title: Evidence for marsh mallow (Malva parviflora) toxicosis causing myocardial disease and myopathy in four horses.
abstract: OBJECTIVE
  Investigation of toxicosis caused by Malva parviflora was required after 4 horses from the same farm developed severe muscle fasciculations, tachycardia, sweating and periods of recumbency leading to death or euthanasia after ingesting the plant.
  
  
  OBJECTIVE
  To describe historical, clinical, clinicopathological and pathological findings of 4 horses with suspected M. parviflora toxicosis. The role of cyclopropene fatty acids (found in M. parviflora) and mechanism for toxicosis are proposed.
  
  
  METHODS
  Case series.
  
  
  METHODS
  Historical, physical examination, clinicopathological and pathological findings are reported. Due to similarities with atypical myopathy or seasonal pasture myopathy acyl carnitine profiles were performed on sera from 2 cases and equine controls. Presence of cyclopropene fatty acids was also examined in sera of 2 cases.
  
  
  RESULTS
  M. parviflora had been heavily grazed by the horses with little other feed available. Horse 1 deteriorated rapidly and was subjected to euthanasia. Horse 2 was referred to hospital where severe myocardial disease and generalised myopathy was determined; this horse was subjected to euthanasia 36 h after admission. Horse 3 died rapidly and Horse 4 was subjected to euthanasia at onset of clinical signs. Post-mortem examinations performed on 3 horses revealed acute, multifocal cardiac and skeletal myonecrosis. Myocyte glycogen accumulation was absent when examined in Horse 2. Acyl carnitine profiles revealed increased C14-C18 acyl carnitine concentrations in cases relative to controls. Cyclopropene fatty acids were detected in sera of cases but not controls.
  
  
  CONCLUSIONS
  These findings suggest aetiology different to that of atypical myopathy or seasonal pasture myopathy. We hypothesise that cyclopropene fatty acids in M. parviflora interfere with fatty acid β-oxidation in horses in negative energy balance, causing the clinical signs and abnormal acyl carnitine profiles. These equine cases suggest a pathophysiological course that closely mimics the human genetic condition very long chain acyl CoA dehydrogenase deficiency.
authors.affiliation: Faculty of Veterinary and Agricultural Sciences, University of Melbourne, Werribee, Victoria, Australia.
authors.forename: J
authors.initials: J
authors.lastname: Bauquier
authors.affiliation: Faculty of Veterinary and Agricultural Sciences, University of Melbourne, Werribee, Victoria, Australia.
authors.forename: A
authors.initials: A
authors.lastname: Stent
authors.affiliation: Victorian Department of Environment and Primary Industries, Bundoora, Victoria, Australia.
authors.forename: J
authors.initials: J
authors.lastname: Gibney
authors.affiliation: Victorian Department of Environment and Primary Industries, Bundoora, Victoria, Australia.
authors.forename: I
authors.initials: I
authors.lastname: Jerrett
authors.affiliation: Faculty of Veterinary and Agricultural Sciences, University of Melbourne, Parkville, Victoria, Australia.
authors.forename: J
authors.initials: J
authors.lastname: White
authors.affiliation: Faculty of Veterinary and Agricultural Sciences, University of Melbourne, Werribee, Victoria, Australia.
authors.forename: B
authors.initials: B
authors.lastname: Tennent-Brown
authors.affiliation: Golden Plains Equine, Bannockburn, Victoria, Australia.
authors.forename: A
authors.initials: A
authors.lastname: Pearce
authors.affiliation: Victorian Clinical Genetics Services, Royal Children's Hospital, Melbourne, Victoria, Australia.
authors.forename: J
authors.initials: J
authors.lastname: Pitt
mesh_terms: D000818:Animals; D009202:Cardiomyopathies / Q000139:chemically induced / Q000473:pathology / Q000662:veterinary*; D017809:Fatal Outcome; D005260:Female; D006734:Horse Diseases / Q000139:chemically induced* / Q000401:mortality; D006736:Horses; D006801:Humans; D008297:Male; D028501:Malva / Q000633:toxicity*; D010939:Plant Poisoning / Q000401:mortality / Q000473:pathology / Q000662:veterinary*
keywords: 
  Malva parviflora
  ; acyl carnitines; cardiomyopathy; fatty acid oxidation; horse; mallow; myopathy