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Topic:Laminitis
Laminitis is a complex and painful condition affecting the hooves of horses, characterized by inflammation and damage to the laminae, the soft tissue structures that secure the hoof wall to the coffin bone. This condition can lead to severe lameness and, in chronic cases, permanent structural changes within the hoof. Factors contributing to laminitis include metabolic disorders, excessive intake of carbohydrates, and mechanical overload, among others. The condition is diagnosed through clinical signs, radiographic imaging, and sometimes histopathological examination. Management strategies often involve dietary modifications, pain relief, and corrective hoof care. This page compiles peer-reviewed research studies and scholarly articles that explore the pathophysiology, risk factors, diagnostic approaches, and management strategies for laminitis in horses.
Endothelin mediated contraction of equine laminar veins. Endothelin-1 (ET-1) may be a key mediator in the pathogenesis of laminitis, but endothelin-mediated responses in the venous microcirculation of the equine foot have yet to be fully characterised. Objective: To characterise the response of equine laminar veins to ET-1 and evaluate the ET-1 receptor subtypes that mediate this response. Methods: Small veins (150-500 microns) draining the equine digital laminae from healthy horses and ponies subjected to euthanasia at an abattoir were investigated using wire myography. Concentration response curves were constructed for ET-1 in the presence of ETA ...
The effect of metformin on measurements of insulin sensitivity and beta cell response in 18 horses and ponies with insulin resistance. Laminitis in equids is a very common debilitating disease, and insulin resistance (IR) and hyperinsulinaemia are increasingly recognised as important predisposing factors. Pharmacological modification of IR and hyperinsulinaemia might reduce the risk of laminitis. Objective: Metformin, a drug commonly prescribed for treatment of human IR, may also decrease IR in equids. Methods: Eighteen horses and ponies with IR and recurrent laminitis were treated with 15 mg/kg bwt metformin per os q. 12 h. Each animal served as its own control by comparing pre- and post treatment proxies for IR, insulin sen...
Determination of the source of increased serotonin (5-HT) concentrations in blood and peritoneal fluid of colic horses with compromised bowel. Increased plasma (5-HT) concentrations are reported in horses predisposed to develop laminitis and after i.v. infusion of endotoxins. In the equine jejunum contractile 5-HT1A-like receptors show tachyphylaxia upon prolonged activation with 5-HT. Therefore, increased systemic 5-HT release in colic horses could play a possible role in the pathophysiology of ileus. Objective: To investigate possible increased systemic release of 5-HT in colic horses with compromised bowel and to identify the source of 5-HT overload. Methods: Concentrations of 5-HT were determined in plasma and peritoneal fluid (P...
Retrospective study of the clinical features of limb cellulitis in 63 horses. A retrospective study of 63 horses diagnosed with limb cellulitis between 1994 and 2005 was conducted. They all had an acute onset of painful, generalised limb swelling, and a clinical diagnosis of limb cellulitis was made by the attending clinician. None of the horses had more than one limb affected. Hindlimbs were significantly more often affected than the forelimbs (P<0.05). Thoroughbreds were significantly over-represented compared with the general distribution of breeds examined at the hospital. Blunt limb trauma, limb surgery and limb injections were associated with the cellulitis in ...
Factors affecting clinical assessment of insulin sensitivity in horses. Insulin resistance is thought to be involved in the pathogenesis of many equine conditions such as pars intermedia dysfunction, equine metabolic syndrome, diabetes mellitus, hyperlipaemia, laminitis, endotoxaemia and osteochondrosis dissecans (OCD); whereas polysaccharide storage myopathy in Quarter Horses and equine motor neuron disease (EMD) have been associated with increased insulin sensitivity. However, it is clear that there is not one ideal test, in terms of both practicality and accuracy, for evaluating insulin sensitivity in horses and improved diagnostic techniques are required. This...
Effects of unfractionated and fractionated heparins on myeloperoxidase activity and interactions with endothelial cells: possible effects on the pathophysiology of equine laminitis. As heparins are sometimes used to prevent equine laminitis, the interactions between equine neutrophil myeloperoxidase (MPO), unfractionated (UFH) and fractionated low molecular weight (LMWH) heparins and digital endothelium have been investigated. The effects of the heparins on purified equine MPO activity were tested by immunocapture followed by enzymatic detection. Endothelium-MPO interactions were assessed by measuring total and active MPO uptake by arterial and venous digital endothelial cells in culture with or without the addition of heparins. A dose-dependent MPO inhibition by UFH and ...
