Cholera
| Attributes | |
|---|---|
| Common Name(s) | Cholera |
| Scientific Name(s) | Vibrio cholera |
| Physical Attributes | Short, curved, gram-negative bacillus, facultatively anaerobic, flagellate, motile, non-spore forming |
| Likely BW Form(s) | Contaminate water |
| Mode(s) of Transmission | Drinking water or food with bacterium; raw shellfish from contaminated waters |
| Geography | World wide; areas without adequate sanitation |
| Pathology | Profuse watery diarrhea (rice water stool), vomiting, and leg cramps; dehydration and shock; bacteria burns out in 5-6 days |
| Host(s) | Human |
| Vector/Dormant Form | Ecotones (regions near estuaries), copepods |
| Incubation Period | A few hours- 5 days |
| Fatality | 50% (without treatment); 1% (with treatment) |
| Vaccine | Oral vaccine is licensed and available outside the US (Dukoral from SBL Vaccines) |
| Treatment | Oral rehydration solution with a prepackaged mixture of sugar and salts; antibiotics avaliable |
Cholera is a diarrheal disease caused by Vibrio cholera, a short, curved, gram-negative bacillus. Humans acquire the disease by consuming water or food contaminated with the organism. In an epidemic, the source of the contamination is usually the feces of an infected person. The disease can spread rapidly in areas with inadequate treatment of sewage and drinking water. The organism multiplies in the small intestine and secretes an enterotoxin that causes a secretory diarrhea.
The cholera bacterium may also live in the environment in brackish rivers and coastal waters. Shellfish eaten raw have been a source of cholera, and a few persons in the United States have contracted cholera after eating raw or undercooked shellfish from the Gulf of Mexico. The disease is not likely to spread directly from one person to another; therefore, casual contact with an infected person is not a risk for becoming ill.
When employed as a biological weapons agent, cholera will most likely be used to contaminate water supplies. It is unlikely to be used in aerosol form. Without treatment, death may result from severe dehydration, hypovolemia and shock. Vomiting is often present early in the illness and may complicate oral replacement of fluid losses. There is little or no fever or abdominal pain.
Watery diarrhea can also be caused by enterotoxigenic E. coli, rotavirus or other viruses, noncholera vibrios, or food poisoning due to ingestion of preformed toxins such as those of Clostridium perfringens, Bacillus cereus, or Staphylococcus aureus.
Treatment of cholera depends primarily on replacement of fluid and electrolyte losses. This is best accomplished using oral dehydration therapy with the World Health Organization solution (3.5 g NaCL, 2.5 g NaHC03, 1.5 g KC1 and 20 g glucose per liter). Intravenous fluid replacement is occasionally needed when vomiting is severe, when the volume of stool output exceeds 7 liters/day, or when severe dehydration with shock has developed. Antibiotics will shorten the duration of diarrhea and thereby reduce fluid losses.
Improved oral cholera vaccines are presently being tested. Vaccination with the currently available killed suspension of V. cholera provides about 50% protection that lasts for no more than 6 months. The initial dose is two injections given at least 1 week apart with booster doses every 6 months.
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