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Shigellosis: essential data |
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Bacterial weapon acting on humans |
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Synopsis,Diagnosis, Symptoms,
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Safety Precautions for Dysentery Casualties |
Standard Precautions as defined by the 1996 CDC guidelines should be adopted for handling patients.Droplet precautions should also be adopted.Biosafety level 2 practices should be adopted for handling of samples. |
| Causative organism: (Systematic name in 1997) |
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| Older names: |
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| Alternative disease names: |
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| Properties: | Gram-negative, facultatively aerobic bacillus, non-motile, non-spore-forming.
(Cells stain red in the Gram stain, they require oxygen for growth, are rod-shaped, do not move by their own power, and do not form spores.) |
| Antibiotic treatments: |
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| Vector involvement: | The disease can be spread by houseflies such as Musca domestica, but it also spread by humans as a result of poor personal hygiene. |
| Epidemiology of natural outbreaks: | Outbreaks are typically caused by eating contaminated food prepared under conditions of poor personal hygiene or improperly stored. Normal epidemiology can be summarized as "food, fingers, feces and flies." |
Differential DiagnosisOther disease or conditions that need to be eliminated | |
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| Other infectious diseases | Other problems |
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Symptoms and effects.
About 1-2 days after exposure there is a sudden onset of abdominal pain and a watery diarrhea as the small intestine is first affected. As the infection begins to affect the lower reaches of the small intestine and the large intestine the diarrhea becomes less watery but contains blood and mucus. Bowel movements are often painful and accompanied by rectal spasms.
The microorganism releases a toxin when the cells die and this is what affects the intestine. It can also act as a neurotoxin in extreme cases affecting the central nervous system leading to coma.
Infection generally passes in 2-5 days but patients may continue to shed the bacterium in stool for up to a month. Some become chronically infected and may have recurrent bouts of the disease.
Medical and Physical Countermeasures.
Vaccination (Immunoprophylaxis)
No vaccines are currently available although several are under development.
Antibiotics
Conduct antibiotic sensitivity tests on isolates before treatment as antibiotic resistance is common.
Supportive care
Decontamination
Many disinfectants - 1% sodium hypochlorite, 70% ethanol, 2% glutaraldehyde, iodines, phenolics, formaldehyde are effective and S. dysenteriae is sensitive to moist heat (121°C for at least 15 min) and dry heat (160-170°C for at least 1 hour)
Agent Properties and Potential Uses
S. dysenteriae is highly infective with a dose of only a few dozen or few hundred bacteria being enough to bring about dysentery. Normally it is contacted from food contaminated with human waste (sources are described as "food, fingers, feces, and flies"). Little is known about aerosol infectivity of the bacterium although there is extensive anecdotal evidence to suggest that it is easily spread by aerosol.
Shigella and related bacteria that live in the human digestive tract can rapidly develop resistance to antibiotics, so trying to prevent the spread of the disease by pretreatment with antibiotics (chemoprophylaxis) can be counterproductive. Good personal hygiene, thorough cooking of food and boiling of water are more effective.
Chronically infected carriers may be a problem and will need to be identified in the wake of an attack.
Terrorist Acquisition and Attempted Use.
Antibiotic Resistance.
Antibiotic resistance is well-documented in the genus Shigella and the occurrence of outbreaks of antibiotic resistant shigellosis, especially in the developing world, are becoming more frequent and a cause for concern.
The genus Shigella is very closely related to Escherichia coli the workhorse of molecular genetics and it would be relatively easy to develop antibiotic resistance plasmids for use in weaponization of Shigella in E. coli and introduce them into Shigella. In principle, this would be much easier than the development of antibiotic-resistant strains of the anthrax agent Bacillus anthracis.
| Disease | ICD-9-CM | ICD-10 |
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| Shigellosis | 004 | A03 |
| Shigella dysenteriae | 004.0 | A03.0 |
| Shigella flexneri | 004.1 | A03.1 |
| Shigella boydii | 004.2 | A03.2 |
| Shigella sonnei | 004.3 | A03.3 |
| Other specified Shigella infections | 004.8 | A03.8 |
| Shigellosis, unspecified | 004.9 | A03.9 |
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