Foodborne Zoonoses

Foodborne Zoonoses - Intro & Tiny Terrors

• Definition: Infections transmitted from animals to humans via contaminated food/water. Major public health concern globally.
• Causative Agents:
  • Bacteria: Salmonella spp., Campylobacter spp., Shiga toxin-producing E. coli (STEC, e.g., O157:H7), Listeria monocytogenes, Brucella spp.
  • Viruses: Norovirus, Hepatitis A virus, Hepatitis E virus.
  • Parasites: Toxoplasma gondii, Trichinella spiralis, Taenia spp. (cestodes).
  • Prions: Variant CJD (linked to Bovine Spongiform Encephalopathy - BSE).

⭐ Listeria monocytogenes uniquely grows at refrigeration temperatures (~4°C) and shows characteristic tumbling motility at 20-25°C.

• Clinical Spectrum: Ranges from mild gastroenteritis to severe, invasive disease with systemic complications.
• Prevention Pillars: Thorough cooking of food, strict hand hygiene, preventing cross-contamination. 📌 Cook, Clean, Chill, Separate!

Bacterial Zoonoses - The Gut Grumbles

• Salmonellosis (Non-typhoidal)
  • Source: Poultry, eggs, meat.
  • Sx: Gastroenteritis. Inc: 6-72h.
  • Dx: Stool culture.
• Campylobacteriosis
  • Source: Undercooked poultry, raw milk.
  • Sx: Bloody diarrhea, fever. Inc: 2-5d.
  • Complication: GBS.
  • Dx: Stool culture (special media).
• E. coli (STEC/EHEC O157:H7)
  • Source: Undercooked beef, produce.
  • Sx: Bloody diarrhea, cramps. Inc: 1-10d.
  • Complication: HUS (<5yr).
  • Dx: Stool culture (SMAC), Shiga toxin.
• Listeriosis
  • Source: Deli meats, soft cheese, raw milk.
  • Sx: Gastroenteritis; invasive (sepsis, meningitis) in at-risk. Inc: 3-70d.
  • Key: Grows at 4°C.
  • Dx: Blood/CSF culture.
• Brucellosis
  • Source: Unpasteurized dairy, animal contact.
  • Sx: Undulant fever, sweats, arthralgia. Inc: 1-3wks+.
  • Dx: Blood culture, serology.

⭐ Campylobacter jejuni is the most common bacterial cause of diarrheal illness worldwide and a leading antecedent to Guillain-Barré Syndrome.

Parasites & Viruses - Microscopic Marauders

Parasites:

• Toxoplasma gondii: Undercooked meat; cat feces. Congenital triad (chorioretinitis, hydrocephalus, intracranial calcifications).
• Cryptosporidium parvum: Contaminated water/food (oocysts). Severe watery diarrhea (AIDS). Acid-fast.
• Trichinella spiralis: Undercooked pork/game (larvae). Myalgia, periorbital edema, eosinophilia.
• Taenia solium (Pork Tapeworm): Undercooked pork (cysticerci → taeniasis); fecal-oral (ova → cysticercosis).

  ⭐ Neurocysticercosis: major cause of adult-onset seizures in endemic areas.

• Diphyllobothrium latum (Fish Tapeworm): Raw freshwater fish. Megaloblastic anemia (Vit B12 def.).

Viruses:

• Norovirus: Shellfish, salads. Explosive vomiting, diarrhea. Cruise ship outbreaks.
• Hepatitis A (HAV): Fecal-oral; food/water. Acute self-limiting hepatitis. Vaccine.
• Hepatitis E (HEV): Undercooked pork/game, water. Acute hepatitis. ⚠️ High mortality in pregnancy.

Prions & Prevention - Safe Food Sentinels

• Prions:
  • Prions (PrPSc): Aberrant proteins causing Transmissible Spongiform Encephalopathies (TSEs).
  • Key Foodborne: Variant CJD (vCJD) via BSE-infected beef.
  • Transmission: Ingesting contaminated neural/lymphoid tissues.
  • Extreme Resistance: To heat, most disinfectants.
    • Decontamination: 1N NaOH / >20,000 ppm NaOCl (1hr); Autoclave 134°C (18-60min).
• Prevention & Control (Safe Food Sentinels):
  • General Food Safety Pillars:
    • WHO Five Keys to Safer Food.
    • HACCP implementation.
  • Prion-Specific Controls:
    • Ban SRMs from animal feed & human food.
    • Surveillance: BSE (cattle), CJD (humans).
  • Note: Prions resist irradiation.

⭐ vCJD is linked to consuming beef contaminated with Bovine Spongiform Encephalopathy (BSE) prions, often affecting younger individuals.

High-Yield Points - ⚡ Biggest Takeaways

• Brucellosis: Undulant fever, unpasteurized dairy, occupational risk (farmers, vets).
• Non-typhoidal Salmonella: Common gastroenteritis from poultry, eggs; often self-limiting.
• Campylobacter jejuni: Leading bacterial gastroenteritis; Guillain-Barré syndrome (GBS) association; poultry source.
• Listeria monocytogenes: Risk for pregnant women (neonatal sepsis), immunocompromised; transplacental; soft cheeses.
• Taenia solium: Pork tapeworm; neurocysticercosis (eggs), taeniasis (larvae in pork).
• Toxoplasma gondii: Congenital toxoplasmosis risk; undercooked meat, cat oocysts_._