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EPIDEMIOLOGY
AND
CONTROL
OF
CHOLERA
BY
DR. AWATIF ALAM
IDENTIFICATION:
- An acute bacterial disease (enteric),
- sudden onset of profuse watery stools,
- occasional vomiting,
- rapid dehydration, acidosis ,
- circulatory collapse.
Prognosis:
* Asymptomatic infection occur much
more frequently than clinical illness,
* In severe cases (untreated) , death
can happen (within few hours ) ,
* C.F.R ≈ 50%, but with proper Rx,
C.F.R. < 1%.
DIAGNOSIS:
- Confirmed by culturing Cholera vibrio
of serotype 01 from feceas ,
or
- significant rise in titer of antitoxic
antibodies,
or
- presence of agglutinating or
virbiocidal antibodies.
Infectious Agent:
Group A – Vibrio cholerae Serogroup 01
(which includes)
- El-Tor
- classical or true :
INABA, Hikojima, or OGAWA
True cholera vibrio is demonstrated by:- presence of specific O antigen and
- no hemolysis of goat or sheep RBCs if added to
suspension of these cells.
Group B – non cholera Vibrios.
(Non pathogenic to man)
- Most vibrio strains elaborate enterotoxin
resulting in similar clinical picture
- In any single epidemic one particular
type tends to be dominant
(presently El Tor biotype is predominant
except in Bangladesh, where the classical
biotype has reappeared).

In 1992, a new serogroup – a genetic
derevative of the EL TOR biotype –
emerged in Bangladesh and caused
an extensive epidemic.
It has now spread over large parts of Asia
and is termed Vibrio Cholerae o139
“ BENGAL”.
Occurrence:-
During 19th century pandemic cholera
repeatedly spread from India to most of the
world.
- During Ist half of 20th century, the disease
was confined largely to Asia
(except for severe epidemic in Egypt in 1947).
- Since 1961, cholera spread from Indonesia
to Western Europe , and AFRICA.
OCCURRENCE:- During 1977 and 1978 outbreaks
were reported from Japan*,
- In 1983; 13 African countries
reported the disease,
- The Western hemisphere was free
from cholera between 1911 – 1973
(except for 2 lab. acquired cases)
OCCURRENCE:

In 1991 cholera appeared in South America,
( it had been absent for > century ).

Within a year it spread to 11 countries, and through the
continent.
In 1992 large outbreaks began in India & Bangladesh.
“Such outbreaks was caused by a previously
unrecognized serogroup” ( O139\Bengal ).


It is a more virulent variant of EL TOR biotype.
Cholera in Southern Sudan
28 Jan. – 3 March 2006
Vibrio cholera Inaba has
been lab. confirmed.
 5 634 cases and 127 deaths
 C.F.R 2.25 %
 For more details check:
www.who.int

SIZE OF THE PROBLEM GLOBALLY:

140 000 – 290 000 cases were reported
between 1997- 1998.

In 1999, global incidence was about
254 000 , and Africa alone accounted for
about 81% of the global total number of
cases.

In 2000, multiple outbreaks were reported
in populations in various islands of
Oceania .

Reservoir:Man :
- A patient during incubation period
(faeces)
- A patient during illness
(faeces & vomitus)
- A patient during convalescence
(faeces)
- Contact through faeces
Mode of Transmission:A. Primary ingestion of water (contaminated
with faeces or vomitus of patients, or
to lesser extent to faeces of carriers).
OR
B. Ingestion of food contaminated by dirty
water, faeces, soiled hands or flies.
C. Use of soiled articles (e.g. utensils,
clothes and bedlinen) “to lesser extent.”
Poor sanitation transmits many diseases. Each year
1.3 million children die from diarrhoeal diseases
alone.
Ensuring safe methods of excreta disposal, access to
latrines at home and in schools, and encouraging
hand washing.
INCUBATION PERIOD:
Few hours – 5 days.
“ The international I.P. is 5- days “.
 Period of Communicability:
- For the duration of stool ve+ stage
(usually few days after recovery)
- Carrier state may persist for few months

*NOTE:
Effective antibiotic eg. (tetracycline) reduce
the period of communicability.
Suscept. And Resistance:
Susceptibility is general and variable

Gastric achlorhydria increases the risk

People with low S.E.S groups are at
higher risk.
Unsanitary environment:
WHO cholera 6th report stated
factors favouring endemicity in India
(lower Bengal area):




High density population,
Increased humidity,
Abundance of uncontrolled H20 supply,
High salinity and organic water contents.
**-An attack gives temporary immunity
(against a homologus serotype through a rise in
agglutinating, vibriocidal and antitoxin
antibodies which all lead to resistance).
METHODS OF CONTROL

A-Preventive measures:1- Sanitary disposal of human faeces
(maintenance of fly proof latrines).
2- Protect, purify and chlorinate public
water supplies.
(avoid cross connectns. with sewer syst.).
3- Control flies by spraying with insectici.
4- Cleanliness in preparation of food,
5- Pasteurize or boil milk ,
6- Sanitary supervision of commercial
milk production, storage and
delivery.
Control of patients, contact and
environment:
Reporting to local health authority,

Cleanliness in preparation of food,

Pasteurize or boil of milk and sanitary
supervision of commercial milk productn.
storage and delivery.


Isolation or hospitalization with enteric
precautions esp. for severely ill pts.
eg. (effective hand washing + fly control
measures).
Disinfection of articles soiled with faeces
or vomits of patients (by heat, carbolic
acid or other effective disinfectant).

Contacts:- Surviellance for 5-days.
- Chemoprophylaxis with tetracycline.
- No immunization necessary.
- Investigate contacts with source of
infection.
- Specific Rx:* Prompt fluid replacement using
adequate volumes of electrolytes
solutions, to correct dehydration.
Epidemic Measures:1- Essential measures :

- Hygienic disposal of human faeces.
- Adopting emergency measures to
assure a safe water supply (boiling and
chlorination).
- Good food hygiene.
Effective Food Hygiene Measures:
a- Cooking food thoroughly & eating it while
still hot;
b- Preventing cooked food from being
contaminated by contact with raw food
(water & ice), or with contaminated surfaces
or flies.
c- Avoiding raw fruits or vegetables unless they
are first peeled.
d- Hand washing after defecation, esp. before
contact with food or drinking water.
2- Two available types of vaccines which
provide high level of protection for
several months against
vibrio cholerae serotype o1.
( Of use for travellers to endemic countries,
but not yet used for public health purposes ).
3- Notification ( of WHO & adjacent
countries) is required if any case is first
diagnosed in a country.
4- Health education in personal hygiene.
5- Search for source of infection.
6- Specific measures during pilgrimage
season.
Viability of Cholera Vibrio
outside the body:- In tap water (contam. with feces)
days
- In stool: (in summer)
=
- In stool: (in winter)
=
- In corpes
=
- In clothings
=
- In dates (peelings)
=
- In fish
=
- In milk (raw)
=
- In milk (boiled)
=
=
5
2 days
8 days
4 wks
2-6 days
3 days
2-10 days
3 days
10 days