Emerging Zoonotic Diseases

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.

⭐ 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.

Bacterial Zoonoses - Typhus & Lepto Lowdown

• Typhus Group (Rickettsial)
  • Scrub Typhus: Orientia tsutsugamushi. Vector: Chiggers. Eschar common, fever, rash. Weil-Felix (OX-K+). Rx: Doxycycline.
  • 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.

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.