DNA polymorphism analysis of hereditary multiple exostoses in horses

Genomic DNA polymorphisms obtained by restriction fragment-length polymorphism from healthy horses and horses with hereditary multiple exostoses were analyzed. These DNA were digested by 12 restriction enzymes and were hybridized against 6 isotopically labeled oncogene probes. Hybridization was not detected with the viral oncogene, v-ras, which indicated this oncogene was absent in the equine genome. Oncogenes (c-raf-1, c-fes, c-myb, c-myc, and c-sis) were present and had similar hybridization patterns and signal intensities in DNA from healthy horses and horses with hereditary multiple exostoses. Unique and distinct restriction fragment-length polymorphisms were detected with the c-raf-1 probe only in BamHI- and PstI-digested equine DNA.     

Nutritional aspects of post exercise skeletal muscle glycogen synthesis in horses: A comparative review

Carbohydrate (CHO) stored in the form of skeletal muscle glycogen is the main energy source for glycolytic and oxidative ATP production during vigorous exercise in mammals. In man, horse and dog both short‐term high intensity and prolonged submaximal exercise deplete muscle glycogen. In horses, however, muscle glycogen synthesis is 2–3‐fold slower than in man and rat, even when a diet high in soluble CHO is fed. There appear to be significant differences in CHO and glycogen metabolism between horses and other mammals, and it is becoming increasingly clear that many conclusions drawn from human exercise physiology do not apply to horses. This review aims to provide a comprehensive, comparative summary of the research on muscle glycogen synthesis in horse, man and rodent. Species differences in CHO uptake and utilisation are examined and the issues with feeding high soluble CHO diets to horses are discussed. Alternative feeding strategies, including protein and long and short chain fatty acid supplementation and the importance of rehydration, are explored.     

Exostoses of the caudal perimeter of the radial physis as a cause of carpal synovial sheath tenosynovitis and lameness in horses: 10 cases (1999-2003)

OBJECTIVE: To determine the clinical, radiographic, ultrasonographic, and arthroscopic findings associated with tenosynovitis of the carpal synovial sheath induced by exostoses that originate from the caudal surface of the physeal scar of the distal radius and determine the results of surgical removal of those exostoses in horses. DESIGN: Retrospective study. ANIMALS: 10 horses. PROCEDURE: Medical records of horses with effusion in the carpal synovial sheath and lameness evaluated from 1999 to 2003 were examined. RESULTS: All horses had a history of intermittent mild to moderate effusion of the carpal synovial sheath and lameness of 1 forelimb. Results of regional perineural and intrathecal anesthesia of the carpal synovial sheath confirmed that the lameness originated in the carpal synovial sheath. Radiography revealed exostoses originating from the caudal cortex of the distal radius at the level of the closed physis. Arthroscopy was performed for confirmation and removal of exostoses that penetrated the carpal synovial sheath and impinged on the deep digital flexor tendon. All horses returned to previous athletic activity. One horse had a recurrence of clinical signs 12 months after surgery, which resolved with medical treatment. CONCLUSIONS AND CLINICAL RELEVANCE: Tenosynovitis of the carpal synovial sheath and lameness were caused by impingement of exostoses of the caudal radius on the lining and contents of the carpal synovial sheath. Although the clinical signs and surgical treatment were similar to that caused by osteochondromas, these exostoses developed at the level of the closed physis of the distal radius and were not radiographically or histologically similar to osteochondromas.     

Dorsomedial articular fracture of the proximal aspect of the third metacarpal bone in standardbred racehorses: seven cases (1978-1990).

Seven Standardbred horses, all pacers, with a mean age of 2.9 years (range, 2 to 4 years), had dorsomedial articular fracture of the proximal aspect of the third metacarpal bone. Fracture caused acute, unilateral, severe lameness after training or racing. Lameness was abolished by midcarpal joint anesthesia in 4 horses. Six horses had a palpable bony swelling, which caused signs of pain. Radiography revealed a nondisplaced, articular, oblique fracture extending distad toward the dorsomedial cortex for a mean distance of 28 mm (range, 15 to 40 mm). In all horses, chronic periosteal proliferative changes, seen near the distal aspect of the fracture, corresponded to palpable bony exostoses and were associated with the medial attachment of the extensor carpi radialis tendon. In 1 horse, internal fixation followed by a 6-month rest resulted in a successful outcome. All other horses were given 3 months' rest without surgery and were not lame. Five horses raced successfully and lowered the lifetime race records, 1 horse was sound and trained successfully, but died of colic, and 1 horse was not lame in early training.     

