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Lameness in the Western performance horse
47TH ANNUAL AAEP CONVENTION The 47th Annual Convention of the American Association of Equine Practitioners was held in San Diego, CA, on November 24-28, 2001. The meeting was well attended with a large variety of topics presented. Lameness in the western performance horse The topic for the “In Depth” seminar was “Lameness in the Western performance horse, with special presentations on the rodeo horse, cutting and reining horses, the Western pleasure horse, and the team roping horse. Speaking about the rodeo horse, Dr. Robert Lewis said, “Many lamenesses are presented with a complaint of poor performance. When dealing with such cases, lameness may not be readily apparent during a traditional examination. Often it is of value to have the owner ride them under saddle. It is common in our practice at the time appointments are made to suggest the owner bring videotapes of the horse performing, preferably displaying runs when the horse was performing well followed by tapes of poor performances. These videos, especially if you can view them in slow motion, often aid in identifying abnormal limb use. I find this is especially true with hindlimb lameness.” Dr. Lewis mentioned the importance of forelimb lamenesses in barrel racing horses. “Relatively minor forelimb lamenesses in barrel horses frequently impair performance significantly,” he said. He described other lamenesses that are significant in rodeo horses such as navicular disease, degenerataive joint disease, fractures, proximal suspensory desmitis, and various acute joint injuries. Volume 22, Number 2, 2002
Dr. Jerry Black presents Dr. C. Wayne McIlwraith with the outgoing AAEP president's bronze.
Dr. Bradley Jackman said that cutting and reining horses are exceptionally agile athletes that sustain athletic injuries. The recent popularity of these sports has dramatically increased the competition and participation in these events. As the competition has been enhanced, so has the breeding and training of the horses because it takes an exceptional athlete to be competitive in the industry today. This increased athletic ability and rigorous training predisposes the cutting and reining horse to athletic injury. Dr. Jackman described eight specific problems encountered in cutting and reining horses: forelimb lameness; palmar heel pain/navicular syndrome; suspensory ligament desmitis; hindlimb lameness; inflammation/arthritis of the distal tarsal joints; stifle lameness; traumatic stifle conditions; and developmental stifle conditions. He said, “Due to the increasing popularity and nationwide growth of the cutting and
reining industry, it is imperative for equine practitioners to become familiar with the diagnosis and treatment options of injuries common to these horses.” Dr. Joe Noble said that Western pleasure is one of the most popular events in the United States in which equine enthusiasts participate. He emphasized that special attention should be paid to both the fore and hind feet, and that the shoeing of the horse should be examined carefully. Hindlimb lameness is common in Western pleasure horses, especially the tarsus. Dr. Richard Galley said the most popular equestrian competition in the United States is the sport of team roping, with approximately one million individuals competing in team roping competitions nationally, at all levels. “When attempting to diagnose problems in the team roping horse, as in all equine athletes, it is extremely important to remember that very often, in the early stages of pathology, little or 65
no lameness may be present,” he said. “This is especially true in the case of tarsitis of the distal tarsal joints.” Dr. Galley said that the tremendous growth of the sport of team roping has arguably made the team roping horse the western performance horse that is most commonly seen by the equine practitioner, regardless of geographic location. “The increased demand for these horses combined with their current high purchase prices has contributed to these horses being presented to the equine practitioner for evaluation of even the slightest of problems,” said Dr. Galley. Cushings disease Dr. Harold Schott described a field study of horses with naturally occurring equine Cushing’s disease at Michigan State University. He said it provides a number of novel observations about the treatment and progression of an important problem of older horses. First, the results clearly demonstrate that treatment with pergolide produced clinical and laboratory responses that were superior to treatment with cyproheptadine. In fact, treatment with cyproheptadine was found to be of little benefit when responses were compared with those observed in horses receiving no treatment. Second, measurement of plasma ACTH concentration was found to produce both false positive and false negative results, when compared with DST or TRH results for diagnosis of a pituitary adenoma. Third, identification of a group of horses with abnormal fat deposition and laminitis, without hirsutism, which had elevated serum insulin concentrations and normal DST or TRH results, provides further support that a recently described peripheral Cushing’s disease syndrome- may be a differential diagnosis for horses with a suspected 66
