Emerging Zoonotic Diseases

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Intro & Drivers - Rising Tide Alert

  • Emerging Zoonotic Diseases (EZDs): Infections newly identified in a population, or previously existing but rapidly ↑ in incidence or geographic range.
  • Key Definitions:
    • Zoonosis: Disease naturally transmissible from vertebrate animals to humans.
    • Emerging: New, or rapidly ↑ incidence/range.
    • Re-emerging: Previously controlled, now ↑ again.
  • Core Drivers (Multifactorial - "One Health" Perspective):
    • Ecological Changes: Deforestation, climate change, agricultural intensification, habitat encroachment.
    • Human Demographics & Behavior: ↑Population density, urbanization, global travel & trade, changing food habits.
    • Pathogen Adaptation: Genetic mutation/reassortment (e.g., antigenic drift/shift), antimicrobial resistance.
    • Public Health Infrastructure: Weak surveillance systems, inadequate vector control, breakdown in sanitation. image

⭐ Approximately 75% of recently emerging infectious diseases affecting humans are of animal origin (zoonotic).

Viral Zoonoses - Nipah & KFD Spotlight

  • Nipah Virus (NiV)
    • Paramyxoviridae; Reservoir: Fruit bats (Pteropus).
    • Transmission: Contaminated date palm sap, animal contact (pigs), human-to-human.
    • Clinical: Acute respiratory distress, severe encephalitis. Incubation: 4-14 days. Mortality: 40-75%.
    • Diagnosis: RT-PCR (throat/nasal swab, CSF, urine), IgM/IgG ELISA.
    • Outbreaks: Kerala, West Bengal.
  • Kyasanur Forest Disease (KFD) - "Monkey Fever"
    • Flaviviridae; Vector: Haemaphysalis spinigera ticks.
    • Reservoirs: Rodents, shrews. Monkeys: sentinels & amplifying hosts.
    • Clinical: Biphasic. Phase 1: Fever, headache, myalgia, GI symptoms, hemorrhagic signs. Phase 2: Meningoencephalitis. Case fatality: 3-10%.
    • Diagnosis: RT-PCR (blood), virus isolation, serology (ELISA IgM/IgG).
    • Endemic: Karnataka (Western Ghats).

⭐ A formalin-inactivated KFD vaccine is available and recommended for individuals in endemic areas of India. Factors influencing zoonotic disease emergence

Bacterial Zoonoses - Typhus & Lepto Lowdown

  • Typhus Group (Rickettsial)
    • Scrub Typhus: Orientia tsutsugamushi. Vector: Chiggers. Eschar common, fever, rash. Weil-Felix (OX-K+). Rx: Doxycycline. Scrub Typhus Eschar
    • Murine (Endemic) Typhus: Rickettsia typhi. Vector: Rat flea. Reservoir: Rodents. Fever, rash.
    • Epidemic Typhus: Rickettsia prowazekii. Vector: Louse. High fever, rash. Brill-Zinsser (recrudescence).
  • Leptospirosis
    • Leptospira interrogans (spirochete).
    • Source: Animal urine (rodents); contaminated water/soil.
    • Clinical:
      • Phase 1 (Anicteric): Fever, headache, myalgia (calf), conjunctival suffusion.
      • Phase 2 (Icteric/Weil’s Disease): Jaundice, AKI, hemorrhage, myocarditis. High mortality.
    • Dx: MAT (gold standard).
    • Rx: Doxycycline; Penicillin/Ceftriaxone (severe).

⭐ Weil's Disease: Classic triad of jaundice, hemorrhage, and acute kidney injury (AKI).

Prevention & One Health - United Front Shield

  • Core Preventive Measures:
    • Surveillance: Robust, integrated (human-animal) systems for early warning.
    • Vaccination: Strategic for at-risk human & animal populations.
    • Vector Control: Targeted interventions (e.g., mosquitoes, ticks).
    • Food Safety: From farm-to-fork; hygienic processing, thorough cooking.
    • Biosecurity: Strict protocols on farms, in markets, and laboratories.
    • Public Education: Promoting awareness and responsible practices.
  • One Health: The Unified Strategy 📌 ACE for One Health
    • Animal Health 🐕
    • Community (Human) Health 🧑‍⚕️
    • Environmental Health 🌳
    • Principle: Interdependence of these three pillars.
    • Action: Collaborative, multi-sectoral (health, veterinary, agriculture, environment) approach.
    • Goal: Coordinated surveillance, rapid response, effective control measures.

    ⭐ The "One Health" approach is critical for tackling antimicrobial resistance (AMR) linked to zoonotic pathogens.

One Health Triad for Disease Prevention

High‑Yield Points - ⚡ Biggest Takeaways

  • Nipah virus: Reservoir fruit bats (Pteropus); causes severe encephalitis; human-to-human transmission documented.
  • Kyasanur Forest Disease (KFD): Tick-borne (Haemaphysalis); monkeys are amplifying hosts; causes hemorrhagic fever.
  • Avian Influenza (e.g., H5N1, H7N9): Contact with infected poultry; high mortality; severe respiratory illness.
  • MERS-CoV: Reservoir dromedary camels; causes severe acute respiratory syndrome (SARS).
  • Zika Virus: Aedes mosquito vector; linked to microcephaly in newborns & Guillain-Barré syndrome.
  • Ebola Virus Disease: Reservoir likely fruit bats; transmission via direct contact with bodily fluids; high fatality rate.
  • SARS-CoV-2 (COVID-19): Suspected bat origin; causes acute respiratory distress syndrome (ARDS); pandemic potential demonstrated globally.

Practice Questions: Emerging Zoonotic Diseases

Test your understanding with these related questions

KFD is transmitted by:

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Flashcards: Emerging Zoonotic Diseases

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_____ is a zoonotic bacteria that forms a painful ulcer with a black base at the site of infection

TAP TO REVEAL ANSWER

_____ is a zoonotic bacteria that forms a painful ulcer with a black base at the site of infection

Francisella tularensis

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