Effects of dietary energy source and physical conditioning on insulin sensitivity and glucose tolerance in standardbred horses. There is evidence that adaptation to diets rich in nonstructural carbohydrates (NSC) contributes to the development of insulin resistance in horses. To date, however, no study in horses has examined the effects of physical conditioning on diet-associated alterations in insulin sensitivity and glucose tolerance. Objective: To examine the effects of adaptation to concentrate feeds rich in NSC or fat on insulin sensitivity and glucose tolerance in horses, both in the sedentary state and after a subsequent period of physical conditioning. Methods: Fourteen mature Standardbred horses underwent both...
Incomplete rupture of the gastrocnemius and superficial digital flexor muscles in a Quarter Horse stallion. A 16-year-old 500-kg (1,100-lb) Quarter Horse stallion was examined because of acute severe lameness involving the left hind limb. Results: Examination revealed signs of failure (concurrent flexion of the tarsus and extension of the stifle [femorotibial] joint) of the caudal component of the reciprocal apparatus. Results of radiographic evaluation ruled out fracture or joint injury as causes of the lameness. During the next 48 hours, the reciprocal apparatus on the left hind limb progressively deteriorated until the horse became non-weight bearing on the limb. Results: The horse wore a full-li...
Thermographic study of in vivo modulation of vascular responses to phenylephrine and endothelin-1 by dexamethasone in the horse. In vitro, glucocorticoids potentiate vasoconstriction of equine digital vessels to catecholamines and this has been implicated as a mechanism of glucocorticoid-induced laminitis. This observation has never been confirmed in vivo. Objective: To study the effects of glucocorticoid therapy on vasoconstrictor responsiveness in the horse in vivo. Methods: In a blinded, randomised cross-over experiment, 9 horses were treated with either dexamethasone (0.1 mg/kg bwt i.v. q. 24 h) or saline i.v. for 6 days. The changes in local average skin temperature before (baseline) and after intradermal injection...
Evaluation using hoof wall strain gauges of a therapeutic shoe and a hoof cast with a heel wedge as potential supportive therapy for horses with laminitis. To evaluate using strain gauges, a hoof cast with heel wedge, and a therapeutic shoe with unsupported toe for their effectiveness in redistribution of load from the dorsal hoof wall. Methods: In vitro biomechanical study. Methods: Twenty forelimb specimens. Methods: Rosette strain gauges were placed on the dorsal and lateral hoof wall of 20 normal shaped hooves. Limbs were loaded vertically using a tensile testing machine with a 1 Hz sinusoidally cycling load up to 3000 N during 15 seconds. Mean values of principal strain and direction at 2500 N load were calculated for 3 experimental conditio...
Black walnut extract-induced laminitis in horses is associated with heterogeneous dysfunction of the laminar microvasculature. Equine laminitis purportedly involves haemodynamic dysfunction at the level of the laminar vasculature. However, to date, no studies have been performed characterising the function of laminar arteries and veins during the prodromal stages of equine laminitis. Objective: That the prodromal stages of laminitis are associated with contractile dysfunction of the equine laminar vasculature. Objective: To assess contractile function of laminar arteries and veins to phenylephrine (PE) and 5-hydroxytryptamine (5-HT). Methods: Horses were administered black walnut heartwood extract (BWHE) or water (con...
Unilateral basement membrane zone alteration of the regenerated laminar region in equine chronic laminitis. Between the laminar epidermis and the laminar dermis of laminar region (LR) in equine foot, it can be observed the basement membrane zone (BMZ), which is composed of a basement membrane and its accompaniments like the hemidesmosome and anchoring fibril. Alteration in the BMZ in equine laminitis is possibly related with not only development but also recovery outcome and recurrence of this disease. However, there is little known about the structure of the BMZ during the recovery phase of this disease. To assess the condition of the BMZ of LR affected by chronic laminitis, the tissue was examined...
Evaluation of pituitary gland anatomy and histopathologic findings in clinically normal horses and horses and ponies with pituitary pars intermedia adenoma. To determine size and weight of the pituitary gland and associations between pituitary gland size and weight and sex and age in horses without clinical signs associated with pituitary pars intermedia adenoma (PPIA) and horses and ponies with PPIA. Methods: Pituitary glands from 100 horses without clinical signs of PPIA and 19 horses and 17 ponies with PPIA. Methods: Pituitary glands were weighed, measured, and examined histologically by use of H&E stain. Masson trichrome and periodic acid-Schiff staining were used, when appropriate. Histologic lesions in the pars intermedia, pars distalis,...
