Tetanus in the Horse: A Review of 20 Cases (1970 to 1990)

The case records of 20 horses with tetanus referred to the Ontario Veterinary College-Veterinary Teaching Hospital between 1970 and 1990 were reviewed. The fatality rate was 75%. There was a strong association with previous vaccination and survival ( P = .03). Most of the animals had been injured an average of 9 days (range 2 to 21 days) prior to development of clinical signs. Hyperesthesia and prolapse of the third eyelid were the most common clinical signs. Treatment regimens varied during hospitalization; however, all horses received parenteral penicillin, tranquilizers, tetanus toxoid, and antitoxin. Five of the nonsurviving animals were given intrathecal tetanus antitoxin. One animal had seizures as a complication of intrathecal treatment. The prognosis was best for horses that (1) had been vaccinated prior to the injury, (2) responded to the phenothiazine tranquilizers, and (3) did not rapidly (over 24 to 48 hours) become recumbent. Considering the species susceptibility, potential for contaminated wounds, and the increased survival of vaccinated horses, yearly revaccination is recommended.     

Pharmacology of Furosemide in the Horse: A Review

Furosemide, a diuretic, is frequently administered to horses for the prophylaxis of exercise-induced pulmonary hemorrhage and the treatment of a number of clinical conditions, including acute renal failure and congestive heart failure. Furosemide increases the rate of urinary sodium, chloride, and hydrogen ion excretion. Plasma potassium concentration decreases after furosemide administration but urinary potassium excretion in horses is minimally affected. Renal blood flow increases after furosemide administration. Systemically, furosemide increases venous compliance and decreases right atrial pressure, pulmonary artery pressure, pulmonary artery wedge pressure, and pulmonary blood volume. The systemic hemodynamic effects of furosemide are only manifest in the presence of a functional kidney, but can occur in the absence of diuresis, emphasizing the importance of the renal-dependent extra-renal effects of furosemide. The renal and systemic hemodynamic effects of furosemide are modified by prior administration of nonsteroidal anti-inflammatory drugs. Furosemide administration attenuates exercise-induced increases in right atrial, aortic, and pulmonary artery pressures in ponies. Furosemide prevents exercise and allergen-induced bronchoconstriction in humans and decreases total pulmonary resistance in ponies with recurrent obstructive airway disease. These pharmacologic effects are frequently used to rationalize its questionable efficacy in the prevention of exercise-induced pulmonary hemorrhage. Neither the effect of furosemide on athletic performance nor its efficacy in the prevention of exercise-induced pulmonary hemorrhage has been convincingly demonstrated.     

A Review of the Efficacy of Tiludronate in the Horse

Tiludronate is a compound in the bisphosphonate class of drugs. The main pharmacologic action of bisphosphonates is to inhibit bone resorption; they cause osteoclast apoptosis and disrupt intercellular trafficking of pro-inflammatory mediators. Bisphosphonates are used to treat humans with diseases such as osteoporosis and Paget's disease. Recently tiludronate has been studied as a treatment for bone resorptive diseases in horses. Tildren, an injectable form of tiludronate made for the horse, has been licensed to treat navicular disease and distal tarsal osteoarthritis in Europe. Some clinical studies have been completed to assess the efficacy of tiludronate in the horse. Many of the studies are reviewed here, and their standards of research are evaluated individually. Tiludronate may be beneficial in managing lameness isolated to the navicular bone and distal tarsal osteoarthritis by decreasing bone resorption and inflammation.     

Differentiation of Chronic Lymphocytic Leukemia in the Horse: A Report of Two Cases

Chronic lymphocytic leukemia (CLL) was diagnosed in two horses: an 18-year-old Quarter Horse gelding that was examined because of edema of the prepuce and ventral abdomen; and a 20-year-old mixed breed gelding that was referred because of lymphocytosis, ventral edema, and weight loss. The first horse had enlarged peripheral lymph nodes and cool nonpainful pitting edema of the ventral abdomen and prepuce. The second horse had enlarged peripheral lymph nodes, cool nonpainful pitting edema of the ventral thorax and cranial ventral abdomen, and a 3/5 holosystolic heart murmur. The diagnosis of CLL was based on increased blood lymphocyte counts and infiltration of marrow and other tissues by lymphocytes. In horse 1, the lymphocytosis persisted for 2 months between initial examination and death. The results of flow cytometric analysis on blood lymphocytes using anti-lymphocyte antibodies suggested that horse 1 had T-cell CLL, and horse 2 had B-cell CLL. In addition, the second horse had a monoclonal gammopathy (IgG), with light-chain proteinuria.     

