What is Cholera? Vibrio Cholerae Bacteria Traveler’s Diarrhea
Cholera is a bacterial disease where the intestinal infection leads to profuse watery diarrhea. The cholera bacteria is spread by consuming contaminated food or water. Although diarrhea is not an uncommon symptom, cholera diarrhea is so severe that it can cause severe dehydration within a very short while. The degree of dehydration leads to complications and ultimately death if appropriate medical intervention is not forthcoming. There are vaccines for cholera prevention but it only offers immunity for short periods. Therefore vaccination is only considered when there is a risk of outbreaks.
How common is cholera?
Cholera is a very uncommon intestinal infection in the United States. Globally there are about 5 million cases of cholera that occur every year killing some 100,000 people annually. Although it is uncommon in the United States, and the risk for an outbreak is low, it is nevertheless important for Americans to be cautious when traveling to endemic areas. Although cholera is not contagious and cannot be spread through direct contact from person-to-person, it is possible that certain foods containing cholera, like fruit, vegetables and seafood, can be imported into the country and pose a danger when eaten raw. Many new cases of cholera in the United States has been linked to seafood from the Gulf of Mexico.
What is the cholera germ?
The germ that causes cholera is known as a bacterium (plural ~bacteria). It cannot be seen by the naked eye and even water that looks clean can be contaminated. It can also be present on fresh fruit, vegetables and shellfish which are more likely to cause disease if eaten raw. The cholera bacteria, Vibrio cholerae, is found is salt water sources as it travels on tiny crustaceans known as copepods. These crustaceans tend to aggregate at food sources. There are many different types of cholera bacteria. Some can cause severe disease and are known as pathogenic cholera bacteria. Those types that do not cause any disease in humans are considered non-pathogenic cholera bacteria.
Types of Cholera Bacteria
Although some cholera bacteria are pathogenic and others non-pathogenic, it is important to look at the types of pathogenic Vibrio cholerae bacteria. The most common pathogenic type is Vibrio cholera 01. It is referred to as the O-type because it has O class of antigens on its surface. Different serotypes based on the difference in O antigen structure includes :
- O antigens A and B are known as the serotype Inaba.
- O antigens A and C are known as serotype Ogawa.
- O antigens A, B and C are known as serotype Hikojima.
What does cholera bacteria look like?
The cholera bacteria are not visible to the human eye and it can only be seen under a microscope. These bacteria are said to be comma-shaped and measure between 1 to 3 um in length and about 0.5 to 0.8 um in diameter. It is very small – about one-thousandth of a millimeter (0.001mm). To put this in perspective, one grain of very fine sea sand is about 1/16th of a millimeter which is approximately 60 times bigger than a cholera bacterium.
How do you get cholera?
The cholera bacteria enters the body by drinking water or eating food contaminated with the cholera bacteria. In the United States, proper sanitation and water treatment means that it is highly unlikely to contract the infection through drinking water. However, the risk remains even in the United States through consuming contaminated food.
Foods that can cause cholera
Although it is not the food itself that may cause cholera, there are some foods where the risk of contamination is greater than others. Imported foods from outside of the United States can be a problem if it has been grown in endemic regions and not cooked before eating.
- Shellfish. Oysters are one of the potential problem foods as it is eaten raw. Other shellfish that may be eaten raw in sushi and related cuisine can also be risky.
- Vegetables. Any vegetable that has been exposed to contaminated water either during the irrigation or food preparation phase may be a risk if eaten raw.
- Fruit. Since fruits are mainly eaten raw, it is important that the peel is removed and the fruit then washed thoroughly in clean water. Unpeeled fruits are the bigger risk.
- Meat. Although a less common food source for cholera, raw or undercooked meat can still be a problem if it has been contaminated with cholera, usually through contaminated water or feces, during the food preparation phase.
How does cholera cause death?
In order to understand how cholera can kill a person, it is first important to understand the disease itself. The cholera bacteria can be consumed in contaminated water, food washed in contaminated water or seafoods. However, it may not always cause disease in humans but is still passed out in the stool of the infected person. In fact the cholera bacteria is much more likely to cause disease when food or water contaminated with the feces of infected people is consumed.
The cholera bacteria produce a powerful toxin known as CTX. It is this toxin that causes disease when in the small intestine. However, to reach the small intestine the bacteria first have to pass the potent stomach acid and enzymes. Most of the bacteria are killed off by the stomach juices therefore a person has to consume a large number of the bacteria to become sick. The toxin does not enter the wall of the intestine but acts on its surface to disturb the normal flow of electrolytes like sodium and chloride.
The intestinal wall then passes out large amounts of water into the lumen which causes severe watery diarrhea. Although the colon is not usually affected by the toxin, it may not be able to reabsorb all the water that enters in at the small intestine. The watery diarrhea causes severe fluid loss, often with large amounts of essential electrolytes. This leads to dehydration which can affect nerve and muscle activity in particular. It can affect normal heart and kidney function, as well as disrupt other organs, and eventually progress to death.
