Eosinophilic Myositis

General description
  • Sarcosporidiosis is a parasitic disease of cattle and other mammals and birds.
  • Eosinophilic myositis is a collective term describing an inflammatory condition of some muscles in cattle characterised by major, green lesions, often produced by sarcocystis spores.
  • They are most likely to be seen in skeletal muscle, heart and the oesophagus.
  • Cattle become infected with intermediate stages of Sarcocystis spp by grazing infected pasture contaminated by the faeces of an infected host animal (e.g. fox, cat, dog).
  • The infected primary hosts pass spores in their faeces and cattle become secondary hosts when they ingest these spores which spread through the body to form infective cysts in muscle.
  • Sarcocystis spp. are the primary cause of eosinophilic myositis, which is mostly identified at meat inspection.
  • Some regions have a very high prevalence of infected cattle, reflecting the high number of infected primary hosts having access to cattle pastures.
  • Prevalence is highest in the northern and more extensive grazing cattle industries.
Clinical signs
  • Most infected cattle are clinically normal.
  • The sarcocystis cysts in muscle are mostly microscopic and not detected at meat inspection.
  • Carcases with eosinophilic myositis are trimmed or condemned, if severely affected.
  • There is no effective treatment for affected cattle.
  • Revolves around primary host management. Limiting access by dogs, cats, foxes and other carnivores to cattle pastures is the key control.
  • The spores can live on pasture for several years under favourable conditions.
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