CHOLERA

 

by LINDA AHIARAH

 

Cholera is an acute intestinal infection caused by toxigenic Vibrio cholerae o group 1 or 0-group 139.The infection can be mild or subclinical, but in severe cases it may lead to volume depletion (1). Drinking contaminated water or eating contaminated food with cholera bacterium transmits this infection. The source of the contamination is usually the feces of an infected person. Shellfish eaten raw or undercooked has been reported as a source of cholera (2). The reservoir for this infection is aquatic environment and food.

 

The genus Vibrio consists of Gram-negative straight or curved rods, motile by means of a single polar flagellum. Vibrios are capable of both respiratory and fermentative metabolism. O2 is a universal electron acceptor; they do not denitrify. Most species are oxidase-positive (3). The most current diagnosis of cholera and the detection of the carrier in a household is with the use of a Cholera Test Kit. The principle of the test is a membrane ELISA  which serogroup specific monoclonical antibodies are used as the antigen detection reagents (4). This test detects both the V. cholerae 0:1 or 0:139 or both. Also, stool specimen should be analysis and the characteristics features of this microorganism identified.

 

Cholera is characterized by acute, profuse watery diarrhea, described as "rice-water stool", vomiting also is associated with disease condition leading to volume depletion. Other signs and symptoms noted include tachycardia, loss of skin turgor, dry mucous membranes, hypotension, and thirst (1).

 

Cholera was originally endemic to the Indian subcontinent, with the Ganges River likely serving as a contamination reservoir. It spread by trade routes (land and sea) to Russia, then to Western Europe, and from Europe to North America. It is now no longer considered an issue in Europe and North America, due to filtering and chlorination of the water supply. Between 1816-1826 first pandemic was noted, previously restricted, the pandemic began in Bengal, then spread across India by 1820. It extended as far as China and the Caspian Sea before receding. From 1829-1851  Second pandemic reached Europe, London and Paris in 1832. In London, it claimed at least 3000 victims according to a 1832 article; in Paris, 20,000 succumbed (out of a population of 650,000) with 100,000 victims in all of France. It reached Russia (Cholera Riots), Quebec, Ontario and New York in the same year and the Pacific coast of North America by 1834. 1849 - Second outbreak in Paris. An outbreak in North America took the life of former U.S. President James K. Polk 1852-1860 - Third pandemic mainly affected Russia, with over a million deaths. 1854 - Outbreak of cholera in Chicago took the lives of 5 1/2 per cent of the population.1863-1875 - Fourth pandemic spread mostly in Europe and Africa. 1866 - Outbreak in North America. 1899-1923 - Sixth pandemic had little effect in Europe because of advances in public health, but Russia was badly affected again. 1961-1970s - Seventh pandemic began in Indonesia called El Tor after the strain, and reached Bangladesh in 1963, India in 1964, and the USSR in 1966. From North Africa it spread into Italy by 1973. In the late 1970s there were small outbreaks in Japan and in the South Pacific. There were also many reports of a cholera outbreak near Baku in 1972, but information of this was suppressed in the USSR (5)

 

The virulence of V.cholera is based on the lysogenic convergence with the CTX phage resulting in the production of a protein toxin, that consist of two chains namely A-peptide chain and the light chain. The A-chain consists of two sub-fragments that cause protein toxicity. Fragment A-1 acts on the adenylate cyclase system and A-2 facilitates entry of toxin into the cell. The non-toxic B-peptide protein fragment binds the whole protein to the host cells by way surface receptors. In combination, the toxin is released to infect bound cells (6).

 

To control and treatment of Cholera is done by immediate replacement of the fluid and salt lost through diarrhea. Patient is also encouraged to drink large amount of oral rehydration solution. With severe cases, intravenous fluid replacement is recommended. Antibiotic is also incorporated in the treatment regime to shorten the severity of the illness (2). Cholera can be prevented by drinking only water that have being boiled or treated with chlorine or iodine, especially for people travelling to areas with epidemic cholera. Other recommendations include eating only foods that have been thoroughly cooked and still hot. Avoiding undercooked or raw fish or shellfish, ensuring all vegetables are cooked and avoiding salads (2). Although vaccines are not yet available in US, there are currently 3 vaccines namely Wyett Ayerst, Dukoral from Biotec AB, and Mutacol froj Berna. These vaccines provide partial protection, and the latter two vaccines provide better immunity with fewer side effects but with limited duration (6).

 

Report shows that current global cholera outbreak has killed at least seven people and infected 33 others in December 2007 in western Kenya. The fatalities included three children and four adults. 20 Cases of cholera were reported in November 2007 in the central Zambezia province in Mozambique. 2 people died. In August 2007 a serious cholera outbreak hit northern Iraq. An estimated 30 000 people fell ill with acute watery diarrhoea (AWD), usually associated with cholera. In August 2007 WHO reported 2060 cases of AWD in Somaliland, in the eastern “Horn of Africa” region. 31 people died.

From April 2006 to February 2007, 680 people died in Ethiopia (also in East Africa) from a suspected cholera outbreak, however, country health officials never officially declared the outbreak. Djibouti, also situated on the eastern “Horn of Africa” reported 322 cases and 23 deaths from cholera in February 2007. By May another 76 cases has occurred, five of whom died. In 2006 Angola was hit by a severe cholera outbreak. The country reported a total of almost 70 000 cases including 2760 deaths. Between January and June 2006 a total of 16 187 cases, including 476 deaths of AWD was reported in southern Sudan (7). No major outbreaks of this disease have occurred in the United States since 1911. Sporadic cases did occur between 1973 and 1991, from reintroduction of the organism into the U.S. marine and estuarine environment. Environmental studies have demonstrated that strains of this organism may be found in the temperate estuarine and marine coastal areas surrounding the United States (8).

 

References

1.Center for Disease Control and Prevention. "Prevention of Specific Infectious Diseases". 6/20/2007.URL:  http://wwwn.cdc.gov/trael/yellowBookCh4-Cholera.aspx accessed on 5/6/08.

2.Center for Disease Control and Prevention. "Cholera". 3/27/08. URL: http://www.cdc.gov/nczved/dfbmd/disease_listing/cholera_gi.html accessed on 5/6/08.

3. Todar Kenneth. "Vibrio cholerae and Asiatic Cholera". 2005.URL: http://www.textbookofbacteriology.net/cholera.html accessed on 5/6/08.

4.Antigent-E. "Cholera Test Kits". URL: http://www.biotec.or.th/cybermart/antigent_E/antigent_e.html accessed on 5/6/08.

5.WD. "Cholera in Wikipedia". 5/6/08. URL: http://www.wrongdiagnosis.com/c/cholera/wiki.htm accessed on 5/6/08.

6. UC BSO. "Vibrio cholera". URL: http://ehs.ucdavis.edu/ucbso/FactSheet_Vibrio_cholera.html accessed on 5/6/08.

7.Health 24.com. "Global Cholera Outbreaks". URL: http://www.health24.com/medical/Condition_centres/777-792-803-2877,44284.asp accessed on 5/6/08.

      8.U.S Food and Drug Administration. "Vibrio cholerae Serogroup 01". 12/28/07. URL: http://www.cfsan.fda.gov/~mow/chap7.html accessed on 5/6/08