Overview of Cholera
Cholera is a bacterial infection of the small intestines. It causes violent diarrhea and severe dehydration. If untreated cholera is fatal in 30%-50% of cases. Death can occur in as little as four hours or take as long as several days depending upon the initial health of the victim.
In the USA, cholera is tracked, monitored, and handled by the Enteric Diseases Laboratory Branch of the Division of Foodborne, Bacterial, Mycotic Diseases of the CDC (Centers for Disease Control). The Enteric Diseases Laboratory Branch works on an international level in conjunction with the WHO (World Health Organization). Internationally, cholera is combated by WHO and UNICEF.
The seventh, and current, pandemic of cholera began in 1961. This pandemic started in Indonesia and is caused by the biotype El Tor serogroup O1. Some epidemiologists believe that the world is currently in the eighth pandemic of cholera and mark that beginning in 1991 in Peru.
It is believed that number of cases of cholera is underreported on an international level due to an unreliable reporting superstructure and infrastructure, the risk of international sanctions, fear of a loss of money from a downturn in tourism, and other reasons. The WHO reports that in 2007 a total of 53 countries noted cases of cholera. There were a total of 177,963 cases with 4,031 deaths. 2007 had a case fatality rate (CFR) of 2.3%. These numbers should be compared to the current outbreak of cholera in Zimbabwe. This outbreak began in August of 2008 and by February of 2009 there had been 79,613 cases with 3,731 deaths and a CFR of 4.7%.
The most common infectious strain of cholera is the El Tor O1 strain. The strain “Bengal” O139 was discovered in 1993 in the Ganges Delta in Bangladesh. A handful of cases dating back to 1992 in the Ganges Delta have been retro-diagnosed as “Bengal” O193. Exposure to the O1 serogroup confers no immunity to the “Bengal” O139 type of cholera. The “Bengal” O139 strain is a more virulent than the El Tor O1 strain. The 1993 outbreak in the Ganges Delta started a regional outbreak in Asia.
In recent years, there have been outbreaks in Afghanistan, Bangladesh, Burma, Bolivia, China, India, Indonesia, Iraq, Malaysia, Papua New Guinea, Vietnam, and Yemen.
On the African continent, there have been reported outbreaks in Benin, Chad, Cote d’lvoire, Eritrea, Ghana, Liberia, Mozambique, Namibia, Niger, Nigeria, Sierra Leone, Somalia, Sudan, Togo, Zambia, and Zimbabwe. 99% of cases of cholera come out of Africa.
Some countries reported experiencing imported cases of cholera, but did not experience outbreaks. These geographic regions and countries are Australia, Botswana, Eastern Europe, Europe, Ireland, Kazakhstan, the Netherlands, North America and the United Kingdom.
Cholera was first identified in 1817 by Thomas Sydenham. Filippo Pacini named cholera “Vibrio Cholerae” after establishing the bacterial aetiology in 1854.
Cholera is known as Vibrio Cholerae, v. cholerae, El Tor O1, or “Bengal” O139. El Tor O1 and “Bengal” O139 are specific types of cholera.
Non-O1 strains of cholera are found in the environment worldwide, but are not considered a public health hazard.
In many instances, cholera is asymptomatic or presents as mild gastroenteritis. Severe cholera presents differently. Diarrhea is the keystone symptom of cholera. So called “rice water stools” occur with a bad cholera infection. “Rice water stools” do not look the same as normal diarrhea. The stool is a pale liquid. The flecks of rice like granules are actually bits of the intestinal lining. In the early stages, the diarrhea may appear like normal diarrhea, but it will advance to “rice water stools” diarrhea. Sometimes “rice water stools” will have a fishy odor.
Most victims of severe cholera present with signs and symptoms of dehydration. These include: lethargy, tachycardia, vomiting, dry eyes, dry mouth, the inability to produce tears, sunken eyes, reduced or no urine, and a stark thirst. Leg and muscle cramps may also be present and are the result of an electrolyte imbalance brought on by dehydration. Infants will present with sunken soft spots.
If these symptoms are ignored it may result in hypovolemic shock and death.
The WHO reports that dehydration as the result of diarrhea causing infections causes 18% of the deaths of children age five and under worldwide. Cholera, one these types of infections, is especially dangerous for young children, the elderly, and people with compromised immune systems. Typically, cholera will strike children the hardest. The “Bengal” O193 strain was atypical. It primarily struck male, young adult, agricultural workers. The first victims of the “Bengal” O193 strain were rice paddy workers. Anyone can fall ill with cholera.
