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?