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.
Cause
- 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.
Diagnosis
- 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.
Treatment
- There is no effective treatment for affected cattle.
Prevention
- 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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