Cholera: An Infectious Waterborne Disease

Abstract

Having completed your GP training you decide to deploy and you take a post working in a large camp for people displaced following an earthquake. Given the total destruction of health and sanitation facilities you are unsurprised that disease is rife in the camp. One day a young girl is brought to you by her mother. She is dehydrated having produced a large quantity of watery diarrhoea in the previous 6 h. You send a sample off for investigation. Before the result returns your health centre becomes inundated with similar cases. The sample returns positive for Vibrio cholerae.

An epidemic ensues and you endeavour to manage the patient swell in a country unaccustomed to cholera and unprepared for an epidemic.

Reviewed by Daniele Lantagne

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Learning Objectives

• Discuss the infection risk associated with poor sanitation.

• Outline the common diseases transmitted through the fecal-oral route.

• Describe the clinical presentation of a cholera patient.

• Outline the pathophysiology and clinical course of cholera infection.

• Explain the treatment of severe dehydration.

• Identify the initial management of a cholera outbreak.

• Outline a policy for planning for a cholera epidemic.

Fig. 18.1

Collecting safe drinking water. In the aftermath of the Haitian earthquake, tankers brought drinking water into displacement camps for distribution (Reproduced with permission from SOS children’s villages worldwide)

Initial Scenario

With sweaty palms and a thousand butterflies dancing in your stomach you wait outside the interview room. Having completed your GP training, you decided to work abroad for a year and following reports of an earthquake you knew you had to apply. Hundreds of thousands of survivors are displaced and living in overcrowded camps. Waterborne diseases are rife due to damaged sanitation and drinking water supplies. You knock and enter the room.

The interviewers describe the situation on the ground. They tell you many responders who deploy are a resource burden who consume more than they contribute. “How will you be different?”

While acknowledging your inexperience, you describe how you would use your medical and technical skills and knowledge in a practical way. The interviewees seem ambivalent.

Later that day, you receive the call you hoped for. You will be working in an improvised health center in a damaged town near the capital. It is time to buy your ticket.

Prompt 1: Why Does Poor Sanitation Pose an Infection Risk?

• Poor sanitation is common in overcrowded camps following disasters and conflict where the swell of survivors overwhelms existing sanitation facilities. Efforts to maintain Sphere Standards for the provision of water and sanitation frequently fail [1, 2].

• Poor sanitation results in the improper disposal of feces and the subsequent contamination of water used for drinking, cooking, and cleaning.

• Through eating or drinking, fecal matter and the associated waterborne pathogens are consumed resulting in infection. The infected individual then spreads the infection through their own feces. This is the fecal-oral route of disease transmission.

Prompt 2: List and Summarize the Most Important Waterborne, Fecal-Oral Diseases

Typhoid

• An acute infectious enteric fever caused by the gram-negative, motile bacillus Salmonella typhi. The disease has an insidious onset with malaise, headache, lack of appetite, and nausea followed by fever. Fever increases slowly and gradually reaches a peak in the second week. The fever may continue for a third week, with the patient recovering in week 4. Severe disease may result in bowel perforation which is a common complication in sub-Saharan Africa.

Giardia

• Giardia is a protozoan parasite that colonizes the upper portions of the small intestine. The disease is characterized by the sudden onset of explosive, watery, foul-smelling diarrhea. Stools associated with Giardia infection are loose, bulky, and frothy with the absence of blood or mucus. Patients suffer from flatulence, bloating, anorexia, cramps, and foul belching.

Dysentery

• Dysentery is an enteric illness caused by pathogenic bacteria or parasitic protozoa which is characterized by bloody diarrhea. Bacterial dysentery is caused by a gram-negative, rod-shaped bacterium called Shigella, whereas parasitic dysentery is caused by the amoeba Entamoeba histolytica. Pathogens invade the epithelial cells of gut mucosa causing tissue damage resulting in inflammation and bleeding with fever and severe abdominal pain. The diarrhea is mixed with mucus and blood, and defecation is painful.

Cholera

• Cholera is an acute diarrheal disease caused by infection with the Vibrio cholerae bacterium. After entry into the gut, the bacteria attaches to the small intestine, multiplies rapidly, and in the process produces cholera toxin. The toxin results in profuse watery stool and rapid and severe dehydration of the body due to loss of large quantities of fluid and electrolytes with the stool.

