Ileitis is an inflammation of the ileum

Ileum

The ileum is the final section of the small intestine in most higher vertebrates, including mammals, reptiles, and birds. In fish, the divisions of the small intestine are not as clear and the terms posterior intestine or distal intestine may be used instead of ileum.The ileum follows the duodenum...

, a portion of the small intestine

Small intestine

The small intestine is the part of the gastrointestinal tract following the stomach and followed by the large intestine, and is where much of the digestion and absorption of food takes place. In invertebrates such as worms, the terms "gastrointestinal tract" and "large intestine" are often used to...

. Crohn's ileitis is a type of Crohn's disease

Crohn's disease

Crohn's disease, also known as regional enteritis, is a type of inflammatory bowel disease that may affect any part of the gastrointestinal tract from mouth to anus, causing a wide variety of symptoms...

affecting the ileum. Ileitis is caused by the bacteria Lawsonia intracellularis.
Human inflammatory bowel disease does not associate with Lawsonia intracellularis infection. >www.ncbi.nlm.nih.gov › Journal List › BMC Microbiol › v.6; 2006