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A V I A N F L U Ginny Codd Viruses: Infection and Ecology Zoonotic Disease Rapidly emerging viral infections Zoonosis: Transmission to human from non-human vertebrate Examples in USA: Monkey pox – chimpanzee (importation as pets)

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Ginny Codd

Viruses: Infection and Ecology


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Zoonotic DiseaseRapidly emerging viral infections

  • Zoonosis: Transmission to human from non-human vertebrate

  • Examples in USA:

    • Monkey pox – chimpanzee (importation as pets)

    • Lyme disease – deer, deer mice ticks (urban expansion + proximity to deer population)

    • Hanta virus - mice

      (recall Helen’s Four corners trailer tale)

    • SARS – corona virus – quail – human

    • H5N1 – oxym virus – poultry – human


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"Habitat" of influenza A viruses. Ecological and phylogenetic studies suggest that wild waterfowl are the principal reservoirs for influenza A viruses, which occasionally are transmitted to other host animals such as horses, pigs, and chickens, leading to influenza outbreaks among these species. Some of the viruses may become established in these new hosts and cause epidemics and epizootics. Viruses are transmitted among these new host animals (e.g., between humans and pigs or between chickens and humans, as occurred in 1997 in Hong Kong).


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Potential for virulence and genetic mutation:

  • Determinants affecting pathogenicity of influenza virus

    -HA cleavability

  • -PB2 amino acid at position 627 and others

  • -NS1 protein

  • SARS(corona virus) and H5N1–both RNA viruses show ease of variation in:

    mutation + deletion + reassortment + recombination.

  • Clusters isolated in Indochina ( Cambodia, Laos, Malaysia, Thailand and Vietnam genetically and antigenetically similar

  • Clusters isolated in China, Indonesia, Japan and Sth Korea show greater genetic divergence.

  • Rapid mutation of the virus in Vietnam.


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H5N1Public Health Threat

  • Globalization:

    • Challenge in isolation of outbreaks

    • Threat to global markets – international commerce

    • International trade – livestock, birds

    • $6 billion global Illegal trade – exotic animal and plant species

  • Population Density:

    • Increased expansion and concentration:

    • increased risk of zoonotic transmission

    • greater proximity of human and non-human vertebrates.

    • Agricultural methods

    • Deforestation

  • ‘Weaponized’ virus:

    • Pathogens as biological weapon

    • Deliberate or accidental release of genetically modified highly virulent strains


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Asian Wet Markets

  • Wet markets:

    Selling of live animals, vertebrate and invertebrate at market

    • SARS ( corona virus)

    • Live Himalayan palm civet in southern China

    • H5N1

    • Live quail

      Changes in practices

      Hong Kong – aquatic birds eliminated/sold chilled

      quail eliminated

      introduction of two ‘clean days’ per month

      inactivated vaccine on poultry markets

      improved sanitation

      Indochina peninsula – greater challenge in implementing change

      geographical diversity



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Chicken

600,000 doses to chicken in Ho Chi Minh city ( april 2005)

Current practice in Hong Kong and parts of Mainland China that serve the HK market.

Human

Current methods

Egg-based manufacture ( 300+ million eggs needed annually for influenza)

6-9 months to develop

Dedendant upon effective method for production and equitable distribution

Vaccination

Potential emerging practice:

Genetic engineering of strains containing the correct prescription of genes

Reverse recombination


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Anti-virals

  • Amantadine

  • Rimantadine

  • Neuraminidase inhibitors

    -Tamiflu (oseltamivir)

    Zanamivir


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So what if ?………

  • Pandemic of immense proportion

  • 1968 pandemic: China population 790 million

    • Pig population 5.2 million

    • Poultry population 12.3.million

  • 2004 China population 1.3 billion

    • Pig population 508 million

    • Poultry population 13 billion

      If H5N1 were to mimic 98 pandemic predict 1.7 million deaths U.S.

      180 – 360 million deaths globally

  • Halt to global economy

  • Lack of medical resources

  • Inadequacy of vaccines and anti-virals

    • Production and availability.


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    What are we doing about it?

    • World health organization ( WHO)

      - meeting in Manila in May to address global concerns.

      - focus on increased surveillance

      - vaccine development

      - education and change of farming and market practices


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