Cholera Cholera. A life-threatening secretory diarrhea induced by enterotoxin secreted by V....

CholeraCholera

A life-threatening secretory A life-threatening secretory diarrhea induced by enterotoxin diarrhea induced by enterotoxin secreted by V. cholerae ( non-secreted by V. cholerae ( non-invasive)invasive)

Water-borne illness caused by Water-borne illness caused by ingesting water/food contaminated ingesting water/food contaminated by copepods infected by V. choleraeby copepods infected by V. cholerae

A major epidemic diseaseA major epidemic disease

CholeraCholera

Transmitted by fecal-oral routeTransmitted by fecal-oral route

Endemic in areas of poor Endemic in areas of poor sanitation (India and Bangladesh )sanitation (India and Bangladesh )

May persist in shellfish or May persist in shellfish or planktonplankton

7 pandemics since 1817 – first 6 7 pandemics since 1817 – first 6 from Classical strains, 7from Classical strains, 7thth from El from El TorTor

V. choleraeV. cholerae

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

People with low gastric acid levelsPeople with low gastric acid levels Children: 10x more susceptible than Children: 10x more susceptible than adultsadults

ElderlyElderly

Blood typesBlood types O>> B > A > AB O>> B > A > AB

People Most at RiskPeople Most at Risk

Incubation PeriodIncubation Period

• Ranging from a few hours to 5 daysRanging from a few hours to 5 days• Most cases presenting within 1-3 daysMost cases presenting within 1-3 days

• As expected for organisms passing As expected for organisms passing through the gastric barrier, the incubation through the gastric barrier, the incubation period is shortest when: period is shortest when: • highest dose of ingested organsimhighest dose of ingested organsim• High gastric pHHigh gastric pH

• Infectious dose ranges from 10Infectious dose ranges from 106_6_ 10 101111 colonizing colonizing unitsunits

SymptomsSymptoms Occur 2-3 days after consumption Occur 2-3 days after consumption of contaminated food/waterof contaminated food/water Usually mild, or no symptoms at allUsually mild, or no symptoms at all

75% asymptomatic75% asymptomatic 20% mild disease20% mild disease 2-5% severe2-5% severe

VomitingVomiting CrampsCramps Watery diarrhea (1L/hour)Watery diarrhea (1L/hour) Without treatment, death in 18 Without treatment, death in 18 hours-several dayshours-several days

Cholera GravisCholera Gravis

More severe symptomsMore severe symptoms Rapid loss of body fluidsRapid loss of body fluids

6 liters/hour6 liters/hour101077 vibrios/mL vibrios/mL

Rapidly lose more than Rapidly lose more than 10% of bodyweight10% of bodyweightDehydration and shockDehydration and shockDeath can occur within Death can occur within 2-3 hours2-3 hours

Consequences of Severe Consequences of Severe DehydrationDehydration

Intravascular volume Intravascular volume depletiondepletion

Severe metabolic Severe metabolic acidosisacidosis

HypokalemiaHypokalemia

Cardiac and renal failureCardiac and renal failure

Sunken eyes, decreased Sunken eyes, decreased skin turgorskin turgor

Almost no urine Almost no urine productionproduction

MortalityMortality

• In untreated patients, mortality can In untreated patients, mortality can reach 50-70%reach 50-70%

• Risk much higher in children Risk much higher in children • 10x greater than adults 10x greater than adults

• As well as pregnant women As well as pregnant women • 50% risk of fetal death in 350% risk of fetal death in 3rdrd trimester trimester

• Patients can die within 2-3 hours of first Patients can die within 2-3 hours of first sign of illness also seen from 10 hours- sign of illness also seen from 10 hours- several daysseveral days

DiagnosisDiagnosis

No clinical manifestations help No clinical manifestations help distinguish cholera from other distinguish cholera from other causes of severe diarrhea: causes of severe diarrhea:

Enterotoxigenic e. coliEnterotoxigenic e. coli

Viral gastroenteritisViral gastroenteritis

Bacterial food poisoningBacterial food poisoning

Laboratory DiagnosisLaboratory Diagnosis

• Made through isolation of bacteria from Made through isolation of bacteria from stool samplesstool samples

• Specimens are collectedSpecimens are collected• Gram Stain show sheets of curved Gram Gram Stain show sheets of curved Gram

negative rodsnegative rods• Untreated patients have 10Untreated patients have 1066 to 10 to 1088 organisms / organisms /

mL of stoolmL of stool

• Important toImportant to start treatment before thestart treatment before the cause of infection is identified: death can cause of infection is identified: death can occur within hoursoccur within hours

Labroratory Diagnosis Cont.Labroratory Diagnosis Cont.