Exercise and Immunity: A Review with Emphasis on the Horse

Exercise has been recognized as a stress, which can significantly alter the host's immune response and, therefore, its susceptibility to disease. Whereas research in this area has previously focused primarily on human subjects and laboratory animals, it has more recently extended to domestic animals, especially the equine athlete. Despite several studies, defining the relationship among exercise, the immune response, and disease has proven difficult due to a number of factors, including the complexity of the immune system and the variable nature of exercise itself. It now appears that exercise has dual effects on the immune system. Suppressive effects, such as a decline in the ratio of CD4+ to CD8+ cells, diminished lymphocyte function, and a decline in the number and cytolytic activity of natural killer cells have been observed in response to brief high-intensity exercise, prolonged exhaustive exercise, and overtraining. In contrast, moderate training generally has beneficial effects on host defense mechanisms. The mechanisms for regulating the dual effects of exercise are complex, involving a network of neuroendocrine hormones and cytokines.     

Nonsurgical Management of Ulnar Fractures in the Horse: A Retrospective Study of 43 Cases

Forty-three cases of nonsurgically managed ulnar fractures in the horse were reviewed. Twenty-three per cent of the horses were euthanized, 44% survived but were unsound, and 33% of the horses were sound when surveyed 6 months to 11 years following fracture. Best results were obtained when treating distal semilunar notch fractures (70% sound). Prognosis was poorest for horses with fractures of the olecranon affecting the semilunar notch (0% sound).     

Surgical Reduction of Ileal Impactions in the Horse: 28 Cases

Objective —To evaluate the seasonal influence, signalment, type of hay consumed, clinical examination findings, and outcome after surgery for horses with ileal impaction. Study Design —A retrospective study. Results —Between 1988 and 1993, 28 horses had surgical correction of ileal impaction. There was a significantly higher rate of ileal impaction during the Fall (September-November, P= .0041). Mean duration of clinical signs of abdominal pain before referral was 15 hours. Transrectal palpation was used to localize the impaction in 11 horses. The ileal impaction was reduced by extraluminal massage aided by admixing of intestinal fluid oral to the impaction or injection of fluids intraluminally and then movement of the ingesta into the cecum alone in 24 horses. A total of 26 horses recovered from surgery; 24 horses were discharged from the hospital and eventually returned to previous use. Two horses had fatal postoperative complications: jejunocec-ostomy dehiscence and development of extensive small intestine adhesions after manual reduction of the impaction. One horse initially treated by manual reduction required jejunocecostomy twice for management of recurrent ileal impaction. Follow-up information was obtained for 21 horses, of which 20 were alive 1 year or longer after surgery. A total of 27 of 28 horses were fed Coastal Bermudagrass hay as the primary type of hay consumed. A total of 9 horses continued to be fed Coastal Bermudagrass hay as the only roughage source, whereas 6 horses were fed Coastal Bermudagrass with at least 50% other hay, and in 6 horses, Coastal Bermudagrass hay was entirely eliminated from the diet. Conclusion and Clinical Relevance—Ileal impactions can be successfully reduced by celiotomy and extraluminal massage and injection techniques to soften the ingesta for passage into the cecum without enterotomy or bypass techniques in most horses. Changes in weather and feeding practices in the Fall may account for an increased risk of ileal impaction in horses in the southeastern United States at that time of year.     

