Cholera overview
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [2]
Overview
Cholera is a severe bacterial gastrointestinal, diarrheal disease. In its most severe forms, cholera is one of the most rapidly fatal illnesses known. A healthy person may become hypotensive within an hour of the onset of symptoms and may die within 2-3 hours if no treatment is provided. More commonly, the disease progresses from the first liquid stool to shock in 4-12 hours, with death following in 18 hours to several days without rehydration treatment.[1][2]
Pathophysiology
Most of the V. cholerae bacteria do not survive the very acidic conditions of the human stomach[3]. The few bacteria that manage to survive the stomach's acidity conserve their energy and stored nutrients during passage through the stomach by shutting down much protein production and restart production in the favorable small intestine's environment. The toxins that interact with host cell mechanisms pump chloride ions into the small intestine, creating an ionic pressure which prevents sodium ions from entering the cell. The chloride and sodium ions create a salt water environment in the small intestines which through osmosis can pull up to six liters of water per day through the intestinal cells creating the massive amounts of diarrhea. The host can become rapidly dehydrated if an appropriate mixture of dilute salt water and sugar is not taken to replace the blood's water and salts lost in the diarrhea.
Causes
Cholera is a severe diarrheal disease caused by the gram negative bacterium Vibrio cholerae.[4]. Transmission to humans is by ingesting contaminated water or food. The major reservoir for cholera was long assumed to be humans, but some evidence suggests that it is the aquatic environment.
History and symptoms
Patient may give a history of consumption of contaminated food or water, and travel to an endemic area. The symptoms usually develop within 24-48 hour of consumption of contaminated food. Patient presents with sudden onset, painless, odorless, rice watery large volume stool, abdominal cramps, vomiting and fever. If the severe diarrhea and vomiting are not aggressively treated, they can, within hours, result in life-threatening dehydration and electrolyte imbalances. The typical symptoms of dehydration include dizziness ( due to low blood pressure), wrinkled hands (poor skin turgor) , sunken eyes, mucle cramps (decreased potassium), and decreased urine output.
Physical examination
The signs on physical examination depends on the level of dehydration and patient may present with tachycardia, postural hypotension, somnolence, dry mucous membrane, sunken eyes,oliguria. If the severe diarrhea and vomiting are not aggressively treated, they can, within hours, result in life-threatening dehydration and electrolyte imbalances. The typical symptoms of dehydration include dizziness ( due to low blood pressure), wrinkled hands (poor skin turgor) , sunken eyes, muscle cramps (decreased potassium), and decreased urine output.
Lab tests
Lab tests are not mandatory for diagnosis and treatment of cholera. In endemic areas when suspected, treatment should be started as early as possible with fluid replacement and antibiotics. In areas where cholera is uncommon, performing lab tests are worthwhile.Tests used for identification of organisms are: Direct microscopic examination of organism, dark field examination, gram staining, culture, antigen, polymerase chain reaction and serotype tests
References
- ↑ McLeod K (2000). "Our sense of Snow: John Snow in medical geography". Soc Sci Med. 50 (7–8): 923–35. PMID 10714917.
- ↑ WHO Cholera [1]
- ↑ Hartwell LH, Hood L, Goldberg ML, Reynolds AE, Silver LM, and Veres RC (2004). Genetics: From Genes to Genomes. Mc-Graw Hill, Boston: p. 551-552, 572-574 (using the turning off and turning on of gene expression to make toxin proteins in cholera bacteria as a "comprehensive example" of what is known about the mechanisms by which bacteria change the mix of proteins they manufacture to respond to the changing opportunities for surviving and thriving in different chemical environments).
- ↑ Ryan KJ, Ray CG (editors) (2004). Sherris Medical Microbiology (4th ed. ed.). McGraw Hill. pp. 376&ndash, 7. ISBN 0838585299.