What is Cholera disease and its Diagnosis and controlling methods
Cholera is an acute diarrhoeal disease caused by V. Cholera 01 (Classical or E1 Tor).Cases ranges from symptomless to severe infections. Unless there is rapid replacement of and electrolytes, the case fatality may be as high as 30% to 40%.Cholera transmission Methods | Clinical diagnosis methods | How to control Cholera | Homeopathy Prevention
Global experience of the current pandemic have shown that cholera can get introduced into any country, but create problem only in areas where other acute enteric infections endemic, i.e. where sanitation is defective. Currently the seventh pandemic which began in 1961 in Indonesia is still continuing. This pandemic is due to El Tor vibrio. India got involved in the pandemic in 1964.
Choler is both epidemic and epidemic disease. Epidemics of Cholera are characteristically abrupt and often create an acute public health problem. The epidemics reach a peak and subsides gradually as the “force of infection” declines.
The “force of infection” is composed of 2 components, namely the force of infection through water and the force of infection through contacts.
The seasonal variation differs between countries and even between regions of same country.
- Agent: The organism that causes cholerae as V. cholera 0 Group 1 or Vibrio cholerae 01.Within the o Group 1, Classical and El Tor, have been differentiated Classical and El Tor are further divided into 3 serological types namely, Inaba, Ogawa, Hikojima.
- Resistance: V. Cholera are killed:-
- within 30 minutes by heating at 56 deg. C or within few seconds by boiling.
- by drying in sunshine as cresol.
- by coal tar such as cresol.
- By bleaching powder at 6mg / lit.
They remain viable in ice for 4-6 weeks or longer.
- Toxin Production:
The vibrios multiply in lumen of small intestine and produces an exotoxin.
- Reservoir of infection: The human being is the only known reservoir of cholera infection. He may be a case or carrier.
- Infective Material:The immediate source of infection are the stools and vomit of cases and carries. Large no. of vibrios (about 107 to 109 vibrios per ml of fluid) are present in watery stool of cholera patients.
- Infective Dose: Cholera is dose related. A very high dose like 1011 organisms is required to produce the clinical disease.
- Period of Communicability: A case of cholera is infectious for period of 7-10 days. Convalescent carries are infectious for 2-3 weeks. The chronic carries state may last from a month upto 10 years or more.Carriers in Cholera: A cholera carrier may be defined as an apparently healthy person who is excreting V. Cholerae.
- Preclinical or incubatory carrier: 1-5 days.
- Convalescent carrier: Patient who have recovered from an attack of cholera – usually 2-3 week.
- Contact or healthy carrier: This is the result of subclinical infection contracted through Association with source of infection, be it a case or infected environment. Usually less than 10 days.
- Chronic carrier: A chronic carrier stage occurs infrequently.
- Age & Sex: Cholera affects all ages & both sexes.
- Gastric acidity: The vibrio cholerae destroyed in acidic ph 5 or low.
- Population mobility: Movement of population (e.g. pilgrimages marriages, fairs & festivals) results in increased risk of exposure.
- Economic status: Incidence of cholera tends to be highest in low socio economic group & this is attributable to poor hygiene.
- Immunity: Natural infection confers quits effective immunity.
- Transmission is readily possible in a community with poor environmental sanitation.
- Environmental factors of imp. Are contaminated water & food.
- Files may carry vibrio.
- Social factors like certain human habits favoruring water & soil pollution, low standard of personal hygiene, lack of education & poor quality of life.
Mode of transmission
- Faecally contaminated water: uncontrolled water source such as wells, ponds, streams & rivers pose a great threat.
- Contaminated food and drinks
- Direct contact: Person to person transmission through contaminated fingers while carelessly handing excreta and vomit of patients and contaminated linen and formites.
Incubation Period: Few hours upto 5 days but commonly 1-2 days
- Stage of evacuation: onset abrupt with profuse, painless watery diarrhea followed by vomiting. Patients may pass stools 40 times per day. The stools may have rice water appearance.
- Stage of collapse: Patient soon passes in stage of collapse because of dehydration. Classical signs are: sunken eyes, hollow cheeks, scaphoid abdomen, subnormal temp. loss of skin elasticity. The output of urine decreases. Death may occur at this stage due to dehydration and acidosis.
- Stage of recovery: If death does not occur, the patient begins to show signs of clinical recovery.
Laboratory Diagnosis of Cholera:
- Collection of stools: A fresh specimen of stool should be colleted for laboratory examination.
- Vomitus: This is practically never used as the chance of isolating vibrios are much less & there is no advantage.
- Water: Samples containing 1-3 liters of suspect water should be collected in sterile bottles (for the filter method), or 9 volumes of the sample water added to 1 volume of 10% peptone water & dispatched to the laboratory by quickest method of transport.
- Food samples: Samples of food suspected to be contaminated with vibrio cholerae amounting to 1 to 3 gm. Are collected in transport media & sent to laboratory.
- Transportation: The stools should be transported in sterilized Mc Cartney bottles 30ml capacity containing alkaline peptone water or VR medium. The specimen should be transported in alkaline peptone water or Cary – Blair medium if it is collected by rectal swab.
- Direct examination: If a microscope with dark illumination is available, it may be possible to diagnose about 80% of the cases within a few minutes & more cases after 5-6 hours incubation in alkaline peptone water. In dark field, the vibrios evoke the image of many shooting stars in a dark sky.