Treatment of Degenerative Joint Disease of the Horse: A Review and Commentary

Some of the predisposing factors for the development of degenerative joint disease, such as fatigue, early training, conformation defects, and others, are outlined. Swimming, a controlled weight-bearing exercise, is discussed and strongly recommended for treatment of degenerative joint disease in the horse. A brief review of counterirritants and vesicants, as well as current therapeutic suggestions, are presented. Cryotherapy, which is a relatively new form of counterirritation, is discussed. The benefits and limitations of radiation therapy are briefly discussed, and gamma rays are felt to be superior to x-rays. The most frequently used antiinflammatory drugs are discussed, and the two main categories, corticosteroids and nonsteroidal antiinflammatory drugs, are presented in detail. Among the nonsteroidal antiinflammatory drugs, hyaluronic acid, DMSO, and superoxide dismutase are presented and their mode of action, as well as benefits and disadvantages, are evaluated. Joint lavage is an effective tool in the management of joint disease, because it removes degenerative debris and inflammatory cells from the joint. The management of degenerative joint disease generally involves more than one of the therapeutic regimens mentioned. On the other hand, there is not a single treatment combination that is superior in all situations. The clinician treating degenerative joint disease must select the treatment regimen that works best for him and for the case to be treated. Such a choice must be based on a thorough understanding of applicable therapeutic agents and modes of physical therapy.     

Pancarpal Arthrodesis for Treatment of Carpal Collapse in the Adult Horse A Report of Two Cases

Two mares with multiple carpal bone fractures, malarticulation and degenerative joint disease were successfully treated with unilateral arthrodeses of the antebrachiocarpal, middle carpal, and carpometacarpal joints. Arthrodesis was achieved by removal of articular cartilage, autogenous cancellous bone graft, and double dynamic compression plating. In one horse, wedge ostectomy corrected the severe, acquired angular limb deformity. External coaptation supplemented the internal fixation. Postoperative complications were limited to cast sores that healed with treatment, although protracted in one horse. Both mares adapted to the "peg leg" condition and ambulated without pain by 3 months. The first mare treated survived for at least 2 1/2 years after surgery and has had at least one foal. The most recently treated mare will be bred next year.     

Bypass Surgery for the Treatment of Small Intestinal Ileus in the Horse A Report of Three Cases

The medical management of three horses with simple and strangulating small intestinal obstructions was unsuccessful and was therefore supported by surgical bypasses. Jejunocecostomies were used to treat horses with postoperative paralytic ileus that was unresponsive to medical management. These horses had abdominal pain, gastric distention, heart rate elevations greater than 60/minute, and small intestinal distention on rectal palpation. Two horses experienced weight loss which responded to bypass removal. The bypass effectively decreased the need for intravenous fluid administration and repeated nasogastric intubation.     

Hydrocephalus in an American Miniature Horse Foal: A Case Report and Review

A 6-year-old multiparous American Miniature Horse mare was presented at 324 days of gestation for evaluation of vaginal bleeding. A manual obstetrical examination was performed and the cervix was found to be open with the fetus in transverse position. The mare was sedated and placed under general anesthesia. Attempts made to mutate the fetus were unsuccessful. A cesarean section was performed and the foal was noted to be in transverse position with marked enlargement of the cranium. The abdominal incision was closed in a routine manner, and the mare recovered from anesthesia without incident. Postoperative treatment consisted of flunixin meglumine, gentamicin sulfate, potassium penicillin, oxytocin, and intravenous fluid therapy. The mare was discharged to the owners 4 days after surgery. A lateral radiograph of the fetus was obtained and confirmed hydrocephalus. On necropsy, it was found that the calvarium measured 59 cm in circumference and was dome-shaped, the neuropil and leptomininges measured only 1 to 2 mm in thickness, the brainstem and cerebellum were reduced in size, and there was moderate distension of the third ventricle with stenosis of the mesencephalic aqueduct. Inflammatory and neoplastic causes of mesencephalic aqueductal obstruction were ruled out by histopatholgy. This represents a classic case of hydrocephalus because of stenosis of the mesencephalic aqueduct, which to our knowledge has not been previously reported in a miniature foal. Further investigation is warranted into the pathogenesis of mesencephalic aqueduct stenosis in foals, which has now been reported in several equine breeds.     

Pancarpal Arthrodesis in the Dog: A Review of Forty-five Cases

This report describes an open surgical technique for pancarpal arthrodesis and its efficacy in 45 canine cases. Indications for carpal arthrodesis include hyperextension injuries, severe fracture/luxations, end-stage arthritis, and selected neurologic deficits. Chronic joint instability was the major indication for surgery (76%). Degenerative joint disease (18%) and neurologic deficits (6%) accounted for the other cases. In a subjective owner survey, 97% of the owners reported that their animals' gait improved following arthrodesis, and 74% stated that their animals walked and ran normally.     