Hepatitis

• Hepatitis A is an acute infectious disease of the liver caused by the hepatitis A virus. Early symptoms can be mistaken for influenza and include fatigue, fever, abdominal pain, nausea, jaundice, and clay-colored feces. Some sufferers, especially children, exhibit no symptoms at all.

Polio

• The poliovirus invades and then resides in the intestinal tract and the mucus of the nose and throat. Up to 95 % of people infected with poliovirus will have no symptoms, but approximately 1 % of those infected get paralytic poliomyelitis and 1–2 % will get aseptic meningitis [3].

Further Information 1

You are welcomed by representatives of the NGO and are brought to a tented treatment center on the edge of town. There are hundreds of people awaiting treatment –you will start immediately.

During the morning, a lady presents you with a child suffering with sudden onset diarrhea which began that morning. Her family lives in a camp for displaced people 10 miles away. Nobody else in the family has had diarrhea. The mother says the family uses a collection tank in the camp for drinking water. She does not let her daughter use the latrines because they are too dangerous.

Prompt 3: What Information Do You Want to Elicit in the History?

General Information

• How has the child been? A drowsy, lethargic, and/or irritable child may be dehydrated and will require prompt treatment.

Time Course of the Diarrhea

• Is the disease acute or chronic? Acute diarrhea is defined as a greater number of stools of decreased form than normal lasting for less than 14 days.

Specific Diarrhea Symptoms such as Stool Consistency, Frequency, Volume, and Blood

• What is the volume produced? Large volumes of watery diarrhea suggest small bowel or proximal colonic disease.

• What is the frequency? Small frequent stools with urgency are associated with left colon or rectal disease.

• Is it dysentery? The presence of blood is suggestive of infection by invasive organisms and inflammation.

• What is the color? Pale stools suggest biliary and/or hepatic disease.

Associated Symptoms such as Nausea and Vomiting, Pain, or Fever

• Diarrhea with severe nausea and vomiting may suggest toxigenic infection or the ingestion of external toxins.

• Diarrhea with severe abdominal pain and high fever may suggest infection with invasive bacteria or organisms that produce cytotoxins.

Drug History and Diet

• Many drugs (e.g., antibiotics), foods (e.g., milk products and shellfish), and nutritional supplements can cause acute diarrhea.

• Ask about food hygiene.

Family and Social History

• Are other family members affected? Infectious acute diarrhea is contracted through ingestion of contaminated food and water which are generally shared by the family.

• The place of residence gives an indication of available drinking water and demands on sanitary facilities (see Fig. 18.1).

Past Medical History

• Has the child had diarrhea before? The diarrhea may be due to an underlying condition such as inflammatory bowel disease or celiac disease [4].

Further Information 2

The child’s name is Eva, and she is 7 years old weighing 19 kg. She has been voiding large quantities of watery diarrhea since this morning (6 hours ago) and had several bouts of vomiting. There is no blood in the diarrhea.

On examination, she looks drowsy and lethargic. She is very dry with sunken eyes and reduced skin turgor. Her heart rate is high, and her blood pressure low. You cannot feel her radial pulse.

You look for a WHO leaflet regarding treatment of dehydration. You read:

Cholera should be suspected when:

• A patient older than 5 years develops severe dehydration from acute watery diarrhea (usually with vomiting) or

• Any patient above the age of 2 years has acute watery diarrhea in an area where there is an outbreak of cholera

You explain you must keep the child in hospital overnight as she may need urgent IV fluids to restore her fluid balance. You start her on oral rehydration solution (ORS). Strongly suspecting cholera, you take a stool sample and send it to the lab for analysis. You call the Ministry of Health and the regional PAHO (WHO) office to let them know. Before dusk, there is an influx of 50 patients, all complaining of watery, voluminous, acute diarrhea.

Prompt 4: How Is Information Managed in a Suspected Cholera Outbreak?

• Under the terms of the International Health Regulations (1969), it is mandatory for health authorities to notify the WHO of a cholera outbreak. Often, countries fail to do this because they fear it will damage tourism and interfere with exports [5]. Laboratory confirmation should be sought as soon as possible.

• If a cholera outbreak is confirmed, the health authorities must make weekly reports to the WHO. Reports must confirm the number of new cases and deaths since the last report, and the cumulative death totals for the year [5].

Prompt 5: What Is the Clinical Course of Cholera Infection?

