Myopathy in horses refers to a group of muscle disorders that affect the skeletal muscles, leading to symptoms such as weakness, stiffness, and muscle damage. These disorders can result from various causes, including genetic factors, nutritional deficiencies, metabolic imbalances, or external stressors. Myopathies can be classified into different types, such as exertional myopathies, which are related to physical activity, and non-exertional myopathies, which occur independently of exercise. Common forms of equine myopathy include polysaccharide storage myopathy (PSSM), recurrent exertional rhabdomyolysis (RER), and atypical myopathy. Diagnosis often involves clinical examination, muscle biopsy, and genetic testing. This page gathers peer-reviewed research studies and scholarly articles that explore the pathophysiology, diagnosis, and management of myopathy in horses, providing insights into the underlying mechanisms and therapeutic approaches.
Myhre MG, Azeem A, Barrett M.Medical records from 2009 to 2021 from a private equine referral hospital in Rochester, NH, USA were analysed for cases that underwent general anaesthesia for low-field MRI of the distal limb. These were used to determine peri-anaesthetic morbidity and mortality. Unassigned: Two hundred and forty-three anaesthetic episodes were recorded in horses undergoing low-field MRI. The peri-anaesthetic complication rate prior to discharge was 6.2% (15/243). No patients experienced a fatal complication. Ninety two of the 243 patients had multiple sites imaged, 90/243 received pre-anaesthetic dantrolene, ...
Quarter horses (QH), a prominent athletic breed in Brazil, are affected by muscular genetic disorders such as myosin-heavy chain myopathy (MYHM), polysaccharide storage myopathy (PSSM1), hyperkalemic periodic paralysis (HyPP), and malignant hyperthermia (MH). Bull-catching (vaquejada), primarily involving QH, is a significant equestrian sport in Brazil. Since the allele frequencies (AF) of MYHM, PSSM1, HyPP, and MH in vaquejada QH remain unknown, this study evaluated the AF in 129 QH vaquejada athletes, specifically from the Brazilian Northeast. These variants were exclusively observed in hete...
Inflammatory myopathy and perivasculitis have been recently described in horses with chronic equine piroplasmosis (EP). These alterations may be linked to poor performances. The aims of this study were to evaluate the prevalence for EP in clinically healthy Italian Standardbred (IS) racehorses and to compare laboratory parameters and performance metrics between positive and negative horses. Real-time PCR was applied for the detection of T. equi and B. caballi positivity. Haematology parameters, blood chemistry results, subjective muscle mass scores, and performance metrics were compared betwee...
Kruse CJ, Dieu M, Renaud B, François AC, Stern D, Demazy C, Burteau S, Boemer F, Art T, Renard P, Votion DM.Equine atypical myopathy (AM) is a severe environmental intoxication linked to the ingestion of protoxins contained in seeds and seedlings of the sycamore maple (Acer pseudoplatanus) in Europe. The toxic metabolites cause a frequently fatal rhabdomyolysis syndrome in grazing horses. Since these toxic metabolites can also be present in cograzing horses, it is still unclear as to why, in a similar environmental context, some horses show signs of AM, whereas others remain clinically healthy. Label-free proteomic analyses on the serum of 26 diseased AM, 23 cograzers, and 11 control horses were per...
Aleman M, Vedavally U, Pusterla N, Wensley F, Berryhill E, Madigan JE.Comprehensive descriptions of equids with granulocytic anaplasmosis (EGA) with neurologic or muscle disease and other atypical presentations are scarce in the literature. Objective: Describe the clinical signs, laboratory findings, treatment, and outcome of equids with EGA with emphasis on neurologic and muscle disease. Methods: Thirty-eight horses, 1 donkey. Methods: Retrospective study. Equids with EGA were included. The electronic data base was searched from January 2000 to December 2022 using the words anaplasmosis, ehrlichiosis, granulocytic, and rickettsia. Signalment and clinical data w...