Immune-mediated hemolytic anemia induced by penicillin in horses

Three horses developed severe, immune-mediated hemolytic anemia after treatment with penicillin. The horses had positive direct antiglobulin (Coombs) tests and high titers of IgG antibody that agglutinated penicillin-coated equine red cells. Two of the horses were tested for antibodies to autologous red cell antigens; autoantibodies were not present. Titers of antipenicillin antibody decreased after penicillin was discontinued but IgG antibody was detectable months after recovery. One of the horses was challenged with penicillin; antibody titer increased slightly, but anemia did not develop. Antipenicillin antibody of the IgM class was present in low titer in 23 (77%) of 30 non-anemic horses tested. Apparently, the horse is similar to man in that penicillin-induced anemia is rare but the percentage of individuals with antipenicillin antibody is high.     

Overview of the Current Situation in a Sample of Headshakers and Owner Assessment of Effective Therapeutic Measures Used in Germany

Equine headshaking syndrome is a problematic behavior that has been described in literature for more than 100 years. The signs of headshaking syndrome appear frequently and violently so that riding the horse can be dangerous. The aim of this research was to gain an overview of the underlying causes of equine headshaking syndrome to identify effective treatment options, reduce the distress of horses and, in a second step, potentially improve therapeutic possibilities for horse owners and veterinarians. Most studies on prevalence originate from Anglo-American countries, so this research was to provide an overview of German horses; therefore, an online survey was designed by experts in the field (researchers and veterinarians) and answered by German horse owners. Questionnaires were pretested by a small group of horse owners (n = 5) and redesigned accordingly. The final questionnaire consisted of 27 questions, which were divided into seven open questions with an associated text field and 20 multiple-choice questions (Supplementary Material 1). For some of the multiple-choice questions, multiple answers were permitted. In total, 163 completed questionnaires were obtained from owners of headshaking horses (n_total = 163). Gender distribution of the horses resulted in 64.4% geldings, 33.7% mares, and 1.8% stallions. Most horses were German warmbloods (55.4%). The average age was 12.7 years (with a wide range of 5 to 34 years). The vertical movement of the head was the most frequently mentioned symptom in 75.5% of the evaluated horses. In 18.4% of the cases, the horse owners identified stress as the main trigger for headshaking. Furthermore, 18.4% claimed that their horses suffered from additional stereotypical behavior. The percentages do not refer to the same horses here. 11.0% of the participants in this study tried scientifically evaluated therapies such as surgical therapy (1.2%) or medical treatment (9.8%). In addition, 54.0% of the owners utilized a nose cover to reduce the symptoms of the headshaking syndrome. A high percentage of 84.0% used alternative therapies such as physiotherapy (31.9%), change of equipment (22.7%), or change of riding style (29.4%). Overall, this study provides a useful overview of causes and effective therapies.     

Blood lipid, glucose, and insulin concentrations in Morgan horses and Thoroughbreds

Insulin resistance has been detected in obese Morgan horses and it has been suggested that horses of this breed are predisposed to this condition. The objective of this study was to determine whether blood lipid, glucose, and insulin concentrations differed between Morgan horses and Thoroughbreds housed at the same facility. Fourteen Morgan horses (five mares, nine geldings) ranging in age from 4 to 14 years were compared with 21 Thoroughbreds (11 mares, 10 geldings; age range 7–20 years) from the same herd. A single blood sample was collected from each horse after grain was withheld overnight. Variables were compared between breed groups and breed-specific reference ranges were calculated. Triglyceride, cholesterol, nonesterified fatty acid, glucose, and insulin concentrations did not differ between breeds of horse in this study. This may be because horses included in this study did not suffer from obesity and were regularly exercised.     

