Vibrio Cholera
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Transcript Vibrio Cholera
Cholera
Cholera
A life-threatening secretory diarrhea
induced by enterotoxin secreted by
V. cholerae ( non-invasive)
Water-borne illness caused by
ingesting water/food contaminated
by copepods infected by V. cholerae
A major epidemic disease
V. cholerae
Transmitted by fecal-oral route
Endemic in areas of poor sanitation
(India and Bangladesh )
May persist in shellfish or plankton
7 pandemics since 1817 – first 6 from
Classical strains, 7th from El Tor
Cholera is not transmissible personto-person, but can easily be spread
through contaminated food and water
People Most at Risk
People with low gastric acid levels
Children: 10x more susceptible than
adults
Elderly
Blood types
O>> B > A > AB
Incubation Period
• Ranging from a few hours to 5 days
• Most cases presenting within 1-3 days
• As expected for organisms passing through the
gastric barrier, the incubation period is shortest
when:
• highest dose of ingested organsim
• High gastric pH
• Infectious dose ranges from 106_ 1011 colonizing units
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 hoursseveral days
Cholera Gravis
More severe symptoms
Rapid loss of body fluids
6 liters/hour
107 vibrios/mL
Rapidly lose more than 10%
of bodyweight
Dehydration and shock
Death can occur within 2-3
hours
Consequences of Severe
Dehydration
Intravascular volume
depletion
Severe metabolic
acidosis
Hypokalemia
Cardiac and renal failure
Sunken eyes, decreased
skin turgor
Almost no urine
production
Mortality
• In untreated patients, mortality can reach 5070%
• Risk much higher in children
• 10x greater than adults
• As well as pregnant women
• 50% risk of fetal death in 3rd trimester
• Patients can die within 2-3 hours of first sign
of illness also seen from 10 hours- several
days
Diagnosis
No clinical manifestations help
distinguish cholera from other causes
of severe diarrhea:
Enterotoxigenic e. coli
Viral gastroenteritis
Bacterial food poisoning
Laboratory Diagnosis
• Made through isolation of bacteria from stool
samples
• Specimens are collected
• Gram Stain show sheets of curved Gram negative
rods
• Untreated patients have 106 to 108 organisms / mL of
stool
• Important to start treatment before the cause of
infection is identified: death can occur within
hours
Labroratory Diagnosis Cont.
Vibrios often detected by dark field
microscopy of stool
Organisms are motile, appearing like
“shooting stars”
When plated on sucrose dishes, yellow
colonies appear confirming cholera
Additional methods of detection include
PCR and monoclonal antibody-based stool
tests.
Treatment
• Three options prove most effective:
• Oral Rehydration
• Intravenous Rehydration
• Antimicrobial Therapy
Treatment: Oral Rehydration
Salts (ORS)
Reduces mortality from
over 50% to less than
1%
O.R.S.
• The WHO recommends a solution
containing:
•
•
•
•
3.5 g NaCl
2.9 g trisodium citrate/ NaHCO3
1.5 g KCl
20 g glucose or 40 g sucrose
• Per liter of water
• Min. of 1.5 x the stool volume losses should be
administered
• Commercially sold over-the-counter
Intravenous Rehydration
•
•
Used in patients who lost more than
10% of body weight from diarrhea or
are unable to drink due to vomiting
Ringer’s Lactate is usually used in
hospitals.
Intravenous Rehydration –
Additional Options
•
Saline can be used, however bicarbonate and
potassium losses are not being replaced
Antimicrobial Therapy
Seen as an adjunct to appropriate rehydration
• Reduce the volume of diarrhea by a half and the
duration of excretion to about 1 day, therefore,
they lower the expense of treatment and play a
role in cholera control.
• Due to short duration of illness, antibiotics not
highly recommended
•
Dosage – Antibiotic Agents
Given orally when vomiting
stops.
• Tetracycline is the standard
treatment
• Administered in single dose
primarily to prevent spread
of secondary infection
•
WHO guidelines
Prevention
V. Cholerae is spread through contaminated
food and water, therefore, prevention
depends upon the interruption of fecal-oral
transmission
• Antibiotic prophylaxis, vaccines and
surveillance of new cases are the answer to
preventing the spread of disease.
•
Antibiotic prophylaxis
The WHO recommends prophylaxis if 1
household member in a family becomes ill.
• Mass administration of antibiotics to a whole
community is not effective nor recommended
•
Vaccines
•
Two types :
– Killed-whole-cell formulation:
Provides immunity to only 50% of adult
victims and to less than 25% of children
– Live-attenuated vaccine, geneticallyengineered
Provides >90% protection against classical
biovar and 65-80% against El-Tor biovar.
Traveling Precautions
Boil or treat water with chlorine or
iodine
No ice
Cook everything
Rule of thumb: “Boil it, cook it, peel
it, or forget it.”
Wash hands frequently