Faccin M, Landsgaard KA, Milliron SM, Jennings AH, Keith Chaffin M, Giaretta PR, Rech RR.A 1.5-year-old American quarter horse gelding (case 1) and an 11-month-old American quarter horse filly (case 2) were presented for acute onset pelvic lameness and lethargy. Case 1 had nasal discharge, while case 2 developed rapid muscle atrophy. Both horses had elevated serum creatine kinase activity. The horses showed similar polyphasic histiocytic and lymphoplasmacytic myositis with necrosis, mineralization, and regeneration. Additionally, case 1 had Streptococcus equi subsp. equi-induced suppurative retropharyngeal lymphadenitis with renal purpura hemorrhagica and myoglobinuric nephropathy...
Wouters CP, Toquet MP, Renaud B, François AC, Fortier-Guillaume J, Marcillaud-Pitel C, Boemer F, De Tullio P, Richard EA, Votion DM.Atypical myopathy (AM) is a severe rhabdomyolysis syndrome that occurs in grazing horses. Despite the presence of toxins in their blood, all horses from the same pasture are not prone to display clinical signs of AM. The objective of this study was to compare the blood metabolomic profiles of horses with AM clinical signs with those of healthy co-grazing (Co-G) horses. To do so, plasma samples from 5 AM horses and 11 Co-G horses were investigated using untargeted metabolomics. Metabolomic data were evaluated using unsupervised, supervised, and pathway analyses. Unsupervised principal component...
Wimmer-Scherr C, Taminiau B, Renaud B, van Loon G, Palmers K, Votion D, Amory H, Daube G, Cesarini C.Equine atypical myopathy (AM) is caused by hypoglycin A (HGA) and methylenecyclopropylglycine (MCPG) intoxication resulting from the ingestion of seeds or seedlings of some Acer tree species. Interestingly, not all horses pasturing in the same toxic environment develop signs of the disease. In other species, it has been shown that the intestinal microbiota has an impact on digestion, metabolism, immune stimulation and protection from disease. The objective of this study was to characterize and compare fecal microbiota of horses suffering from AM and healthy co-grazers. Furthermore, potential d...
Sander J, Terhardt M, Janzen N.Plants from the Sapindaceae family that are consumed by horses (maple) and humans (ackee and litchi) are known to contain the toxins hypoglycin A and methylenecyclopropylglycine which cause seasonally occurring myopathy in horses and entero-encephalopathic sickness in humans. Vertical transmission of these toxins from a mare to her foal has been described once. However the mare's milk was not available for analysis in this case. We investigated mare's milk in a similar case. Objective: We hypothesized that hypoglycin A and methylenecyclopropylglycine, like other amino acids' are secreted into ...
Bochnia M, Sander J, Ziegler J, Terhardt M, Sander S, Janzen N, Cavalleri JV, Zuraw A, Wensch-Dorendorf M, Zeyner A.Atypical myopathy (AM) in horses is caused by ingestion of seeds of the Acer species (Sapindaceae family). Methylenecyclopropylacetyl-CoA (MCPA-CoA), derived from hypoglycin A (HGA), is currently the only active toxin in Acer pseudoplatanus or Acer negundo seeds related to AM outbreaks. However, seeds or arils of various Sapindaceae (e.g., ackee, lychee, mamoncillo, longan fruit) also contain methylenecyclopropylglycine (MCPG), which is a structural analogue of HGA that can cause hypoglycaemic encephalopathy in humans. The active poison formed from MCPG is methylenecyclopropylformyl-CoA (MCPF-...
Krägeloh T, Cavalleri JMV, Ziegler J, Sander J, Terhardt M, Breves G, Cehak A.Intestinal absorption of hypoglycin A (HGA) and its metabolism are considered major prerequisites for atypical myopathy (AM). The increasing incidence and the high mortality rate of AM urgently necessitate new therapeutic and/or preventative approaches. Objective: To identify a substance for oral administration capable of binding HGA in the intestinal lumen and effectively reducing the intestinal absorption of the toxin. Methods: Experimental in vitro study. Methods: Substances commonly used in equine practice (activated charcoal composition, di-tri-octahedral smectite, mineral oil and activat...
Boemer F, Detilleux J, Cello C, Amory H, Marcillaud-Pitel C, Richard E, van Galen G, van Loon G, Lefère L, Votion DM.Equine atypical myopathy (AM) is caused by hypoglycin A intoxication and is characterized by a high fatality rate. Predictive estimation of survival in AM horses is necessary to prevent unnecessary suffering of animals that are unlikely to survive and to focus supportive therapy on horses with a possible favourable prognosis of survival. We hypothesized that outcome may be predicted early in the course of disease based on the assumption that the acylcarnitine profile reflects the derangement of muscle energetics. We developed a statistical model to prognosticate the risk of death of diseased a...