Antibodies to elastin peptides in sera of Warmblood horses at different ages

REASONS FOR PERFORMING STUDY: Early diagnosis and monitoring progression of chronic diseases in elastin-rich tissues, such as chronic progressive lymphoedema in draught horses and chronic obstructive pulmonary disease (COPD) is still a real challenge in the horse. Use of an enzyme-linked immunosorbent assay (ELISA) to detect anti-elastin antibody (AEAb) levels might be useful to assess the status of such diseases. Baseline levels, representing physiological breakdown of elastin in normal horses, are not available at present. HYPOTHESIS: Levels of AEAb in healthy horses are generally low and follow the same age-related pattern as found in man. Therefore, elevation of AEAb levels in serum can be used to evaluate pathological elastin breakdown in elastin-rich tissues. METHODS: Sera of 84 clinically healthy Warmblood horses were evaluated for the presence of AEAbs by means of a modified version of an ELISA technique used in man. The horses were divided in 5 age groups: A) < 4 months; B) 4-23 months; C) 2-3 years; D) 4-10 years; and E) > 11 years. RESULTS: Antibodies to elastin were found in all equine serum samples tested. Their levels were lowest in Group A, low in Groups B and E and highest in animals age 2-10 years. CONCLUSIONS: Measuring AEAbs in serum of horses by an ELISA technique proved to be possible and levels were stable during well-defined life stages. POTENTIAL RELEVANCE: Changes in AEAb levels are expected to be useful for early diagnosis and for monitoring progression of diseases that affect elastin-rich tissues, such as chronic progressive lymphoedema and COPD.     

Intramuscular desmoid tumor (musculoaponeurotic fibromatosis) in two horses.

Intramuscular desmoid tumors (musculoaponeurotic fibromatosis) were discovered in two young adult horses. The tumor in one horse was in the lateral cervical musculature, and that in the second horse occurred in the pectoral musculature. Histopathologic features were similar in both horses and included proliferation of fibroblasts and cells expressing muscle actin (myofibroblasts), with extensive dissecting fibrosis within muscle. These features are similar to those of desmoid tumors in humans, particularly those also known as musculoaponeurotic fibromatosis. Dissection of these lesions revealed a single central (horse No. 1) or multiple central (horse No. 2) fluid-filled cavities with associated sterile inflammation. The presence of these cavities supports the hypothesis that equine desmoid tumors are traumatic in origin, possibly occurring at sites of injections or bursal rupture. Surgical excision of the tumor in horse No. 1 was apparently curative, but the extent of the tumor in horse No. 2 precluded surgical excision.     

Anaplastic malignant melanoma of the tail in non‐grey horses

Information regarding signalment, clinical findings, treatment and outcome of 5 previously reported cases of anaplastic malignant melanoma of the tail in non‐grey horses and of 5 additional cases are summarised. Age was recorded for 9 horses and mean age was 16 years, range 8–23 years. Gender was recorded for 8 horses and 6 of these 8 horses were male horses over 14 years of age. The most common coat colour was bay (6 horses). Other coat colours were palomino (one horse), chestnut (one horse) and black (one horse); coat colour of one non‐grey horse was not specified. Follow‐up information was available for 9 horses and only one horse, a palomino, survived more than 10 months following diagnosis and tail amputation. Surgical excision, including tail amputation and medical therapy with oral cimetidine, was not effective in non‐grey, non‐palomino horses. Tumour recurred on tail tissue remaining after amputation in 2 horses, widespread metastases were documented in 4 cases and metastasis was suspected at the time of death or euthanasia in 3 cases, including one case with amputation site regrowth. No subjective histopathological differences were detected in the palomino horse that survived as compared to horses of other coat colours. Findings suggest that anaplastic malignant melanoma of the tail in non‐grey horses is most often a very aggressive neoplasm, but that there are rare exceptions.     

Surgical management of compound odontoma in two horses

Two horses were admitted for evaluation of mandibular swelling (horse 1) or maxillary distortion (horse 2). Both horses had radiographic evidence of tumors of dental origin that had the appearance of a compound odontoma. Extensive surgical resection was performed for treatment. Horse 1 was treated with 1-stage surgical resection, but an iatrogenic fracture occurred during surgery, which was managed successfully with a type I external fixator and extraoral alimentation. Horse 2 was treated in multiple stages to remove all portions of the tumor. To manage an extensive orosinal fistula, a custom-designed dental bridge was constructed to occlude the fistula. For both horses, the histopathologic diagnosis was compound odontoma. Compound odontomas are benign, locally expansive tumors of dental origin. Compound odontomas can be treated successfully; however, multiple surgeries may be necessary.     

