Emerging Infectious Disease, Zoonoses and the HumanLivestockWildlife Health Interface

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Emerging Infectious Disease, Zoonoses and the
Human-Livestock-Wildlife Health Interface

• A Primer for Conservationists

College of African Wildlife Management Mweka,
Tanzania July 2008
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19-year-old Egyptian Dies of Avian Flu (Bloomberg)

• Anthrax Claims 20 Cows, Cattle Market Closed (New
  Indian Express)

Two Die in Spain from Human Form of Mad Cow
Disease (Reuters)
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Emerging Infectious Disease

• Emerging Infectious Disease
• An infectious disease that has newly appeared in
  a population or is rapidly increasing in
  incidence or geographic range
• On average, 1 newly identified infectious disease
  every year for each of the last 30 years (WHO)

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Zoonoses

• Zoonotic Disease
• Disease entities readily transmissible between
  human and animal populations

• Avian Influenza
• Severe Acute Respiratory Syndrome (SARS)
• Monkeypox virus
• Rabies virus
• Brucellosis
• Ebola virus
• West Nile virus
• Nipah virus
• Bovine tuberculosis (mycobacterium bovis)

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Emerging Infectious Disease

• Approximately 75 of recent emerging infectious
  diseases have been zoonoses

Ebola Virus
Anthrax
Avian Influenza Virus
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Nature Study

• 335 emerging infectious diseases identified
  between 1940 and 2004
• Outbreaks were positively correlated with growing
  population densities
• US/Europe had highest frequency of reported
  outbreaks Why?
• 60.3 were zoonoses
• 71.8 of these originated in wildlife
• Jones, Patel, Levy, et. al. Nature, 2008 Feb. 21
  451 (7181)990-3

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Nature Study

• EID events 1940 - 2004

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Nature Study

• Regression analysis adjusted for
• Human population density and growth
• Rainfall
• Latitude
• Wildlife host species richness

Global Distribution of Relative Risk of an EID
Event (a) zoonotic pathogens from wildlife, (b)
zoonotic pathogens from non-wildlife, (c)
drug-resistant pathogens, (d) vector borne
pathogens
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Human-Livestock-Wildlife Interface

• Food Security
• Public Health
• Conservation

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Human-Livestock-Wildlife Interface

• Global Commerce in Livestock Products
• Increased Demand for Animal Protein
• Loss of Wildlife Habitat
• Ecosystem Degradation
• Cleared Land for Agricultural Use

• Increased Opportunity for Human-Animal
  Interaction

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Human-Livestock-Wildlife Interface

• Bush Meat Trade

N. Wolfe
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Human-Livestock-Wildlife Interface

• Logging, Agricultural Encroachment, and Wildlife
  Habitat Loss

NGS
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Human-Livestock-Wildlife Interface

• Wet Markets

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Public Health Challenges in Africa

• Poverty/malnutrition
• Lack of infrastructure
• Inadequate water and sanitation
• Difficulty accessing medical care
• Weak public health services
• /- post-conflict
• High degree of human/animal co-existence

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Zoonotic DiseaseImpacts in Africa

• 70 of continents rural poor are linked to
  livestock production ( 200 million people)
• Population is exquisitely vulnerable
• Loss of livelihoods associated with livestock
  disease/disease control efforts (cull/quarantine)
• Threats to human health
• Contribute to entrenched cycles of illness,
  malnutrition and poverty

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Non-Zoonotic Livestock Disease Impacts

• Foot and Mouth Disease
• Endemic in Tanzania
• Costs
• Loss of livelihoods/poor productivity
• Loss of export markets movement restrictions
• Direct threats to wildlife health
• Others Rinderpest, African Swine Fever
• Threats to Domestic and International
• Food Security
• Biodiversity
• Economic Development

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Threats to Biodiversity Conservation

• Why should conservationists be concerned about
  zoonoses and emerging infectious disease?