Karlíková R, Široká J, Jahn P, Friedecký D, Gardlo A, Janečková H, Hrdinová F, Drábková Z, Adam T.Atypical myopathy (AM) is a potentially fatal disease of grazing horses. It is reportedly caused by the ingestion of sycamore seeds containing toxic hypoglycin A. In order to study metabolic changes, serum and urine samples from nine horses with atypical myopathy and 12 control samples from clinically healthy horses were collected and then analysed using a high-performance liquid chromatography coupled with tandem mass spectrometry; serum metabolic profiles as the disease progressed were also studied. Metabolic data were evaluated using unsupervised and supervised multivariate analyses. Signif...
Westermann CM, van Leeuwen R, van Raamsdonk LW, Mol HG.Atypical myopathy (AM) in horses is caused by the plant toxin hypoglycin A, which in Europe typically is found in the sycamore maple tree (Acer pseudoplatanus). Owners are concerned about whether their horses are in danger if they graze near maple trees. Objective: To measure hypoglycin A in the most common maple tree species in the Netherlands, and to determine whether concentration of toxin is a predictor of AM in horses. Methods: A total of 278 samples of maple tree leaves, sprouts, and seeds were classified by species. Mean concentrations of hypoglycin A were compared for the type of sampl...
Baise E, Habyarimana JA, Amory H, Boemer F, Douny C, Gustin P, Marcillaud-Pitel C, Patarin F, Weber M, Votion DM.Ingestion of sycamore seeds (Acer pseudoplatanus) is the likely source of hypoglycin A in atypical myopathy (AM) but ingestion of seedlings in spring might also contribute to intoxication. Objective: To test for hypoglycin A in seeds and seedlings collected on pastures where AM cases were reported and compare its concentration in serum of affected and healthy horses. Methods: Field investigation of clinical cases. Methods: Whenever present, samaras (the winged nuts that each contain one seed) and/or seedlings were collected from pastures of 8 AM cases and 5 unaffected horses from different pre...
Lotstra RJ, van den Broek J, Power T, Marr CM, Wijnberg ID.Atrial fibrillation is a common equine arrhythmia. Quinidine alone, or with digoxin are common treatments. Studies on outcome in Warmblood populations in which duration of the AF is often unknown are limited. Objective: To identify the factors that are associated with the success of full treatment cardioversion with oral medication, and establish whether there are differences in these factors between institutions. Methods: Retrospective case series using patient records of Equine University Clinic of Utrecht University and Rossdales Equine Hospital, Newmarket. Methods: Forty-nine horses treate...
Unger L, Nicholson A, Jewitt EM, Gerber V, Hegeman A, Sweetman L, Valberg S.Hypoglycin A, found in seeds of Acer negundo, appears to cause seasonal pasture myopathy (SPM) in North America and is implicated in atypical myopathy (AM) in Europe. Acer negundo is uncommon in Europe. Thus, the potential source of hypoglycin A in Europe is unknown. Objective: We hypothesized that seeds of Acer pseudoplatanus were the source of hypoglycin A in Europe. Our objective was to determine the concentration of hypoglycin A in seeds of A. pseudoplatanus trees located in pastures where previous cases of AM had occurred. Methods: None. Methods: University of Berne records were searched ...
Pruitt BN.Rhabdomyolysis in equines occurs in horses due to physical overexertion or underlying pathologic myopathy. Methocarbamol is a muscle relaxant that can be used in equines to treat symptoms associated with Rhabdomyolysis. Methocarbamol is available as a solution for injection but is not commercially available as an oral suspension. This article focuses on the treatment of Tying-up caused by overexertion, and details the treatment of Rhabdomyolysis with an oral suspension that was prepared for a veterinarian by a compounding pharmacist.
