A review of chronic enterocolitis of rhesus macaques (Macaca mulatta) and potential as a naturally occurring model for post-infectious irritable bowel syndrome

Chronic enterocolitis (CE) is a disease of significant concern in colony-housed rhesus macaques, leading to chronic diarrhea and severe weight loss necessitating euthanasia in up to 25% of adults. Despite over three decades of research into this syndrome, mitigating strategies have been met with variable success and chronic diarrhea remains an ongoing problem in research colonies. Some risk factors, clinicopathologic characteristics, and histopathologic characteristics have been investigated, but an underlying cause has yet to be determined, making identification of at-risk individuals and development of specific therapies difficult. There is some evidence for the syndrome occurring as a post-infectious sequela, particularly with respect to Campylobacter spp. infections, though associations with protozoal agents and other bacteria have been investigated as well. If causality is proven, the syndrome could be used as a naturally occurring model for post-infectious irritable bowel syndrome (PI-IBS) in humans, a syndrome which develops in over one-third of people following an episode of infectious gastroenteritis. Existing animal models fail to replicate PI-IBS in its entirety, preventing the development of effective therapies for this disruptive disease. Given the impact CE has on research colonies, particularly when macaques are in short supply for critical research, as well as the potential as a translational research model, further investigation into this syndrome is crucial. This review will aim to revisit the characterization of CE in rhesus macaques, provide a brief summary of existing animal models for PI-IBS, and discuss recent work on the suitability of CE as a model for the human disease.