Intestinal causes of weight loss

Question 1

What is the most common mechanism of weight loss? And the next 2?

Answer 1

• loss of nutrients (malabsorption/maldigestion)
• increased rate of utilisation
• decreased dietary intake

Question 2

What are small intestinal causes of weight loss?

Answer 2

• Chronic inflammatory bowel disease (CIBD):
  ◦ Granulomatous enteritis (GE)
  ◦ Eosinophilic Entercolitis (EE)
  ◦ Lymphocytic-Plasmacytic Enterocolitis (LPE)
• Proliferative Enteropathy
• Alimentary tract neoplasias

Question 3

What is proliferative enteropathy?

Answer 3

• Lawsonia intracellularis
  ◦ Obligate intracellular bacterium
• Affects cytoplasm of proliferative crypt epithelial cells
• In the jejunum & ileum
• Weanling foals between 3 to 8 months age
• Individuals or outbreaks
• Uncommonly in yearlings and adult horses
• Close proximity to swine

Question 4

What are risk factors for proliferative enteropathy?

Answer 4

• Overcrowding
• Feed changes
• ATB usage
• Mixing & transportation
• Weaning

Question 5

What are large intestinal causes of weight loss?

Answer 5

• Parasite infestation
• Right dorsal colitis (RDC)
• Sand enteropathy
• EEs

Question 6

What parasites cause weight loss?

Answer 6

Large strongyles - vulgaris, edentatus and equinus
Small strongyles

Question 7

How do parasites cause weight loss?

Answer 7

Large strongyles
* Migration of larvae through intestinal wall
◦ 4th stage larvae migrates
◦ Lumen → mucosa & submucosa
◦ Affects myoelectrical activity
◦ Infiltration with inflammatory cells
◦ Edema & hemorrhage
◦ Increased secretion + decreased absorption

Small strongyles
* Migration of L4 through mucosa of LI
* Include a period of hypobiosis
* Larvae emerge in response to unknown stimulus
* Sudden emergence causes:
◦ Mucosal injury
◦ Ulceration
◦ Inflammatory reaction
* Affects motility patterns
* Seasonality
* Diarrhea:
◦ ⇈ secretion 2ry to granulomatous inflammation
◦ Disruption of interstitium
* Protein loss is often significant

Question 8

What is the aetiology of right dorsal colitis?

Answer 8

• PGE2 and PGI2
  ◦ Mucosal blood flow
  ◦ ⇈ secretion of mucus, H2O & HCO3-
  ◦ ⇈ mucosal cell turnover & migration
• NSAIDs inhibit PG production (specially non-selective NSAIDs)