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Food Borne Diseases and Food Safety

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1. Definition and Burden

• (a) History of ingestion of a common food
• (b) Attack of many persons at the same time
• (c) Similarity of signs and symptoms in the majority of cases

• Food-borne illness affects an estimated 600 million people worldwide each year, causing approximately 420,000 deaths
• Low- and middle-income countries bear the greatest burden
• Children under 5 years are disproportionately affected (about 125,000 deaths/year)
• The economic impact includes lost productivity, healthcare costs, and trade losses

• Park's Textbook of Preventive and Social Medicine, p. 280
• P.C. Dikshit Textbook of Forensic Medicine and Toxicology, p. 580

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2. Causes and Classification

A. NON-BACTERIAL (Chemical / Natural Toxins)

• Lathyrus sativus (grass pea - causes lathyrism)
• Poisonous mushrooms (Amanita species)
• Rye, oats, barley contaminated with ergot
• Poisonous berries such as Atropa belladonna
• Argemone mexicana (adulterant in mustard oil - epidemic dropsy)
• Cotton seeds, groundnuts, cabbage, soybeans, sweet clover

• Poisonous fish (e.g., puffer fish - tetrodotoxin)
• Mussel/shellfish poisoning

• Intentionally added: Flavouring agents, colouring agents, preservatives, solvents for fat extraction (e.g., hydrocarbons)
• Accidentally added: Pesticides, insecticides
• Products of food processing: Smoking of fleshy foods, radionuclides
• Environmental contaminants: Fertilizers, cadmium, mercury, arsenic, lead

B. BACTERIAL

C. VIRAL

• Norovirus (most common cause of food-borne gastroenteritis worldwide)
• Hepatitis A virus
• Rotavirus
• Astrovirus

D. PARASITIC

• Giardia lamblia
• Cryptosporidium
• Cyclospora cayetanensis
• Taenia saginata/solium (via undercooked beef/pork)
• Trichinella spiralis
• Park's Textbook of Preventive and Social Medicine, p. 280-281
• P.C. Dikshit Textbook of Forensic Medicine and Toxicology, p. 580

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3. Signs and Symptoms

• Nausea and vomiting (often sudden onset)
• Abdominal cramping and pain
• Diarrhoea (watery to bloody depending on pathogen)

• Fever (present in infection-type, usually absent in pure toxin-type)
• Chills, malaise, fatigue
• Dehydration and electrolyte imbalance (in severe cases)

• Botulism: dysphagia, diplopia, ptosis, dysarthria, blurred vision, muscle weakness, quadriplegia (descending flaccid paralysis) - fever generally absent, consciousness retained
• Ciguatera: paresthesias/dysesthesias perioral and extremities, cold allodynia (pathognomonic - cold objects feel burning hot), ataxia, visual hallucinations
• Scombroid: facial flushing (sunburn-like), throbbing headache, palpitations, urticaria

• Rosen's Emergency Medicine, p. 1315
• Park's Textbook of Preventive and Social Medicine, p. 280-281

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4. Transmission of Food-Borne Pathogens and Toxins

Key Vehicles of Transmission:

• Meat and poultry: Salmonella, Campylobacter, E. coli O157:H7, C. perfringens
• Milk and dairy products: Salmonella, Staphylococcus (mastitic cows), Brucella, Listeria
• Eggs and egg products: Salmonella enteritidis
• Home-canned/preserved low-acid foods: Clostridium botulinum (anaerobic conditions essential)
• Salads, custards, processed foods: Staphylococcus aureus
• Rice (reheated/fried rice): Bacillus cereus (emetic form)
• Raw/undercooked seafood: Vibrio parahaemolyticus, hepatitis A, norovirus
• Dark meat fish (tuna, mahi-mahi, mackerel): Scombroid poisoning (histamine)
• Coral reef fish (barracuda, grouper, snapper): Ciguatera toxin
• Water/food contaminated by faeces: Shigella, E. coli, hepatitis A, typhoid

