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Bacillary Dysentery

Synonym: shigellosis

This disease is a notifiable form of gastroenteritis in the UK under the Public Health (Infectious Diseases) Regulations 1988.
The Public Health Laboratory must be informed.

Shigella is a genus of aerobic, nonmotile, glucose-fermenting, Gram-negative bacilli that are highly contagious. As few as 100 organisms may cause symptoms.1 This compares with <500 organisms for Campylobacter spp.2 Salmonella is however even more infective (as few as 15-20 cells in a vulnerable host).3 They cause damage by 2 mechanisms. Invasion of the colonic epithelium is dependent on a plasmid-mediated virulence factor whilst production of an enterotoxin is not essential for colitis but it enhances virulence.

Shigella spp. has considerable similarity with Escherichia spp. and its ubiquitous species E. coli but is classified separately for historical reasons. They are serotyped according to their somatic 'O' antigens. Man and gorillas appear to be the only natural hosts.4


There are 4 species of shigellae. To give an indication of relative frequency in the UK the figures in parentheses are the number notified for England and Wales in 2005.5 In 1998 and 1999 the incidence was significantly higher in females than males and the age specific rate was highest in children aged one to four years and adults aged 25 to 29 years.

  • Shigella sonnei (889)
  • Shigella flexneri (334)
  • Shigella boydii (114)
  • Shigella dysenteriae (58)

The numbers vary greatly from year to year with a peak of over 17,000 cases reported in 1992 to a trough of just over 1,000 in 2003 but the order of frequency of the various species remains constant. S. sonnei is the commonest but also the mildest form. Many milder cases are probably never diagnosed and so never reported, so the true incidence may be substantially higher. In developing countries the predominant species is S flexneri.

The organism is spread by faeco-oral contact via infected food or water, during travel, or in long-term care facilities, day care centres, or nursing homes. Worldwide, shigellosis causes 1.1 million deaths and over 164 million cases each year, with the majority of cases occurring in the children of developing nations. It tends to be most prevalent when flies are at their most prolific.1

Risk factors

It is typically a disease of children although the elderly are vulnerable. Worldwide it is associated with overcrowding and poor water supplies.6 There is evidence that it may be spread by swimming in infected waters. It can also be transmitted by homosexual practices.7



  • A recent travel history may be pertinent10
  • The incubation period is 1 to 3 days, but usually nearer to just 1 day
  • There is acute watery and possibly bloody diarrhoea
  • Abdominal pain and tenesmus
  • Fever and malaise
  • Mild cramps and diarrhoea may persist for days to weeks after infection
  • It is usually a self-limited disease of 3 days to 1 week and rarely lasts as long as a month


Differential diagnosis8
  • A fresh stool specimen should be sent for culture. Red and white blood cells may be seen in the specimen
  • FBC may show a leukocytosis and even a raised haematocrit if there is dehydration but often it is normal
  • Urea and electrolytes may be disturbed if there is dehydration
  • Sometimes sigmoidoscopy and colonic biopsy is required to differentiate from acute ulcerative colitis
  • Oral rehydration fluid should be given.
  • In children especially, antipyretic medicines can reduce temperature and help to prevent convulsions.
  • Antibiotics are often helpful for those with symptoms but resistance is becoming a problem. Although fluoroquinolones are currently effective in treating adults, resistance to fluoroquinolones among Shigella spp. is emerging, and their use in children is subject to limitations. Azithromycin and third-generation cephalosporins are also effective in the treatment of shigellosis, but monitoring of Shigella spp. isolates to detect the emergence of resistance is essential.11
  • Codeine is not recommended but loperamide may be helpful.12 More recent expert advice is that antimotility agents are contraindicated.13

Return to work14

When diarrhoea has settled the vast majority are not a risk to others and may return to work with no further testing. The following need advice from Environmental Health officers or a Consultant in Communicable Disease Control (CCDC):

  • Food handlers who touch unwrapped food to be consumed raw or without further cooking.
  • Health-care, nursery or other staff who have direct contact with people who are susceptible to infection or for whom a salmonella infection would have very serious consequences. This includes simply serving food to them.
  • Children under 5 years attending nurseries, play groups, nursery schools etc.
  • Older children or adults with poor standards of personal hygiene like the mentally ill, handicapped or the elderly infirm.

Bacteraemia occurs primarily in malnourished children and carries a mortality rate of 20% as a result of acute renal failure, haemolysis, thrombocytopenia, gastrointestinal haemorrhage, and shock. Haemolytic uraemic syndrome may complicate infections with Shigella spp. and E. coli, and it carries a mortality rate in excess of 50%. Haemolytic uraemic syndrome is characterised by acute haemolysis, renal failure, uraemia, and disseminated intravascular coagulation.

Reiter's syndrome can occur. It is commonest in men aged 20 to 40 and with the HLA-B27 antigen. It starts 2 to 4 weeks after infection and may be chronic and relapsing.


The disease tends to last from 1 day to 1 month with an average of 1 week. Mortality is rare but can occur in malnourished children and the elderly.


There are currently no vaccines against shigellae although trials are underway in America.15,16 Sanitation and clean water is important in developing countries. In developed nations the concern is hand washing and personal hygiene. Preparation of fresh produce is also important.17


It is estimated that the Shigella genus originated between 35,000 and 270,000 years ago.18 By evolutionary standards that is very recent. The disease has been described by Hippocrates and Herodicus.