An analgesic evaluation of isoxsuprine in horses. Isoxsuprine is used clinically to treat navicular disease and laminitis in horses. Although it is thought to increase digital and laminar blood flow, isoxsuprine's mechanism of action remains controversial, and analgesia has been suggested recently as such possible mechanism. This research investigated the analgesic potential of isoxsuprine in healthy horses submitted to a mechanical nociceptive test. Isoxsuprine (1.2 mg/kg), xylazine (1.1 mg/kg), distilled water : ethanol 95% (2 : 1, v/v, 20 ml) and saline (0.9%, 20 ml) were injected intravenously, and nociceptive thresholds were measured ove...
Assessment of apoptosis in epidermal lamellar cells in clinically normal horses and those with laminitis. To determine and compare the number, type, location, and distribution of apoptotic epidermal cells in the laminae of clinically normal horses and horses with laminitis. Methods: Formalin-fixed samples of digital lamellar tissue from 47 horses (including clinically normal horses [controls; n = 7], horses with acute [4] and chronic [7] naturally acquired laminitis, and horses with black walnut extract-induced [11] or carbohydrate overload-induced [18] laminitis). Methods: Blocks of paraffin-embedded lamellar tissues were stained for DNA fragmentation with the terminal deoxynucleotidyl transferas...
Evaluation of suspected pituitary pars intermedia dysfunction in horses with laminitis. To determine prevalence and clinical features of pituitary pars intermedia dysfunction (PPID) in horses with laminitis. Methods: Case series. Methods: 40 horses with laminitis. Methods: Horses with laminitis that survived an initial episode of pain and were not receiving medications known to alter the hypothalamic-pituitary-adrenal axis were tested for PPID by evaluation of endogenous plasma ACTH concentration. Signalment, suspected cause, month of onset and duration of laminitis, Obel grade of lameness, pedal bone rotation, physical examination findings, results of endocrine function tests, t...
Prevention and treatment of thrombosis, phlebitis, and laminitis in horses with gastrointestinal diseases. Organ thrombosis and laminitis are life-threatening complications in horses with acute gastrointestinal disease, especially those diseases that cause disruption of the protective mucosal barrier. Prevention of these complications should be a high priority when treating horses with gastrointestinal diseases because even with proper and intensive treatments, laminitis or organ thrombosis may not be curative. Preventative therapy should include expedient and appropriate treatment of the primary disease, normalization of tissue perfusion and oxygenation, and inhibition of gut-derived toxins or the...
Evaluation of systemic immunologic hyperreactivity after intradermal testing in horses with chronic laminitis. To determine whether systemic immunologic hyperreactivity exists in horses with chronic laminitis, compared with responses for nonlaminitic horses. Methods: 7 nonlaminitic horses and 7 CL horses. Methods: In experiment 1, intradermal testing (IDT) was performed on 7 nonlaminitic and 7 CL horses to evaluate the response to a combination of 70 allergens at 15 and 30 minutes and 4 and 24 hours after injection. Three nonlaminitic and 3 CL horses used in experiment 1 were used in experiment 2 to determine whether histologic differences existed between the 2 groups. The H&E-stained tissue sectio...
Equine Cushing’s disease. Equine Cushing's disease (ECD) is a chronic progressive disease of the intermediate pituitary gland of older horses. Horses with Cushing's disease often have other health problems, such as laminitis, chronic infections, pseudolactation, and other issues. Diagnosis of ECD is usually based on clinical signs and endocrine tests. Medical management of affected horses is usually a long-term or lifelong commitment. The goal of this article is to review the pathophysiology of ECD, outline diagnostic tests, and present treatment options.
Evaluation of a combined laser Doppler flowmetry and iontophoresis technique for the assessment of equine cutaneous microvascular function. A combined laser Doppler flowmetry and iontophoresis (LDFI) technique, used routinely to assess human microvascular function, was evaluated as a noninvasive technique for assessment of equine microvascular function, to facilitate the study of diseases such as laminitis. Baseline and vasoactive agonist-induced (acetylcholine and nitroprusside) microvascular flux was quantified at 2 sites (on the dorsal pastern adjacent to the coronary band and over the gluteals) in 6 clinically normal horses on 5 or 6 separate occasions under standardised conditions. Both agonists significantly increased microv...