Mechanisms of Contamination:

1. Animal reservoir to food: Farm animals, poultry carry organisms that contaminate meat/milk
2. Human carriers/handlers: Staphylococcal skin lesions (boils, pyogenic infections), nasal carriage
3. Environmental contamination: Rodents (rats, mice) contaminating foodstuffs with urine and faeces
4. Insect vectors: Flies, cockroaches transmitting pathogens to food
5. Soil contamination: C. botulinum and C. perfringens spores enter food as spores from soil
6. Cross-contamination: Raw to cooked food via surfaces, utensils, or hands
7. Temperature abuse: Leaving cooked food at room temperature allows spore germination (C. perfringens) or bacterial multiplication (Staphylococcus)

The Infectious Dose:

• Salmonella: as few as 15-20 cells may suffice
• Toxin-producing organisms: even dead bacteria leave heat-stable toxins (e.g., Staphylococcus enterotoxins resist boiling for 30+ minutes)
• Park's Textbook of Preventive and Social Medicine, p. 280-283
• P.C. Dikshit Textbook of Forensic Medicine and Toxicology, p. 580

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5. Early Identification, Initial Management and Referral

Early Identification (Key Steps):

• Time and nature of food consumed
• Number of persons affected (cluster = suggestive of outbreak)
• Incubation period (helps identify likely pathogen)
• Specific symptoms (neurological signs suggest botulism or ciguatera)

• Usually not needed for uncomplicated, self-limited cases
• Stool cultures if: outbreak investigation, severe illness, bloody diarrhoea, immunocompromised host
• Specific tests: stool PCR/culture panels, serology for hepatitis A
• In botulism: mouse bioassay, ELISA for toxin in stool/serum

Initial Management:

• Oral hydration is the cornerstone of treatment for the vast majority of food-borne illnesses
• ORS (WHO formula) for moderate dehydration
• IV fluids for severe dehydration, vomiting preventing oral intake

• Antiemetics: Ondansetron 0.15 mg/kg up to 8 mg PO, or metoclopramide 10 mg PO
• Antidiarrheals: use cautiously; avoid in bloody diarrhoea or suspected STEC (risk of HUS)

• Severe/invasive Salmonella (fluoroquinolone or ceftriaxone)
• Shigellosis (azithromycin, fluoroquinolone)
• Cholera (doxycycline, azithromycin)
• Listeria (ampicillin)
• C. difficile (metronidazole or vancomycin)

• Botulism: Antitoxin IV (50,000-100,000 units) - must be given before toxin fixes to nerve tissue; guanidine hydrochloride 15-40 mg/kg orally may reverse neuromuscular block; supportive care (mechanical ventilation for respiratory failure)
• Scombroid poisoning: Antihistamines (H1 blockers - diphenhydramine), H2 blockers; cimetidine if severe; symptoms resolve within 6 hours

Referral Criteria:

• Suspected botulism (any neurological symptoms after food ingestion) - emergency referral
• Severe dehydration (particularly children/elderly)
• Bloody diarrhoea with high fever (suggests invasive infection)
• Immunocompromised patients
• Signs of systemic sepsis
• Suspected outbreak requiring public health investigation
• Rosen's Emergency Medicine, p. 1315-1316
• Park's Textbook of Preventive and Social Medicine, p. 280-285

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6. Food Poisoning: Epidemiological Features and Clinical Characteristics

Types of Food Poisoning in Detail

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A. Salmonella Food Poisoning (Infection Type)

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B. Staphylococcal Food Poisoning (Toxin/Intoxication Type)

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C. Botulism (Toxin/Intoxication Type - Most Serious)

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D. Clostridium perfringens Food Poisoning

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E. Bacillus cereus Food Poisoning (Two Syndromes)

• Park's Textbook of Preventive and Social Medicine, p. 280-284
• Rosen's Emergency Medicine, p. 1315

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7. Food Intoxication: Features, Preventive and Control Measures

Distinction: Food Intoxication vs. Food Infection

Special Food Intoxications:

