Zoonosis

• zoon = animal (Gr.)
• noson = disease (Gr.)

definition

• disease of vertebral animals that can be transmitted to human, either directly or indirectly through an insect vector
  • dengue is not zoonosis
• 73% of human-affecting 1,415 pathogens are zoonotic

• exclusions
  • fish and reptile toxins
  • allergies to vertebrates
  • animal-derived food-borne
    • eg. hep A

• zooanthroponosis = non-human to human
• anthropozoonosis = human to non-human
• amphixenosis = both direction between human and non-human

• orthozoonosis = perpetuated in nature by a single vertebrate species
  • rabies (skunk in natural host), brucellosis, anthrax
• cyclozoonosis = requires more than one vertebrate species
  • cestoda (tapeworm)
• metazoonosis = requires both of vertebrates and invertebrates
  • all arboviral pathogens, some bateria (plague, rickettsia), some parasite (leischmania)

virus

Ebola and Marburg virus

• Filoviridae
• natural host of Marburg virus is almost defined as fruit bat
  • Marburg virus has been isolated from fruit bat
• natural host of Ebola virus is still not defined as fruit bat
  • viral isolation from fruit bat is required to define
  • indirect evidences have been identified
    • fragments of genome of Ebola virus have been detected from fruit bat by PCR
    • antibody against Ebola virus has been detected from fruit bat sera
    • experimental infection of Ebola virus to fruit bat was successful and bat didn't show any symptoms

Lassa virus

• endemic in western Africa
• mortality 1-2%
• 100,000-300,000 cases/year
• 5,000 deaths/year

Zika virus

• Flaviviridae
• incubation 2-12 days
• Aedes
• natural host unknown
  • rodents? non-human primates?
  • first identification was from rhesus macaque

SFTS virus

• Bunyaviridae
• first identified in China in 2011
• natural host unknown
• tick-borne

Variola virus

• first pathogen to which concept of ring vaccination was established

bacteria

Bacillus anthrasis

• anthrax
• G(-) rod, aerobic
• spore-forming, capsule-forming
• primarily infects herbivore (cattle, sheep, goat)
• no direct human to human transmission
• there is vaccine for animal
• endemic in many countries

• gastrointestinal anthrax
  • ingestion of contaminated meat
  • incubation hours to 7 days
  • fever, hematemesis, bloody diarrhea
  • mortality when untreated 25-60%
  • penicillins
• cutaneous anthrax
  • common in human; 95% of human anthrax
  • inoculation of spores under skin
  • incubation hours to 7 days
  • small itchy raised blister
  • produces ulcer and eschar
  • mortality when untreated 20%
• inhalational anthrax
  • inhalation of spores
  • most likely due to bioterror
  • incubation 1-6 days up to 43 days
  • mortality 100% despite immediate Tx