"Haysickness" in Icelandic horses: precipitin tests and other studies

Blood samples were taken from 18 healthy horses (Group A), 15 horses clinically diagnosed to have "haysickness" ("farmer's lung") (Group B), 10 closely related horses (Group C) and 14 inbred horses (Group D). Precipitins in sera were measured by double gel diffusion test against Micropolyspora faeni, Thermoactinomyces vulgaris, Aspergillus fumigatus, Alternaria, Penicillium and Rhizopus species. In Group A, all the horses were precipitin negative except one with a faint reaction to Rhizopus species. In Group B all had precipitin against M faeni. One horse also had precipitins against Rhizopus species and another against A fumigatus. In Group C, seven of the 10 horses had precipitins against M faeni. Of these, five had a history of respiratory signs, but two horses with a faint reaction had no such history. In Group D, four out of 14 horses had positive precipitin tests against M faeni. Of these four horses, three also had a faint reaction to A fumigatus and one a faint reaction to Alternaria species. All were asymptomatic. These results indicate that "farmer's lung" in man and "haysickness" in horses are of the same origin. However, further studies are necessary to substantiate the diagnostic or prognostic value of these precipitin tests in equine practice. The question of whether hereditary factors play a role in causing this disease also warrants further studies.     

Blood Gas Tensions, Acid-base Status, Heart Rates, and Venous Profiles in Exercising Horses with Laryngeal Hemiplegia Before and After Corrective Surgery

The physiologic effects of exercise were studied in four horses with complete laryngeal hemiplegia. Right carotid arteries were surgically elevated to a subcutaneous position for percutaneous catheterization. Each horse was fitted with a device designed to obtain multiple arterial samples while the horse was exercised over a 1.6-km course. After each horse completed 10 test gallops, the laryngeal hemiplegia was treated using a laryngeal prothesis and ventriculectomy. The horses were then reconditioned, and the exercise test and sampling were repeated. Horses with laryngeal hemiplegia became acidotic, hypoxic, and hypercapnic compared to normal horses. Surgical treatment improved blood gas and acid-base status, but the values were not equivalent to those in normal horses similarly tested.     

Frequent deworming in horses; it usually does not do any good, but it often harms

Due to excessive and inappropriate use of dewormers anthelmintic resistance has developed as a significant problem in horse parasites in the Netherlands. Since it is unlikely that new classes of anthelmintics against horse nematodes will be introduced in the near future, it is important to use the present drugs wisely. Veterinarians should advice horse owners about worm control programs with a more targeted approach. The number of anthelmintic treatments should be reduced and, through selective anthelmintic treatments, further development of anthelmintic resistance should be delayed. Preferably, horses with a low faecal egg count should not be treated at all to ascertain a reduction of the selection pressure for anthelmintic resistance. The propensity for low faecal egg counts is hereditary. This implies that mature horses with consistent low egg counts can be detected by faecal examination and that it is not necessary to repeat faecal examination each time in these animals. New horses on the farm should always be dewormed on arrival and should be introduced only after the efficacy of treatment has been determined. Anthelmintic resistance can also be introduced with the arrival of a new animal that is infected with drug-resistant parasites.     

Evaluation of FOXC2 as a candidate gene for chronic progressive lymphedema in draft horses

Chronic progressive lymphedema (CPL) is a debilitating condition identified in Clydesdales, Shires and Belgian draft horses and results in progressive swelling of the lower legs associated with the development of thick skin folds, ulcerations, fibrosis and marked hyperkeratosis. The result is severe discomfort and recurrent secondary infection, often requiring euthanasia. Due to the delayed onset, many horses are bred prior to diagnosis. CPL has only been documented in three related draft horse breeds, suggesting a genetic cause. Determining the molecular basis would enable owners to test horses prior to breeding and facilitate the elimination of CPL. Mutations in the FOXC2 gene cause a comparable condition in humans, lymphedema-distichiasis. This gene was sequenced in affected and unaffected draft horses and a control horse. Four single nucleotide polymorphisms (SNPs) were identified in unaffected draft horses and the control horse, indicating that they were not associated with CPL. A fifth SNP was seen in a single affected draft horse and the control horse. Since it was not seen in all affected draft horses, this SNP is not associated with the CPL phenotype.     