Isoxsuprine hydrochloride in the horse: a review. Isoxsuprine hydrochloride has been suggested for use in horses for treatment of navicular syndrome and laminitis. The drug has been shown to be a beta-adrenoreceptor antagonist with beta-adrenoreceptor agonistic properties, with both characteristics contributing to vasodilation and uterine relaxation. In addition, the drug is capable of decreasing blood viscosity and platelet aggregation. Studies have shown i.v. isoxsuprine to have a plasma half-life of <3 h with a large apparent volume of distribution. Cardiovascular effects resolve rapidly following i.v. administration, but are absent wit...
Measurement of basal serum insulin concentration in the diagnosis of Cushing’s disease in ponies. A high basal plasma or serum insulin concentration is commonly accepted as an indicator of Cushing's disease in horses. The results of the combined dexamethasone suppression test and thyrotropin-releasing hormone stimulation test were compared with the basal insulin concentrations and insulin response tests of eight hyperinsulinaemic and insulin-resistant ponies with clinical histories of chronic or recurrent laminitis that were suspected of having Cushing's disease. Seven of the eight ponies had normal responses to the combined test indicating that basal insulin concentrations are not a speci...
Expression of interleukin-1beta in the digital laminae of horses in the prodromal stage of experimentally induced laminitis. To study expression of interleukin-1beta (IL-1beta) in the digital laminae of horses in the prodromal stage of experimentally induced laminitis. Methods: 8 healthy adult horses with no signs of laminitis. Methods: Black walnut extract was administered via nasogastric tube to 4 horses, and water was administered to the remaining 4 (controls). Complete blood counts and physical examinations were performed every 30 minutes after administration of black walnut extract or water. General anesthesia was induced when total WBC count decreased by 30% in horses given the black walnut extract and 3 hours...
Pharmacokinetics and metabolic effects of triamcinolone acetonide and their possible relationships to glucocorticoid-induced laminitis in horses. Experiments were performed to establish the pharmacokinetics of triamcinolone acetonide and the effects of the glucocorticoid on glucose metabolism in horses. The pharmacokinetics after intravenous (i.v.) dosing was best described by a three-compartment open model. There was rapid distribution from the central compartment followed by two phases of elimination. The half-life of the rapid elimination phase was 83.5 min and of the slower phase was 12 h. The term (Vss/Vc)-1was 12.3 indicating extensive distribution into the tissues. Triamcinolone acetonide given i.v. or intramuscularly (i.m. ) ind...
Endotoxin and dietary amines may increase plasma 5-hydroxytryptamine in the horse. Uptake of 5-hydroxytryptamine (5-HT) into platelets is an important mechanism by which low plasma concentrations are maintained, and platelet activation may therefore result in significant release of this vasoconstrictor. The present study examined the kinetics of active uptake of radiolabelled [3H]5-HT by washed equine platelets in vitro, and investigated the effects on this process of 4 other naturally occurring monoamines which may be released from the caecum in conditions of carbohydrate overload. The release of [3H]5-HT by platelets was also studied, since platelet accumulation and activa...
Laminar microvascular flow, measured by means of laser Doppler flowmetry, during the prodromal stages of black walnut-induced laminitis in horses. To measure changes in laminar microvascular blood flow (LMBF) over time in healthy horses and horses in the prodromal stage of black walnut-induced laminitis and to determine the effects of glyceryl trinitrate application on LMBF in horses with acute laminitis. Methods: 10 healthy adult horses. Methods: Laser Doppler flowmetry was used to measure LMBF Baseline measurements were obtained, horses were given deionized water via a nasogastric tube, and measurements were obtained hourly for 12 hours. Twenty-four hours later, baseline measurements were again obtained, and horses were given black wal...
[Clinical symptoms of and diagnostic possibilities for hypophyseal adenoma in horses]. Hirsutism was the most often observed symptom in horses with a pituitary gland tumor and was present in all 13 examined horses. Other symptoms were atrophy of muscles (n = 10), hyperhidrosis (n = 8), polyuria/polydipsia (n = 5), bulging or supraorbital fat (n = 3), polyphagia (n = 2), apathy (n = 2) and seizures (n = 2). Laminitis was the most frequently observed concurrent disease (n = 8). Hyperglycaemia (mean, 9.9 +/- 3.71 mmol/l) in 13 horses and glucosuria (median, 55 [range, 2-55] mmol/l) in 7 horses were the most important laboratory results. The dexamethasone suppression test was positi...
