A clinical state arising from acute infection of the colon or rectum; there is abdominal COLIC, diarrhoea, and passage of blood/mucus in the stool. Although the two major forms are caused by Shigella (bacillary dysentery) and Entamoeba histolytica (amoebic dysentery), other organisms including entero-haemorrhagic Escherichia coli (serotypes 0157:H7 and 026:H11) and Campylobacter are also relevant. Other causes of dysentery include Balantidium coli and that caused by schistosomiasis (bilharzia) – Schistosoma mansoni and S. japonicum infection.
This form is usually caused by Shigella dysenteriae-1 (Shiga's bacillus), Shigella flexneri, Shigella boydii, and Shigella sonnei. It is transmitted by food and water contamination, by direct contact, and by flies; the organisms thrive in the presence of overcrowding and insanitary conditions. The severity of the illness depends on the strain responsible. Duration of illness varies from a few days to two weeks and can be particularly severe in young, elderly and malnourished individuals. Complications include perforation and haemorrhage from the colo-rectum, the haemolytic uraemic syndrome (which includes renal failure), and REITER'S SYNDROME. Diagnosis is dependent on demonstration of Shigella in (a) faecal sample(s) – before or usually after culture.
If DEHYDRATION is present, this should be treated. While Shigella is eradicated by antibiotics such as trimethoprim and AMOXICILLIN. widespread resistance has developed, especially in Asia and southern America, where the agent of choice is now a quinolone compound, for example, ciprofloxacin. Prevention depends on improved hygiene and sanitation, careful protection of food from flies, fly destruction, and garbage disposal. A Shigella carrier must not be allowed to handle food.
Most cases occur in the tropics and subtropics. Dysentery may be accompanied by weight loss, anaemia, and occasionally DYSPNOEA. E. histolytica contaminates food (e.g. uncooked vegetables) or drinking water. After ingestion of the cyst-stage, and following the action of digestive enzymes, the motile trophozoite emerges in the colon causing local invasive disease (amoebic colitis). These organisms may gain access to the liver, causing amoebic liver abscess. Other sites of ‘abscess’ formation include the lungs (usually right) and brain. Clinical symptoms usually occur within a week, but can be delayed for months, or even years; onset may be acute, as for Shigella spp. infection. Diagnosis is by demonstration of E. histolytica trophozoites in a fresh faecal sample; other amoebae affecting humans do not invade tissues. Research techniques can be used to differentiate between pathogenic (E. dysenteriae) and non-pathogenic strains (E. dispar).
Treatment consists of one of the 5-nitroimidazole compounds – metronidazole, tinidazole, and ornidazole;. A five- to ten-day course is usually advised followed by diloxanide furoate for ten days.