- Culture method:5 to 1.0 ml of material is inoculated into peptone water tellurite medium for enrichment. After 4-6 hours subcultured on Bite salt agar medium. After overnight incubation plates are screened under obique illumination for vibrio colonies.
- Gram stain & motility: Gram negative & curved tods with characteristically scintillating motility in hanging drop preparation are very characteristic of V. cholerae.
- Serological tests: Slide agglutination test.
- Other tests are – direct haemagglutination test with chicken or
sheep red blood cells- Polymyxin B sensitivity test using 50microgm. discs- Sensitivity to cholera phage iv- V-p reaction- Haemolysin tests
How to Control cholera
The following account is based on the “Guideline for Cholera Control” proposed by who
- Verification of the diagnosis: For specific diagnosis of v. cholerae identify v. cholerae 01 in the stools of the patient.
- Notification: Cholera is notifiable disease locally, nationally & internationally. Health workers at all levels should be trained to identify & notify cases immediately to local health authority. Under the international health regulations cholera is notifiable to the WHO within 24 hours of its occurrence by the national government. An area is declared free of cholera when twice the incubation period (i.e. 10 days) has elapsed since the heath, recovery or isolation of the last case.
- Early case finding: An aggressive search for cases mild, moderate, severe should be made in community for prompt treatment.
- Establishment of treatment center: Midly dehydrated patients should be treated at home with oral rehydration solution. Severely dehydrated patients, requiring intravenous fluids should be transferred to the nearest treatment center or hospital.
- Rehydration Therapy: Cholera is now most effectively treated disease. Mortality rates have been about down to 1% by effective rehydration therapy. Rehydration may be oral or intravenous.Oral Rehydration:The aim of oral fluid therapy is to prevent dehydration & reduce mortality.Oral fluid therapy is bases on the observation that glucose give orally enhances the intestinal absorption of salt & water & it is capable or correcting electing electrolytes & water deficit.The composition of oral rehydration fluids recommended by WHO.
Composition of ORS-BICARBONATES
Ingredients Quantity Sodium chloride 3.5 gm Sodium bicarbonate 2.5 gm Potassium bicarbonate 1.5 gm Glucose 20.0 gm Potable water 1 lit.
Composition of ORS-CITRATE
Ingredients Quantity Nacl 3.5 gm Trisodium citrate dehydrate 2.9 gm Kcl 1.5 gm Glucose 20.0 gm Potable water 1 lit.
Packets of ORS are freely available at all primary health centre, subcentre & hospitals. The contents of packets are to be dissolved in 1 litre of water . the solution should be made fresh daily & used within 24 hours.
If the W.H.O. MIXTURE IS NOT available, a simple mixture of table salt (5g) & sugar (20 g) dissolved in 1 litre of water may be safely used.
Intravenous Rehydration: Requires only in initial cases of severely dehydrated patients who are in shock or unable to drink.
The solutions which are recommended by W.H.O. are:
- RINGER LACTATE SOLUTION
- DIARRHOEA TREATMENT SOLUTION
Maintenance therapy: the general principle is that the oral fluid intake should be equal to the stool loss.
- Adjuncts:: Antibiotics should be given along with ORS as soon as vomiting stops. doxycycline, tetracycline, spectrum can be used.
- Epidemiological Investigation:: Epidemiological studies should be undertaken to define extent
of out break & find out modes of transmission can be used.
- Sanitation Measures
- Water control: All steps should be taken to provide properly treated water or safe water for all purposes (drinking, washing, cooking)
- Excreta disposal: Provision of simple, cheap & effective excreta disposal.
- Food sanitation: Steps should be taken to improve food sanitation particularly sale of food under hygienic conditions.
- Disinfection: The most effective disinfectant is a disinfectant with a Rideal – Walker coefficient of 10 or more, such as cresol.
- Chemoprophylaxis:: Mass chemoprophylaxis is not advised for the total community because in order to prevent one serious case of cholera, some 10,000 people must be given the drug.Chemoprophylaxis is advised only for household contacts or of a closed community in which cholera has occurred.Tetracycline is the drug of choice for chemoprophylaxis
- Vaccination:: Cholera vaccine is the only specific prophylactic available against cholera.The vaccine employed at present is a saline suspension of approximately 6,000 million each of classical Ogawa & Inaba serotypes of V. cholera 01 per ml, so that each ml of the vaccine contains a total of 12,000 million vibrios. The organisms are killed & preserved by 0.5% phenol.Dosage: Primary immunization consist of 2 equal doses, injected subcutaneously, at an interval of 4 to 6 weeks.
1st dose 2nd dose Adult & children over 10 years 0.5 ml 0.5 ml Children aged 2 to 10 years 0.3 ml 0.3 ml Children aged 1 to 2 year 0.2 ml 0.2 ml
If 2 doses can not be given a month apart, than a single dose equivalent to the double of the first dose should be given. The vaccine not given to children below 1 year. Boosters are every 6 months.
Reactions: Locally tenderness, swelling, redness & sometimes fever.
Contraindication: Person with previous history of sensitivity reaction.
Protective value: About 50% for a period of 3-6 months.
- Identification of cases and their notification
- Health education – should be directed mainly regarding,
- Effectiveness & preparation of ORS
- The benefits of early reporting for prompt treatment.
- Food hygiene practices
- Hand washing after defection & before meals.
- Benefits of cooked, hot foods & safe water.
- An active and passive surveillance for cases
- Distribution of ORS packets.
- Purification of water supply & proper excreta disposal.
- Ensure cholera vaccination, in people during fairs, festivals and large religious functions.e.g. Kumbha-melas