Bacillary Dysentery

Bacillary Dysentery (Shigellosis)

Bacillary dysentery (shigellosis) is an acute bacterial infection involving the large and distal small intestines, and is characterized by small-volume, loose stools. Typically, the stools contain blood and mucus diarrhoea (dysentery). Asymptomatic and mild infections occur, many cases presenting as watery diarrhea. . Uncomplicated disease is usually self-limiting and resolves in 4–7 days. In endemic areas, the disease is more severe in young children than in adults.

Symptoms(Ranges from mild to severe)

  • The stools contain blood and mucus diarrhoea (dysentery), and are associated with fever, nausea, vomiting, abdominal cramps and rectal pain (tenesmus).
  • Complications include intestinal perforation, toxic megacolon, rectal prolapse, haemolytic uraemic syn- drome and convulsions (in young children)

Infectious Agents

The genus Shigella includes four species: S. dysenteriae, S. flexneri, S. boydii andS. sonnei, designated as serogroups A, B, C and D, respectively. Each serogroup is further subdivided into serotypes.

S. flexneri is the main cause of endemic shigellosis in developing countries. However, S. dysenteriae serotype 1 (Sd1) causes the most severe disease and is usually responsible for epidemics, which are often large and may even be regional.

S. sonnei and S. boydii usually cause relatively mild illness

Mode of transmission

Shigella is transmitted orally and through faeces, particularly through contaminated water and food. Street food stalls are a common source of contaminated food. Flies may also transmit the organism.


Prevention of shigellosis in any community relies mainly on adequate clean water, sanitation and hygiene; this involves:

Safe drinking water- Provision of adequate quantities of safe drinking-water.

Safe disposal of human waste – Provision of adequate facilities for disposal of human waste.

Hygiene –

  • Provision of sufficient, clean, quantities of water and soap and provision of adequate supplies for hand-washing, bathing and laundry needs.
  • Promotion of hygiene – including use of latrines and prevention of human defecation on the ground, or in or near water; disposal of children’s excreta in latrines; thorough hand-washing before eating, after defecation, before food preparation, and after cleaning children or changing their diapers.
  • Promotion of food safety – through provision of clean, appropriately cooled and spatially adequate food storage facilities (for both uncooked and cooked food, and clean cooking utensils), and adequate quantities of water and fuel for cooking and re-heating

promotion of “five keys to safer food” – keep clean, separate raw and cooked food, cook food thoroughly, keep food at safe temperatures, use clean water and cooking tools

  • Promotion of breastfeeding – by providing information on the importance and protective qualities of breastfeeding for all infants and young children, and especially for those who are ill.


1. Quarterly Epidemiological Bulletin, Epidemiology Unit. Sri Lanka, Ministry of Health, Nutrition & Welfare, 2008 (Quarterly Epidemiological Report)

Further reading

Factsheet on Diarrhoeal disease Diarrhoeal disease (

Factsheet on Cholera Cholera (