This type of enteritis is caused by the bacterium salmonella typhi,ingested in contaminated food and water. As human are it’s only host,it is acquired from an individual who is either suffering from the disease or is a carrier.
After infection,there is an incubation period of about 14 days before signs of the disease appears. During this period the microbes invade lymphoid tissue in the walls of the small and large intestines,especially the aggregated lymph follicles and solitary lymph nodes. The microbes then enter the blood vessels and spread to the liver,spleen and gall bladder. In the bacteraemic period acute inflammation develops with necrosis of intestinal lymphoid tissue and ulceration of overlying mucosa. The spleen becomes enlarged and red spots are typically seen on the skin,especially of the chest and back.
Without treatment,severe,and often fatal,illness is common 2 weeks after the onset of illness. Complications due to spread of microbes during the bacteraemic phase include pneumonia,meningitis and typhoid cholecystitis in which microbes multiply in the gall bladder and are secreted in the bile,reinfecting the intestine. Bacterial toxins can cause disorders of the heart and kidneys. In the bowel,ulcers may perforate a blood vessel wall resulting in haemorrhage or erode the intestinal wall causing acute peritonitis.