Votion DM, van Galen G, Sweetman L, Boemer F, de Tullio P, Dopagne C, Lefère L, Mouithys-Mickalad A, Patarin F, Rouxhet S, van Loon G, Serteyn D....It is hypothesised that European atypical myopathy (AM) has a similar basis as seasonal pasture myopathy in North America, which is now known to be caused by ingestion of hypoglycin A contained in seeds from the tree Acer negundo. Serum from horses with seasonal pasture myopathy contained the conjugated toxic metabolite of hypoglycin A, methylenecyclopropyl acetic acid (MCPA). Methods: Retrospective study on archived samples. Objective: 1) To determine whether MCPA-carnitine was present in serum of European horses confirmed to have AM; 2) to determine whether Acer negundo or related Acer speci...
Streeter RM, Divers TJ, Mittel L, Korn AE, Wakshlag JJ.Selenium and vitamin E deficiency have been associated with nutritional myopathy, more commonly known as white muscle disease (WMD) in horses. However, correlations between selenium concentrations and presenting clinical signs, age, breed, gender, serum vitamin E, creatine kinase (CK) and final diagnosis, have not previously been evaluated. Objective: To determine the number of hospitalised horses in 3 age groups that were selenium tested and the proportions of horses with categorised presenting clinical signs; the association/odds risk of final diagnosis with selenium deficiency and to examin...
van Galen G, Cerri S, Porter S, Saegerman C, Lefere L, Roscher K, Marr C, Amory H, Votion DM.Descriptions of acid-base disturbances in atypical myopathy (AM) are limited. Objective: Describe and compare traditional and quantitative acid-base abnormalities and cardiovascular shock status in horses with AM at admission. Methods: 34 horses with AM, 15 healthy controls. Methods: Retrospective case-control study. Records were searched for shock variables (packed cell volume [PCV], blood urea nitrogen [BUN], heart and respiratory rate) and acid-base variables (venous blood gas analysis, electrolytes, total protein, lactate) on admission. Base excess (BE) of free water (BEfw), chloride (BEcl...
Verheyen T, Decloedt A, De Clercq D, van Loon G.Atypical myopathy (AM) is an acute, fatal rhabdomyolysis in grazing horses that mainly affects skeletal muscles. Postmortem examinations have shown that myocardial damage also occurs. Limited information is available on the effect of AM on cardiac function in affected and surviving horses. Objective: To describe electrocardiographic and echocardiographic changes associated with AM in the acute stage of the disease and after follow-up. Methods: Horses (n = 12) diagnosed with AM in which cardiac ultrasound examination and ECG recording were available. Methods: All horses underwent clinical exami...
Westermann CM, Dorland L, van Diggelen OP, Schoonderwoerd K, Bierau J, Waterham HR, van der Kolk JH.Earlier research on ten horses suffering from the frequently fatal disorder atypical myopathy showed that MADD (multiple acyl-CoA dehydrogenase deficiency) is the biochemical derangement behind atypical myopathy. From five horses that died as a result of this disease and seven healthy control horses, urine and plasma were collected ante mortem and muscle biopsies were obtained immediately post-mortem (2 patients and 7 control horses), to analyse creatine, purine and carbohydrate metabolism as well as oxidative phosphorylation. In patients, the mean creatine concentration in urine was increased...
Aleman M, Nieto JE.To investigate gene expression of the major proteolytic systems and growth regulators in skeletal muscle of horses with myopathy associated with pituitary pars intermedia dysfunction (PPID). Methods: 14 horses with PPID-associated myopathy and 7 healthy control horses. Methods: Horses with PPID and controls were age matched (15 to 28 years old). Muscle biopsy specimens were collected from both groups and processed for RNA and cDNA extraction. Validation of the most stable housekeeping genes for skeletal muscle was performed and used to compare gene expression of the following proteolytic syste...
Votion DM, Linden A, Saegerman C, Engels P, Erpicum M, Thiry E, Delguste C, Rouxhet S, Demoulin V, Navet R, Sluse F, Serteyn D, van Galen G, Amory H.The emergent nature of atypical myopathy or atypical myoglobinuria (AM) necessitates precise description of its clinical and epidemiologic features. Objective: To define key features of AM to help practitioners recognize the disease and to advise owners to take preventive measures. Methods: Belgian cases of AM confirmed by histology (CC horses; n = 57) from autumn 2000 to spring 2005 were included in the study. Co-grazing horses (Co-G horses; n = 77) that remained free of any abnormal clinical signs constituted a control group. Methods: History, environmental characteristics, clinical signs, a...
