This comprises a group of conditions involving pathological changes in the small intestine associated with the bacterium Lawsonia intracellularis. This exists on most if not all farms. Disease takes four different forms: porcine intestinal adenopathy (PIA) an abnormal proliferation of the cells that line the intestines; necrotic enteritis (NE) where the proliferated cells of the small intestine die and slough off with a gross thickening of the small intestine (hosepipe gut); regional ileitis (RI), inflammation of the terminal part of the small intestine and proliferative haemorrhagic enteropathy (PHE). In the latter there is massive bleeding into the small intestine, hence the common name bloody gut and this is the commonest form in growing pigs. The other three forms are rarer and progress from PIA. PHE is more common in 60-90kg pigs and gilts.
All are uncommon in the mature female but outbreaks of one of the forms, bloody gut or porcine haemorrhagic enteropathy (PHE), are occasionally seen in maiden and pregnant gilts.
The organism is impossible to keep out of farms probably because it also infects other species. Infected faeces are the major vehicle for spread around the farm.
Symptoms
Weaners & Growers
Clinical signs of PIA, NE, RI are different from PHE.
PIA:
- The pig appears clinically normal.
- Initially eats well.
- Chronic watery, sloppy diarrhoea.
- Necrosis.
- Gradual wasting.
- Loss of condition.
- In some cases a pot bellied bloated appearance.
- Pigs with the chronic form of the PIA recover over a period of four to six weeks, however there can be considerable losses in feed efficiency and daily gain of up to 0.3 and 80g/day respectively. As a consequence there can be marked variations in sizes of pigs.
- NI or RI follow from it with similar signs.
PHE is an acute disease:
- Bloody scour.
- The pig may die suddenly.
- Appears very pale and passes black bloody faeces.
- Anaemic.
Sows
- Gilts with PHE have pale skins.
- Appear weak.
- Bloody or black tarry diarrhoea.
- May suddenly die.
- Abortions
Piglets
- N/A
Causes / Contributing factors
These are not fully understood.
- The use of continually populated pens.
- Lack of all-in, all-out production.
- Naive animals.
- Change of environment.
- Changes in feed.
- Carry over of infection between batches appears to be a main means of spread.
- Associated with continual population of finishing pens.
Diagnosis
This is based on the clinical picture, post-mortem examinations, histology of the gut wall and demonstrating the organism in faeces by an ELISA test. A serological test is also available. Only a few laboratories can do these tests. Tissue cultures have been recently developed.