Colitis, Granulomatous

• Affects the horse.
  • Usually young to middle age adults.
• Unknown cause.
• Is a one-off occurence rather than a herd problem.
• As in Johnes Diseaase, there is chronic ongoing diarrhoea with eventual death.
• Thickening of mucosa is seen mainly in the caecum and colon.
  • Lamina propria contains granulomatous inflammatory tissue (as in Johne's Disease).
  • Sometimes large numbers of eosinophils are seen.
• Mesenteric lymph nodes are very large.
• At laparotomy lymph node appears like lymphosarcoma (very large).
• Cannot do much to remedy the condition once it has started.
  • Progresses to death.

Proposed Pathogenesis

• Hypersensitivity reaction to trichoneme parasite?
  • Possibly an idiosyncratic response to the encysted larvae.
• Dysbacteriosis or disordered immune response?