Category:Enteritis, Villus Atrophy

Villus Atrophy

• Commonly seen in enteric disease.
• Occurs when more enterocytes are lost than are produced in the crypts.
• Causes malabsorption of nutrients and water.
• There are two main types of villus atrophy:

Villus atrophy with intact/hypertrophic crypt glands

• Insult affects the villus enterocytes leading to increased loss.
  • Under mild insult, villi may fully regenerate.
  • Severe insult leads to immature cells on the villus.
    • Secrete water and electrolytes into lumen.
• Examples include:
  • Rotavirus, Coronavirus
    • Infect villus enterocytes.
  • Coccidia
    • Infect surface enterocytes.
  • Nematodes
    • Abrase surface.

Villus atrophy with damage to crypts

• The primary insult is to crypt cells.
  • Crypt cell death leads to dilated gland lumens (cysts).
  • Production is impaired, eventually leading to insufficient cells for villi.
• Enterocytes lost to lumen are replaced by increasingly immature cells.
  • Gives rise to severe malabsorption.
• If damage is severe, erosions/ulcers may form which may eventually heal.
  • Even if there are no ulcers, damage can be long-term
    • Causes long-term malabsorption.
• Examples include:
  • Parvovirus
    • Target crypt cells.
  • Lymphoma
    • Numerous neoplastic lymphocytes compress crypts.
  • Cytotoxic chemicals
    • Dividing crypt cells are susceptible.

Enteritis Particularly Associated with Villus Atrophy

Rotavirus

Cryptosporidium

• Small coccidial parasite.
• Affects calf, lamb, piglet, kitten.
• Increasingly important as part of the neonatal diarrhoea complex in calves.
• Zoonosis.

Pathology

Gross

• Intestines diffusely reddened, with fluid contents.

Histological

• Tiny parasites on surface of epithelium.
• Villus atrophy and fusion.
• Iinflammation (mainly lymphoid) in crypts and lamina propria.