Vercauteren G, van der Heyden S, Lefère L, Chiers K, Laevens H, Ducatelle R.This report concerns 2 horses that suffered typical clinical signs of atypical myopathy (AM) and equine grass sickness (EGS) concurrently. Clinical details and pathological lesions of the cases are described. EGS and AM are relatively rare diseases and the concurrency of the diseases in the same animals is therefore considered unlikely to be a coincidence. However, it is not suggested that the evidence shows a common aetiology but rather the existence of common predisposing causes.
Trim CM.Hemorrhagic myelopathy or myelomalacia is an uncommon cause of failure to stand after general anesthesia. Affected horses are usually young and have been anesthetized for relatively short times in dorsal recumbency. Clinical signs involve the hind limbs and include loss of deep pain perception. Etiology of this condition is not known. Differentiation from other forms of neuropathy and myopathy is important to the prognosis.
Unger L, Nicholson A, Jewitt EM, Gerber V, Hegeman A, Sweetman L, Valberg S.Hypoglycin A, found in seeds of Acer negundo, appears to cause seasonal pasture myopathy (SPM) in North America and is implicated in atypical myopathy (AM) in Europe. Acer negundo is uncommon in Europe. Thus, the potential source of hypoglycin A in Europe is unknown. Objective: We hypothesized that seeds of Acer pseudoplatanus were the source of hypoglycin A in Europe. Our objective was to determine the concentration of hypoglycin A in seeds of A. pseudoplatanus trees located in pastures where previous cases of AM had occurred. Methods: None. Methods: University of Berne records were searched ...
Votion DM, Linden A, Saegerman C, Engels P, Erpicum M, Thiry E, Delguste C, Rouxhet S, Demoulin V, Navet R, Sluse F, Serteyn D, van Galen G, Amory H.The emergent nature of atypical myopathy or atypical myoglobinuria (AM) necessitates precise description of its clinical and epidemiologic features. Objective: To define key features of AM to help practitioners recognize the disease and to advise owners to take preventive measures. Methods: Belgian cases of AM confirmed by histology (CC horses; n = 57) from autumn 2000 to spring 2005 were included in the study. Co-grazing horses (Co-G horses; n = 77) that remained free of any abnormal clinical signs constituted a control group. Methods: History, environmental characteristics, clinical signs, a...
Baise E, Habyarimana JA, Amory H, Boemer F, Douny C, Gustin P, Marcillaud-Pitel C, Patarin F, Weber M, Votion DM.Ingestion of sycamore seeds (Acer pseudoplatanus) is the likely source of hypoglycin A in atypical myopathy (AM) but ingestion of seedlings in spring might also contribute to intoxication. Objective: To test for hypoglycin A in seeds and seedlings collected on pastures where AM cases were reported and compare its concentration in serum of affected and healthy horses. Methods: Field investigation of clinical cases. Methods: Whenever present, samaras (the winged nuts that each contain one seed) and/or seedlings were collected from pastures of 8 AM cases and 5 unaffected horses from different pre...
Verheyen T, Decloedt A, De Clercq D, van Loon G.Atypical myopathy (AM) is an acute, fatal rhabdomyolysis in grazing horses that mainly affects skeletal muscles. Postmortem examinations have shown that myocardial damage also occurs. Limited information is available on the effect of AM on cardiac function in affected and surviving horses. Objective: To describe electrocardiographic and echocardiographic changes associated with AM in the acute stage of the disease and after follow-up. Methods: Horses (n = 12) diagnosed with AM in which cardiac ultrasound examination and ECG recording were available. Methods: All horses underwent clinical exami...
Muylle E, Vandenhende C, Oyaert W, Thoonen H, Vlaeminck K.Thirty-two horses were examined with a history of poor performance and unthriftiness several months after the ingestion of feed containing monensin sodium. Cardiac abnormality was diagnosed in 8 cases and suspected in 4 others. Necropsy examinations were performed on 6 cases with marked clinical symptoms and evidence of circulatory failure was found. Marked cardiac myopathy and fibrosis was a consistent feature. It is concluded that ingestion of monensin sodium by horses may cause either acute death or delayed cardiac circulatory failure as a result of specific cardiac myodegeneration.
