BY- SURAJ SAXENAROLL NO – 135

G.S.V.M MEDICAL COLLEGEPARA H 2

EPIDEMIOLOGY PREVENTION AND CONTROL OF CHOLERA

INTRODUCTION• Cholera is an acute diarrhoeal disease caused by

Vibrio Cholerae O1 (classical or El Tor) and O139.• Cases range from symptomless to severe

infection . Majority of infection are mild or asymptomatic .• Characterised by sudden onset of profuse,

effortless watery diarrhoea followed by vomiting, rapid dehydration, muscular cramps and suppression of urine.• Unless there is rapid replacement of fluid and

electrolytes, case fatality may be as high as 30 to 40 per cent

PROBLEM STATEMENT• In 2013 , a total of 129,060 cases were notified from 47 countries including 2,102 death . The true burden of disease is estimated as 1.4-4.3 million cases and 28,000 to 142,000 deaths annually.

• V. Cholerae O1causes majority of outbreaks,while O139(first identified in Bangladesh in 1992) is confined to South East Asia.

• Global warming creates a favourable environment for bacteria.• Transmission is closely related to inadequate

environmental management. Typical at risk areas include-

peri urban slumsplaces where as a consequence of disaster

disruption of water and sanitation takes placeOvercrowded camps

• Cholera is a key indicator of lack of social development

PROBLEM STATEMENT IN INDIA

• Since the introduction of cholera El Tor type in 1964, geographical distribution has considerably changed.

• West Bengal has lost its reputation as “home of cholera”. In several of recently invaded states, the disease is seen persisting as smouldering infection.

• El Tor biotype has replaced the classical V. O1 in all parts of the country. Most of the El Tor isolated today belongs to Ogawa serotype. There have been no large scale outbreaks since 1964

• During 2013, about 1,127 cholera cases were reported in India with 5 deaths. Majority were in Gujarat(327) followed by Maharashtra(247) , Karnataka(105),Tamil Nadu(93) and West Bengal(120).

EPIDEMIOLOGICAL DETERMINANTS

• AGENT- causative organism is vibrio O1 and O139.

.• RESISTANCE- Killed within 30 minutes of heating

at 56 degree Celsius or within few seconds by boiling.

They can remain in ice for 4-6 weeks. Easily destroyed by cresol and bleaching powder.El Tor is more resistant than classical vibrios.

Agent factors -

• TOXIN PRODUCTION- Vibrios produce enterotoxin in the lumen of intestine. The toxin produces diarrhoea through its effect on adenylate cyclase-cyclic AMP system of mucosal cells in small intestine

• RESERVOIR OF INFECTION- human being is the only known reservoir.

• INFECTIVE DOSE- about 10 organisms required to produce clinical disease.

• INFECTIVE MATERIAL- Sources of infection are stool, vomitus and fomites of patient.

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CARRIERS IN CHOLERA• Carrier is an apparently healthy person who excretes V.

cholerae O1 in stools• Four types of cholera carriers are described- PRECLINICAL OR INCUBATORY CARRIERS- Incubation period

of cholera is 1-5 days. They are potential patients.CONVALESCENT CARRIER- Patient who has recovered from

attack of cholera and excretes vibrios for period of 2-3 weeks. They often become chronic or long term carriers.

CONTACT OR HEALTHY CARRIER- It is a result of subclinical infection. Duration of chronic carrier state is less than 10 days, gall bladder is not effected, stool culture is positive

CHRONIC CARRIER- antibody titre along with bacteriological examination is used to detect long term carriers. Gall bladder is also effected.

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• AGE AND SEX- affects all age and both sexes. Children more affected in endemic areas.

• GASTRIC ACIDITY- An effective barrier. Vibrio are killed in pH of 5.0 or lower.

• Population mobility- Increases risk of exposure and spread.

• ECONOMIC STATUS- Incidence is highest in lower socio-economic groups, attributed to poor hygiene.

• IMMUNITY- Vaccines give only partial immunity for 3-6 months.

Host factors -

• Environmental factors of importance include contaminated food and water.

• Flies may carry Vibrio but not vectors of proven importance.• Human habits favouring water and soil pollution, low

standard of personal hygiene, lack of education and poor quality of life

• From few hours up to 5 days, but commonly 1-2 days.

• FAECALLY CONTAMINATED WATER• CONTAMINATED FOOD AND DRINKS• DIRECT CONTACT

ENVIRONMENTAL FACTORS

INCUBATION PERIOD

MODE OF TRANSMISSION

CLINICAL FEATURES• More than 90% of El Tor cases are mild• Typical case of cholera has three stages-STAGE OF EVACUATION- Abrupt onset with profuse,

painless, watery diarrhoea followed by vomiting. Stools may be as many as 40 in number with “rice water” appearance.

