Title: Epidemiology and Control of Zoonotic Infections
1Epidemiology 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
2Overview Emerging Zoonoses
- Background
- Examples
- Monkeypox
- Nipah virus
- Avian Influenza
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11Monkeypox
12Monkeypox - 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
13Monkeypox Virus
- Orthopoxvirus
- Double stranded DNA
- Similar but distinct from Smallpox and Vaccinia
14Clinical Features - Animals
- Fever
- Cough
- Ocular discharge
- Lymphadenopathy
- Dermal rash
- Decreased appetite
- Death possible
Gambian giant rat
15Clinical 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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19Monkeypox outbreak - 2003
- April 9, 2003 762 African rodents imported to
Texas ? Midwest
20Monkeypox outbreak - 2003
- Redistribution leads to prairie dogs infected at
pet stores
21Monkeypox outbreak - 2003
- Infected prairie dogs infect buyers
22Monkeypox 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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24Californias 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?
25NIPAH VIRUS
26Nipah Virus - Background
- First identified in 1999 in Malaysia
- Paramyxoviridae
- Single stranded RNA virus
- Natural host Fruit Bats (Flying Fox)
27Nipah Virus Malaysia and Singapore Outbreak
- Sept 1998-April 1999
- 265 human cases
- 105 Deaths
- 93 Pig farm/abattoir workers
- gt900,000 pigs culled
28Nipah Virus Epidemic Curve
Update Outbreak of Nipah Virus -- Malaysia and
Singapore, 1999 MMWR, 199948
29Nipah Virus - Transmission
Pigs
?
Humans
?
Close contact
30Nipah Virus - Animal Disease
- Natural Reservoir - Fruit bats
- Asymptomatic
- Virus in urine
- Pigs
- Other animals
- Cats
- Dogs
- Horses
31Nipah 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?)
32Nipah 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
33Nipah Virus - Diagnostic Tests
- Serology
- Immunohistochemistry
- MRI
- Histopathology
- Vasculitis
- Endothelial damage
- Characteristic viral inclusions
34Nipah Virus Control Prevention
- Swine control
- Slaughter
- Transportation bans
- Education
- Protective equipment
- Surveillance to detect swine and human cases
35Nipah 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?
36Avian Influenza
See presentation by Dr. Janice Louie, Key
Microbial Threats Seasonal and Pandemic
Influenza CIDER (Feb 1, 2005) Web-cast
37Influenza - Background
- Orthomyxoviridae family
- Gene segments can re-assort
- Infected species include birds, pigs, humans,
horses and sea mammals.
38Influenza - 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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40Genetic 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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46The Ultimate Mixing Vessel?
47Virus 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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49Influenza - 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?
50Influenza 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
51Influenza - 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
52Influenza - 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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54Impact 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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58H5N1 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
59H5N1 in Asia, 2003-05
60H5N1 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
61Additional H5N1 Issues
- Can infect cats
- domestic
- tigers, leopards (Thailand)
- Can infect pigs
- Ducks may be infected without illness
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63U.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.
64Avian 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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66Prediction 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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