Cyathostomosis

• In the horse.
• Small strongyles - Cyathostomins
• L3 to L4 development in nodules in mucosa/submucosa of caecum and colon
  • Can cause diarrhoea if mass emergence.

Pathology

Gross

• Encysted larvae appear as pinhead grey to red mucosal nodules.
• Mass emergence results in:
  • Mucosal erosions.
• Ulcers.
• Fibrinous exudates.
• Haemorrhage.

Histopathology

• Larvae in deep mucosa/sumucosa surrounded by fibrous capsule and mixed inflammatory cells.
• Intense eosinophil, neutrophil and macrophage infiltration when larvae emerge
  • May also be oedema and, if severe, mucosal ulceration.