4. Cholera is an acute diarrhoeal disease can kill
within hours if left untreated. Cholera is caused by
ingestion of food or water contaminated with the
bacterium “ Vibrio cholerae”.
5. Two serogroups of and
cause outbreaks.
causes the majority of outbreaks, while –– is
confined to South-East Asia.
can cause mild diarrhoea but do not
generate epidemics.
new variant strains have been detected in several parts of Asia
and Africa. Observations suggest that these strains cause more severe
cholera with higher case fatality rates.
Cholerae strains
6. The main reservoirs of V. cholerae are people
and aquatic sources such as brackish water
and estuaries, often associated with algal
blooms. Recent studies indicate that global
warming creates a favourable environment
forthe bacteria.
7. ingestion of food or water contaminated with the bacterium stomach
The small intestine (thick mucus to get to the intestinal walls,that lines the
small intestine )cholerae bacteria start up production of the hollow
cylindrical protein flagellin to make flagella , the curly whip-like
tails, cholerae start producing the toxic proteins that give the infected
person a watery diarrhea. This carries the multiplying new
generations of V. The cholera toxin (CTX or CT) is an oligomeric
complex made up of six protein subunits: a single copy of the A
subunit (part A), and five copies of the B subunit (part B), connected
by a disulfide bond.
8. Among people who develop
symptoms,
80% have mild or moderate
symptoms,
while around 20% develop
acute watery diarrhoea
with severe dehydration.
This can lead to death if
untreated.
9. clinical diagnosis may be made by taking a history and doing a briefexamination
A rapid dip-stick test is available to determine the presence of V. cholerae
Stool and swab samples collected in the acute stage of the disease
The special media have been employed for the cultivation for cholera vibrios. are classified as
follows:
Enrichment media
Alkaline peptone water at pH 8.6
Monsur's taurocholate tellurite peptone water at pH 9.2
Plating media
Alkaline bile salt agar (BSA): The colonies are very similar to those on nutrient agar.
Monsur's gelatin Tauro cholate trypticase tellurite agar (GTTA) medium: Cholera
produce translucent colonies with a greyish black center.
TCBS medium: This the mostly widely used medium; it contains thiosulphate, citrate,
bile salts and sucrose. Cholera vibrios produce flat 2–3 mm in diameter, yellow
nucleated colonies.
Direct microscopy of stool is not recommended, as it is unreliable.
Diagnosis can be confirmed, as well, as serotyping done by agglutination with specific
sera.
10. Treatment
Cholera is an easily treatable disease . Up to
80% of people can be treated successfully
through prompt administration of oral
rehydration salts ,There are an estimated 3–5
million cholera cases and 100 000–120 000
deaths due to cholera every year. Treatment
is usually started without or before
confirmation by laboratory analysis.
13. In most cases, cholera can be successfully treated with oral
rehydration therapy (ORT), which is highly effective, safe,
and simple to administer. Rice-based solutions are preferred
to glucose-based ones due to greater efficacy. In severe cases
with significant dehydration, intravenous rehydration may be
necessary. Ringer's lactate is the preferred solution
If commercially produced oral rehydration solutions are too
expensive or difficult to obtain, solutions can be made. One
such recipe calls for 1 liter of boiled water, 1 teaspoon of salt,
8 teaspoons of sugar, and added mashed banana for
potassium and to improve taste]
Fluids
16. Electrolytes
As there frequently is initially acidosis, the potassium level
may be normal, even though large losses have occurred.As
the dehydration is corrected, potassium levels may decrease
rapidly, and thus need to be replaced.
18. Antibiotic treatments for one to three days shorten the course of
the disease and reduce the severity of the symptoms.
People will recover without them, however, if sufficient hydration.
Doxycycline is typically used first line, although some strains of
V. cholerae have shown resistance.
Other antibiotics that have been proven effective include
1-cotrimoxazole, erythromycin,
2-tetracycline, chloramphenicol,
3- furazolidone.
4-Fluoroquinolones, such as norfloxacin.
In many areas of the world, antibiotic resistance is increasing ,New
generation antimicrobials have been discovered which are
effective against in in vitro studies.
19. Oral cholera vaccines
There are two types of safe and effective oral cholera
vaccines currently available on the market. Both
are whole-cell killed vaccines, one with a
recombinant B-sub unit, the other without. Both
have sustained protection of over 50% lasting for
two years in endemic settings.
One vaccine (Dukoral) is WHO prequalified and
licensed in over 60 countries. has been shown to
provide short-term protection of 85–90%against V.
cholerae O1 among all age groups at 4–6 months
following immunization
20. The other vaccine (Shanchol) is pending WHO
prequalification and provides longer-term
protection against V. cholerae O1 and O139 in
children under five years of age.
Both vaccines are administered in two doses
given between seven days and six weeks apart.