Karlíková R, Široká J, Jahn P, Friedecký D, Gardlo A, Janečková H, Hrdinová F, Drábková Z, Adam T.Atypical myopathy (AM) is a potentially fatal disease of grazing horses. It is reportedly caused by the ingestion of sycamore seeds containing toxic hypoglycin A. In order to study metabolic changes, serum and urine samples from nine horses with atypical myopathy and 12 control samples from clinically healthy horses were collected and then analysed using a high-performance liquid chromatography coupled with tandem mass spectrometry; serum metabolic profiles as the disease progressed were also studied. Metabolic data were evaluated using unsupervised and supervised multivariate analyses. Signif...
Sander J, Terhardt M, Janzen N.Plants from the Sapindaceae family that are consumed by horses (maple) and humans (ackee and litchi) are known to contain the toxins hypoglycin A and methylenecyclopropylglycine which cause seasonally occurring myopathy in horses and entero-encephalopathic sickness in humans. Vertical transmission of these toxins from a mare to her foal has been described once. However the mare's milk was not available for analysis in this case. We investigated mare's milk in a similar case. Objective: We hypothesized that hypoglycin A and methylenecyclopropylglycine, like other amino acids' are secreted into ...
van Galen G, Cerri S, Porter S, Saegerman C, Lefere L, Roscher K, Marr C, Amory H, Votion DM.Descriptions of acid-base disturbances in atypical myopathy (AM) are limited. Objective: Describe and compare traditional and quantitative acid-base abnormalities and cardiovascular shock status in horses with AM at admission. Methods: 34 horses with AM, 15 healthy controls. Methods: Retrospective case-control study. Records were searched for shock variables (packed cell volume [PCV], blood urea nitrogen [BUN], heart and respiratory rate) and acid-base variables (venous blood gas analysis, electrolytes, total protein, lactate) on admission. Base excess (BE) of free water (BEfw), chloride (BEcl...
Aleman M, Nieto JE.To investigate gene expression of the major proteolytic systems and growth regulators in skeletal muscle of horses with myopathy associated with pituitary pars intermedia dysfunction (PPID). Methods: 14 horses with PPID-associated myopathy and 7 healthy control horses. Methods: Horses with PPID and controls were age matched (15 to 28 years old). Muscle biopsy specimens were collected from both groups and processed for RNA and cDNA extraction. Validation of the most stable housekeeping genes for skeletal muscle was performed and used to compare gene expression of the following proteolytic syste...
Streeter RM, Divers TJ, Mittel L, Korn AE, Wakshlag JJ.Selenium and vitamin E deficiency have been associated with nutritional myopathy, more commonly known as white muscle disease (WMD) in horses. However, correlations between selenium concentrations and presenting clinical signs, age, breed, gender, serum vitamin E, creatine kinase (CK) and final diagnosis, have not previously been evaluated. Objective: To determine the number of hospitalised horses in 3 age groups that were selenium tested and the proportions of horses with categorised presenting clinical signs; the association/odds risk of final diagnosis with selenium deficiency and to examin...
Trim CM.Hemorrhagic myelopathy or myelomalacia is an uncommon cause of failure to stand after general anesthesia. Affected horses are usually young and have been anesthetized for relatively short times in dorsal recumbency. Clinical signs involve the hind limbs and include loss of deep pain perception. Etiology of this condition is not known. Differentiation from other forms of neuropathy and myopathy is important to the prognosis.
Wouters CP, Toquet MP, Renaud B, François AC, Fortier-Guillaume J, Marcillaud-Pitel C, Boemer F, De Tullio P, Richard EA, Votion DM.Atypical myopathy (AM) is a severe rhabdomyolysis syndrome that occurs in grazing horses. Despite the presence of toxins in their blood, all horses from the same pasture are not prone to display clinical signs of AM. The objective of this study was to compare the blood metabolomic profiles of horses with AM clinical signs with those of healthy co-grazing (Co-G) horses. To do so, plasma samples from 5 AM horses and 11 Co-G horses were investigated using untargeted metabolomics. Metabolomic data were evaluated using unsupervised, supervised, and pathway analyses. Unsupervised principal component...
