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Epidemiology and Control of Zoonotic Infections

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Epidemiology and Control of Zoonotic Infections Emerging Infections: Monkeypox, Nipah virus, Avian influenza Jason Stull, CDHS, Veterinary Public Health – PowerPoint PPT presentation

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Title: Epidemiology and Control of Zoonotic Infections


1
Epidemiology and Control of Zoonotic Infections
  • Emerging Infections
  • Monkeypox, Nipah virus, Avian influenza
  • Jason Stull, CDHS, Veterinary Public Health
  • Jstull_at_dhs.ca.gov
  • 916-552-9740

2
Overview Emerging Zoonoses
  • Background
  • Examples
  • Monkeypox
  • Nipah virus
  • Avian Influenza

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Monkeypox
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Monkeypox - Background
  • Rare zoonosis found in Western and Central Africa
  • 1st identified in1958 in primates
  • Documented in numerous animal species
  • 1st human infection 1970
  • gt 400 documented human cases

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Monkeypox Virus
  • Orthopoxvirus
  • Double stranded DNA
  • Similar but distinct from Smallpox and Vaccinia

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Clinical Features - Animals
  • Fever
  • Cough
  • Ocular discharge
  • Lymphadenopathy
  • Dermal rash
  • Decreased appetite
  • Death possible

Gambian giant rat
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Clinical Features - Humans
  • Transmission - bite or contact, respiratory
    droplets
  • Incubation 10-14 days
  • Clinical signs Fever, headache, muscle aches,
    swollen lymph nodes
  • Papular rash, lesions in the same stage, milder
    than smallpox, illness lasts 2-4 weeks before
    lesions crusted
  • Rarely fatal no specific treatment
  • Smallpox vaccine is protective

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Monkeypox outbreak - 2003
  • April 9, 2003 762 African rodents imported to
    Texas ? Midwest

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Monkeypox outbreak - 2003
  • Redistribution leads to prairie dogs infected at
    pet stores

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Monkeypox outbreak - 2003
  • Infected prairie dogs infect buyers

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Monkeypox outbreak - 2003
  • 71 cases
  • 35 lab-confirmed
  • Several states
  • Median age 28 y.o.
  • 26 hospitalized, no deaths
  • 30 get smallpox vaccination

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Californias Response
  • Alerted animal-related professionals
  • Conducted onsite inspections of the 13 facilities
    possessing prairie dogs
  • CDFG permit required to possess most wildlife
  • No cases identified, illegal importation?

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NIPAH VIRUS
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Nipah Virus - Background
  • First identified in 1999 in Malaysia
  • Paramyxoviridae
  • Single stranded RNA virus
  • Natural host Fruit Bats (Flying Fox)

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Nipah Virus Malaysia and Singapore Outbreak
  • Sept 1998-April 1999
  • 265 human cases
  • 105 Deaths
  • 93 Pig farm/abattoir workers
  • gt900,000 pigs culled

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Nipah Virus Epidemic Curve
Update Outbreak of Nipah Virus -- Malaysia and
Singapore, 1999 MMWR, 199948
29
Nipah Virus - Transmission
  • Flying Foxes

Pigs
?
Humans
?
Close contact
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Nipah Virus - Animal Disease
  • Natural Reservoir - Fruit bats
  • Asymptomatic
  • Virus in urine
  • Pigs
  • Other animals
  • Cats
  • Dogs
  • Horses

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Nipah Virus - Human Disease
  • Incubation 3 to 14 days
  • Symptomatic cases
  • Onset influenza-like illness
  • Progresses to encephalitis
  • 40 fatal if symptomatic
  • Treatment
  • Supportive care
  • Ribavirin (efficacy?)

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Nipah Virus - Human Disease
  • Live virus found in human respiratory secretions
    and urine
  • No known human-to-human transmission during
    outbreak
  • Relapse encephalitis (12 cases)
  • Late-onset encephalitis (10 cases)
  • Mean time for complications 8.4 months

33
Nipah Virus - Diagnostic Tests
  • Serology
  • Immunohistochemistry
  • MRI
  • Histopathology
  • Vasculitis
  • Endothelial damage
  • Characteristic viral inclusions

34
Nipah Virus Control Prevention
  • Swine control
  • Slaughter
  • Transportation bans
  • Education
  • Protective equipment
  • Surveillance to detect swine and human cases

35
Nipah Virus Continues
  • Outbreaks in 2001 and 2003 in Bangladesh
  • 25 cases
  • No obvious zoonotic source
  • Transmission
  • Close contact with other patients?
  • Exposure to common source?

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Avian Influenza
See presentation by Dr. Janice Louie, Key
Microbial Threats Seasonal and Pandemic
Influenza CIDER (Feb 1, 2005) Web-cast
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Influenza - Background
  • Orthomyxoviridae family
  • Gene segments can re-assort
  • Infected species include birds, pigs, humans,
    horses and sea mammals.

