterinarians may hesitate to use it because it requires an injection of steroids, which may trigger laminitis in horses already showing signs of PPID. A blood test for ACTH is the simplest diagnostic measure, but the results must be interpreted carefully, because levels of this hormone can fluctuate widely in the spring and fall, leading to false positives and negatives. The TRH stimulation test is sensitive, accurate and safe; the downside is that it requires giving the horse a dose of synthetic TRH, which is currently available only in either a very expensive human grade or a nonsterile commercial grade. Veterinarians will choose the diagnostic test that best suits an individual case. (“Special Report: The Latest on PPID,” EQUUS 424)
Reading Body Language
Q: A horse expresses his emotional states with a variety of subtle changes in expression, posture and movements. If you enter a horse’s stall and notice that his nostrils flare slightly, he purses his lips and a wrinkle forms over his eye, what is he telling you?
a. “I’m hungry.” b. “I’m a little anxious.” c. “I’m happy to see you.” d. “I’m extremely upset.”
A: b. “I’m a little anxious.” These signs of tension in the muscles of the face are often the first indictors that a horse is fearful or nervous. If these subtle clues are not heeded, the horse may escalate to “louder,” more obvious signals, such as pawing, pinned ears, a rapidly swishing tail, or even a kick or lunge. Learning to read and respond to the finer points of your horse’s body language will help you to improve your horsemanship skills, both on the ground and in the saddle. (“On Behavior: How to Read Your Horse’s Body Language,” EQUUS 424)
Progress in anesthesia
Q: Years ago, the possibility of complications, ranging from respiratory or cardiac failure to muscle or nerve damage, made general anesthesia for horses a fairly risky proposition. Fortunately, scientific advances have made putting a horse under safer today than ever before. Nonetheless, horses under anesthesia are supervised very carefully. At which phase of a surgery is the horse most at risk of injury?
a. going under—when the horse is sedated, receives an intravenous anesthetic and helped to go down in a padded stall b. moving into position—when the horse is hoisted, typically via a hydraulic lift with chains attached to his legs, and placed on the surgical table on his back or side c. during the surgery—when an anesthesiologist continuously monitors the horse’s vital signs, reflexes, eye positions and movements and constantly adjusts the amount of anesthetic gas he receives—just enough to keep him unconscious but not so much as to lead to cardiac or respiratory collapse d. while recovering—when after the procedure the horse is transferred to a padded recovery stall and allowed to regain consciousness
A: d. While recovering.Waking up from anesthesia can be extremely disorienting and frightening. A horse who panics as he begins to recover may thrash about and attempt to get up before he is fully coordinated—which can be catastrophic if he tears sutures or strikes a just-repaired limb. To help horses recover more safely, a number of ingenious techniques have been developed, including an air-mattress floor that does not deflate until the horse is ready to stand or a warm-water pool that allows the horse to float until the floor is raised under his feet. (“Anesthesia Without Fear,” EQUUS 425)
Threat in the pasture
Q:The toxic weed white snakeroot was long believed to be responsible for seasonal pasture myopathy, a muscle disorder that causes fatal respiratory and cardiac paralysis, usually within three days. But the facts never quite added up. Finally, after a six-year investigation, a team of researchers led by Stephanie Valberg, DVM, PhD, of the University of Minnesota discovered the true culprit. Horses succumb to this fatal illness after eating which of these plant parts:
a. pokeberries b. wild poppy flowers c. box elder seedpods d. red oak leaves
A: c. box elder seedpods. The female box elder tree (Acer negundo), also called ash maple or river maple, produces clusters of distinctive long, narrow “helicopter” seedpods during the autumn months. The seeds contain a toxin called hypoglycin-A that blocks the enzymes that metabolize fat, creating the fatal myopathy in horses. Box elder trees are most common across the central United States from the Appalachians to the Rocky Mountains, from Canada down to eastern Texas. (“Mystery Solved,” EQUUS 426)
Common cause of laminitis
Q: The completion of the equine genome project (the comprehensive “map” of the horse’s genetic code) and the development of new technologies for genetic analysis have accelerated the progress of research in many fields of study in the past decade. In recent years, for example, great strides have been made in our understanding of laminitis—the devastating, painful breakdown of the connective tissues within a horse’s hoof that can cause the coffin bone to separate from the overlying hoof wall. What is now thought to be—by far—the most common cause of laminitis?
