cholera epidemiology

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CHOLERA Roshni.R [3yr BAMS] Amrita school of Ayurveda9/2/20171

Cholera is an acute diarrheal diseaseCaused by Vibrio cholerae O1[classical/EL Tor biotype] & O139Ranges from symptomless to severe infections Majority of cases are asymptomatic and mild infection

CLINICAL SYMPTOMS INCLUDE SUDDEN ONSET OF PROFUSE VOMITINGEFFORTLESS WATERY DIARRHEA FOLLOWED BY VOMITINGRAPID DEHYDRATIONMUSCULAR CRAMPSSUPPRESSION OF URINE

Case fatality is rapid unless there is rapid replacement of fluid and electrolytes

9/2/20172CHOLERA

2

9/2/20173Outbreaks in World caused by 2 sero groups O1 and O139Majority by O1

Also Global warming creates favorable environment for bacteriaCholera transmission is closely linked to inadequate environmental management

TYPICAL AT RISK AREAS .. Peri-urban areas Disaster resulting in disruption of water and sanitation systemOver crowed camps

It is the key indicator for social development

9/2/20174

9/2/20175

INDIA Cholera EL Tor biotype got introduced in India in 1964 Prior to this classical strain was widely prevalent West Bengal used to be the home of cholera before, but it is now overtaken by other states Disease is seen persisting as smouldering infection in new areas There have been no large scale epidemic of classical cholera since 1964 because the classical type have been replaced by Vibrio cholerae O1 EL Tor biotype

9/2/20176EPIDEMOLOGICAL FEATURES OF CHOLERA Cholera is both an epidemic and endemic disease Disease depends on characteristics of agent and environment

Introduction of cholera cannot be prevented but it creates problem to those places where there is poor sanitation

9/2/20177Epidemics of cholera are characteristically abrupt, and have high potential to spread fast and cause deaths The epidemic reaches a peak and subsides gradually as FORCE OF INFECTION declines peak It is ultimately self limiting Temporary infection Large no, of sub-clinical cases

FORCE OF INFECTION

Through water Through contacts

Elimination of contaminated water does not cause an end to the outbreakinstead it produce a TAIL due to continuation of transmission through contact.

9/2/20178ENDEMICITY OF CHOLERA Endemicity is not stable like typhoid due to Seasonal fluctuationsEpidemic outbreaks Seasonal variations differs between regions and countries and changes with time EL Tor biotype have greater endemic tendency than classical biotype(ie: more of asymptomatic mild cases than classical)

INTER-EPIDEMIC PERIODS

Cholera occurs @ INTERVALS even in endemic areasHumans are the only KNOWN RESERVOIR then how Bacteria survives between outbreaks?????????????????????????????????? 3 Explanations Existence of long term carriersExistence of diminished but continuous transmission involving asymptomatic cases Persistence of organism in the form of free living / altered form in the environment

9/2/20179Epidemiological determinants

9/2/201710AGENT The organism which causes cholera is labeled as Vibro cholerae O1 & O139 Vibrios which are biochemically same as that of O1&O139 termed as non cholera vibrios Some of them are pathogenic to human ,may cause cholera like diarrhea but not termed as cholera . Hence it is important to the agent for special diagnosis

V.Cholerae having two biotypes CLASSICAL EL Tor

3 serological types OgawaInabaHikojima Ogawa serotype is mostly seen in India ..

9/2/201711RESISTANCE

Heating at 56*c. killed within 30 minutes

Boiling within few seconds

Ice survive for 4-6 weeks[may be even longer] EASILY DESTROYED BY Cresol Bleaching powder (6mg/L)

El Tor biotype is more resistant than classical

9/2/201712TOXIC PRODUCTION Multiply inside the lumen of small intestine Produce exotoxin This toxin produce diarrhoea ..effect on adenylate cyclase-cyclic AMP System of mucosal cells of small intestine exotoxin dont have any effect on other cells

RESERVOIR OF INFECTION HUMAN BEING is the only reservoir

CASE : In apparent to severe [75% are asymptomatic but shed bacteria after 7- 1 1 14 days of infection] Among 20% develop will have severe watery diarrhoea and dehydration Low immunity people Malnourished children

CARRIERS : Carriers may be temporarily ,rarely,chronic Carriers excrete fewer vibrios than clinical cases Detected by bacteriological examination of purged stool purgation done through 30-60ml of MgSO4 in 100ml water

9/2/201713INFECTIVE MATERIALSImmediate infective materials stool and vomits of cases and carriers INFECTIVE DOSECholera is dose relatedNormal dose is 10^11 organisms for producing clinical illness PERIOD OF COMMUNICABLITY CASE : 7-10 daysCONVALSCENT CARRIERS : 2-3 WEEKS CHRONIC CARRIERS : one month to 10 years

9/2/201714CARRIERS IN CHOLERACholera carrier can be defined as an apparently healthy person who is excreting V.Cholerae O1 in stools 4TYPES..

9/2/201715 PRE CLINICAL OR INCUBATORY

Incubation period is short (1-5 days) Incubatory carriers are potential patients

CONVALESCENT CARRIER The patient recovered from an attack of cholera may continue to excreteduring convalescence for 2-3 days This stage occurs to a patient who have not received any proper antibiotic treatment Chronic or long term CONTACT OR HEALTHY CARRIER

Subclinical infection acquired from case or carriers Duration is