Cholera

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Cholera

Cholera is as an acute infection of the small intestines that is caused when water or food contaminated with the bacterium Vibrio cholerae (Peters, 2004). Vibrio cholerae is a member of the family Vibrionaceae of Proteobacteria. This type of bacteria is Gram-negative curved rod that is non-spore forming and which is about 1 micrometer in width, and about 2 or 3 micrometers lengthwise. The organism is capable of both fermentative and respiratory metabolism. It also reduces nitrate, is oxidase-positive, and is motile by means of one sheathed polar flagellum. In Bergey’s Manual, Vibrionaceae, Enterbacteriaceae and Pseudomonadaceae are leveled in Gammaproteobacteria (1994). Vibrionaceae differ from the other two because they are oxidase-positive and motile by means of polar flagella. Most Cholera in the world is caused by V. cholerae serogroup O1, biotype EI Tor or Classical (Peters, 2004). The biotypes can further be divided into three serotypes: Ogawa, Inaba and a rarer one, Hikojima.

V. cholerae has a life cycle that is divided into two distinct phases. The first phase is the aquatic phase, when it still outside the host. In this phase, the bacterium are free swimming and attach to surfaces provided by insects, egg masses, plants, green algae, and other objects. The second phase is the infection phase where the organism spends its time in the small intestines of the host. Once in the host, the organism attaches itself to the intestinal mucosa, and secretes a toxin called cholera enterotoxin, which disrupts the normal intestinal cell physiology. Because they are not part of the host’s body, V. cholerae exist as transients, therefore resulting in problems for the host in the form of Cholera. Once in the

Cholera is transmitted through ingestion of water or food contaminated with V. cholerae. The source of the contamination is often the feces of a person infected with cholera in an epidemic. This happens most often in developing countries where feces come in contact with drinking water due to inadequate drainage and treatment of drinking and sewage water. In developed countries on the other hand, seafood is the major transmitter of Cholera. Seafood, especially Shellfish that is eaten raw, has caused a number of cases of Cholera in the United States (Peters, 2004). Cholera can kill within a few hours of infection if left untreated. In fact, there are about 120,000 deaths caused by cholera each year.

There are two types of strains: toxic and nontoxic. However, nontoxic strains can acquire toxicity through temperate bacteriophage (World Health Organization [WHO], 2010). Cholera is highly epidemical and has caused numerous deaths throughout history and currently in developing countries. However, Cholera cannot be transmitted through causal contact with an infected person. Transmission of cholera is therefore solely due to ingestion of contaminated food or water and not all strains of the bacterium cause Cholera even though they can acquire toxicity.

Cholera is highly virulent and affects both adults and children. Additionally, most people who are infected with V. cholerae – about 75 percent – do not develop any symptoms. However, the bacteria appear in their feces from seven to fourteen days after infection, where they have the potential to infect other people. Most of those who develop symptoms show only mild symptoms and only few develop severe dehydration caused by watery diarrhea, the main symptom of cholera. Other symptoms include low urine output, extreme thirst, glassy eyes and abdominal cramps. For this reason, many people who die from cholera have not had a chance of being diagnosed with the disease, even though outbreaks are an indicator that they suffered from Cholera (Peters, 2004).

When a doctor is making a cholera diagnosis, they look at a person’s recent history of travel, as well as any drinks or food he may have ingested recently. In addition, the doctor will often ask a patient about any current medical conditions and current medication in order to confirm that the symptoms are not caused by another disease or a reaction to medication. However, it is only through a laboratory test that an accurate diagnosis of Cholera can be made. Possible tests include stool culture and blood culture. When a doctor uses a stool culture, he will be looking for presence of V. cholerae in the stool, an indication that they are present in the small intestines. Blood culture on the other hand reveals the presence of antibodies that formed against V. cholerae. Through these tests, the doctor is able to diagnose Cholera and prescribe the adequate treatment.

As mentioned, V. cholerae gets into the host’s body through ingestion of contaminated water or food. As the bacteria pass through the stomach, there numbers are depleted due to the unfavorable acidic environment of the stomach. However, water or food ingested often contains large amounts of the bacteria therefore depletion of all of them rarely happens here and they pass on to the small intestines. Once in the small intestines, they multiply rapidly and produce cholera enterotoxin (CT), which causes large volumes of electrolytes and water to be secreted into the bowels. This toxin is secreted through the bacterial outer membrane. This toxin also plays an important role in V. cholerae’s ability to cause epidemics (Bergey, 1994). Symptoms begin to occur about three days after infection.

Prevention of Cholera can be done by observation of proper food and water hygiene. In addition, oral cholera vaccines are available in all parts of the world. Treatment of Cholera focuses on replacement of electrolytes and fluids lost through vomiting and diarrhea. Treatment may either be oral, antibiotics, zinc supplements or intravenous (Peters, 2004). The World Health Organization approved Oral Rehydration Solution (ORS) consisting of sugar and electrolytes is used internationally, especially in areas where alternative methods of treatment may be expensive. The solution is in powder form and may be reconstituted in water for ingestion. Rehydration is the focus of treatment for Cholera as more than half of those who do not rehydrate die. Antibiotics may be administered to a patient even though they are not a part of the treatment of cholera. This is because they reduce the duration and amount of diarrhea. Also used to decrease the duration and amount of diarrhea especially in children are zinc supplements. Finally, some severe cases of Cholera require administration of intravenous fluids as oral rehydration may not be adequate.

Cholera epidemics and pandemics usually occur in low-income regions across the world where hygiene of water and food is inadequate. Additionally, poor drainage and sanitation are contributing factors to the spread of Cholera. This especially happens when such calamites as wars and natural disasters lead to displacement of populations into congested, poorly-drained areas. The disease often occurs in pandemics and epidemics with most of the pandemics largely confined to Asia in the 19^th Century and originating from the Ganges delta in India. The current pandemic is seventh in the history of Cholera and is caused by V. cholerae O1 EI Tor, having originated in Indonesia in 1961 (WHO, 2010). The biotype was introduced into Africa through West Africa in 1970 where it is now endemic in many countries. Its introduction into Latin America in 1991 was through Peru, even though it is largely under control. In addition to this biotype, V. cholerae O 139 also caused Cholera epidemics in Bangladesh and India in 1992 and since then has spread to other countries. In 2009, 98 percent of Cholera cases were reported in Africa, causing 4,000 deaths on the continent. No cases of Cholera were reported in Central America in 2009 (WHO, 2010).

While Cholera’s causes, prevention and treatment are known, it still poses a major problem in the world. The future of Cholera should therefore focus on complete eradication of the disease in low-income parts of the world and in instances where natural disasters are likely to cause outbreaks. Efforts should be concentrated on ending the seventh pandemic that has lasted for about fifty years and on learning the best control of pandemics through studying of past pandemics.

References

Bergey, D. H., & Holt, J. G. (1994). Bergey’s manual of determinative bacteriology.Philadelphia, PA: Lippincott Williams & Wilkins.

Peters, S. T. (2004). Cholera: Curse of the Nineteenth Century.Tarrytown, NY: Marshall Cavendish.

World Health Organization. (2010). Cholera. Fact Sheet No. 107. WHO Media Centre.