Difference between revisions of "Colibacillosis"

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*** Sheep do not suffer as commonly as calves, as they are normally better managed.
 
*** Sheep do not suffer as commonly as calves, as they are normally better managed.
 
** Pigs less than 1 week of age may suffer.
 
** Pigs less than 1 week of age may suffer.
* Bacteria adhere to enterocyte receptors using pili e.g. K87 (Especially in pigs), K88, K99 (especialoly in cattle).  
+
* Bacteria adhere to enterocyte receptors using pili e.g. K87 (Especially in pigs), K88, K99 (especially in cattle).  
 
** Toxins produced by the bacteria encourage loss of Cl<sup>-</sup>, Na<sup>+</sup> and water in gut secretions.
 
** Toxins produced by the bacteria encourage loss of Cl<sup>-</sup>, Na<sup>+</sup> and water in gut secretions.
 
*** Causes [[Diarrhoea|diarrhoea]] and dehydration.  
 
*** Causes [[Diarrhoea|diarrhoea]] and dehydration.  

Latest revision as of 17:21, 20 November 2011

  • The enteritis caused by colibacillosis is relatively mild although the diarrhoea can be severe.
  • Only a few strains of coliform organisms cause disease.
    • These are identified by their serotypes.

Pathogenesis

  • There are three mechanisms by which coliform organisms cause diarrhoea.
Enterotoxigenic E. Coli (ETEC)
  • Cause neonatal and post-weaning diarrhoea in ruminants and pigs.
    • In calves, ETEC are only seen in animals of 4-5 days, or possibly up to one week, of age.
      • If the animal is older than 1 week, the agent is NOT ETEC.
    • Housed lambs may also suffer from ETEC.
      • Animals are usually under 1 week old.
      • Sheep do not suffer as commonly as calves, as they are normally better managed.
    • Pigs less than 1 week of age may suffer.
  • Bacteria adhere to enterocyte receptors using pili e.g. K87 (Especially in pigs), K88, K99 (especially in cattle).
    • Toxins produced by the bacteria encourage loss of Cl-, Na+ and water in gut secretions.
      • Causes diarrhoea and dehydration.
      • Death is a result of dehydration and electrolyte loss.
  • To be pathogenic, ETECs require 2 qualities not found in non-pathogenic coliform organisms.
    • Adherence factors.
    • Heat stable toxins.
  • Control is by management factors, such as hygiene, good colostral intake and so on.
    • There is the potential in the future to breed from pigs that lack adherence antigen sites for E.coli.
Enteroinvasive E. Coli
  • Not common in animals!
  • These strains act like shigella or salmonella.
    • Penetrate enterocytes, invade lamina propria and spread to lymph nodes and beyond.
  • Toxin damages enterocytes, causing:
    • Blunting of villi.
    • Elongation of crypts.
    • Sometimes mucosal ulceration.
Enteropathogenic (attaching and effacing) E. coli
  • Penetrate glycocalyx, adhere closely to mucosal cell surface and destroy the microvilli.
  • Cause:
    • Blunting of villi.
    • Crypt hypertrophy.
    • Inflammatory cells in the lamina propria.
  • The colon is often more severely affected than the intestine.
  • Septicaemic coliform infections may also occur.
    • Mainly in first 2 days of life.
      • usually due to insufficient colostrum intake.
    • Produce peracute death without diarrhoea.

Pathology

Gross
  • Gut loops filled with gas and fluid.
  • Gut contents are mucoid.
  • Gut wall is flaccid.
  • Mild congestion.
Histological
  • Bacteria on epithelial surface.
  • Mild inflammation in the lamina propria.
  • More severe lesions e.g. villus atrophy are rare.

Treatment

  • It is pointless to try to kill the organism in this disease.
  • Treat the effects of the disease instead.
    • Fluid replacement therapy.
      • Produces a quite good and quick recovery, especially in calves.