epidemiology, prevention, and control

1. BY- SURAJ SAXENA
ROLL NO – 135
G.S.V.M MEDICAL COLLEGE
PARA H2
EPIDEMIOLOGY PREVENTION
AND CONTROL OF CHOLERA

2. 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

3. 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.

4. • Global warming creates a favourable environment for
bacteria.
• Transmission is closely related to inadequate
environmental management. Typical at risk areas
include-
 peri urban slums
places where as a consequence of disaster disruption of
water and sanitation takes place
Overcrowded camps
• Cholera is a key indicator of lack of social development

6. 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).

8. 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.

9. • 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.

10. 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.

11. •
• 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.

12. • 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

13. 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.

14. LABORATORY DIAGNOSIS
• Laboratory methods employed are-
COLLECTION OF STOOL- fresh sample should be
collected before treatment with antibiotics in-
1) Rubber catheter
2) Rectal swab
WATER- 1 to 3 litres of suspected water or 9 volumes of
sample added to 1 volume of 10% peptone

15. 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.

16. CONTROL OF CHOLERA
Following 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.

17. • 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.

18. • 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 CONTROL
EXCRETA DISPOSAL
FOOD SANITATION
DISINFECTION

19. • 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).

20.  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 eating
IV. Benefits of cooked food and safe water.

21. 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.

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