Single stage urethroplasty for perineal hypospadias in a foal

The incidence of hypospadias is increasing in man, but the condition is rarely reported in horses. There are few available data regarding the surgical management of this disorder in horses, with no previous published report of urethral reconstructive surgery and only two reports documenting phallectomy procedures. This case report documents hypospadias repair, not previously reported in the horse, in a Thoroughbred foal with proximal hypospadias. The indication for surgery was contact dermatitis of the hind leg, which was impairing the foal's ambulation and had the potential to impair the foal's racing ability. Preoperative examination revealed a proximal hypospadias with a wide urethral plate. The anus was normal. The foal was otherwise thriving. A single stage urethroplasty was performed, during which the urethral plate was tubularised in two layers and the urethral meatus was successfully relocated distally to open upon the glans. The urethroplasty was covered with dartos fascia and the penile shaft skin and prepuce were reconstructed. Minor superficial dehiscence of the wound was successfully managed conservatively. Post‐operatively, urine was voided through the opening created on the glans penis, resolving the contact dermatitis. Follow‐up after 3 years confirmed that the horse continues to void through the re‐sited meatus without complication and had gone on to race successfully. In conclusion, we present the first report of reconstructive urethroplasty for the treatment of a horse for proximal hypospadias with good functionality and long‐term outcome.     

Proteomic analysis in canine leishmaniasis

In horses, Recurrent Airway Obstruction (RAO) is an allergic disease that involves IgE mediated Type I Hypersensitivity responses. The development of this type of allergy involves a series of events that begins with reaginic antibodies, mainly IgE and some IgG subclasses. These reaginic antibodies bind with high affinity, via the Fc portion, to FcεRI receptors on the membrane of mast cells and basophils. Once bound, environmental allergens cross-link the antibodies, which results in mast cell degranulation leading to the production of histamine and other chemical mediators that act together to induce airway inflammation. RAO-affected horses present with coughing, respiratory distress, airway obstruction and poor performance. The aspect of the RAO has been extensively studied, yet the precise sequence of events is still not well understood. Therefore, this study proposes a bioassay for reaginic antibody detection from horse serum of RAO-affected individuals, in order to determine the etiology of disease, which mediate immediate type reactions. The technique involves measuring in vitro calcium mobilization in RBL-2H3 cells following incubation with horse serum from affected or unaffected horses and one of the RAO antigens (Aspergillus fumigatus). The results presented here demonstrate that 30% of RAO-affected horses react positively in this in vitro bioassay, whereas unaffected horses do not. This bioassay may facilitate further research on RAO and other allergic diseases in horses.     

Obstructive enterolith in an 11-month-old miniature horse.

An obstructive enterolith was diagnosed in an 11-month-old 68-kg miniature horse with a 24-hour history of mild, intermittent colic. Abdominal radiography revealed gas distention of the cecum and the right and left ascending colon, and a radiodense elliptical structure in the area of the left kidney. During exploratory laparotomy, the right dorsal colon was noticed to contain ecchymotic hemorrhage and generalized discoloration in the portion proximal to the location of the enterolith. While exteriorizing the ascending colon, it ruptured caudal to the diaphragmatic flexure in the right dorsal colon. Radiography of the enterolith did not reveal a metallic center, but division of the stone allowed identification of a canvas cloth, and chemical analysis determined the stone's composition to be ammonium magnesium phosphate. Although equine enteroliths were reported over 100 years ago and the factors involved in their formation were investigated, the reasons for their development have yet to be determined. The mean reported age of horses requiring abdominal surgery because of an obstructive enterolith is 10 years, with the youngest being 4 years. The time required for an enterolith to enlarge is unknown, although a true enterolith has not been reported in horses younger than 4 years of age.     

African Horse Sickness Fever in Vaccinated Horses: Short Communication

Our investigation has shown that multiple vaccinations with inactivated African horse sickness (AHS) vaccines containing all 9 serotypes and produced at the Central Veterinary Research Laboratory in Dubai, UAE, protect horses from AHS. However, the immunization did not prevent African horse sickness fever (AHSF) in approximately 10% of the vaccinated horses despite high enzyme-linked immunosorbent assay and virus neutralizing antibodies. African horse sickness fever is a very mild form of AHS with similar clinical signs. From all 6 horses which had developed AHSF, no virus was isolated from EDTA blood withdrawn during the acute phase of infection. Despite high neutralizing antibodies, serotype 9 was detected by polymerase chain reaction in 4 of them. All 6 horses recovered within 72 hours, after they developed mild clinical signs of AHS.