1. Cholera

2. 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

3. 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

4. Cholera is not transmissible person-to-person, but can easily be spread through contaminated food and water

5. People Most at Risk People with low gastric acid levels Blood types
Children: 10x more susceptible than adults
Elderly
Blood types
O>> B > A > AB
Not sure why O more susceptible—allows bacteria to adhere to gut lining—guess
a)e1tor and 0139—cholera gravis—mostly O blood type
endemic regions
a)bangladesh—low attack rates in adults
b) Antibodies– resistance--- intestinal IgA prevent attachment to mucosal surface, neutralize cholera toxin
b)Cmmon in children

6. 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

7. Symptoms Usually mild, or no symptoms at all Cramps
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 hours-several days
1)No fever—not invasive
2) clever-viable even after exit body—take host’s liquid

8. 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

9. Consequences of Severe Dehydration
Intravascular volume depletion
Severe metabolic acidosis
Hypokalemia
Cardiac and renal failure
Sunken eyes, decreased skin turgor
Almost no urine production
1)Fluid and electrolyte loss
2)Hypokalemia—low levels of K+ in blood
a)necessary for proper nerve, muscle, heart function
b)cramping, cardiac arrest
2)why sunken eyes?
3)Phosphates move out of cells

10. Mortality In untreated patients, mortality can reach 50-70%
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

11. Diagnosis
No clinical manifestations help distinguish cholera from other causes of severe diarrhea:
Enterotoxigenic e. coli
Viral gastroenteritis
Bacterial food poisoning
Look up those diseases

12. 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

13. 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.

15. Treatment Three options prove most effective: Oral Rehydration
Intravenous Rehydration
Antimicrobial Therapy

16. Treatment: Oral Rehydration Salts (ORS)
Reduces mortality from over 50% to less than 1%
1)Sodium transport coupled to glucose transport in small intestine
a)glucose accelerates absorption of glucose and water
2)Glucose Enables small intestine to absorb fluids and salts more efficiently
3)Boil water for at least 10 minutes
4)Bicarbonate—corrects acidosis
5)Sports drinks
a)excess sugar—worsen condition bc of osmolosis

17. O.R.S. The WHO recommends a solution containing: Per liter of water
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

18. 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.

19. Intravenous Rehydration – Additional Options
Saline can be used, however bicarbonate and potassium losses are not being replaced

20. 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

21. 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

22. 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.

23. 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

24. 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, genetically- engineered
Provides >90% protection against classical biovar and 65-80% against El-Tor biovar.

25. 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