pituitary adenoma. This latter observation is important because horses with a peripheral Cushing’s disease syndrome would not be expected to improve with treatment with pergolide. Airway reactivity in urban horses Dr. Melissa Mazan said that many horses now live an urban life, and are exposed to the pollutants that abound in urban ambient air. Because horses are a highly athletic, outdoor species, they are sampling the ambient air, along with the pollutants that it holds, on a continual basis. Many horses suffer from SAID, which can severely inhibit performance. It is hypothesized that human asthma can be caused or exacerbated by air pollution; a similar mechanism may exist with SAID in horses. "Interestingly, we found that airway reactivity was higher in rural than in urban horses," she said, "despite normal baseline respiratory resistance in both groups." This suggests an innate cause of airway reactivity in the rural group, rather than being attributable purely to airways geometry. It seems likely that environmental triggers other than air particulate matter determined AWHR in this group of horses. This confirms similar findings from studies of human asthmatics. In a study at Tufts University, in which Dr. Mazan was involved, they found higher, although not statistically significant, iron levels in the brochoalveolar lavage fluid (BALF) of urban horses, which may be caused by air pollution particles. Alternatively, the iron may be the result of extravasation from the serum due to airway in flammation; however, horses from urban environments had significantly less airway reactivity when tested with histamine bronchoprovocation, and had no greater evidence of airway inflammation in the bronchoalveolar lavage fluid. "As we excluded horses with a history or evidence of EIPH, we do not consider this to be a confounding variable," she said. "Higher ferritin
levels in horses from urban environments may reflect a protective mechanism against oxidative stress by sequestering iron, and may thus explain the lack of greater airway inflammation in urban horses." It is possible that there were too few horses in this study to establish definitively whether increased exposure to particulate air pollution (as suggested by increased iron and ferritin in the BALF of urban horses) is associated with airway inflammation. "Although we did not find statistically significant differences between iron and ferritin levels in horses from urban versus rural environments," she said, "this is likely due to the small number of horses in the study. The trend toward increased iron and ferritin in BALF in urban horses supports further study in urban versus rural horses. It is only by understanding the role that particulate air pollution plays in the development of lung injury in horses that we can make progress in treating or even preventing lung injury in horses in urban environments. Moreover, horses, by continually sampling the outside air, have the potential to function as a valuable sentinel and model for the role of the environment in airway disease in other species such as humans." Endotoxemia One of the most commonly encountered life-threatening conditions in horses with gastrointestinal disease is endotoxemia, according to Dr. James Moore. He said the results of studies of horses presented with abdominal pain (colic) to university clinics in various parts of the world indicate that gram-negative bacterial endotoxins commonly are detected in circulation. Although much of the focus of research on endotoxemia in horses has centered on diseases that produce intestinal strangulation obstruction, these are not the only disease conditions characterized by endotoxemia. Similar clinical findings and problems often occur in adult horses with colitis, pleuropneumonia, retained placenta,
JOURNAL OF EQUINE VETERINARY SCIENCE
Dr. Jerry Black presents Dr. C. Wayne McIlwraith with the outgoing AAEP president's bronze.
Dr. Bradley Jackman said that cutting and reining horses are exceptionally agile athletes that sustain athletic injuries. The recent popularity of these sports has dramatically increased the competition and participation in these events. As the competition has been enhanced, so has the breeding and training of the horses because it takes an exceptional athlete to be competitive in the industry today. This increased athletic ability and rigorous training predisposes the cutting and reining horse to athletic injury. Dr. Jackman described eight specific problems encountered in cutting and reining horses: forelimb lameness; palmar heel pain/navicular syndrome; suspensory ligament desmitis; hindlimb lameness; inflammation/arthritis of the distal tarsal joints; stifle lameness; traumatic stifle conditions; and developmental stifle conditions. He said, “Due to the increasing popularity and nationwide growth of the cutting and
reining industry, it is imperative for equine practitioners to become familiar with the diagnosis and treatment options of injuries common to these horses.” Dr. Joe Noble said that Western pleasure is one of the most popular events in the United States in which equine enthusiasts participate. He emphasized that special attention should be paid to both the fore and hind feet, and that the shoeing of the horse should be examined carefully. Hindlimb lameness is common in Western pleasure horses, especially the tarsus. Dr. Richard Galley said the most popular equestrian competition in the United States is the sport of team roping, with approximately one million individuals competing in team roping competitions nationally, at all levels. “When attempting to diagnose problems in the team roping horse, as in all equine athletes, it is extremely important to remember that very often, in the early stages of pathology, little or 65