• Dark-meat fish (tuna, mahi-mahi, mackerel, herring, sardines) improperly refrigerated
• Bacteria (normal marine flora) convert histidine in fish muscle to histamine via histidine decarboxylase
• Toxins are heat-stable - not destroyed by cooking
• Symptoms (within 20-30 min): Facial flushing (sunburn-like), severe throbbing headache, diarrhoea, palpitations, abdominal cramping, urticaria, dry mouth, nausea/vomiting; conjunctival injection; often a metallic/peppery taste noted while eating
• Duration: generally <6 hours; benign course
• Treatment: H1 antihistamines (diphenhydramine), H2 blockers

• Coral reef fish (barracuda, grouper, snapper, amberjack) accumulate ciguatoxin produced by dinoflagellate Gambierdiscus toxicus
• Ciguatoxin is heat- and acid-stable, odourless, tasteless - not destroyed by cooking, freezing, drying, salting, smoking, or pickling
• Acts on sodium channels - causes spontaneous neuronal firing
• Symptoms (2-6 hour incubation): Early GI (nausea, vomiting, profuse watery diarrhoea) followed by classic neurological signs: perioral/extremity paresthesias, cold allodynia (pathognomonic - cold objects feel burning hot), ataxia, weakness, visual hallucinations; worsening with alcohol
• Duration: average 1-2 weeks; 50% still symptomatic at 9 weeks
• Attack rate: 80-90%
• No specific antidote; supportive care; avoid alcohol

Prevention and Control of Food Intoxication:

1. Keep clean - wash hands, surfaces, utensils; protect food from insects/rodents/pests
2. Separate raw and cooked - prevent cross-contamination; separate raw meat/poultry/seafood from other foods; use separate utensils
3. Cook thoroughly - cook food especially meat, poultry, eggs and seafood; use a thermometer; bring soups/stews to boiling
4. Keep food at safe temperatures - do not leave cooked food at room temperature >2 hours; refrigerate below 5°C; keep hot food above 60°C ("danger zone" = 5-60°C); do not store food too long even in refrigerator
5. Use safe water and raw materials - use safe water; select fresh foods; wash fruits and vegetables; do not use food past expiry date

• Proper refrigeration of all perishable foods
• Adequate cooking temperatures (≥75°C internal temperature for meat)
• Avoidance of storing cooked food at room temperature
• Rapid cooling of cooked foods if not consumed immediately
• Heating preserved/canned food to 100°C before consumption (destroys botulinum toxin)

• Regular handwashing with soap and water before handling food
• Exclusion of food handlers with diarrhoea, vomiting, skin infections, or nasal discharge
• Food handlers with staphylococcal skin lesions must not handle food

• Safe slaughtering practices and hygienic processing of meat and poultry
• Pasteurization of milk
• Proper canning techniques and industrial food safety standards (HACCP)
• Veterinary supervision of food animals
• Control of rats, mice, flies, and cockroaches in food storage areas

• Food standards and labelling requirements
• Regular inspection of food establishments, abattoirs, and markets
• Licensing of food vendors and catering establishments
• Import controls for food products
• Park's Textbook of Preventive and Social Medicine, p. 280-285

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8. Public Health Response to Food-Borne Diseases

Outbreak Investigation Steps:

1. Confirm the diagnosis - verify that reported illnesses are truly food-borne; clinical and laboratory confirmation
2. Define a case - establish a case definition (person, place, time) to identify who is affected
3. Find cases - active case finding through hospitals, clinics, community outreach; line listing of cases
4. Describe the outbreak - epidemic curve (time), spot map (place), person characteristics (age, sex, food items consumed)
5. Generate hypotheses - based on incubation period, attack rate, food items; calculate food-specific attack rates using 2x2 tables
6. Test hypotheses - analytic epidemiology (case-control or cohort study); laboratory testing of food samples, environmental samples, clinical specimens
7. Identify the vehicle and source - trace back the contaminated food item; identify the point of contamination in the supply chain
8. Implement control measures - recall contaminated food; close/remediate implicated establishments; treat cases
9. Communicate findings - report to health authorities; inform the public through appropriate channels; publish outbreak report