Vibrios often detected by dark field Vibrios often detected by dark field microscopy of stoolmicroscopy of stool

Organisms are motile, appearing like Organisms are motile, appearing like “shooting stars”“shooting stars”

When plated on sucrose dishes, yellow When plated on sucrose dishes, yellow colonies appear confirming cholera colonies appear confirming cholera

Additional methods of detection Additional methods of detection include PCR and monoclonal antibody-include PCR and monoclonal antibody-based stool tests.based stool tests.

TreatmentTreatment

• Three options prove most effective:Three options prove most effective:• Oral RehydrationOral Rehydration• Intravenous RehydrationIntravenous Rehydration• Antimicrobial TherapyAntimicrobial Therapy

Treatment: Oral Rehydration Treatment: Oral Rehydration Salts (ORS)Salts (ORS)

Reduces mortality Reduces mortality from over 50% to less from over 50% to less than 1%than 1%

O.R.S.O.R.S.

• The WHO recommends a solution The WHO recommends a solution containing:containing:• 3.5 g NaCl3.5 g NaCl• 2.9 g trisodium citrate/ NaHCO32.9 g trisodium citrate/ NaHCO3• 1.5 g KCl1.5 g KCl• 20 g glucose or 40 g sucrose20 g glucose or 40 g sucrose

• Per liter of waterPer liter of water• Min. of 1.5 x the stool volume losses should Min. of 1.5 x the stool volume losses should

be administered be administered • Commercially sold over-the-counter Commercially sold over-the-counter

Intravenous RehydrationIntravenous Rehydration

• Used in patients who lost more Used in patients who lost more than 10% of body weight from than 10% of body weight from diarrhea or are unable to drink due diarrhea or are unable to drink due to vomitingto vomiting

• Ringer’s Lactate is usually used in Ringer’s Lactate is usually used in hospitals.hospitals.

Intravenous Rehydration – Intravenous Rehydration – Additional OptionsAdditional Options

• Saline can be used, however Saline can be used, however bicarbonate and potassium losses are bicarbonate and potassium losses are not being replacednot being replaced

Antimicrobial TherapyAntimicrobial Therapy

• Seen as an adjunct to appropriate Seen as an adjunct to appropriate rehydrationrehydration

• Reduce the volume of diarrhea by a half Reduce the volume of diarrhea by a half and the duration of excretion to about 1 and the duration of excretion to about 1 day, therefore, they lower the expense of day, therefore, they lower the expense of treatment and play a role in cholera treatment and play a role in cholera control.control.

• Due to short duration of illness, antibiotics Due to short duration of illness, antibiotics not highly recommendednot highly recommended

Dosage – Antibiotic AgentsDosage – Antibiotic Agents

• Given orally when Given orally when vomiting stops.vomiting stops.

• Tetracycline is the Tetracycline is the standard treatmentstandard treatment

• Administered in single Administered in single dose dose

primarily to prevent primarily to prevent spread spread

of secondary infectionof secondary infectionWHO guidelines

PreventionPrevention

• V. Cholerae is spread through V. Cholerae is spread through contaminated food and water, contaminated food and water, therefore, prevention depends upon the therefore, prevention depends upon the interruption of fecal-oral transmissioninterruption of fecal-oral transmission

• Antibiotic prophylaxis, vaccines and Antibiotic prophylaxis, vaccines and surveillance of new cases are the surveillance of new cases are the answer to preventing the spread of answer to preventing the spread of disease.disease.

Antibiotic prophylaxisAntibiotic prophylaxis

• The WHO recommends prophylaxis if 1 The WHO recommends prophylaxis if 1 household member in a family becomes ill.household member in a family becomes ill.

• Mass administration of antibiotics to a Mass administration of antibiotics to a whole community is not effective nor whole community is not effective nor recommendedrecommended

VaccinesVaccines

• Two types :Two types :– Killed-whole-cell formulationKilled-whole-cell formulation: :

Provides immunity to only 50% of adult Provides immunity to only 50% of adult victims and to less than 25% of children victims and to less than 25% of children

– Live-attenuatedLive-attenuated vaccine, genetically- vaccine, genetically- engineeredengineered

Provides >90% protection against Provides >90% protection against classical biovar and 65-80% against El-classical biovar and 65-80% against El-Tor biovar.Tor biovar.

Boil or treat water with chlorine Boil or treat water with chlorine or iodineor iodine

No iceNo ice

Cook everythingCook everything

Rule of thumb: “Boil it, cook it, Rule of thumb: “Boil it, cook it, peel it, or forget it.”peel it, or forget it.”

Wash hands frequentlyWash hands frequently

Traveling PrecautionsTraveling Precautions