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.     

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.     

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.     

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.     

Osseous Sequestration in the Horse A Review of 68 Cases

Sixty-eight cases of cortical bone sequestration in 67 equine patients were reviewed with regard to the clinical presentation, method of treatment, and outcome. All lesions were located in skeletal areas with minimal soft tissue coverage, with 53% of them in the metatarsal and metacarpal bones. At the time of admission, 60% of the patients with limb lesions were lame; the majority improved with therapy. After sequestrectomy, there was a trend for surgical wounds which could be managed by primary closure to heal more rapidly (3.8 weeks) than wounds which required second intention healing (6.4 weeks). The appearance of healed wounds, as evaluated by owners, was acceptable in 45 cases. Dissatisfaction with the appearance of the healed wounds in 22 cases suggested a need to address the issue of cosmetic results.     

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.     

Characterization of Horse Use in Therapeutic Horseback Riding Programs in the United States: A Pilot Survey

With increasing public scrutiny on animal welfare, it behooves those involved in the equine industry to revisit best management practices to ensure these support healthy horses. There is little published research on how horses are used in the equine industry, particularly in therapeutic horseback riding (THR) programs. Although there is a large amount of information on the benefits of THR programs to the participants, there is little published information available about the horses. Therefore, the objective of this survey was to gather data regarding horse use and care in Professional Association of Therapeutic Horsemanship International (PATH Intl.)–affiliated THR programs in the United States to help establish a foundation for a standard of care. A 20-question survey sent to 659 PATH Intl.–affiliated THR programs returned a 40% response rate. Demographics demonstrated that the median number of horses in each program was 10; geldings outnumbered mares; most horses were between 16 and 20 years of age; and Quarter Horse or stock-type breeds predominated. Median session length was 8 weeks and median lesson length was 45 minutes. Horses were typically ridden by clients 4 days/week and 2 hours/day. Most horses were donated to the programs, participated for approximately 7 years, and left because of aging. Limb lameness and back soreness were the top health issues noted, with only a small percentage of colic and ulcers reported. More horses received nonsteroidal anti-inflammatory drugs for a lameness issue, chiropractic adjustment, and massage than any other supplemental care or complementary therapy. Based on data gathered in this survey, THR horses were not worked excessively. Horses were ridden less than PATH Intl.’s maximum recommendation of 6 hours/day and 6 days/week and less than those used in university programs. Horses in THR programs also appeared to have fewer reported health issues as compared with data in other national reports.     

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.     

乳酸菌益生功能及作用机制研究进

综述了近几年公开发表的一些研究结果,就乳酸菌对促进营养物质的吸收、预防和治疗疾病以及增强机体免疫力等益生功能的研究现状作了介绍,探讨了乳酸菌益生功能的作用机制,并对今后研究的发展方向作了简单分析。