Surveillance and Reporting:

• Food-borne illnesses are notifiable diseases - physicians and laboratories must report to local/state/federal health departments
• Notifiable food-borne diseases include: Salmonella, Shigellosis, Cholera, STEC, Norovirus, Hepatitis A
• Physicians should suspect an outbreak when they see a larger-than-normal number of patients with the same symptoms
• National surveillance systems (e.g., CDC FoodNet, WHO INFOSAN) track trends

Control Measures at Population Level:

• Identification and removal of the contaminated food from the market (food recall)
• Closure of implicated food premises pending investigation and remediation
• Treatment of cases; prophylaxis of contacts (e.g., botulism antitoxin for co-diners)
• Environmental sampling and laboratory investigation
• Alert to healthcare facilities to watch for further cases

• HACCP (Hazard Analysis and Critical Control Points) enforcement in food processing
• Food safety legislation enforcement
• Outbreak report and recommendations

• Public health education on safe food handling
• Training of food handlers
• Strengthening food safety inspection systems
• International cooperation in food safety (WHO, FAO Codex Alimentarius)
• Kitchen sanitation monitoring in mass feeding programs (shelters, camps, school canteens)
• Personal hygiene monitoring for food preparers
• Clean water supply and safe excreta disposal

Food Safety in Disaster Situations:

• Poor hygiene is the major cause of food-borne diseases in disaster settings
• In shelters or camps where feeding programmes operate, kitchen sanitation is of utmost importance
• Personal hygiene must be monitored in all food preparation staff
• Emergency latrines should be provided; washing and cleaning facilities made available
• Ensure adequate water supply for food preparation and hand-washing
• Park's Textbook of Preventive and Social Medicine, p. 280-285, 3923-3925
• Rosen's Emergency Medicine, p. 1315-1316

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Quick Reference: Summary Comparison Table

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• Park's Textbook of Preventive and Social Medicine, pp. 280-285, 3923-3925
• Rosen's Emergency Medicine: Concepts and Clinical Practice, pp. 1315-1320
• P.C. Dikshit Textbook of Forensic Medicine and Toxicology, pp. 579-581

🍽️ Food Borne Diseases & Food Safety

Exam ke liye Short & Easy Notes

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1. Definition (Kya hota hai?)

"Disease caused by agents entering body through ingestion of food" — either infectious ya toxic nature ki

1. Ek common khaana khaya ho
2. Bahut log ek saath beemar pade
3. Sabke symptoms same hon

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2. Causes & Classification

FOOD POISONING
├── NON-BACTERIAL
│   ├── Chemicals (pesticides, mercury, arsenic)
│   ├── Vegetable (poisonous mushroom, belladonna)
│   └── Animal (poisonous fish, mussel)
│
└── BACTERIAL
    ├── INFECTION TYPE → organism body mein multiply karta hai
    │   └── Salmonella, Shigella, E. coli
    │
    └── TOXIN TYPE → pehle se bana hua toxin khaane mein hota hai
        └── Staph aureus, C. botulinum, B. cereus

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3. Signs & Symptoms

• Infection type → Fever HOGA ✅ (Salmonella)
• Toxin type → Fever NAHI ❌ (Staph, Botulism)

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4. Incubation Period (Ye yaad karo - exam mein aata hai!)

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5. Transmission (Kaise failta hai?)