a. endocrine disorders—such as equine metabolic syndrome associated with obesity or PPID (often called Cushing’s disease) b. inflammation—systemic inflammatory events, such as those caused by carbohydrate overloads in the gut, retained placental material in the uterus or diseases such as Potomac0 horse fever c. weight bearing or mechanic strain—caused when an injury to one leg causes a horse to bear too much weight on his “good” hoof as he convalesces d. poor circulation within the hoof—caused by conformation issues or overgrown toes with underrun heels
A: a. endocrine disorders. For years, laminitis was believed to be primarily an inflammatory disease—inflammation within the soft tissues of the hoof, it was thought, somehow led to the breakdown of the connections between the hoof wall and coffin bone, causing it to detach and drop away. And, indeed, studies often found large numbers of pro-inflammatory agents in the tissues of a horse with laminitis. Also, for years, these studies were done primarily with horses who had laminitis induced in laboratory settings—which relied on inflammatory methods, such as grain overloads or black walnut extract. However, when advances in technology allowed researchers to look into the biochemical processes of horses developing laminitis related to high levels of insulin (endocrinopathic), they found no evidence of inflammation at the outset. Rather, it was the detachment of the coffin bone that led to inflammation; it was not inflammation that led to the detachment of the coffin bone. And endocrinopathic laminitis, related to obesity, PPID and high levels of insulin, is far more common than inflammatory forms of the disease. (“Rethinking Laminitis,” EQUUS 427)
Achieving hoof balance
Q: Few domestic horses have perfectly symmetrical feet that are balanced in all directions. Hooves can be distorted from side to side, from front to back, or in a rotary direction, as the capsule twists upon the end of the leg. The causes—from chronic unbalanced forces—can be equally varied: Many horses do not stand square but habitually lean to one side or the other. Diseases such as laminitis may alter the shape of a hoof, neglected hooves may become overgrown, or they may be trimmed poorly. When examining a hoof to look for evidence of imbalance, which anatomical feature provides an immovable reference point for judging the correct position of the rest of the foot?
a. the heels b. the white line c. the pastern bones d. the frog
A: d. the frog. The bridge of the frog—the spot located just behind the tip—will always remain in a stable position relative to the coffin bone within the hoof wall and the column of leg bones that rises above it. And so the frog, and its underlying cartilaginous structure, forms the most immovable center point for the hoof. If, when looking straight at the sole of the hoof, the frog appears to be “pointing” to one side, it means that the entire hoof capsule has rotated away from its normal position. (“Conformation Insights: Hoof Balance,” EQUUS 428)
A basis for bad behavior
Q:To seek out causes for equine misbehavior, researchers in Australia asked the owners of 84 Pony Club horses to record any undesirable actions—including bucking, pulling at the bit and resistance to the aids—they observed over a 13-month period. The owners were also asked to keep daily records of how they managed, fed, cared for and exercised their horses. Which of these factors was most closely linked to higher rates of misbehavior?
a. being ridden for more than eight hours per week b. back pain or other chronic injuries c. obesity d. mineral imbalances in the diet
A: c. obesity. The risk of misbehavior was increased when the horse was rated as fat or obese, given supplementary feed daily, grazed on paddocks with green grass cover and exercised less than five times per month. All of these factors add up to horses who are untrained and unfit. Misbehaviors also became slightly more common in horses during competitions, which researchers suggest may reflect the riders’ higher expectations and stresses, combined with horses who are not fully fit and prepared for the activity. (“Fat and Sassy?” Medical Front, EQUUS 428)
Joint-health challenges
Q: We tend to think of arthritis as a disease of aging, but in reality the foundation for an older horse’s joint health is set much earlier in life. In other words, the management and training decisions made from a horse’s first year onward will have a huge impact upon the severity of any arthritis he experiences as he ages. Regular farriery care is essential for joint health at every age. In addition to that, can you match the age of the horse with the primary care concerns that will influence his joint health? (“Fight Arthritis at Every Age,” EQUUS 429)
a. foals and weanlings, 4 to 24 months b. youth, 2 to 5 years c. middle age, 5 to 15 years d. older age, 15 years or more
1. consistent activity, with rest periods 2. progressive stiffness 3. training too fast, too soon 4. developmental orthopedic disease
A: a. 4. A young horse’s feed ration plays a crucial role in whether he will contract developmental orthopedic disease (DOD), a collection of bone and joint abnormalities that follows too-rapid growth. Diets that contribute to DOD are overly rich in excess calories and nutrients. Offer age-appropriate feeds that provide basic nutrition. Turnout is also important to help growing horses develop healthy bones and joints, but avoid forced exercise because it is easy to overstrain young joints.