Cholera is considered endemic to India, Bangladesh, parts of Africa, and a few other sections of the world. Some epidemiologists report that cholera becomes endemic to an area after it experiences an epidemic of cholera.
Causes and risk factors
The causes and risk factors of cholera are interdependent.
Cholera is caused by tainted food and water supplies. War, famine, natural disaster, and overcrowding of displaced persons and refugees are precursors to cholera outbreaks. In Bangladesh and India, cases of cholera spike after the monsoon season. In other parts of the world, cholera outbreaks are preceded by the rainy season.
The basic pathogenesis is that a person ingests infected food or water, the bacteria passes through the human body and is expelled as human waste. The waste seeps back into the water supply and is set to attack another victim. An infectious dose of cholera in healthy North American volunteers is 100,000 bacteria. In 24 hours, the output contains 20 billion bacteria. The bacteria undergo genetic changes inside the human intestines which makes it more virulent. Vibrio Cholerae experiences biomass amplification via the human digestive system.
Bengal O139 Strain
The sine qua non of cholera can best be illustrated with the case of the “Bengal” O139 strain. Dr. Gary Schoolnik, MD and professor at Stanford School of Medicine, in his lecture titled, “Environment Degradation Begets Epidemics” posits that global environmental changes increase the severity of cholera outbreaks. The severity of monsoons is influenced by global environmental changes.
Monsoon runoff, irrigation runoff, deforestation, the use of chemical fertilizers, and runoff of human and animal waste increases the presence of nitrates in the water supply. The nitrates spark algal blooms. Algal blooms are comprised of Anabaena Variabilis. Cholera forms at the junction between the heterocyst and the vegetative cells in Anabaena Variabilis. Vibrio Cholerae experiences biomass amplification via the algal blooms. The algal blooms will create copepod blooms. Copepods feed on algal blooms. Copepod blooms are made up of zooplankton and other small crustaceans.
Zooplankton & Microbes
The zooplankton, Tigriopus Califonicus, have an exoskeleton made of chitin. Cholera microbes are attracted to the chitin. Vibrio Cholerae feeds on the chitin. The feeding breaks down the chitin to its elemental building blocks. These elements are absorbed by Vibrio Cholerae as nutrients and these nutrients cause fundamental changes to the DNA of Vibrio Cholerae. This genetic change converts the El Tor O1 strain into the “Bengal” O193 strain.
This change happens with the alteration of less than 100 genes. Vibrio Cholerae gains genetic diversity by digesting the chitin and is especially primed to infect a human host where it will achieve another round of biomass amplification.
The algal bloom biomass amplification is not limited to the Ganges Delta. It can occur in any body of water experiencing an algal bloom. The algal bloom/copepod bloom evolutionary course is not limited to the Ganges Delta either. The biomass amplification that occurs in humans happens anytime the bacteria pass through the human body.
In War-torn areas of the world and places of natural disasters, damage done to the sanitation infrastructure causes the drinking water supply to become tainted with cholera bacteria. In developing nations and refugee camps, the sanitation systems are often inadequate to retard the development of cholera.
If a person consumes tainted water directly, they may become infected. If food is washed in infected water, the food supply may become tainted. If a person washes their hands with infected water and then handles food, the food supply may become tainted. If a person improperly handles human waste or tainted garbage, they may become infected. Infection from person to person is extremely rare.
It is commonly believed that cholera outbreaks are sparked by the decomposition of corpses. This is a myth.
Cholera is easily preventable in theory. In areas of the world where clean drinking and washing water are available, cases of cholera are extremely rare. In places of the world where cholera is endemic to the environment, sanitation efforts can be used to prevent cholera outbreaks. Simply speaking, if the population has access to clean drinking water and an adequate sewage system, cholera outbreaks would be substantially reduced if not eliminated completely.
War, natural disaster, political posturing, and insufficient funds make the implementation of proper sanitation practices difficult.
In some parts of the world, such as the Ixil Triangle in Guatemala, cholera and other foodborne and waterborne illnesses are combated with washing vegetables, fruits, and other foods that are eaten raw in a bleach-water solution. The ingestion of bleach comes with another set of health complications. In some areas of the world, water is boiled or treated with sanitization tablets before consumption.
After natural disasters, areas of the world that normally do not see cholera will go under “a boil water order” temporarily. This is intended to keep down foodborne and waterborne illnesses until the sanitation systems are repaired.
The key to preventing cholera is clean drinking water and proper sewage and sanitation systems.