• Meat/Poultry → Salmonella, Campylobacter, C. perfringens
• Milk/Dairy → Staph (mastitis cows), Brucella, Listeria
• Eggs → Salmonella enteritidis
• Home-canned food → Botulinum (anaerobic)
• Fried rice → B. cereus
• Dark meat fish → Scombroid (histamine)
• Coral reef fish → Ciguatera toxin
• Rats/Mice/Flies → contaminate stored food

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6. Types - Exam Important Wale (5 Big Ones)

🔴 Staphylococcal (Toxin type)

• Agent: Staph aureus enterotoxin
• IP: 1-8 hrs (preformed toxin)
• Food: Custard, salads, dairy
• Key: No fever, vomiting prominent
• Toxin: Heat STABLE (30 min boiling se nahi marti)

🟠 Salmonella (Infection type)

• IP: 12-24 hrs
• Food: Poultry, eggs, dairy
• Key: Fever hoga, diarrhoea, chills
• Carrier state banta hai

🟡 Botulism (Toxin type - MOST DANGEROUS)

• Agent: C. botulinum exotoxin (Type A/B/E)
• IP: 18-36 hrs
• Food: Home-canned, smoked fish, low-acid preserved food
• Key: Neuro symptoms — Dysphagia, Diplopia, Ptosis, Dysarthria, Paralysis
• No fever, no GI symptoms (GI bahut kam)
• Toxin: Heat LABILE (100°C pe kuch min mein destroy)
• Treatment: Antitoxin IV (50,000-1,00,000 units)

🟢 C. perfringens

• IP: 6-24 hrs (peak 10-14 hrs)
• Food: Cooked meat stored at room temp
• Key: Diarrhoea + cramps, no vomiting, no fever
• Self-limiting, no deaths

🔵 B. cereus (2 types!)

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7. Food Intoxication - Special Types

🐟 Scombroid Fish Poisoning

• Fish: Tuna, mahi-mahi, mackerel (dark meat fish)
• Cause: Bacteria histidine → histamine banate hain (improper refrigeration se)
• IP: 20-30 minutes (bahut jaldi!)
• Symptoms: Face flushing (sunburn jaisa), headache, urticaria, palpitations
• Treatment: Antihistamines (H1 blockers)
• Toxin heat-stable hai

🐡 Ciguatera Fish Poisoning

• Fish: Barracuda, grouper, snapper (coral reef fish)
• Toxin: Ciguatoxin (dinoflagellate se) - heat/acid stable, no taste/smell
• IP: 2-6 hrs
• Key symptom: Cold allodynia → thandi cheez GARAM lagti hai (pathognomonic!)
• Also: Paresthesias, ataxia, weakness
• No antidote — sirf supportive treatment
• Symptoms weeks tak reh sakte hain

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8. Management (Treatment)

• Botulism suspicion (koi bhi neuro symptom)
• Severe dehydration
• Bloody diarrhoea + high fever
• Elderly, children, immunocompromised

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9. Prevention (WHO 5 Keys - Exam Favourite!)

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10. Public Health Response (Outbreak mein kya karo)

1. Confirm karo - sach mein food poisoning hai?
2. Case define karo - kaun, kahan, kab?
3. Cases dhundo - hospitals check, line listing banao
4. Epidemic curve banao - time/place/person
5. Hypothesis banao - kaunsa food suspect?
6. Lab confirm karo - food sample, stool culture
7. Source trace karo - supply chain mein kahaan contamination?
8. Control karo - food recall, establishment band, treat cases
9. Report karo - health department ko notify

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⭐ Last Minute Exam Tricks

Food Borne Diseases & Food Safety

Short & Easy Exam Notes

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1. Definition

1. History of ingestion of a common food
2. Many persons attacked at the same time
3. Similarity of symptoms in majority of cases

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2. Causes & Classification

FOOD POISONING
├── NON-BACTERIAL
│   ├── Chemical → pesticides, mercury, arsenic, cadmium
│   ├── Vegetable → poisonous mushroom, belladonna berry
│   └── Animal → poisonous fish, mussel
│
└── BACTERIAL
    ├── INFECTION TYPE → organism multiplies in the body
    │   └── Salmonella, Shigella, E. coli
    │
    └── TOXIN TYPE → preformed toxin already present in food
        └── Staph aureus, C. botulinum, B. cereus

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3. Signs & Symptoms

• Infection type → Fever PRESENT ✅ (Salmonella, Shigella)
• Toxin type → Fever ABSENT ❌ (Staph, Botulism, C. perfringens)

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4. Incubation Periods (High Yield!)