In 1897 the Japanese bacteriologist Kiyoshi Shiga described Bacillus dysenteriae as the cause of bacillary dysentery. He had isolated the organism now known as Shigella dysenteriae from faeces and intestinal walls in patients suffering from dysentery. In 1900 he developed a dysentery antiserum. It was given a different name from Bacillus (now Escherichia) coli, because it was not thought at the time, that a commensal species could also have pathogenic strains. Koshi Shiga was born in 1871 and died in 1957.19 He graduated MD from the Imperial University of Tokyo in 1896. He worked with Kitasato Shibasaburo who discovered the tetanus bacillus. Between 1901 and 1903 he worked with Paul Erlich in Berlin. His research also included work on leprosy, beriberi, and tuberculosis.

Shigella was one of species investigated by the Japanese between 1932 and 1945 as an agent of biological warfare, and is considered a category B agent. Contamination of food supplies would be the the most likely method. Biological warfare was used in the First World War but outlawed by the Geneva Convention in 1925. Japan started the development of biological weapons in 1932, using them on China and Manchuria in 1940 and in 1942 the USA started to research biological weapons too.

In 1984 members of a cult contaminated salad bars in Oregon restaurants with salmonella, and in 1996 S. dysenteriae was put in muffins and doughnuts in Dallas.20

Document references
  1. Jennison AV, Verma NK; Shigella flexneri infection: pathogenesis and vaccine development. 1: FEMS Microbiol Rev. 2004 Feb;28(1):43-58.
  2. Walderhaug M; Campylobacter jejuni U.S. Food and Drug Administration 1992.
  3. Walderhaug M; Salmonella spp U.S. Food and Drug Administration 1992.
  4. Nizeyi JB, Innocent RB, Erume J, et al; Campylobacteriosis, salmonellosis, and shigellosis in free-ranging human-habituated mountain gorillas of Uganda. J Wildl Dis. 2001 Apr;37(2):239-44. [abstract]
  5. Health Protection Agency Shigella.; Laboratory reports of faecal isolates in England & Wales, 1986-2006.
  6. Finkelman Y, Yagupsky P, Fraser D, et al; Epidemiology of Shigella infections in two ethnic groups in a geographic region in southern Israel. Eur J Clin Microbiol Infect Dis. 1994 May;13(5):367-73. [abstract]
  7. No authors listed; From the Centers for Disease Control and Prevention. Shigella sonnei outbreak among men who have sex with men--San Francisco, California, 2000-2001. JAMA. 2002 Jan 2;287(1):37-8.
  8. Kroser JA; Shigellosis. eMedicine, 2005.
  9. Sur D, Ramamurthy T, Deen J, et al; Shigellosis : challenges & management issues. Indian J Med Res. 2004 Nov;120(5):454-62. [abstract]
  10. Travel Health; CDR Weekly Volume 16 Number 51 December 2006
  11. Niyogi SK; Increasing antimicrobial resistance--an emerging problem in the treatment of shigellosis. Clin Microbiol Infect. 2007 Dec;13(12):1141-3. Epub 2007 Oct 22. [abstract]
  12. Murphy GS, Bodhidatta L, Echeverria P, et al; Ciprofloxacin and loperamide in the treatment of bacillary dysentery. Ann Intern Med. 1993 Apr 15;118(8):582-6. [abstract]
  13. Bhattacharya SK, Sur D; An evaluation of current shigellosis treatment. Expert Opin Pharmacother. 2003 Aug;4(8):1315-20. [abstract]
  14. Newman C; Surveillance and control of Shigella sonnei infection Communicable Disease Report 1993;3(5):R63-68
  15. Shigella Flexneri 2a Invaplex 50 Vaccine Dose Finding and Assessment of Protection; 2008
  16. Levine MM, Kotloff KL, Barry EM, et al; Clinical trials of Shigella vaccines: two steps forward and one step back on a long, hard road. Nat Rev Microbiol. 2007 Jul;5(7):540-53. [abstract]
  17. Selma MV, Beltran D, Allende A, et al; Elimination by ozone of Shigella sonnei in shredded lettuce and water. Food Microbiol. 2007 Aug;24(5):492-9. Epub 2006 Nov 13. [abstract]
  18. Pupo GM, Lan R, Reeves PR; Multiple independent origins of Shigella clones of Escherichia coli and convergent evolution of many of their characteristics. Proc Natl Acad Sci U S A. 2000 Sep 12;97(19):10567-72. [abstract]
  19.; Kiyoshi Shiga
  20. Kolavic SA, Kimura A, Simons SL, et al; An outbreak of Shigella dysenteriae type 2 among laboratory workers due to intentional food contamination. JAMA. 1997 Aug 6;278(5):396-8. [abstract]
Acknowledgements EMIS is grateful to Dr Laurence Knott for writing this article. The final copy has passed scrutiny by the independent Mentor GP reviewing team. ©EMIS 2008.
DocID: 1840
Document Version: 20
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Last Updated: 3 May 2008
Review Date: 3 May 2010
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PS - Health and Poverty

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