In the submucosa there are multiple, coalescing infiltrates of neutrophils, macrophages, and lymphocytes. This submucosal inflammation is indicative of infection by an invasive organism and is compatible with the group B Salmonella sp . The life cycle is direct and eggs can persist in the environment for several years. 7-10 days before they reenter the gut lumen and move to the cecum. There is a prepatent period that lasts from 6-12 weeks depending upon the species.
Infection is usually light and there is little alteration of the mucosa.
Mucohemorrhagic typhlocolitis may develop in heavy infections and is characterized by mucus hypersecretion from hypertrophied colonic glands, focal hemorrhage, erosions, and a mixed inflammatory infiltrate within the lamina propria. Balantidium coli is a large ciliated protozoan with both a macronucleus and micronucleus. It is a commensal parasite in the cecum and colon of swine but often complicates necrotizing or ulcerative diseases of the cecum and colon, especially trichurid infection, intestinal adenomatosis, swine dysentery, and salmonellosis. Salmonella cholerasuis causes a septicemic disease that induces endothelial damage due to endotoxemia and localization of bacteria. Characteristic lesions include hemorrhage in lymph nodes, laryngeal mucosa, spleen, liver, and intestine.