Cholera

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Introduction

  • Cholera ek acute, severe diarrheal disease hai jo bacterium Vibrio cholerae ke kaaran hoti hai.
  • Iski pehchan bahut zyada watery diarrhea se hoti hai, jo agar time par treat na kiya jaye to rapidly severe dehydration aur death tak le ja sakti hai.
  • Yeh disease mainly contaminated water aur food ke through transmit hoti hai, isliye yeh poor sanitation aur hygiene se closely associated hai.
  • Cholera abhi bhi kai developing countries me ek major public health problem bana hua hai, especially outbreaks aur natural disasters ke dauran.
  • Disease ka rapid progression early diagnosis aur immediate treatment ko zaroori bana deta hai.
  • Laboratory diagnosis cases confirm karne, therapy guide karne aur effective outbreak control measures implement karne me critical role play karta hai.
  • Preventive strategies jaise safe water supply, sanitation, hygiene aur vaccination cholera-related morbidity aur mortality ko reduce karne ke liye essential hain.

 

Epidemiology and Transmission 

Epidemiology

Cholera ek global public health problem hai, jo mainly developing aur underdeveloped countries ko affect karta hai.

Yeh following regions ke kuch parts me endemic hai:

  • South aur Southeast Asia

  • Sub-Saharan Africa

  • Latin America

Periodic epidemics aur pandemics aksar in situations ke baad occur karte hain:

  • Floods, cyclones, earthquakes

  • Wars, refugee crises aur population displacement

  • Water supply aur sewage systems ka breakdown

High-risk settings me include hain:

  • Urban slums

  • Refugee camps

  • Areas jahan sanitation poor hai aur drinking water unsafe hai

Sab age groups affect hote hain, lekin children aur malnourished individuals me severe disease ka risk zyada hota hai.

Transmission

Cholera fecal–oral route se transmit hota hai, mainly contaminated water ya food ingestion ke through.

Major Modes of Transmission

Contaminated drinking water

  • Sabse common aur important route

  • Water sources me sewage contamination ki wajah se hota hai

Contaminated food

  • Raw ya undercooked seafood (especially shellfish)

  • Contaminated water se prepared food

  • Poor hygiene practices ke saath prepared street food

Poor personal hygiene

  • Defecation ke baad proper handwashing na karna

  • Improper food handling

Reservoir and Source of Infection

  • Humans primary reservoir hote hain

  • Infected individuals (symptomatic ya asymptomatic) stool me large numbers of organisms shed karte hain

  • Contaminated water bodies temporary environmental reservoirs ke taur par act kar sakti hain

Factors Favoring Transmission

  • Poor sanitation aur open defecation

  • Unsafe water supply

  • Overcrowding

  • Low socioeconomic conditions

  • Health education ki kami

Seasonal Variation

Cholera me seasonal peaks dekhe jate hain, often:

  • Rainy seasons ke dauran

  • Warmer months me jab water contamination common hota hai

 

Pathogenesis

Cholera ka pathogenesis non-invasive aur toxin-mediated hota hai, jisme intestinal inflammation ke bina massive fluid loss hota hai.

1. Entry and Colonization

Infection contaminated food ya water ke through Vibrio cholerae ingest hone se hota hai.

Usually ek large inoculum required hota hai, lekin reduced gastric acidity (achlorhydria, antacids) infectious dose ko kam kar deti hai.

Organism gastric acid ko survive karke small intestine tak pahunchta hai.

2. Adherence to Intestinal Mucosa

Bacteria small intestine ke epithelial cells se attach hota hai using:

  • Toxin-coregulated pilus (TCP)

Intestinal mucosa me koi invasion ya tissue destruction nahi hota.

3. Production of Cholera Toxin

Vibrio cholerae cholera toxin (CT) produce karta hai, jo ek AB₅ exotoxin hai.

  • B subunit enterocytes ke GM1 ganglioside receptors se bind karta hai

  • A subunit cell ke andar jaakar adenylate cyclase activate karta hai

4. Increased cAMP Levels

Adenylate cyclase activation → ↑ intracellular cAMP

cAMP ke effects:

  • Chloride secretion increase

  • Sodium absorption inhibit

  • Intestinal lumen me water aur electrolytes ka massive efflux

5. Resulting Effect

  • Profuse watery diarrhea

  • Severe dehydration aur electrolyte imbalance

  • No fever ya inflammatory response (non-inflammatory diarrhea)

 

Clinical Features

Clinical presentation asymptomatic infection se lekar severe, life-threatening dehydration tak range karti hai.

1. Incubation Period

Usually 1–5 days hota hai.