b. 3. Riding a young horse too early—or putting him into intense, repetitive training too soon after starting him under saddle—is likely to cause injuries to his still-maturing cartilage that will culminate in serious arthritis down the road. Instead, wait until the horse is physically mature before starting him under saddle, then take a slow, conservative approach to your early training efforts.
c. 1. To maintain healthy joints, an active adult horse needs regular exercise that doesn’t overstress him combined with periods of rest to allow routine wear-and-tear injuries to fully heal before he works again. Long periods of inactivity, however, can take a toll on a horse’s overall health and fitness. When bringing back a horse who hasn’t been ridden in months or years, ease into the work gradually to give his bones and cartilage time to regain strength.
d. 2. Some degree of stiffness is almost inevitable in any aging horse, but the sooner the problem is addressed, the more likely it is that he can be helped to remain comfortable as he grows older. Often, the first signs of trouble aren’t outright unsoundness but a decline in performance or a new grumpiness or attitude problem. Today, horses with arthritis can often continue to work at some level with the aid of supplements, medications and a variety of treatments, including joint injections.
Ahead of the game
Q: Since the ASTM/SEI0 standards for protective helmets were first published in 1988, countless riders have walked away from falls and head blows that might once have been fatal. Today most people wouldn’t dream of taking a horse over jumps, for example, without wearing protective headwear, but it took time—and significant cultural shifts—for the safety helmets to become accepted across various disciplines. The governing body for one of these sports was the first in the United States to require all participants to wear protective helmets while in competition. Which one was it?
a. polo b. Thoroughbred racing c. eventing d. show jumping
A: b. Thoroughbred racing. After the 1956 death of jockey LeRoy Nelson from head injuries sustained after a fall during a race at Agua Caliente Racetrack in Tijuana, Mexico, the track’s executive director, John Alessio, pushed for the development of the “Caliente safety helmet” and made it mandatory at his track. After jockeys started walking away from accidents that might have been fatal without the helmets, the new gear was quickly endorsed by the Jockeys’ Guild and adopted as standard, if not mandatory, equipment within a few years at racetracks across the United States. Polo players were among the first to begin wearing hard helmets, as early as the first years of the 1900s, but their use was not mandatory in the sport. The American Horse Show Association passed rules requiring protective helmets for show jumping in 1964 and for the cross-country phase of eventing in 1978. (“The Safety Helmet Success Story,” EQUUS 429)
The power of the pecking order
Q: Knowing where your horse ranks in the herd’s social hierarchy—at the top, middle or bottom of the pecking order—can give you insights into his personality, and it also tells you what kind of leadership he expects and needs from you. An individual’s personality and level of training are important, of course, but if you were asked to select a mount for a novice rider, where in the herd’s pecking order would you expect to find the best choice?
a. the alpha mare, for her natural leadership instincts b. a herd leader gelding, who is naturally protective c. a mid-ranking mare, for her balance of dominance and submission d. the bottom mare or gelding, who is naturally submissive
A: c. a mid-ranking mare. The mare right in the middle of the herd is neither naturally dominant nor especially submissive. She tends to be quiet and laid back and accepting of training and human leadership; she doesn’t expect to be in charge. The horse at the very bottom of the pecking order is naturally quiet and submissive and could also be a good choice for a novice—however, these horses may be fearful and spooky and require strong leadership to give them confidence. Both the herd leader gelding and the alpha mare are used to being the boss, and they may resist—sometimes aggressively—having people tell them what to do. (“On Behavior: The Herd Factor,” EQUUS 430)
In case of choke
Q: Choke—the condition that occurs when a wad of incompletely chewed food or a foreign object becomes lodged in a horse’s esophagus—can look alarming, but most horses will make a full recovery. That said, it’s important to take action if your horse suddenly stops eating, shakes his head and makes coughing or retching noises. What needs to be done?
