Liphook Equine Hospital (LEH) would like to alert colleagues that they have diagnosed five cases of atypical myopathy (myoblobinuria/myoglobinaemia) in the past seven days.  LEH are also aware of a further four cases attended by veterinarians which have died in the Hampshire/Sussex/Surrey area.  They have advised that co-grazing horses should be removed from affected pastures.


Cases have been treated with analgesics (non-steroidal anti-inflammatory drugs, opioids, lidocaine), parenteral nutrition, isotonic intravenous fluids, nasogastric laxatives and supportive nursing care, multivitamin supplementation and electrolyte optimisation.  LEH's current survival rate (two of five horses are alive) supports previously published survival rates of 10-25%.


At the time of referral these horses demonstrated recognisable signs of atypical myopathy such as sweating, increased respiratory rate and effort, muscle fasciculations, reluctance to walk, tachycardia, tachyarythmias and increased periods of recumbency. All had dark brown urine (myoglobin) with marked elevations in CK (creatinine kinase), LDH (lactate dehydrogenase) and AST (aspartate aminotransferase) (CK levels 55,000 to 89,000 iu/L) and moderate acute inflammatory responses (serum amyloid A; 80-120 mg/L).


Notably, for a day or two prior to referral these horses displayed clinical signs less well recognised in atypical myopathy cases. These signs included:-


  • vigorous head shaking and nodding
  • frenzied vocalisation
  • recurrent choke-like retching neck spasms without a persistent oesophageal obstruction
  • stiffness and lethargy when ridden.


This alert aims to draw attention to this recent outbreak of atypical myopathy and these unusual early signs of the disease, in order that new cases may be detected and treated promptly and so that co-grazing horses may be removed from affected pastures as soon as suspicions are raised.


Further information for vets can be obtained from the following website:  http://www.myopathieatypique.fr/en/ .  Vets are also encouraged to report cases to Dominique Votion (dominique.votion@ulg.ac.be) who co-ordinates the AM website above and their associated alert group.