Porcine Adenomatosis Complex

Synonyms

Porcine intestinal adenomatosis or Porcine Proliferative Enteropathy

Introduction

This is a disease caused by the obligatory intracellular organism Lawsonia intracellularis, a spirochete that does not grow well in the laboratory excpet in tissue culture. It is only seen in pigs, worldwide, including the United Kingdom. It is characterised by proliferative changes in the epithelium of the small and large intestinal mucosa. 
It is a disease that can affect pigs of all ages, but most severe clinical signs tend to appear in weanlings and growers. The infection is transmitted orally.

The disease appears in four different presentations:
Intestinal adenomatosis - The basic hyperplastic and metaplastic changes are seen in the epithelium, which causes chronic weight loss and diarrhoea.
Necrotic enteritis - Predominately affects the colon and terminal ileum and parts of the hyperplastic mucosa develop erosions and ulcerations which then become colonised by Fusiformis baceria.
Terminal ileitis - Characterised by marked hypertrophic thickening of the muscular portion of the wall of the terminal ileum and there is associated thickening of the mucosa due to hypertrophy and secondary granulomatous inflammation, which is caused by a degree of obstruction to the passage of ingesta along the bowel caused by the mucosal hypertrophy. Its appearance is very similar to Johnes disease with 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 but may involve a type of hypersensitivity reaction or secondary infection of some type.

Clinical Signs

Clinical signs are variable and can range from anything from poor weight gain to diarrhoea, weight loss, cachexia and death and appears usually in weaned pigs from age 3-4 weeks to adulthood.
It is seen often as a problem in closed, low infection herds and can lead to a decrease in production of up to 8%. It is not seen in pigs with lots of other pathogens in guts.

Diagnosis

Clinical signs and history of a closed herd plus signalment of pigs is indicative. On post mortem examination the terminal small intestine and colon are affected by proliferation of the mucosal epithelium. Signs will include thickened mucosal epithelium, polypoid-like nodules several millimetres in diameter. there may also be undifferentiated epithelium replaces goblet cells. Its appearance is almost neoplastic.
Histologically it will appear similar to a virus induced proliferation. Organisms seen in the apical part of epithelial cells lining glands of terminal ileum, colon and caecum.