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Influenza - Key Viral Features
  • Surface proteins
  • Hemagglutinin (HA)
  • Site of attachment to host cells
  • Antibody to HA is protective
  • Neuraminadase (NA)
  • Helps to release virions from cells
  • Antibody to NA can help modify disease severity

NA
HA
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Genetic Changes
  • Drift constant small genetic changes caused by
    natural selection when antibodies to virus are
    made
  • Partial antibody protection
  • May result in epidemic
  • Shift- abrupt, major genetic change creating new
    hemagglutinin and/or neuraminidase proteins
  • Little or no antibody protection
  • May result in pandemic

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The Ultimate Mixing Vessel?
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Virus Classification - Birds
  • Low Pathogenic (LPAI)
  • Most AI virus strains
  • Cause little or no clinical disease
  • Can mutate to HPAI
  • Highly Pathogenic (HPAI)
  • Highly infectious to chickens
  • Can inflect flocks without warning
  • Spreads rapidly in flocks and flock to flock
  • Morbidity and mortality can approach 100
  • Death within 12 days of onset

Source USDA, APHIS
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Influenza - Birds
  • Clinical signs
  • Decline egg production
  • Mild respiratory disorder
  • Chronic respiratory infection
  • Death
  • Diagnosis serology, egg inoculation
  • Control
  • Management is best prevention (Biosecurity)
  • De-population
  • Vaccinate?

50
Influenza A - Birds
  • Outbreaks occur throughout the world
  • Low pathogenic avian influenza
  • Limited to poultry
  • Sporadic
  • Recently in U.S.
  • Texas (2004) H5N2
  • Maryland (2004) H7N2
  • Pennsylvania (2004) H2N2
  • Delaware New Jersey (2004) H7N2

51
Influenza - Animal Transmission
  • Migratory waterfowl natural reservoir
  • Initial source of infection
  • Poultry, migratory waterfowl, domestic pigs, pet
    birds
  • Shed by feces, nasal secretions, saliva
  • Aerosol
  • Shared drinking water
  • Fomites

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Influenza - Humans
  • Transmission
  • Droplets/aerosol, contact
  • Incubation 1-4 days
  • Shedding day before onset to 5 days after
  • Acute febrile respiratory illness
  • Symptoms may differ by age
  • Types A and B viruses cause substantial illness
    and death among humans

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Impact of Influenza - Humans
  • Seasonal epidemics in temperate regions
  • U.S., Canada, Europe, Russia, China, Japan,
    Australia, Brazil, Argentina
  • Year-round activity in tropical climates
  • Equatorial Africa, Southeast Asia
  • U.S. impact
  • Average of gt200,000 influenza-related
    hospitalizations/year
  • Average of gt36,000 influenza-related deaths/year
  • 3 global pandemics in the 20th century

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H5N1 in Asia, 2003-05
  • Unprecedented highly pathogenic avian influenza A
    (H5N1) outbreak among poultry
  • Farms, backyard flocks affected
  • Millions of chickens, ducks died gt100 million
    culled

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H5N1 in Asia, 2003-05
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H5N1 in Asia - Human cases
  • Cumulative of confirmed cases (Jan. 2004 Feb.
    2, 2005)
  • Cambodia 1 case (1 death)
  • Thailand 17 cases (12 deaths)
  • Vietnam 37 cases (29 deaths)
  • Total 55 cases (42 deaths)
  • Most cases had contact with sick or dead poultry
  • Majority of cases children, young adults
  • Viruses resistant to antiviral drugs amantadine,
    rimantadine (susceptible to oseltamivir)
  • No evidence of sustained human-to-human
    transmission

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Additional H5N1 Issues
  • Can infect cats
  • domestic
  • tigers, leopards (Thailand)
  • Can infect pigs
  • Ducks may be infected without illness

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U.S. Surveillance for H5N1
  • Testing for avian influenza (H5N1) should be
    considered for hospitalized or ambulatory
    patients with
  • a.   Documented temperature of gt38C (gt100.4F),
    AND
  • b.   One or more of the following cough, sore
    throat, shortness of breath, AND
  • c.   History of contact with poultry (e.g.,
    visited a poultry farm, a household raising
    poultry, or a bird market) or a known or
    suspected human case of influenza A (H5N1) in an
    H5N1-affected country within 10 days of symptom
    onset.

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Avian Influenza - Public Health
  • Can spread from poultry to humans
  • Genetic re-assortment ? virus more easily
    transmitted among people
  • Infection is uncommon, but preventive measures
    are critical
  • If sustained human-human transmission

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Prediction Prevention of Emerging Zoonoses
  • Enhanced communications across disciplinary and
    agency boundaries
  • Assessment/development of surveillance tools
  • Examination of link between animal-human health
    outcomes
  • Cross-disciplinary training and research

Perspectives on emerging zoonotic disease
research Can Vet J, 20054665-78
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