Chronic colitis in Macaca fascicularis: similarities with chronic colitis in humans.

In recent years, a substantial number of macaques have died at the Southwest Foundation for Biomedical Research, USA, following protracted intractable diarrhea. The diarrhea could last for up to two years and occurred in infant, juvenile or young adult animals. The histopathological diagnosis at autopsy was chronic colitis. The histopathological subtype of chronic colitis is here assessed in a relatively large number of colonic specimens obtained at autopsy (n = 90). The colonic mucosa was well preserved for histological examination in 83 of the 90 macaques. At review, various histological phenotypes of chronic colitis were found. Chronic lymphocytic-plasmacytic colitis occurred in 78.3% (65 out of 83), chronic ulcerative colitis in 20.5% (17 out of 83) and Crohn's colitis in 1.2% (1 out of 83). In macaques, some histological phenotypes of chronic colitis (ulcerative and Crohn's colitis) closely mimic chronic colitis in humans. The awareness that chronic colitis in macaques is not one disease but a series of chronic inflammatory changes, with common clinical symptoms and similar gross appearances, may lead to the correct histological diagnosis of the subtype of the disease.