Shorter incubation ka matlab more severe disease hota hai.

2. Diarrhea

  • Sudden onset of profuse, painless watery diarrhea

  • Stools ko “rice-water stools” kaha jata hai

  • Colorless, cloudy fluid with mucus flecks

  • No blood ya pus

3. Vomiting

  • Frequent aur effortless hoti hai

  • Rapid fluid loss me contribute karti hai

4. Dehydration

Dehydration ke signs rapidly appear karte hain, jaise:

  • Thirst

  • Sunken eyes

  • Dry tongue aur skin

  • Reduced urine output (oliguria)

  • Loss of skin turgor

5. Electrolyte Imbalance

Sodium, potassium aur bicarbonate ka loss hota hai, jisse:

  • Muscle cramps (especially calves)

  • Metabolic acidosis

  • Weakness

6. Severe Disease (Cholera Gravis)

  • Hypovolemic shock

  • Rapid pulse, low blood pressure

  • Cold clammy skin

  • Cyanosis

  • Anuria

  • Agar untreated ho → death within hours

7. Absence of Certain Features

  • Usually no fever

  • No abdominal pain

  • Stool me no blood ya leukocytes

 

Laboratory Diagnosis

Laboratory confirmation early treatment, outbreak detection aur public health surveillance ke liye crucial hai.

1. Specimen Collection

  • Fresh stool sample (preferred) ya rectal swab

  • Antibiotic therapy se pehle collect kiya jata hai

  • Agar delay expected ho to Cary–Blair medium me transport

  • Samples ko promptly process karna chahiye taaki viability preserve rahe

2. Microscopic Examination

Hanging drop / wet mount:

  • Rapid darting motility dikhti hai

  • Motility specific antisera se inhibit ho jati hai

  • Outbreaks me ek rapid presumptive test ke roop me useful

3. Culture Methods (Gold Standard)

Step-wise approach:

Enrichment:

  • Alkaline peptone water (pH ~8.5)

Selective plating:

  • TCBS agar (Thiosulfate–Citrate–Bile salts–Sucrose)

Colony characteristics:

  • Sucrose fermentation ke kaaran large yellow colonies

4. Biochemical Identification

  • Oxidase positive

  • Sucrose ferment karta hai

  • Indole positive

  • String test positive (sodium deoxycholate se mucoid string)

5. Serological Identification

  • Specific antisera ke saath slide agglutination

  • Detection of:

    • O1 (El Tor, Classical biotypes)

    • O139 (epidemic potential)

Epidemiological tracking ke liye important.

6. Rapid Diagnostic Tests (RDTs)

  • Immunochromatographic dipstick tests

  • Stool se directly cholera antigens detect karte hain

Advantages:

  • Fast (minutes me result)

  • Field aur outbreak settings me useful

Limitation:

  • Culture se less specific

7. Molecular Methods

  • PCR for toxin aur species-specific genes

  • Highly sensitive aur specific

  • Mainly reference aur research laboratories me use hota hai

 

Public Health Importance

Cholera explosive outbreaks cause kar sakta hai jo kuch hi dinon me thousands ko affect kar dete hain.

Laboratory diagnosis help karta hai:

  • Early outbreak detection

  • Suspected cases ki confirmation

  • Spread aur severity monitoring

  • Control strategies planning

Public Health Aspects

  • Ek infected person large water sources contaminate kar sakta hai

  • Asymptomatic carriers transmission me role play karte hain

  • Untreated cases me case fatality high hoti hai, lekin proper care se <1%

 

Prevention and Control

1. Water Safety

  • Safe drinking water ka provision

  • Water ka boiling ya chlorination

  • Sewage contamination se water sources ki protection

2. Sanitation Measures

  • Proper sewage disposal

  • Sanitary latrines ka use

  • Open defecation ki prevention

3. Food Hygiene

  • Proper cooking of food

  • Raw seafood se avoidance

  • Clean food handling practices

4. Personal Hygiene

  • Defecation ke baad aur meals se pehle soap se handwashing

  • Community hygiene education

5. Case Management

  • Prompt oral rehydration therapy (ORT)

  • Severe dehydration me intravenous fluids

  • Duration aur shedding kam karne ke liye antibiotics

6. Surveillance and Outbreak Control

  • Cases ka reporting

  • Laboratory confirmation

  • Jahan possible ho wahan isolation

  • Stools aur contaminated materials ka disinfection

7. Vaccination

Oral cholera vaccines use kiye jate hain:

  • Endemic areas me

  • High-risk populations me

  • Outbreaks ke dauran preventive strategy ke roop me

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