Tetanus in Equids: A Review of 76 Cases

Data on the clinical examination and treatment of 76 tetanus cases in equids was reviewed, aiming to verify factors that may assist veterinarians in establishing a prognosis for this disease. Overall mortality was 76.3%. Treatment was provided to 61 animals. Of those, 18 (29.5%) survived. Data analysis led to identification of the following indicators for fair to good prognosis: greater than 5 days' timespan between onset of signs of the disease and initial assistance (7 of 13 animals survived, 53.9%) and greater than 7 days of hospitalization (all of 17 animals survived, 100%). Conversely, indicators of poor prognosis included presence of dysphagia or aphagia at first examination (52 of 60 animals died, 86.7%), decubitus (all of 20 animals died, 100%), and hoof sole perforating lesions by nails (all of 8 animals died, 100%). Based on the high mortality rate of this disease, the importance of prophylaxis is reinforced.     

Equine Nutrition in the United States: A Review of Perceptions and Practices of Horse Owners and Veterinarians

Nutrition plays a critical role in equine health. The horse owner and/or manager has a multitude of equine nutrition sources available to them, with preferences for how, and from whom, this information is delivered. Despite this, poor feeding practices continue to negatively affect the health, wellness, and welfare of equids and have a detrimental impact on the environment. The veterinarian is the primary expected source of equine nutrition information; yet, little is known about their recognition and acceptance of such a role. Doubt has arisen concerning the quality and provision of nutrition education within the veterinary curriculum and subsequent continuing education. Moreover, the value equine nutrition education plays in the veterinarian's practice philosophy, and the resulting provision of such in clinical practice, remains under evaluated. This review examines the present state of equine nutrition and how horses are being fed in practice, in the United States. It considers feeding horses from the horse owner's perspective and the expected role the veterinarian plays in such. Last, it goes on to evaluate this expected role from the veterinarian's perspective, examining how current nutrition education and practices may be falling short and offering recommendations for future research.     

Mechanisms of Gastrointestinal Ischemia-Reperfusion Injury and Potential Therapeutic Interventions: A Review and Its Implications in the Horse

Restoration of blood flow after a period of intestinal ischemia is necessary to maintain cell function and viability; however, the reintroduction of oxygen can initiate a cascade of events that exacerbates tissue injury. Intestinal I-R injury is manifested as increased microvascular and mucosal permeability, and mucosal necrosis. Reperfusion injury begins with the accumulation of hypoxanthine from ATP metabolism and the conversion of XDH to XO during ischemia. Upon reperfusion, the XO catalyzes the conversion of hypoxanthine to superoxide radicals in the presence of oxygen. Superoxide radicals are further reduced to highly reactive hydroxyl radicals, which initiate lipid peroxidation. Lipoperoxidation causes functional and structural alterations in cell membrane lipids and can release numerous inflammatory mediators, which exacerbate tissue damage. Neutrophils are recruited into tissues during ischemia and on reperfusion; then they undergo degranulation and release destructive products (proteases and OFRs), which mediate further tissue injury. A limited number of experimental studies in the gastrointestinal tract of horses have shown I-R injury. Additional studies are necessary to further elucidate and sequence the precise pathophysiologic mechanisms occuring in the equine intestine during I-R. Therapy should be focused on prevention of I-R injury by pharmacologic or chemical inhibition or modification of these pathophysiologic pathways. Selected pharmacologic agents or drug combinations may offer novel, scientifically relevant and yet practical approaches to alleviating intestinal I-R injury in horses. This may improve survival of horses with naturally acquired intestinal strangulation obstruction.     

Laryngeal Hemiplegia in Draft Horses A Review of 27 Cases

Case records of 27 draft horses with laryngeal hemiplegia were reviewed. Twenty-one horses were treated by ventriculectomy with or without prosthetic laryngoplasty, and 17 owners were contacted to determine the results. Fifteen horses improved after surgery and were able to perform to the owners' expectations. Performance improved significantly and hospitalization was shorter after ventriculectomy alone. Results of this study indicate that the clinical signs of exercise intolerance and excessive inspiratory noise associated with left laryngeal hemiplegia in draft horses can be treated successfully by ventriculectomy without prosthetic laryngoplasty.