a. stop the horse from eating or drinking b. remove all food but provide water c. hose or syringe water into his mouth d. syringe vegetable oil into his mouth
A: a. stop the horse from eating or drinking. When a horse is experiencing choke, any additional food that he takes in will only increase the size of the blockage, and even water can be dangerous. If any particles of food or fluids are drawn into his airways or lungs, the horse may develop aspiration pneumonia, a potentially fatal complication. The best course is to remove all food and water from the horse, and lead him into a dry lot or stall if he’s in pasture. Then try to keep him calm and encourage him to stand quietly with his head lowered. The good news is that most cases of choke will resolve on their own as the horse continues to produce saliva, which lubricates the blockage and helps it to dislodge and pass on down to the stomach. But call your veterinarian anyway. She will want to examine your horse to evaluate the cause of the episode and check for signs of injury to his esophagus. (“The Challenge of Choke,” EQUUS 431)
Air-quality improvements
Q: Fresh air is essential to the respiratory health of horses kept in stalls. Even when the interior of a barn looks and smells clean, particles of dust, mold spores, ammonia gases and other pollutants can linger in the air and be drawn into a horse’s airways. These low levels of dust and other particles can trigger an inflammatory response, and over time a horse may develop recurrent airway disease, also known as heaves. Maximizing ventilation, to keep fresh air flowing through the barn, is the key to keeping horses’ lungs healthy. Which two of these factors are the most important to healthy barn air?
a. good air distribution—to circulate air in and out of each stall b. frequent air exchanges—the complete replacement of all the barn air with fresh air from outside c. fast movement—keeping the air moving around the barn disperses pollutants faster d. warm temperatures—hot air rises, so the warmer the barn, the faster stale air will rise toward the roof vents
A: a. good air distribution and b. frequent air exchanges. Air exchange means the complete replacement of all of the stale air in the barn with fresh outside air; in a horse barn, an air exchange rate of four to eight times per hour is the goal. Distribution is important, too—the air needs to not just come into the barn but to circulate throughout all of the stalls. By itself, fast movement of the air does not help if it is just moving stale air around. Temperatures do not matter. In fact, opening the windows in winter can bring in beneficial ventilation; horses generally do not mind the colder temperatures. (“Clear the Air,” EQUUS 431)
Growth areas
Q:Melanomas—tumors of the pigment-producing cells that cause firm, black lumps on the skin—are a common fact of life for older gray horses. About 80 percent will develop them by the age of 15. The good news is that the lumps usually do little harm to the horse and cause only aesthetic concerns. However, there are circumstances when equine melanomas do pose a threat to a horse’s health and well being. Three of the following choices identify situations when a melanoma may require veterinary attention; the fourth can be left alone and simply monitored. Which one is not a reason to call a veterinarian?
a. Tumors burst, slough, ulcerate or drain. b. Tumors appear on the nostrils and lips. c. Tumors appear on a horse younger than 5 years old. d. Tumors grow and multiply rapidly.
A: b. Tumors appear on the nostrils and lips. Melanomas can appear anywhere on the body, and most do no harm, unless they interfere with a horse’s bodily functions. The lips are a common site for the lumps, but as long as they remain small and do not get in the way of tack or hinder a horse’s eating, they can be left alone. Large tumors that outgrow their blood supply may ooze debris and dead tissue, and those located where they may rub against tack may become irritated and raw—these may require treatment to prevent infections. Melanoma tumors typically appear later in a horse’s life and then grow slowly—they may remain the same size for years. Lumps that appear on horses younger than 5 or that multiply or enlarge quickly are indicators of a more aggressive form of the disease that requires treatment. (“When to Worry About Equine Melanoma,” EQUUS 432)
The inside story
Q: “Navicular disease” has long been a diagnosis that horse owners dreaded, and with good reason: Usually, it meant that all other explanations for a horse’s lameness had been ruled out, and his future likely held a frustrating series of “shot in the dark” treatments that might or might not help him. In recent years, however, one particular advance in veterinary medicine has greatly improved the prospects of horses with pain originating in the area of the heels. What is that advance?
a. genetic testing, which offers insights into a horse’s inherited conformation issues b. stem cell therapy, which enables more complete healing of injured tendons and bones c. magnetic resonance imaging, which shows a clearer picture of pathologies in the foot d. laser surgery, which allows for more precise targeting of damaged tissue
A: c. magnetic resonance imaging (MRI). With only x-rays to work with, veterinarians throughout much of the 20th century could gain only limited information about the interior of a horse’s lower leg. Because x-rays are best at creating images of bones, researchers focused on the navicular bone itself as the source of lameness. But a navicular bone that showed lesions and jagged edges didn’t necessarily mean the horse would be lame, and conversely, others who could barely walk had clean-looking x-rays. MRIs, however, now offer a much clearer view of all of the bone, cartilage and soft tissues within the foot. As a result, veterinarians can now detect signs of injury, such as bruising of the bone and injuries to the tendons, that would not be visible on x-rays or other imaging technologies. And with more accurate diagnoses, veterinarians have been able to offer better targeted, more effective treatments. (“The End of Navicular Disease?” EQUUS 433)