• Most people infected with V. cholerae do not become ill, but everyone infected can spread the disease. The reason for individual resistance to the disease is not known though individuals may differ in the availability of intestinal receptors for binding the bacterium and its toxin. Previously infected individuals have a lower risk of illness following reinfection.

• Of those who become ill, fewer than 20 % develop signs of moderate or severe dehydration. The rest have symptoms indistinguishable from gastroenteritis.

• For those who become ill, symptoms begin following a 24–48-h incubation period.

• Fluid volume depletion can lead to hypovolemic shock and death without adequate replacement of fluids and electrolytes.

• The bacterium remains present in feces for 7–14 days.

• Strains of V. cholerae vary in virulence. Some strains can cause death within 4–6 h of the onset of symptoms.

• In a well-managed outbreak, <1 % case fatality rate (CFR, total number of registered deaths/total number of registered cases) is considered good treatment [6, 7].

Prompt 6: Outline the Pathophysiology of Cholera Infection

• 1. Following ingestion, the bacterium colonizes the mucosa of the small bowel (duodenum and upper jejunum).

• 2. The bacterium produces enzymes which allow its enterotoxin to bind with receptors on the surface of intestinal mucosa cells.

• 3. The toxin enters the cell, and once inside, it immediately increases the rate at which cAMP is produced.

• 4. cAMP stimulates mucosal cells to pump large amounts of Cl⁻ into the intestinal lumen.

• 5. Water, Na⁺, and other electrolytes follow the Cl⁻ due to the osmotic and electrical gradient.

• 6. The lost water and electrolytes in the mucosal cells are replaced from blood plasma.

• 7. The process continues with mucosal cells continually pumping water and electrolytes into the intestinal lumen.

• 8. The colon remains in a state of absorption but is overwhelmed by the large fluid volumes resulting in copious watery diarrhea isotonic with blood plasma.

• 9. Water and electrolyte loss from plasma causes dehydration and volume depletion [8].

Prompt 7: How Should a Severely Dehydrated Child with Cholera Be Treated?

The following guidelines for the treatment of cholera have been reproduced with permission from the WHO [9]:

• Step 1: Assess the level of dehydration using Table 18.1.

  Table 18.1 WHO guidelines for assessment of dehydration in a diarrheal patient

• Step 2: Rehydrate the patient, and monitor frequently. Then reassess hydration status.

• Step 3: Maintain hydration: replace continuing fluid losses until diarrhea stops.

• Step 4: Give an oral antibiotic (doxycycline) to patients with severe dehydration (co-trimoxazole in children).

• Step 5: Feed the patient.

The information in the table suggests Eva has severe dehydration. Patients with “severe” dehydration should be given IV fluid immediately to replace their fluid deficit. Ringer’s lactate is recommended (higher sodium concentration), but normal saline is acceptable. The WHO guidelines state patients aged 1 year and older should be given:

• 30 ml/kg as rapidly as possible (within 30 min) (for Eva, 30 × 19  =  570 ml)

• 70 ml/kg in the next 2.5 h (for Eva, 70 × 19  =  1,330 ml)

Eva is able to drink and so she should be given oral rehydration (ORS) solution (5 ml/kg/h  =  5 × 19  =  95 ml/h) and must be monitored frequently. She should be reassessed after 3 h using Table 18.1 and retreated as necessary. Antibiotics should be started once she is adequately hydrated (4–6 h).

Patients with “some” dehydration should be given ORS solution in an amount suitable for patient age and weight and must be monitored frequently. They should be reassessed after 4 h using Table 18.1 and retreated as necessary.

Patients with no obvious signs of dehydration can be treated at home. They should be given enough ORS packets for 2 days and instructed to return if they develop further symptoms of cholera or dysentery.

Box 18.1: Minimum Supplies Needed to Treat 100 Patients During a Cholera Outbreak [8]

Rehydration supplies:

• 650 packets oral rehydration salts (for 1 l each)

• 120 bags Ringer’s lactate solution, 1 l, with giving sets

• 10 scalp vein sets

• 3 nasogastric tubes, 5.3 mm OD, 3.5 mm ID (16 French), 50 cm long for adults

• 3 nasogastric tubes, 2.7 mm OD, 1.5 mm ID (8 French), 38 cm long for children

Antibiotics:

Adults

• 60 capsules doxycycline, 100 mg (3 capsules per severely dehydrated patient)