STAGE OF COLLAPSE- Due to dehydration signs such as: sunken eyes,hollow cheeks, scaphoid abdomen, subnormal temperature, washerman’s hands,absent pulse, unrecordable blood pressure, abnormal respiration. Death may occur due to acidosis.

STAGE OF RECOVERY-B.P. and temperature becomes normal, urine secretion is re-established. If anuria persists patient may die due to renal failure.

LABORATORY DIAGNOSIS• Laboratory methods employed are-COLLECTION OF STOOL- fresh sample should be

collected before treatment with antibiotics in-1) Rubber catheter2) Rectal swab

WATER- 1 to 3 litres of suspected water or 9 volumes of sample added to 1 volume of 10% peptone

FOOD SAMPLES- 1-3 gram sample is sent to laboratory

TRANSPORTATION- Sterilized McCartney bottle, of 30 ml containing alkaline peptone water or VR medium or Cary Blair medium and peptone water is used.

DIRECT EXAMINATION- Dark field illumination can detect 80% cases within a few minutes and more cases after 5-6 hours of incubation

CULTURE METHODS- well shaken sample about 0.5- 1.0 ml is inoculated in Peptone Water Tellurite.Subcultured in Bile salt Agar ( pH 8.6) after 4-6 hrs incubation at 37 deg.

CONTROL OF CHOLERAFollowing account is based on “ GUIDANCE FOR

CHOLERA CONTROL” proposed by WHO.

• VERIFICATION OF DIAGNOSIS-. It is important to identify strains of V cholerae in stool of patient.

• NOTIFICATION- Cholera is a notifiable disease both locally or nationally. Under International Health Regulations, cholera is notifiable to WHO within 24 hours by national government. An area is declared free of cholera when twice the incubation period(10 days) has elapsed since death, recover, isolation of last case.

• EARLY CASE FINDING- helps to initiate prompt treatment and helps epidemiologist to find the means of spread.

• ESTABLISHMENT OF TREATMENT CENTRES- Mildly dehydrated patients(accounting 90%) – treated at

home with oral rehydration fluids. Severely dehydrated patients should be transferred to

nearest hospital. Rehydration therapy should be given on the way.

• REHYDRATION THERAPY- Mortality rates have reaches down to 1% by effective rehydration therapy. It may be oral or intravenous.

• ADJUNCTS TO THERAPY-Antibiotics to be given as soon as vomiting stops. Injectable antibiotics have no special advantages. Flouroquinolones, tetracycline, azithromycin, ampicillin and trimethoprim sulfamethoxazole are commonly used. Persistant diarrhoea after 48 hours of therapy, indicates antibiotic resistance.

• EPIDEMIOLOGICAL INVESTIGATION- Epidemiologist must maintain contact with all health and civic units to ensure detection of new foci. Stool for phage typing may be sent to- NATIONAL INSTITUTE OF CHOLERA AND ENTERIC DISEASES, 3 DR ISAQUE ROAD , KOLKATA where WHO International centre for vibrios is located.

• SANITATION METHODS- WATER CONTROLEXCRETA DISPOSAL FOOD SANITATIONDISINFECTION

• CHEMOPROPHYLAXIS- Tetracycline is the drug of choice. It should be given over a 3 day period in twice daily dose of 500 mg for adults, 125 mg for children aged 4-13 years , 50 mg for children aged 0-3 years.A singe dose oral dose of doxycycline(300 mg for adults and 6 mg/kg for children under 15 years) is found effective.

Mass chemoprophylaxis when attempted failed to stop the spread of cholera

• VACCINATION- Two types of oral vaccines are available-

Dukoral( WC Rbs) – Monovalent vaccine based on formalin and heat killed whole cells( WC) of V cholerae O1 and recombinant cholera toxin B subunit. It is provided as 3 ml single dose vials together with bicarbonate buffer( prevents gastric acid action).

SANCHOL AND mORCVAX- They are bivalent vaccines based on serogroups O1 and O139. They do not contain any buffer or bacterial toxin.

• HEALTH EDUCATION- Most effective prophylactic treatment. It should aim at

I. Effectiveness of oral rehydration therapy.II. Benefits of early reporting.III. Food hygiene practices and hand washing after

defecation and before eatingIV. Benefits of cooked food and safe water.

DIARRHOEAL DISEASE CONTROL PROGRAMME

• During the year 1980-1981, strategy of National Cholera Control Programme has undergone changes. It is now termed as Diarrhoeal Disease Control Programme.

• Oral Rehydration Therapy Programme was started in 1986-87 in a phased manner

• Main objective is to prevent deaths in children due to dehydration.

• Training programme include increased intake of home available fluid and breast feeding.

• ORS is promoted as first line of treatment and is supplied as a part of the sub centre kit.

REFERENCES

• Park’s textbook of Preventive & Social Medicine 23rd Edition• Internet