Veterinary Clinical Medicine-I (General and Systemic)

PATHOGENESIS

Mechanism of diarrhea

• Osmotic diarrhoea
• Exudative diarrhoea
• Secretory diarrhoea
• Abnormal intestinal motility

Osmotic diarrhoea

• Substances within the lumen of the intestine increase the osmotic pressure .
• E.g. saline purgatives, overfeeding indigestible feeds and disaccharides deficiencies. Incomplete digestion and accumulation of large quantities of undigested material
• Epitheliotropic viruses E.g. TGF virus, rotavirus, and corona virus: selective destruction of villous absorptive cells, villous atrophy loss of digestive and absorptive capacities, diarrhoea, crypt hyperplasia and recovery.

Exudative diarrhea

• Acute or chronic inflammation or necrosis of the intestinal mucosa resulting in increase in fluid production, inflammatory products,  E.g diseases caused by bacteria, viruses, fungi, protozoa, chemical agents and tumors. Salmonellosis, swine dysentery, bovine virus diarrhoea and inorganic poisoning.

Secretory diarrhoea

• A secretory absorptive imbalance results in a large net increase in fluid secretion with little structural change in the mucosal cells. The enterotoxin elaborated by E. coli results in intestinal hypersecretion. The integrity of the mucosal structure is maintained and the secreted fluid is isotonic electrolyte rich alkaline and free of exudates.

Abnormal intestinal motility

• Hyperexcitability, convulsions and the stress of unexpected sudden confinement may result in diarrhea
• Reduced intestinal absorption due to rapid passage of intestinal fluids in an otherwise normal intestines.