Cholera | Zoology Optional Notes for UPSC PDF Download

Introduction

• The cause of cholera is infection by the V. cholera bacteria. These bacteria were discovered in 1883.
• The German bacteriologist, Robert Koch (1843-1910), studied the disease during an epidemic in Egypt. He found a bacterium in the intestines of those who had died of cholera but could neither isolate the organism nor infect animals with it.
• Later that year, Koch went to India, where he succeeded in isolating the bacteria. He discovered that they thrived in damp, dirty linen and moist earth, and in the stools of patients with the disease.
• V. cholera bacteria live in shallow, salty water on microscopic crustaceans. They can also exist as colonies of biofilms that coat the surface of the water, plants, stones, shells, and similar items, and they can live among the eggs of midges, which serve as a reservoir for cholera bacteria.
• Toxic strains of cholera bacteria produce a poison that triggers violent diarrhea in humans.
• When the bacteria enter areas where humans live, they can quickly cause severe epidemics. Weather changes, population loss, and improved sanitation can all end an outbreak.

Symptoms

Only around 1 in 20 cholera infections are severe, and a high percentage of infected people show no symptoms.
If symptoms appear, they will do so between 12 hours and 5 days after exposure. They range from mild or asymptomatic to severe.

They typically include:

• large volumes of explosive watery diarrhea, sometimes called "rice water stools" because it can look like water that has been used to wash rice
• vomiting
• leg cramps

A person with cholera can quickly lose fluids, up to 20 liters a day, so severe dehydration and shock can occur.

Signs of dehydration include:

• loose skin
• sunken eyes
• dry mouth
• decreased secretion, for example, less sweating
• fast heartbeat
• low blood pressure
• dizziness or lightheadedness
• rapid weight loss

Shock can lead to collapse of the circulatory system. It is a life-threatening condition and a medical emergency.

Causes

• Cholera bacteria enter the body through the mouth, often in food or water that has been contaminated with human waste, due to poor sanitation and hygiene.
• They can also enter by eating seafood that is raw or not completely cooked, in particular shellfish native to estuary environments, such as oysters or crabs.
• Poorly cleaned vegetables irrigated by contaminated water sources are another common source of infection.
• In situations where sanitation is severely challenged, such as in refugee camps or communities with highly limited water resources, a single affected victim can contaminate all the water for an entire population.

Diagnosis

• A doctor may suspect cholera if a patient has severe watery diarrhea, vomiting, and rapid dehydration, especially if they have recently traveled to a place that has a recent history of cholera, or poor sanitation, or if they have recently consumed shellfish.
• A stool sample will be sent to a laboratory for testing, but if cholera is suspected, the patient must begin treatment even before the results come back.

Treatment

• It is normally dehydration that leads to death from cholera, so the most important treatment is to give oral hydration solution (ORS), also known as oral rehydration therapy (ORT).
• The treatment consists of large volumes of water mixed with a blend of sugar and salts.
• Prepackaged mixtures are commercially available, but widespread distribution in developing countries is limited by cost, so homemade ORS recipes are often used, with common household ingredients.
• Severe cases of cholera require intravenous fluid replacement. An adult weighing 70 kilograms will need at least 7 liters of intravenous fluids.
• Antibiotics can shorten the duration of the illness, but the WHO does not recommend the mass use of antibiotics for cholera, because of the growing risk of bacterial resistance.
• Anti-diarrheal medicines are not used because they prevent the bacteria from being flushed out of the body.
• With proper care and treatment, the fatality rate should be around 1 percent.

Prevention

Cholera is often spread through food and because of poor hygiene. Some simple measures can reduce the risk of contracting cholera.

When traveling in areas where the disease is endemic, it is important to:

• Eat only fruit you have peeled.
• Avoid salads, raw fish, and uncooked vegetables.
• Ensure that food is thoroughly cooked.
• Make sure water is bottled or boiled and safe to consume.
• Avoid street food, as this can carry cholera and other diseases.

Travelers should learn about cholera before visiting a country where it is prevalent.
Individuals should seek medical attention immediately if they experience symptoms such as leg cramps, vomiting, and diarrhea while in a community where the disease exists.

Cholera vaccine

• There are currently three cholera vaccines recommended by the World Health Organization (WHO). These are Dukoral, Shanchol, and Euvichol.
• All three require two doses to give full protection.
• Dukoral needs to be taken with clean water, and it provides roughly 65 percent protection for 2 years. Shanchol and Euvichol do not need to be taken with water, and they provide 65 percent protection for 5 years. All the vaccines offer higher protection nearer to the time they are given.

Risk factors

People most at risk of consuming food or water infected with the V. cholera include:

• people who work in healthcare and treat individuals with cholera
• relief workers who respond to cholera outbreaks
• people who are traveling in areas where cholera can still be transmitted that do not follow hygiene and food safety precautions

Wide-spreading epidemics of cholera often occur due to water supplies that are contaminated with human waste and street food vendors.

The following people are also at risk of a more severe reaction to V. cholera than others:

• people with achlorydia, a condition that removes hydrochloric acid from the stomach
• individuals with blood type O
• people who have chronic medical conditions
• those without access to ORT and other medical services

Effective hygiene measures can help reduce the risk presented by cholera.