Children

• 300 tablets co-trimoxazole, each tablet trimethoprim 20 mg  +  sulfamethoxazole 100 mg (15 tablets per severely dehydrated patient)

Other treatment supplies:

• 2 large water dispensers with tap (marked at 5- and 10-l levels) for making ORS solution in bulk

• 20 bottles (1 l) for oral rehydration solution (e.g., empty IV bottles)

• 20 bottles (0.5 l) for oral rehydration solution

• 40 tumblers, 200 ml

• 20 teaspoons

• 5 kg cotton wool

• 3 reels adhesive tape

The supplies listed are sufficient for IV fluid followed by oral rehydration salts for 20 severely dehydrated patients and for oral rehydration salts alone for the other 80 patients.

If Ringer’s lactate solution is unavailable, normal saline may be substituted.

Further Information 3

In the next 48 hours, the treatment center receives 1,500 further patients ­complaining of acute diarrhea. The center is completely overwhelmed, lacking the staff, resources, and materials to cope. You work around the clock to deal with the patient load, but many patients die before you can see them. The stool sample comes back from the lab positive for Vibrio cholerae.

You contact the directors of the nearest hospital to find out what protocols are in place to deal with the outbreak. They explain that the region has not experienced a cholera epidemic for over 100 years. This epidemic was completely unexpected, and there are no plans in place for dealing with it.

Meanwhile, since her rehydration therapy, Eva has developed tachypnea and tachycardia and is coughing up frothy pink secretions. You sit her up and give oxygen, and she gradually improves. She makes a full recovery.

Prompt 8: What Are the Complications of Rapid Rehydration Therapy?

• Pulmonary edema is caused by giving too much IV fluid too quickly. Rapid fluid replacement overwhelms the heart’s ability to pump the fluid and leads to buildup in the pulmonary circuit causing respiratory distress and pink frothy sputum. Cerebral edema (brain swelling) may also result from the rapid fluid shifts in electrolyte imbalances during rehydration therapy.

• Metabolic acidosis is another complication of rapid administration of normal saline. This is a hyperchloremic acidosis which occurs when the kidneys are unable to generate enough HCO ⁻₃ to compensate for the increase in chloride.

• Acute kidney injury occurs when too little fluid is given and shock is not rapidly corrected or is allowed to recur. Renal failure is rare when severe dehydration is rapidly corrected and normal hydration is maintained according to guidelines.

• Generally, the more acute the fluid loss, the more acutely it can be replaced. When the guidelines for IV rehydration are followed, pulmonary edema should not occur. Oral rehydration solution (ORS) never causes pulmonary edema [9].

Prompt 9: What Are the Local Priorities in Managing a Cholera Epidemic?

Early detection, treatment, and health education are the best control measures in a cholera outbreak. In countries with inadequate rural health services and no experience in controlling cholera, there is a delay in initiating these processes. The WHO recommends the formation of local mobile teams of skilled health workers, epidemiologists, engineers, and educators to work in collaboration with existing or newly arrived NGOs [9].

Early Detection

• As soon as a cholera outbreak is suspected, local authorities should be notified so that plans can be initiated.

Treatment

• Engineers should supervise the construction of emergency treatment centers and rehydration posts and ensure the provision of appropriate environmental sanitary measures and disinfection. These centers provide rapid and efficient treatment for a large number of patients in areas inaccessible to existing health facilities. Cholera beds should be constructed. These beds have a hole with a bucket ­underneath to collect diarrhea during treatment. (See Fig. 18.2)

  Fig. 18.2

  

  Cholera beds (Photo taken by Taseum)

• It is not necessary to impose quarantine or strict isolation measures although it is best to restrict contact between patients and community to a minimum. There must be convenient hand-washing facilities for people working with cholera patients, and the safe disposal of excreta and vomit is essential.

Education

• Health workers should provide on-the-spot training in case management for local health staff. Educators should carry out health education activities and disseminate information to the public to prevent panic. Safe hand washing, drinking water safety/treatment, and food preparation practices must be taught.

Investigation of Outbreak

• Epidemiologists should establish the mode of disease transmission through investigation of outbreaks and assessment of local infrastructure. In reality, stool samples and environmental specimens rarely help with identifying the route of transmission as the data is too variable. Case-control studies are more effective in identifying cholera transmission routes.

• Recording the time and place of suspected and confirmed cases, preferably on a spot map, can help identify sources and routes of infection and spread.

