Lawsonia intracellularis is an intracellular gram-negative bacterium that has been increasingly recognized as a factor responsible for diarrhea in foals. This problem concerns mainly foals just taken from the mares, i.e. at the age of 6-7 months, in which L. intracellularis bacteria invaded the epithelial cells of the ileum causing proliferative pathological conditions within the intestinal tract. In turn patological contitions lead to intestinal absorption disorders as well as to chronic diarrhea. Most commonly the isolated cases of the dissease are observed, but infections of several several animals within the same farm have been also reported.
In the case of swine, this intestinal bacterium causes a number of clinical diseases commonly referred to as porcine proliferative enteropathy (PPE, ileitis). It is believed that the infections of Lawsonia intracellularis occur in 90% of farms worldwide, with around 30% of pigs being affected, what results in significant economic losses.
Chronic illness is referred to as intestinal adenomatosis of pigs (PIA, Porcine Instestinal Adenomatosis). PIA primarily causes growth retardation and unevenness in body size in pigs aged generally between 6 and 20 weeks with or without clinical diarrhea. Other clinical symptoms include acute haemorrhagic disease called proliferative haemorrhagic enteropathy (PHE), which is most common in young adults (4-12 months) and causes acute hemorrhagic anemia in animals due to blood loss to intestinal lumen. Animals are markedly pale and can shed stools of varying hue – from blood red to black tar. Only about 50% of the animals experience acute PHE. L. intracellularis infections in sows may result in miscarries.