Zoonotic Viral Diseases

Question 1

Characteristics of emerging nad reemerging infectious diseases around the world

Answer 1

1. Emerging infections are a global problem and occur in both temperate and tropical regions
2. Most emerging and re-emerging infectious diseases are zoonotic diseases
3. Incredible diversity in types of zoonotic pathogens and the diseases they cause in humans

Question 2

Factors that contribute to emergence/re-emergence of viral diseases

Answer 2

• Improved detection and dx: “Emerging Dx”
• Viral genetic changes: alters properties such as virulence, tropism, transmission
  
  • Mutations in the spike glycoprotein of SARS-CoV enhanced human infection
• • Human susceptibility to infection
• International travel and commerce
  
  • Global spread of Ae. albopictus mosquitoes in old tires
• • Changes in populations of reservoir hosts or vectors
• • Human demographics (e.g. population density, activity)
• Poverty
• • Climate, changing ecosystems
• • Changing land use and agricultural practices

Question 3

Zoonotic viruses that are also human pathogens

Answer 3

• Rabies virus
• Hantaviruses (Sin Nombre)
• Filoviruses (Ebola & Marburg)
• Arenaviruses (Junin, Machupo, & Lassa)
• Paramyxoviruses (Nipah & Hendra)
• Arboviruses
• HIV
• Influenza virus
• MERS-CoV

Question 4

Common zoonotic diseases present in CO

Answer 4

• Rabies
• Hantavirus
• Colorado Tick Fever
• West Nile Virus

Question 5

Characteristics of Rabies

Answer 5

• Global Distribution
• Disease transmitted to humans via the bite of a rabid animal
• Without treatment = Uniformly fatal
• Rabies is completely preventable both before and after infection • Immunization and post-exposure prophylaxis

Question 6

Rabies prevention

Answer 6

• Vaccination of companion animals:
  
  • • Annual turnover of dog population necessitates revaccination of millions of animals each year
  • ==> elimination of canine rabies in US
• Animal control programs and surveillance
• Maintenance of rabies laboratories
• Avoiding common reservoirs
  
  • bats
  • skunks
  • racoons

Question 7

Clinical presentation of Rabies

Answer 7

• Prolonged incubation phase 1-3 months
• Two major forms: Both begin with nonspecific symptoms (fever, headache, nausea)
• • Furious (encephalitic) form (80%) •
  
  • Difficulty swallowing
  • Hydrophobia
  • Episodes of hallucination
  • Hypersalivation
  • Brain stem dysfunction-coma-death
• Paralytic form (20%) • Lack of major features of furious form • Quadriparesis • Multiple organ failure-death

Question 8

Tx of Rabies

Answer 8

• Treatment of animal wounds:
  
  • • Immediately wash with soap (detergent) and water
• Human rabies virus immunoglobulin (HRIG)
  
  • • Passive-immunization around area of wound—neutralize virus
• • Rabies virus vaccine (4 dose vaccine schedule)
  
  • Inactivated vaccine
  • • Administered IM at different site than HRIG
  • • Additional doses at days 3, 7, and 14 (New 2010 recommendations)

Question 9

Algorithm for rabies tx

Answer 9

Question 10

Hantavirus characteristics

Answer 10

• Human infection primarily due to exposure to aerosols of rodent urine
• Causative agents of two major diseases in humans: • Hemorrhagic fever with renal syndrome (HFRS) • Hantavirus pulmonary syndrome (HPS)
• Family of viruses ==> disease
• Common virus in N.A. = “Sin Nombre” and is carried by deer mouse

Question 11

Clinical presentaiton of hantavirus pulmonary sydnrome

Answer 11

• Prodromal phase characterized by: Fever Chills Myalgia
• Clinical recognition of HPS prodrome:
  
  • Pain in legs and back can be very severe
  • Presence of productive cough at onset of illness is NOT consistent with HPS
  • Laboratory findings:
    
    • • Low platelet count
    • • Neutrophilia
    • • Elevated LDH and AST
  • • Rodent exposure: increase in mouse populations around their residence or exposure to mice-infested areas

Question 12

Treatment of HPS

Answer 12

• No specific anti-viral therapy or vaccines available
• • Treatment options limited
  
  • • Supportive Care
  • • Assisted Respiration
  • • Blood oxygenation in severe cases •
• Outcomes significantly improved when:
  
  • • Early recognition of disease (symptoms + rodent exposure)
  • • Immediate hospitalization in ICU
  • • Adequate support for breathing

Question 13

Zoonotic viruses that transmit from animals to humans and can cause limited cycles of human to human transmission

Answer 13

• Lassa fever virus
• Machupo virus
• Ebola virus
• Marburg virus
• Nipah virus
• Monkeypox

Question 14

Major zoonotic viruses that have some person-person transmission + region + host + disease

Answer 14

• Lassa virus (Arenaviridae virus)
  
  • W. Africa
  • Rodent host
  • ==> hemorrhagic fever
• Ebola (filoviridae virus)
  
  • Africa
  • Bat host
  • ==> hemorrhagic fever
• Nipah (paramyxociridae virus)
  
  • Asia
  • Bat host
  • ==> respiratory/neurologic syndrome

Question 15

Originated or persist in animals but can cause self-sustaining chains of transmission in humans (human to human OR vector to human)

Answer 15

• HIV
• Influenza virus
• SARS- and MERS-CoV
• Yellow Fever virus
• Dengue virus
• Chikungunya virus