• Adults are more frequently affected in cholera outbreaks due to their greater exposure to sources of contamination, such as food or drinks taken outside the home. A prevalence of cases in children suggests that the disease is endemic in the area [8].

Further Information 4

One month after the first case of cholera, over 1,000 people have died, and 100,000 have been affected by the disease. You feel aggrieved that resources and reinforcements took so long to reach the communities around the health center. The government has been much maligned for its poor preparatory measures, and there is strong feeling that many deaths could have been prevented. This has prompted the Ministry of Health to begin planning for future epidemics.

Prompt 10: How Should Nations Plan for Future Cholera Epidemics?

Once cholera is established, it can lay dormant for years before reemerging. Emergency measures are needed to minimize the risk of recurring outbreaks developing into epidemics. Improvements in both the water supply and sanitation are the best means of preventing cholera, but in resource-poor countries, this cannot be achieved. Affordable short- and medium-term preparations are the priority. The WHO has suggested a program for the Control of Diarrheal Diseases (CDD) involving education, resource, and surveillance measures [9].

• Training and Education

  Medical personnel must be familiar with the most effective techniques for managing patients with acute diarrhea, including cholera. Public health education programs must continually stress the principles of good personal hygiene and safe food preparation while stressing the importance of using safe water sources and the safe disposal of excreta.

• Resources

  Stocks of rehydration salts, IV fluids, and antibiotics must be maintained at appropriate points in the drug delivery system. Stocks should be kept in local health facilities in addition to district levels with an adequate emergency stock at a central distribution point (see Box 18.1).

• Surveillance

  Daily records should be maintained of diarrheal cases seen in health facilities and by health workers in the community. When changes in the pattern of diarrheal disease occur, the nearest referral facility should be notified. Epidemiological investigation, such as case-control studies, should be promptly arranged to determine the cause of the outbreak, and the manager of the national CDD ­program should be informed [6, 9].

Case Study: The Haiti Cholera Epidemic 2010

Nine months after the Haitian earthquake (2010), a cholera outbreak emerged in the Centre Department (region) of central Haiti. The epidemic was precipitated by an influx of earthquake survivors fleeing the capital Port-au-Prince into the Centre and Artibonite departments. Sanitation and drinking water provision were poor in these departments prior to the earthquake, and the influx increased the exposure of populations to fecal-oral disease transmission. Within 48 h of the cholera outbreak, 1,500 cases were recorded [1].

Epidemiological studies mapped the outbreak along the course of a large river in the Centre and Artibonite Departments. The outbreak was blamed on UN workers from Nepal whose compound backed onto the river. Although not scientifically proven, it was suspected that Nepali workers inadvertently introduced endemic Asian cholera into the river.

Given the availability of safe drinking water (transported by tanker trucks) in the displacement camps, the camps were somewhat protected from severe cholera outbreaks. The major outbreaks were found in existing communities in the Artibonite delta and mountainous areas and in the non-displacement camp slums in Port-au-Prince (Daniele Lantagne, 2012).

Between October 20th and November 9th, the NGO “Partners in Health” recorded 7,159 cases of cholera, of which 161 died in 7 hospitals in the Centre and Artibonite departments (a case fatality rate (CFR) of 2.2 %) [1].

Forty-eight hours after Hurricane Tomas hit (November 6th), Partners in Health reported seven clinical cases of cholera in a large displacement camp, and MSF reported seeing 200 patients with cholera in the nearby Cite Soleil slum where tanker truck water was unavailable. By November 9th, the Ministry of Health reported 11,125 hospitalized patients and 724 confirmed deaths [1].

Relief efforts were hampered by the speed with which the epidemic spread and by Haiti’s inexperience in dealing with cholera. Haiti had very little institutional knowledge about cholera, and it took time to train health workers (who had no prior experience of the disease) to put in place suitable containment and disease treatment measures. The CFR was 10 % in the first 48 h of the outbreak which reflects the delay in appropriate management. Hospitals were completely overwhelmed, and many patients died before treatment [1].

Between the 20th and 26th February 2011, 7,664 new cases and 52 new deaths were registered, and the overall case fatality rate was 1.9 %. Case fatality rates varied widely between regions (Port-au-Prince having 0.9 % and the Sud-Est Department having 8.5 %) which is most likely due to both the variation in logistical reality of accessing healthcare and the variation in the human capacity to deliver training and healthcare in different regions [10].