Especially in older foals, Lawsonia intracellularis causes proliferative enteropathy, which is accompanied by significant hypoproteinaemia. The animals also show abdominal pain, reduced general condition and anorexia. Secondarily, oedema and a pear-shaped abdomen may occur.

Porcine proliferative enteropathy (PPE) in pigs is caused by an infection with the obligate intracellular, gram-negative bacterium Lawsonia intracellularis. Infection occurs via the oral route, the spread mainly through the purchase of infected animals. Often, the infection is subclinical. It is widespread in pig herds, especially among weaners, store pigs and fattening pigs. Infected animals suffer from growth disorders and diarrhoea.

PPE occurs in four clinically apparent forms: as acute and, if untreated, often fatal porcine haemorrhagic enteropathy (PHE) and as porcine intestinal adenomatosis (PIA), or less often as necrotic enteritis (NE) and as terminal regional ileitis (RI) with thickened and stiff ileum. While PHE mainly affects older fattening pigs and younger breeding pigs, the chronic forms PIA, NE and RI mainly occur in weaners and store pigs.