Porcine Intestinal Spirochaetosis
Also Known As – PIS – Porcine colonic spirochaetosis – Spirochaetal diarrhoea
Caused By – Brachyspira pilosicoli
Introduction
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Porcine spirochaetosis is a gastrointestinal disease of pigs caused by the gram negative anaerobic bacterium, Brachyspira pilosicoli. The bacterium can be recognised by its 8-12 flagellae, inserted at each pole of the cell.
The pathogen colonises the lumen and crypts of the large intestine, attaching firmly at one end of the cell to the epithelium.
PIS is also zoonotic and is associated with chronic diarrhoea and rectal bleeding in humans.
This disease is notifiable to the World Organisation for Animal Health (OIE)
Distribution
Porcine spirochaetosis is present in many significant pig rearing countries, including the UK, Europe, Scandinavia, USA, Canada, Brazil and Australasia.
Transmission is mainly faecal: oral. The bacterium can remain viable in lake water for up to 2 months, providing another route of transmission. Birds and rodents may act as vectors for disease.
Signalment
B. pilosicoli has also been isolated from people, dogd, waterfowl, chickens and guinea pigs. Clinical disease is most common in pigs followed by birds.
Overcrowding and movement of pigs between sites predisposes them to infection and clinical disease.
Infection is most common in 8-14 week old piglets, particularly within 1-2 weeks of moving and mixing batches.
Clinical Signs
Clinical disease is generally mild.
Grey or grey-green diarrhoea which may contain blood or mucus, and colitis
Sub-optimal growth rates and feed efficiency. Pigs may require up to 28 additional days to reach slaughter weight.
Occasionally, pigs may become depressed and lethargic.
Diagnosis
B. pilosicoli can be cultured from faeces or intestinal samples and isolated on blood agar with selective antibiotics in anaerobic conditions. Colonies are weakly haemolytic and can be definitively identified as spirochaetes under phase contract or dark field microscopy.
PCR can then confirm species identification.
On post-mortem, animals are in poor body condition and oedema is common between the coils of the large intestine. When the colon is opened, the mucosa is erythematous in patches.
Histologically, a fake brush border of attached spirochaetes is pathognomic.
Treatment
Lincomycin and Tiamulin are the most common antibiotics used against PIS, given in water or by injection.
Control
At risk pigs are sometimes given prophylactic antibiotics although this use is controversial.
Mixing and moving pigs should be avoided where possible.
Feeding meal or mash may reduce the occurrence of diarrhoea.
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References
Animal Health & Production Compendium, Porcine Intestinal Spirochaetosis datasheet, accessed 16/06/2011 @ http://www.cabi.org/ahpc/
Animal Health & Production Compendium, Brachyspira pilosicoli datasheet, accessed 16/06/2011 @ http://www.cabi.org/ahpc/