What are the symptoms of cholera?
The main symptoms of cholera are diarrhea, nausea and vomiting and dehydration. In addition children may have a fever and convulsions in severe cases. The first symptoms of cholera occurs 2 to 3 days after contracting the infection. However, it is possible that it can start as soon as a few hours to 5 days after consuming contaminated food or water.
- Sudden onset of diarrhea.
- Very loose and extremely watery stool that is pale in color.
- Stool appears milky-white in color like rice water.
- “Fishy” odor of the stool.
- Profuse water loss in the stool, as close as 1 liter of water per hour.
- One of the first symptoms seen in cholera.
- May persist throughout the course of the disease.
- Can be plain water vomitus after gastrointestinal contents are expelled.
- Occurs as bouts of vomiting and retching.
Dehydration is a complication of fluid and electrolyte loss in cholera. It can develop within a few hours after the first cholera symptoms become evident.
- Sunken eyes
- Dry skin, mouth and eyes
- Little or no urine output
- Lethargy and eventually drowsiness
- Rapid heart rate
- Low blood pressure
Is cholera contagious?
Cholera is not contagious in that it cannot be easily spread from one person to another through direct contact. A person has to consume a large amount of the cholera bacteria to become ill since these bacteria need to survive the passage through the highly acidic stomach juices. This may be as much as 10 million bacteria in order to develop the disease.
Lower estimates for when a person consumes contaminated water are between 1,000 to 1 million bacteria to become infected. With food, it may be less varying between 100 to 10,000 bacteria. A person is at greater risk of contracting cholera from consuming even small amounts of bacteria if the stomach acid is abnormally low in quantity and high in pH as is seen with using antacids or acid-suppressing drugs like proton pump inhibitors (PPIs).
How do you know if you have cholera?
Tests to confirm a diagnosis of cholera are not usually necessary if the patient lives or has visited in an endemic area. It should be assumed to be cholera and treatments started immediately based on the symptoms and clinical presentation alone. A stool sample or rectal swab should be sent to a laboratory in order to confirm a diagnosis of cholera. The stool is examined under a microscope to identify the actual cholera bacteria and a culture will grow the bacteria in a laboratory for more conclusive identification. There are different immobilization tests to identify the exact type and subtype of the cholera bacteria.
What is the treatment for cholera?
Cholera treatment involves the use of antibiotics and fluid replacement. Zinc tablets may also be prescribed as it has been show to reduce the duration of diarrhea in children with cholera.
Not every person with cholera will need to be treated with antibiotics. The condition can be effectively managed with supportive measures such as bed rest, oral rehydration therapy and a balanced diet once vomiting ceases if the disease is mild. A person with a healthy immune system can recover even without antibiotics. However, antibiotics are required in severe cases and are often used to avoid the possible complications that may arise even if the patient is coping well with just supportive measures. The antibiotics that may be used in the treatment of cholera includes :
- Doxycycline – antibiotic of choice.
- Trimethoprim and sulfamethoxazole
Where available, a person may be placed in a cholera cot so that the amount of fluid loss can be calculated from the collected stool. This allows the doctor to alter the fluid replacement accordingly to ensure that consumed fluid at least matches, if not exceeds, the fluid loss. Fluid replacement can be done orally by drinking oral rehydration solutions (ORS) but in severe cases it needs to be done intravenously (IV drips). A person should start eating balances meals of bland foods the moment vomiting subsides, even if the diarrhea is still ongoing.
What are the ways to prevent cholera?
- Take the cholera vaccine if you are traveling to endemic areas. Even if you feel that you may not be exposed to contaminated food or water sources, it is best to be cautious.
- Never drink any water other than bottled water when visiting an endemic area. Ensure that you buy the water only from reputable outlets and that the seal is intact.
- If in an endemic area where you have to drink water other than that from a bottle, boil the water for at least 1 minute. Filtered water which is treated with household bleach, chlorine tablets or iodine may be safe to drink but should be a last resort.
- Always wash your hands thoroughly with soap and water and then use an antiseptic handwash before eating. Although cholera is not usually transmitted from person-to-person, it is nevertheless important to practice good hygiene to minimize the risk.
- Ensure that all food is thoroughly cooked when visiting an endemic area. Even when in the United States and opting to eat foods that may be a possible risk, ensure that it has come from a reputable source. Foods like sushi and steak tartare are best avoided when on holiday.
- Do not drink milk or eat dairy products that are not cooked thoroughly when in an endemic area.
- When camping, dispose of feces properly to prevent contaminating water sources. Avoid extensive bathing in rivers or lakes which may be contaminated while holiday in endemic regions.
- Death can be prevented by seeking medical treatment the moment symptoms arise and replacing lost fluid and electrolytes with oral rehydration solutions.