Basic Information on Cholera

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Cholera is an acute intestinal infection caused by ingestion of food or water contaminated with the bacterium Vibrio cholera. It has a short incubation period, from less than one day to five days, and produces an enterotoxin that causes a copious, painless, watery diarrhea that can quickly lead to severe dehydration and death if treatment is not promptly given. Vomiting also occurs in most patients. Most persons infected with V. cholera do not become ill, although the bacterium is present in their faeces for 7-14 days. When illness does occur, about 80-90% of episodes are of mild or moderate severity and are difficult to distinguish clinically from other types of acute diarrhea. Less than 20% of ill persons develop typical cholera with signs of moderate or severe dehydration. Cholera remains a global threat and is one of the key indicators of social development. While the disease no longer poses a threat to countries with minimum standards of hygiene, it remains a challenge to countries where access to safe drinking water and adequate sanitation cannot be guaranteed. Almost every developing country faces cholera outbreaks or the threat of a cholera epidemic.

Infectious agent:

Bacterium – Vibrio cholera

Mode of transmission:

Faeco-oral route, contaminated water and food.

Incubation period:

Usually between 1 and 5 days

Case Definition:

Suspected case:
In an area where the disease is not known to be present:

Severe dehydration or death from acute watery diarrhea in a patient aged 5 years or more. For management of cases of acute watery diarrhea in an area where there is a cholera epidemic, cholera should be suspected in all patients with acute watery diarrhea.

Confirmed case:
Any suspected case is confirmed by laboratory through isolation of Vibrio cholera01 or 0139 from stool in any patient with diarrhea.

Management:

Cholera can be simply and successfully treated by immediate replacement of the fluid and salts, which are lost throughout diarrhea period. Patients can be treated with oral dehydration solution (ORS), a pre-packaged mixture of sugar and salts to be mixed with water and drunk in large amounts. Even in cholera, intravenous electrolyte solutions should be used only for the initial dehydration of severely dehydrated patients, including those who are in shock. Ringer’s lactate solution (Hartmann’s solution for injection) is the preferred fluid for intravenous dehydration. Its composition is suitable for treating patients of all ages and with all types of diarrhea. Plain glucose solutions are ineffective and should not be used. After vomiting stops, 500 ml fluid should then be given orally every hour. Total fluid requirements can be in excess of 50 liters over a period of 2-5 days. Food should be given after 3-4 hours of treatment, when dehydration is completed. Breast-feeding of infants and young children should be continued. The choice of antibiotic should take into account local patterns of resistance to antibiotics. In 2004, sensitivity patterns in Pakistan show that Vibrio cholera 01 is sensitive to Doxycycline, Ciprofloxacin, Norfloxacin, Tobramycin, and Tetracycline.

Prevention:

The only sure means of protection against severe gastroenteritis including cholera epidemics is ensuring adequate safe drinking water supply and sanitation. To make water safe for drinking, when the water source has been contaminated, either boil the water or chlorinate it. Bringing water to a vigorous, rolling boil and keep it boiling for one minute will kill Vibrio choleras 01 and most other organisms that cause diarrhea.

Making water safe by chlorination:
To make water safe by chlorination, first make a stock solution of 33 gm (3 tablespoons) of bleaching powder in one litre of water and store it in a brown bottle. Then put 3 drops (0.6 ml) of stock solution in one litre of water or 6 ml in 10 litres of water or 60 ml in 100 litres. Wait 30 minutes before drinking or using the water.

Sanitation:
Good sanitation to avoid the contamination of clean water sources can markedly reduce the risk of transmission of intestinal pathogens, including cholera vibrios. High priority should be given to observing the basic principles of sanitary human waste disposal at appropriate distance from water source and supply. When large groups of people congregate for fairs, funerals, religious festivals, etc., particular care must be taken to ensure the safe disposal of human waste and the provision of adequate facilities for hand washing.

Hygiene and Food Safety:

Wash hands thoroughly with soap after defecating, or after contact with faecal matter, and before preparing or eating food, or feeding children.·
Handle and prepare food in a way that reduces the risk of contamination (e.g. cooked food and eating utensils should be kept separate from uncooked foods and potentially contaminated utensils and crockery).
Avoid raw food, except those undamaged fruits and vegetables from which the peel can be removed in a hygienic manner.
Cook food until it is hot throughout.·Eat food while it is still hot, or reheat it thoroughly before eating.
Wash and thoroughly dry all cooking and serving utensils after use.