no lameness may be present,” he said. “This is especially true in the case of tarsitis of the distal tarsal joints.” Dr. Galley said that the tremendous growth of the sport of team roping has arguably made the team roping horse the western performance horse that is most commonly seen by the equine practitioner, regardless of geographic location. “The increased demand for these horses combined with their current high purchase prices has contributed to these horses being presented to the equine practitioner for evaluation of even the slightest of problems,” said Dr. Galley. Cushings disease Dr. Harold Schott described a field study of horses with naturally occurring equine Cushing’s disease at Michigan State University. He said it provides a number of novel observations about the treatment and progression of an important problem of older horses. First, the results clearly demonstrate that treatment with pergolide produced clinical and laboratory responses that were superior to treatment with cyproheptadine. In fact, treatment with cyproheptadine was found to be of little benefit when responses were compared with those observed in horses receiving no treatment. Second, measurement of plasma ACTH concentration was found to produce both false positive and false negative results, when compared with DST or TRH results for diagnosis of a pituitary adenoma. Third, identification of a group of horses with abnormal fat deposition and laminitis, without hirsutism, which had elevated serum insulin concentrations and normal DST or TRH results, provides further support that a recently described peripheral Cushing’s disease syndrome- may be a differential diagnosis for horses with a suspected 66
pituitary adenoma. This latter observation is important because horses with a peripheral Cushing’s disease syndrome would not be expected to improve with treatment with pergolide. Airway reactivity in urban horses Dr. Melissa Mazan said that many horses now live an urban life, and are exposed to the pollutants that abound in urban ambient air. Because horses are a highly athletic, outdoor species, they are sampling the ambient air, along with the pollutants that it holds, on a continual basis. Many horses suffer from SAID, which can severely inhibit performance. It is hypothesized that human asthma can be caused or exacerbated by air pollution; a similar mechanism may exist with SAID in horses. "Interestingly, we found that airway reactivity was higher in rural than in urban horses," she said, "despite normal baseline respiratory resistance in both groups." This suggests an innate cause of airway reactivity in the rural group, rather than being attributable purely to airways geometry. It seems likely that environmental triggers other than air particulate matter determined AWHR in this group of horses. This confirms similar findings from studies of human asthmatics. In a study at Tufts University, in which Dr. Mazan was involved, they found higher, although not statistically significant, iron levels in the brochoalveolar lavage fluid (BALF) of urban horses, which may be caused by air pollution particles. Alternatively, the iron may be the result of extravasation from the serum due to airway in flammation; however, horses from urban environments had significantly less airway reactivity when tested with histamine bronchoprovocation, and had no greater evidence of airway inflammation in the bronchoalveolar lavage fluid. "As we excluded horses with a history or evidence of EIPH, we do not consider this to be a confounding variable," she said. "Higher ferritin
levels in horses from urban environments may reflect a protective mechanism against oxidative stress by sequestering iron, and may thus explain the lack of greater airway inflammation in urban horses." It is possible that there were too few horses in this study to establish definitively whether increased exposure to particulate air pollution (as suggested by increased iron and ferritin in the BALF of urban horses) is associated with airway inflammation. "Although we did not find statistically significant differences between iron and ferritin levels in horses from urban versus rural environments," she said, "this is likely due to the small number of horses in the study. The trend toward increased iron and ferritin in BALF in urban horses supports further study in urban versus rural horses. It is only by understanding the role that particulate air pollution plays in the development of lung injury in horses that we can make progress in treating or even preventing lung injury in horses in urban environments. Moreover, horses, by continually sampling the outside air, have the potential to function as a valuable sentinel and model for the role of the environment in airway disease in other species such as humans." Endotoxemia One of the most commonly encountered life-threatening conditions in horses with gastrointestinal disease is endotoxemia, according to Dr. James Moore. He said the results of studies of horses presented with abdominal pain (colic) to university clinics in various parts of the world indicate that gram-negative bacterial endotoxins commonly are detected in circulation. Although much of the focus of research on endotoxemia in horses has centered on diseases that produce intestinal strangulation obstruction, these are not the only disease conditions characterized by endotoxemia. Similar clinical findings and problems often occur in adult horses with colitis, pleuropneumonia, retained placenta,
JOURNAL OF EQUINE VETERINARY SCIENCE