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Cholera

Cholera is a severe diarrhea disease caused by the bacteria Vibro cholerae. There are presently 5.5 million cases reported worldwide. Untreated it has a 40% mortality rate. Within Africa 20,000 people die per-year and about 100,000-die per-year in Asia.

Vibrio cholerae Serogroup O1

 

This is responsible for Asiatic or epidemic cholera Environmental studies have demonstrated that strains of this organism may be found in the temperate estuarine and marine coastal areas surrounding the United States.

In 1991 cholera was reported for the first time in this century in South America, starting in Peru. The outbreaks quickly grew to epidemic proportions and spread to other South American and Central American countries, and into Mexico. 1,099,882 cases and 10,453 deaths were reported in the Western Hemisphere between January 1991 and July 1995.

Although the South American strain of V. cholerae O1 has been isolated from Gulf Coast waters, presumably transmitted by ships off-loading contaminated ballast water, no cases of cholera have been attributed to fish or shellfish harvested from U.S. waters. However, over 100 cases of cholera caused by the South American strain have been reported in the United States. These cases were travelers returning from South America, or were associated with illegally smuggled, temperature-abused crustaceans from South America.

In the Autumn of 1993, a new strain, a non-O1 never before identified, was implicated in outbreaks of cholera in Bangladesh and India. The organism, V. cholerae serogroup O139 (Bengal), causes characteristic severe cholera symptoms. Previous illness with V. cholerae O1 does not confer immunity and the disease is now endemic. In the U.S., V. cholerae O139 has been implicated in one case, a traveller returning from India. The strain has not been reported in U.S. waters or shellfish

Cholera is the name of the infection caused by V. cholerae

Symptoms of Asiatic cholera may vary from mild, watery diarrhea to an acute diarrhea, with characteristic rice water stools. Illness is generally sudden, with incubation varying from 6 hours to 5 days. Abdominal cramps, nausea, vomiting, dehydration, and shock; after severe fluid and electrolyte loss, death may occur. Illness is caused when bacteria attach to the small intestine and produce cholera toxin. The production of this cholera toxin by the attached bacteria results in the watery diarrhea associated with this illness.

Antacid consumption markedly lowers the infective dose.

Cholera is confirmed only by isolation of cholera bacteria from the diarrheic stools of infected individuals.

Cholera is generally spread by poor sanitation, and contaminated water supplies. This is the main mechanism for its spread in poor communities in South America.

Sporadic cases occur when shellfish harvested from fecally polluted coastal waters are consumed raw.

Cholera may also be transmitted by shellfish harvested from nonpolluted waters since V. cholerae O1 is part of the normal microbiota of these waters

 

Cholera patients require fluids either intravenously or orally with a solution containing sodium chloride, sodium bicarbonate, potassium chloride, and glucose. The illness is generally self-limiting. Antibiotics shorten the illness. Death occurs from dehydration and electrolyte loss.

References: MMWR 44(20):1995 , MMWR 44(11):1995 , MMWR 42(33):1993 , MMWR 47(19):1998 MMWR 42(26):1993 , MMWR 42(21):1993

 

 

Vibrio cholerae Serogroup Non-O1

Infects only humans and primates. It is related to V. cholerae Serogroup O1, the organism that causes Asiatic or epidemic cholera, but causes a less severe disease than cholera. Strains of the organism are normal inhabitants of marine and estuarine environments of the United States. It has been referred to as non-cholera vibrio (NCV) and nonagglutinable vibrio (NAG) in the past.

Non-Ol V. cholerae gastroenteritis is the name associated with this illness.

Although rare, septicemic infections have been reported and deaths have resulted. Some cases are similar to the primary septicemia caused by V. vulnficus

Diarrhea, abdominal cramps, and fever are symptoms associated with this illness, and vomiting and nausea occurring 25%. Diarrhea occurs within 48 hours after eating these bacteria. Diarrhea may, be severe, lasting 6-7 days. Antibiotics shorten the severity and duration of the illness.

Disease caused by V. cholerae O139 is indistinguishable from cholera caused by V. cholerae O1

Diagnosis of a V. cholerae non-Ol infection is made by culturing the organism from an individual's diarrheic stool or from the blood of patients with septicemia.

Shellfish harvested from U.S. coastal waters frequently contain V. cholerae serogroup non-Ol. So eating raw, improperly cooked or cooked, re-contaminated shellfish may lead to infection.

Septicemia) can occur in individuals with cirrhosis of the liver, or who are immunosuppressed.

 

References: MMWR 42(26):1993 ; MMWR 44(11):1995 ; MMWR 31(39):1982

Cholera Vaccine

The older cholera vaccine was about 50% effective and causes local reactions such as; fever, flu symptoms, and headache.
A newer cholera vaccine is now available with minimal side effects.
Immunization is felt to be effective in controlling cholera epidemics but is not recommended for travelers because of cost effectiveness.
Cholera is characterized by severe diarrhea (early to rapid dehydration), and if left untreated death occurs within 24 hours. Cholera is transmitted through food or water contaminated by cat, dog or human faeces.

It is also transmitted by direct person-to-person contact.

To avoid transmission of cholera drink provided water and consume well cooked food.

Seek help early on if symptomatic. Rehydration with oral or IV fluids may be necessary.
Other countries may require proof of vaccination for travelers arriving from countries where cholera is endemic. Although the WHO does not suggest that a certification of immunization be necessary some countries like Uganda occasionally will insist a letter for arriving travelers.

Checking with each countries Embassy in advance of travel will confirm any recent changes to requirements.

Cholera Links

Center for Disease Control http://www.cdc.gov/ncidod/dbmd/diseaseinfo/cholera_g.htm

John Snow Home Page http://www.ph.ucla.edu/epi/snow.html

(This is one of the most historically important links on our site and celebrates the life of a famous epidemiologist and how he fought against cholera)
World Health Organaization Who http://www.who.int/health_topics/en/