Transmission is via direct contact or via contaminated food or bedding. C. rodentium is generally considered an opportunistic pathogen. For example, the use of antibiotics effective primarily against gram-negative rods may allow an overgrowth of C. rodentium in the mouse intestine. Clinical signs, when present, are nonspecific and may include ruffled coat, weight loss, depression, stunting, perianal fecal staining, and rectal prolapse. Nursing mice are most susceptible.
Infection is transient, and there is no carrier state.
The hallmark pathologic lesion of C. rodentium infection is colonic hyperplasia. Generally, the descending colon is most affected. However, the entire colon and cecum may be involved, with crypt elongation, variable mucosal inflammation, crypt abscesses, occasional erosions and ulcers, and, with healing, goblet cell hyperplasia. Transient colonization of the mouse small intestinal mucosa, followed by colonization of the large bowel, is dependent on the presence of the chromosomal eae gene. Immunity appears to be humoral and may be directed at least partially toward intimin antigens.