Pruitt BN.Rhabdomyolysis in equines occurs in horses due to physical overexertion or underlying pathologic myopathy. Methocarbamol is a muscle relaxant that can be used in equines to treat symptoms associated with Rhabdomyolysis. Methocarbamol is available as a solution for injection but is not commercially available as an oral suspension. This article focuses on the treatment of Tying-up caused by overexertion, and details the treatment of Rhabdomyolysis with an oral suspension that was prepared for a veterinarian by a compounding pharmacist.
Meijer AE, van den Hoven R, Wensing T, Breukink HJ.In this communication, the results of an enzyme histochemical study on m. gluteus medius of horses, sensitive to exertional myopathy, during attacks of rhabdomyolysis are presented. The activity and location of about 25 enzymes were examined. In the present report, the early metabolic changes are discussed. Within 6 min after an attack, some large rounded fibres (approximately 2%) were seen, which showed an intense red staining in the haematoxylin and eosin sections. These hypercontracted fibres showed an increase in activity of mitochondrial adenosine triphosphatase, indicating the presence o...
Valverde A, Boyd CJ, Dyson DH, Pascoe PJ.Dantrolene, a drug used in the prevention and treatment of malignant hyperthermia, was believed responsible for prolonged postanesthetic recumbency in a horse. Prophylactically, dantrolene was given orally before induction of anesthesia. Dantrolene has been recommended for use in horses at risk of developing postanesthetic myopathy. Side effects, including ataxia, may result from dantrolene administration.
Faccin M, Landsgaard KA, Milliron SM, Jennings AH, Keith Chaffin M, Giaretta PR, Rech RR.A 1.5-year-old American quarter horse gelding (case 1) and an 11-month-old American quarter horse filly (case 2) were presented for acute onset pelvic lameness and lethargy. Case 1 had nasal discharge, while case 2 developed rapid muscle atrophy. Both horses had elevated serum creatine kinase activity. The horses showed similar polyphasic histiocytic and lymphoplasmacytic myositis with necrosis, mineralization, and regeneration. Additionally, case 1 had Streptococcus equi subsp. equi-induced suppurative retropharyngeal lymphadenitis with renal purpura hemorrhagica and myoglobinuric nephropathy...
Vercauteren G, van der Heyden S, Lefère L, Chiers K, Laevens H, Ducatelle R.This report concerns 2 horses that suffered typical clinical signs of atypical myopathy (AM) and equine grass sickness (EGS) concurrently. Clinical details and pathological lesions of the cases are described. EGS and AM are relatively rare diseases and the concurrency of the diseases in the same animals is therefore considered unlikely to be a coincidence. However, it is not suggested that the evidence shows a common aetiology but rather the existence of common predisposing causes.
Bain FT, Merritt AM.To investigate the possibility that a disorder of potassium balance may have a role in the development of equine rhabdomyolysis, the potassium concentration within erythrocytes (RBC [K+]) and plasma (P [K+]) was measured in 3 groups of horses: group 1, eight 2-year-old fillies that had postexercise muscle soreness within 48 hours of sample collection; group 2, ten 2-year-old fillies subjected to identical management and training conditions (as fillies of group 1) and that did not have signs of myopathy; and group 3, 32 yearlings of both sexes on the farm of origin of groups 1 and 2 that were p...
Westermann CM, van Leeuwen R, van Raamsdonk LW, Mol HG.Atypical myopathy (AM) in horses is caused by the plant toxin hypoglycin A, which in Europe typically is found in the sycamore maple tree (Acer pseudoplatanus). Owners are concerned about whether their horses are in danger if they graze near maple trees. Objective: To measure hypoglycin A in the most common maple tree species in the Netherlands, and to determine whether concentration of toxin is a predictor of AM in horses. Methods: A total of 278 samples of maple tree leaves, sprouts, and seeds were classified by species. Mean concentrations of hypoglycin A were compared for the type of sampl...
Beech J, Lindborg S, Braund KG.Potassium concentrations were measured in semimembranosus muscle, plasma and erythrocytes, and the urinary fractional excretion determined in normal horses and those that had chronic intermittent exercise-associated rhabdomyolysis. Muscle from the rhabdomyolysis horses was also evaluated microscopically. The horses with rhabdomyolysis had a lower muscle potassium concentration on a dry weight basis. Although the wet weight potassium content was also lower, the difference was not significant. Urinary fractional excretion of potassium (and also sodium and chloride) did not differ significantly b...