Although a blood test can check for cholera antibodies, it is generally not used. Rectal swaps and stool samples are checked for cholera bacteria.
Cholera is treated through rehydration efforts. The biggest danger of death with cholera is the result of dehydration. Clean water can be given orally in some mild cases. Fluids can be administered intravenously also. There’s an oral rehydration solution made up of salts, sugars, and water that is given during outbreaks. These efforts, if started in time, are highly effective and substantially reduce mortality. Even in severe outbreaks the mortality rate is under 5% whereas cholera is fatal 30%-50% of the time when left untreated.
WHO approved oral rehydration salts (ORS) are for sale in packets in many countries that commonly deal with cholera.
ORS can be made at home by combining:
- 1/4 teaspoon of salt (sea salt or table salt)
- 1/4 teaspoon of potassium chloride (“Salt Lite”, “NoSalt”, or a salt substitute. If this is not available four teaspoons of cream of tartar can be used.)
- 1/2 teaspoon of sodium bicarbonate (baking soda)
- 2 1/2 tablespoons of sugar, (honey can be used, but not with infants and small children)
Dissolve the above ingredients in 1 liter (approximately four cups) clean water. To ensure the water is clean boil it for ten minutes and let it cool. The water needs to be measured after boiling. The ingredients need to be measured carefully. Too much sodium or potassium can cause complications or death.
Improper rehydration efforts can result in a worsening of the condition. Many people contract cholera from unsafe drinking water. When their thirst increases, they consume more of the unsafe drinking water. The key to combating cholera in the early stages is access to clean drinking water.
The only side effects and risks of cholera rehydration treatment come with the unsafe handling of the needles used when administering intravenous fluids. As long as a new needle is used when starting the IV and the surface area of the skin is properly swabbed before injection, there are practically no side effects.
In some cases antibiotics will be included in the treatment of cholera. Antibiotics can reduce the duration of symptoms, severity of symptoms, and the fluid requirements of the patient. Ciprofloxacin, doxycycline, erythromycin, furazolidone, and tetracycline are used to treat cholera in addition to other bacterial infections.
These antibiotics do have side effects.
Serious side effects include:
- severe headache
- blurred vision
- body aches
- flu-like symptoms
- a skin rash that may blister and peel
- reduction of urine
- discoloration of urine
- yellowing of skin and eyes
- severe pain in the chest
- pain in the upper stomach
- pain in the joints
- swelling near joints
- nausea and vomiting
- fast heart rate
- easy bruising and bleeding
- confusion, hallucinations, and depression
- numbness and tingling in the extremities
Less serious side effects include:
- mild nausea or stomach upset
- swollen tongue and difficulty swallowing
- insomnia or nightmares
- mild headaches
- slight dizziness
- feelings of anxiety
- white patches or sores in the mouth or on the lips
- swelling or sores in the rectal or genital area
- vaginal itching and discharge.
Some of the antibiotics should not be administered to pregnant or nursing women.
There are two types of vaccines available to combat cholera. The first type is a whole-cell (WC) vaccine. This vaccine has poor efficacy and is highly reactogenic. It is not recommended for use by the WHO.
Side effects of the CW vaccine include:
- sudden and severe lethargy
- swelling of the face, eyes, and the interior of the nasal passages
- discoloration of the skin
- itching particularly of the palms and soles
- difficulty breathing and swallowing
- body aches
- pain and swelling at the site of the injection.
There have not been enough studies to determine if this vaccine is safe to use with pregnant or nursing women.
The second type is an oral vaccine. There are two of these and collectively they are called oral cholera vaccines (OCV). The OCV designated CDV 103-HgR is administered as one dose and is effective eight days after being administered. It is used to combat current outbreaks. It goes by the trade name “Orochol-E”. The other type of OCV is designated WC/rBS. It is administered in two doses at least ten days apart.
The two doses shouldn’t be spaced out more than fourteen days. This vaccine becomes effective ten days after the second dose and is not used once an outbreak has occurred. It goes by the trade name “Dukoral”.
Side effects of OCV include:
- abdominal pain and gurgling
- nausea and vomiting
- and loss of appetite.
Vaccine Safety and Effectiveness
The safety of these vaccines for use with pregnant or nursing women has not yet been determined. Health care practitioners should heed caution when administering OCV vaccines to patients with HIV.
OCV vaccines are 70% effective and the effectiveness continues for at least year. No vaccine protects against the “Bengal” O139 strain.
There is a third vaccine in development called “Shanchol”. It is being used in India. There is little known about it as the side effects and efficiency are still being studied. It can be administered oral or via an injection.