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* Characteristic proliferation of mucosa.
* Known as PIA - porcine intestinal adenomatosis.
====Clinical====
* Really only seen in the pig.
** Can affect all ages of pig.
* Clinical signs are variable.
** Anything from poor weight gain to diarrhoea, weight loss, cachexia and death.
* Seen often as problem in closed, low infection herds.
** Not seen in pigs with lots of other pathogens in guts.
====Pathogenesis====
* Caused by [[Lawsonia intracellularis|''Lawsonia intracellularis'']].
** A spirochete that does not grow well except in tissue culture.
====Pathology====
* The terminal [[Small Intestine - Anatomy & Physiology|small intestine]] and [[Colon - Anatomy & Physiology|colon]] are affected by proliferation of the mucosal epithelium.
* '''Gross'''
** Thickened mucosal epithelium.
** Has almost polypoid-like nodules several millimetres in diameter.
** Undifferentiated epithelium replaces goblet cells.
*** Appears almost neoplastic.
* '''Histologically'''
** Very similar to a virus induced proliferation.
** Organisms seen in the apical part of epithelial cells lining glands of terminal [[Ileum - Anatomy & Physiology|ileum]], [[Colon - Anatomy & Physiology|colon]] and [[Caecum - Anatomy & Physiology|caecum]].
** May produce mild ulceration in mucosa and mild inflammatory infiltration.
* Porcine adenomatosis complex can be divided into four distinct syndromes:
*# '''Intestinal adenomatosis'''
*#* THe basic hyperplastic and metaplastic changes are seen in the epithelium. [[Image:porcine intestinal adenomatosis campylobacter.jpg|thumb|right|150px|Campylobacter mucosalis in intracellular porcine intestinal adenomatosis (Courtesy of Bristol BioMed Image Archive)]]
*#* Causes chronic weight loss and diarrhoea.
*# '''Necrotic enteritis'''
*#* Predominately affects the [[Colon - Anatomy & Physiology|colon]] and terminal [[Ileum - Anatomy & Physiology|ileum]].
*#* Parts of the hyperplastic mucosa develop erosions and ulcerations.
*#** These areas become [[Colon - Anatomy & Physiology|colon]]ised by ''Fusiformis'' baceria.
*#*** Gives areas of coagulative necrosis covered by a thick diptheretic membrane.
*# '''Terminal ileitis'''
*#* Characterised by marked hypertrophic thickening of the muscular portion of the wall of the terminal [[Ileum - Anatomy & Physiology|ileum]].
*#* Gives an attendant stenosis of the lumen of the [[Ileum - Anatomy & Physiology|ileum]].
*#* There is associated thickening of the mucosa due to hypertrophy and secondary granulomatous inflammation.
*#** This is presumably caused by a degree of obstruction to the passage of ingesta along the bowel caused by the mucosal hypertrophy.
*#* Appears very similar to Johnes disease
*#** Lots of mononuclear cells and a chronic granulomatous type of inflammation.
*# '''Proliferative haemorrhagic syndrome'''.
*#* The bowel shows proliferation but with ulceration and copious haemorrhage into the bowel lumen.
*#* Animals are often be found dead.
*#* The pathogenesis is unclear.
*#** May involve a type of hypersensitivity reaction or secondary infection of some type.
====Sequelae====
* Resolution.
* Necrotic enteritis.
* Secondary chronic infection (regional enteritis).
* Porcine haemorrhgaic enteritis (PHE).[[Category:Enteritis,_Proliferative]][[Category:Pig]][[Category:Enteritis,_Bacterial]]