Lotstra RJ, van den Broek J, Power T, Marr CM, Wijnberg ID.Atrial fibrillation is a common equine arrhythmia. Quinidine alone, or with digoxin are common treatments. Studies on outcome in Warmblood populations in which duration of the AF is often unknown are limited. Objective: To identify the factors that are associated with the success of full treatment cardioversion with oral medication, and establish whether there are differences in these factors between institutions. Methods: Retrospective case series using patient records of Equine University Clinic of Utrecht University and Rossdales Equine Hospital, Newmarket. Methods: Forty-nine horses treate...
Krägeloh T, Cavalleri JMV, Ziegler J, Sander J, Terhardt M, Breves G, Cehak A.Intestinal absorption of hypoglycin A (HGA) and its metabolism are considered major prerequisites for atypical myopathy (AM). The increasing incidence and the high mortality rate of AM urgently necessitate new therapeutic and/or preventative approaches. Objective: To identify a substance for oral administration capable of binding HGA in the intestinal lumen and effectively reducing the intestinal absorption of the toxin. Methods: Experimental in vitro study. Methods: Substances commonly used in equine practice (activated charcoal composition, di-tri-octahedral smectite, mineral oil and activat...
Westermann CM, Dorland L, van Diggelen OP, Schoonderwoerd K, Bierau J, Waterham HR, van der Kolk JH.Earlier research on ten horses suffering from the frequently fatal disorder atypical myopathy showed that MADD (multiple acyl-CoA dehydrogenase deficiency) is the biochemical derangement behind atypical myopathy. From five horses that died as a result of this disease and seven healthy control horses, urine and plasma were collected ante mortem and muscle biopsies were obtained immediately post-mortem (2 patients and 7 control horses), to analyse creatine, purine and carbohydrate metabolism as well as oxidative phosphorylation. In patients, the mean creatine concentration in urine was increased...
Wimmer-Scherr C, Taminiau B, Renaud B, van Loon G, Palmers K, Votion D, Amory H, Daube G, Cesarini C.Equine atypical myopathy (AM) is caused by hypoglycin A (HGA) and methylenecyclopropylglycine (MCPG) intoxication resulting from the ingestion of seeds or seedlings of some Acer tree species. Interestingly, not all horses pasturing in the same toxic environment develop signs of the disease. In other species, it has been shown that the intestinal microbiota has an impact on digestion, metabolism, immune stimulation and protection from disease. The objective of this study was to characterize and compare fecal microbiota of horses suffering from AM and healthy co-grazers. Furthermore, potential d...
Boemer F, Detilleux J, Cello C, Amory H, Marcillaud-Pitel C, Richard E, van Galen G, van Loon G, Lefère L, Votion DM.Equine atypical myopathy (AM) is caused by hypoglycin A intoxication and is characterized by a high fatality rate. Predictive estimation of survival in AM horses is necessary to prevent unnecessary suffering of animals that are unlikely to survive and to focus supportive therapy on horses with a possible favourable prognosis of survival. We hypothesized that outcome may be predicted early in the course of disease based on the assumption that the acylcarnitine profile reflects the derangement of muscle energetics. We developed a statistical model to prognosticate the risk of death of diseased a...
Bochnia M, Sander J, Ziegler J, Terhardt M, Sander S, Janzen N, Cavalleri JV, Zuraw A, Wensch-Dorendorf M, Zeyner A.Atypical myopathy (AM) in horses is caused by ingestion of seeds of the Acer species (Sapindaceae family). Methylenecyclopropylacetyl-CoA (MCPA-CoA), derived from hypoglycin A (HGA), is currently the only active toxin in Acer pseudoplatanus or Acer negundo seeds related to AM outbreaks. However, seeds or arils of various Sapindaceae (e.g., ackee, lychee, mamoncillo, longan fruit) also contain methylenecyclopropylglycine (MCPG), which is a structural analogue of HGA that can cause hypoglycaemic encephalopathy in humans. The active poison formed from MCPG is methylenecyclopropylformyl-CoA (MCPF-...