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5. Transmission

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6. Types of Food Poisoning (Most Important!)

🔴 Staphylococcal Food Poisoning

• Agent: Enterotoxin of Staph aureus (heat STABLE - survives boiling 30+ min)
• IP: 1-8 hours (short because toxin is preformed)
• Food: Custard, salads, milk products
• Symptoms: Sudden vomiting, cramps, diarrhoea
• No fever | Death uncommon

🟠 Salmonella Food Poisoning

• Agent: S. typhimurium, S. enteritidis
• IP: 12-24 hours
• Food: Poultry, eggs, dairy, meat
• Symptoms: Chills, fever, nausea, vomiting, profuse watery diarrhoea (2-3 days)
• Convalescent carrier state may persist

🟡 Botulism (Most Dangerous)

• Agent: Exotoxin of C. botulinum (Type A/B/E) — heat LABILE (destroyed at 100°C)
• IP: 18-36 hours
• Food: Home-canned vegetables, smoked/pickled fish, low-acid preserved food
• Symptoms: Dysphagia, Diplopia, Ptosis, Dysarthria, Blurred vision, Muscle weakness → Quadriplegia
• GI symptoms minimal | No fever | Consciousness retained
• Treatment: Antitoxin IV (50,000-1,00,000 units) — give before toxin fixes to nerves
• Kills 2/3 of untreated victims

🟢 C. perfringens Food Poisoning

• IP: 6-24 hours (peak 10-14 hrs)
• Food: Cooked meat/poultry stored at room temperature
• Symptoms: Diarrhoea + abdominal cramps | No vomiting | No fever
• Self-limiting (<1 day), no deaths reported

🔵 B. cereus Food Poisoning (Two forms!)

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7. Food Intoxication - Special Types

Scombroid Fish Poisoning

• Fish: Tuna, mahi-mahi, mackerel, sardines (dark meat fish)
• Cause: Bacteria convert histidine → histamine due to improper refrigeration
• IP: 20-30 minutes
• Symptoms: Facial flushing (like sunburn), throbbing headache, urticaria, palpitations, diarrhoea
• Toxin is heat stable (cooking does not prevent it)
• Treatment: H1 antihistamines (diphenhydramine)

Ciguatera Fish Poisoning

• Fish: Barracuda, grouper, snapper (coral reef fish)
• Toxin: Ciguatoxin from dinoflagellate Gambierdiscus toxicus — heat and acid stable, odourless, tasteless — NOT destroyed by cooking, freezing, or smoking
• IP: 2-6 hours (can be up to 24 hrs)
• Symptoms: GI first (vomiting, diarrhoea) then neurological
• Pathognomonic: Cold allodynia — cold objects feel burning hot
• Also: Perioral paresthesias, ataxia, weakness, visual hallucinations
• Attack rate: 80-90% | Duration: weeks
• No antidote — supportive treatment only

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8. Summary Comparison Table

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9. Early Identification & Management

• Many people sick after eating the same food
• Short incubation + no fever → toxin type
• Neurological symptoms → think Botulism or Ciguatera
• Flushing after fish → think Scombroid

• Any neurological symptoms (Botulism suspected)
• Severe dehydration
• Bloody diarrhoea + high fever
• Children, elderly, immunocompromised

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10. Prevention - WHO 5 Keys to Safer Food

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11. Public Health Response to Outbreaks

1. Confirm the diagnosis (lab + clinical)
2. Define a case (who, where, when)
3. Find all cases - active surveillance, line listing
4. Describe - epidemic curve, spot map
5. Form hypothesis - which food item is suspect?
6. Test hypothesis - lab test food samples + stool cultures
7. Identify source - trace back the supply chain
8. Implement control - food recall, close premises, treat cases
9. Report - notify health authorities

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⭐ Quick Recall Points for Exam