Swine Dysentery

• Swine dysentery gives rise to fibrinous/ haemorrhagic enteritis.
• A quite common and important disease.
• The disease is caused by Brachyspira hyodysenteriae.
  • Is not seen in gnotobiotic animals - other enteric pathogens such as Fusobacterium or Bacteroides may therefore also be required in order to produce disease.
• The disease is NOT systemic.
  • Localised to the large intestine- in particular, the spiral colon.
• Swine dysentery is spread by the faeco-oral route, and is carried by pigs and rodents.

Clinical

• Affects post weaning pigs at approximately 4 months of age.
• White scour becomes a liquid dirty red / brown scour with a foul smell.
  • Contains poorly digested focal shreds of mucosa and fibrin strands.
    • Mucoid covered faeces.
• There are three outcomes to infection; the animal may:
  • Die
  • There is a morbidity up to 90% in the herd, with up to 50% mortality.
  • Recover
  • Become chronically infected.
• Symptoms are due to loss of absorption in colon.
  • The colon is normally a key site of absorption for water and electrolytes in the pig.

Pathology

• The serosa of the spiral colon may appear shiny from the outside.
  • Is turgid and oedematous.
  • In severe cases, haemorrhage may be seen.
• The small intestine NOT affected.
• Fibrinous deposits are seen on the mucosa as the disease progresses.
  • The mucosa underneath is eroded to expose blood vessels in lamina propria.
    • Accounts for the bleeding.
• Animals often recover, but have a low feed conversion ratio for sometime.

Diagnosis

• Silver stains show organisms in the epithelium of the mucosa.
• Clinical signs
  • B. hyodysenteriae causes dysentry in weaned pigs 6-12 weeks old; pigs lose condition and become emaciated; appetite is decreased; large amount of mucous may be present in the faeces; low mortality; poor feed conversion ratio
• Diagnosis
  • History, clinical signs and gross pathology
  • Anaerobic culture on blood agar with added antibiotics for at least 3 days
  • B. hyodysenteriae causes complete haemolysis whereas other spirochaetes cause partial haemolysis
  • Immunofluorescence, DNA probes and biochemical tests
  • Serology using ELISA can be used on a herd basis
  • PCR

• Also by immunofluorescence or electron microscopy.