Vibrio-cholera

Image Courtesy of CDC

 

Frequently Asked Questions

What is cholera?

Cholera is a diarrheal disease caused by infection of the intestine with the bacterium Vibrio cholera. Children as well as adults can get infected. In most cases, infection causes only mild diarrhea or no symptoms at all. In 5-10% of cases, however, patients develop very severe watery diarrhea and vomiting from 6 hours to 5 days after exposure to the bacterium. In these cases, the loss of large amounts of fluids can rapidly lead to severe dehydration. In the absence of adequate treatment, death can occur within hours.

How is cholera spread?

A person can become infected by drinking water or eating food contaminated by the bacterium. Common sources of food borne infection include raw or poorly cooked seafood, raw fruit and vegetables, and other foods contaminated during preparation or storage. Bacteria present in the faeces of an infected person are the main source of contamination. The bacterium can also live in the environment in brackish rivers and coastal waters. The disease can thus spread rapidly in areas where sewage and drinking water supplies are inadequately treated.

Where do outbreaks occur?

Cholera remains an ever-present risk in many countries. New outbreaks can occur sporadically in any part of the world where water supplies, sanitation, food safety, and hygiene are inadequate. The greatest risk occurs in overpopulated communities and refugee settings characterized by poor sanitation and unsafe drinking water. For information of whether there is cholera in the area where you are traveling, contact your health care provider, local office of public health or travel health center.

Can cholera be prevented?

Yes. People living in high-risk areas can protect themselves by following a few simple rules of good hygiene and safe food preparation. These include scrupulous washing of hands, especially before food preparation and eating, thorough cooking of food and consumption while hot, boiling or treatment of drinking water, and use of sanitary facilities. By taking a few basic precautions, travelers can likewise protect themselves against cholera and most other food- and water-borne diseases. Above all, travelers should be very careful with food and water, including ice, and remember this simple rule: boil it, cook it, peel it, or forget it. Drink only water that has been boiled or disinfected with chlorine, iodine or other suitable products. Products for disinfecting water are generally available in pharmacies. Beverages such as hot tea or coffee, wine, beer, carbonated water or soft drinks, and bottled or packaged fruit juices are usually safe to drink. Avoid ice, unless you are sure that it is made from safe water. Eat food that has been thoroughly cooked and is still hot when served. Cooked food that has been held at room temperature for several hours and served without being reheated can be an important source of infection. Avoid raw seafood and other raw foods. The exceptions are fruits and vegetables that you have peeled or shelled yourself. Boil unpasteurized milk before drinking it. Ice cream from unreliable sources is frequently contaminated and can cause illness. If in doubt, avoid it. Be sure that meals bought from street vendors are thoroughly cooked in your presence and do not contain any uncooked foods.

What treatments are available?

The most important treatment is rehydration, which consists of prompt replacement of the water and salts lost through severe diarrhea and vomiting. Early rehydration can save the lives of nearly all cholera patients. Most can be rehydrated quickly and easily by drinking large quantities of a solution of oral rehydration salts. Patients who become severely dehydrated may need to receive fluid intravenously. Packets of oral dehydration salts are available from most city pharmacies and health care facilities. WHO recommends that travelers include oral rehydration salts in their medical kits. If you have diarrhea – especially severe diarrhea – and are in an area where there is cholera, seek treatment immediately from a physician or other trained health care provider. Begin drinking water and other non-sweetened fluids, such as soup, on the way to getting medical treatment.

What about antibiotics and other drugs?

In individual cases of severe cholera, an effective antibiotic can help shorten illness, though rehydration remains the mainstay of treatment. For whole communities, however, preventive mass treatment with an antibiotic does not limit the spread of cholera and is thus not recommended. Antidiarrhoeal medicines, such as loperamide, are not recommended and should never be given.

Do vaccines confer protection?

The injectable cholera vaccine, previously used, conveyed incomplete, unreliable protection of short duration and is no longer recommended. Two new oral cholera vaccines which provide good protection for up to 3 years are now available for use by travelers. However, as these vaccines do not provide 100% protection, basic hygienic precautions should always be followed. For more information, contact your local travel medicine center. No country requires proof of cholera vaccination as a condition for entry, and the international certificate of vaccination no longer provides a space for recording cholera vaccination.

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The writer enjoys medical education and has special interest in community medicine.