What is Cholera?

 A life-threatening secretory diarrhea induced by enterotoxin secreted by V. cholerae  Water-borne illness caused by ingesting water/food contaminated by copepods infected by V. cholerae  An enterotoxic enteropathy (a non-invasive diarrheal disease)  A major epidemic disease Cholera

Recent Cholera Pandemics  1-6th pandemic:  V. cholerae O1 biotype classical  , Asia, Africa, Europe, America and Australia  7 th pandemic:  V. cholerae O1 biotype El Tor  Began in Asia in 1961  Spread to other continents in 1970s and 1980s  Spread to Peru in 1991 and then to most of South & Central America and to U.S. & Canada  By 1995 in the Americas, >10 6 cases; 10 4 dead  1993: Cholera in Bengal caused by O139

 Grows in salt and fresh water  Endemic in areas of poor sanitation (India and Bangladesh ), transmitted by fecal-oral rout  Has over 150 identified serotypes based on O-antigen  Only O1 and O139 are toxigenic and cause Cholera disease V. cholerae

Classification: O1 Antigen 小川型 稻叶型 彦岛型

4. When does cholera become epidemic? After heavy period of rainfall When water temperatures rise When normal diarrhoeal incidence increases Endemic cholera with good sanitation needs permanent source of vibrio, but with poor sanitation higher secondary transmission can maintain endemic status

People with low gastric acid levels ( CFU ) Children: 10 × more susceptible than adults Elderly Blood types O>> B > A > AB People Most at Risk

Transmission Contaminated food or water Inadequate sewage treatment Lack of water treatment Improperly cooked shellfish Transmission by casual contact unlikely

Period of Communicability During acute stage A few days after recovery By end of week, 70% of patients non-infectious By end of third week, 98% non-infectious

Ranges from a few hours to 5 days Average is 1-3 days Shorter incubation period: High gastric pH (from use of antacids) Consumption of high dosage of cholera Incubation

Symptoms Occur 2-3 days after consumption of contaminated food/water Usually mild, or no symptoms at all 75% asymptomatic 20% mild disease 2-5% severe Vomiting Cramps Watery diarrhea (1L/hour) Without treatment, death in 18 hours- several days

Mortality Rate Causes 120,000 deaths/year worldwide With prompt rehydration: <1% Without treatment: 50%-60%

Diagnosis Cholera should be suspected when patients present with watery diarrhea, severe dehydration Based on clinical presentation and confirmed by isolation of vibrio cholera from stool

Treatment *Even before identifying cause of disease, rehydration therapy must begin Immediately because death can occur within hours* Oral rehydration Intravenous rehydration Antimicrobial therapy

Treatment  Up to 80% of cases can be treated through oral rehydration salts  Severe cases require intravenous fluids (Ringer lactate)  Antibiotics can diminish duration of diarrhoea, reduce volume of rehydation fluids needed, and shorten duration of V.cholerae excretion  Up to 80% of cases can be treated through oral rehydration salts  Severe cases require intravenous fluids (Ringer lactate)  Antibiotics can diminish duration of diarrhoea, reduce volume of rehydation fluids needed, and shorten duration of V.cholerae excretion

DRUG THERAPY The goals of drug therapy are to eradicate infection, reduce morbidity and prevent complications. The drugs used for adults include tetracycline, doxycycline, cotrimoxazole & ciprofloxacin. For children erythromycin, cotrimoxazole and furazolidone are the drugs of choice.

7. How is it prevented? Blocking routes of transmission – water disinfection (source and /or household), hand washing, sanitation, good food hygiene and well-cooked Cholera vibrio doesn’t like acid environment (block with acidic water eg. With citrus juice, healthy stomach acid levels, acid food) Oral vaccine

Antibiotic prophylaxis to house-hold contacts.