• Direct threats to wildlife health
• Direct threats to human health (loss of
  conservation capacity)
• Threats to food security (increased use of bush
  meat)
• Threats to livelihoods (contributing to
  unsustainable land use practices)
• Threats to ecotourism initiatives

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ZoonosesCase Studies

• Avian Influenza (H5N1)
• West Nile Virus
• Nipah Virus
• Rift Valley Fever

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Avian Influenza

• 20th century pandemics
• 1918 (50 million deaths globally)
• 1957 (1 million)
• 1968 (750,000)
• 1997 currently circulating H5N1 strain

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Avian Influenza

• Influenza A, H5N1
• Extensive list of susceptible hosts
• Currently Bird ? Bird and Bird ? human
  transmission
• No demonstrated, sustained human to human
  transmission to date

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Avian Influenza

• Pandemic potential
• Rapid viral mutation rates
• Recombination event between HPAI and seasonal flu
• Pandemic influenza poses significant public
  health risk
• No pre-existing immunity to H5N1 in human
  population
• Isolates have demonstrated some anti-viral
  resistance
• Vaccine has been developed, but may not cover
  pandemic strain
• Difficulty of containment
• Projected Pandemic Costs
• 10-180 million deaths worldwide
• Economic Impact 2-3.1 of global GDP (2
  trillion USD) (World Bank)

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Vaccination (FAO)
Cull (FAO)
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West Nile

• August 1999, New York City
• Case clusters of human meningoencephalitis
• 59 patients presented with clinical signs of
  muscle weakness, encephalitis, paralysis
• Case fatality rate of 12

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West Nile

• June, unusual crow die-off observed at Bronx Zoo
• July, veterinarians examined birds with
  neurologic signs
• September, tissue samples positive for WN-like
  virus
• Subsequent months bird die-offs in adjacent
  states (CT, NJ, NY)
• Both human cases and bird-die offs were linked to
  West Nile via identical WN viral genomic
  sequences isolated from bird and human cases

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West Nile

• Flavivirus
• Initially identified West Nile district of Uganda
  1937
• Transmission via infected mosquito
• Primary reservoir in birds
• Dead end hosts humans, horses

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West Nile
ERAP/Cornell
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West Nile

• First documented incidence of West Nile virus in
  the Western Hemisphere
• Within 3 years, had become endemic throughout all
  48 contiguous states, Canada and Mexico
• Role of migrating birds

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West Nile

• National Cumulative 2007 Human Disease Cases 3623

USGS/CDC
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The Nipah Story

• Nipah virus
• Malaysia 1999
• Paramyxovirus
• 265 people exposed on pig farms and at
  slaughterhouses
• Case fatality rate of 40

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The Nipah Story

• Pigs showed mild clinical signs of neurologic and
  respiratory disease
• Human cases presented with fever, headache, signs
  consistent with encephalitis
• 93 of human cases had occupational exposure to
  infected pigs suggesting transmission was via
  direct contact with pigs

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The Nipah Story

• Pork production recently had expanded in Malaysia
• Land had been cleared and farms established in
  close proximity to rainforest
• Prime bat habitat
• Farm on which Nipah outbreak occurred had fruit
  orchards adjacent to the pens
• Increased transmission opportunities between bats
  and pigs

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The Nipah Story

• Suspected that excreta (saliva/feces/urine) of
  bats overhanging pens exposed pigs
• Pigs were present at such high stocking densities
  on the farm that they served as amplifiers of the
  virus
• Humans infected from close contact with pigs
• Social, environmental factors framed the outbreak
• Outbreak cost the Malaysian government 450
  million USD

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The Nipah Story

• Fruit bats subsequently identified as the
  reservoir of Nipah in Malaysia
• Bats are silent carriers of the virus
• Bats -- Pigs -- Humans

CCM
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CCM
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Wildlife Reservoirs

• Bats potential or proven reservoirs for
• Rabies virus - Nipah virus
• Ebola virus - Rift Valley fever
• Lassavirus - West Nile virus
• Rodents (hantaviruses, coronaviruses)
• Japanese wild boars (hepatitis E virus)
• Non-human primates (SFV, SIV)

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Rift Valley Fever

• Virus (Phlebovirus)
• First identified in Kenya, 1930
• Domestic livestock (cattle, small ruminants,
  camels) and humans susceptible
• Transmitted by
• Mosquitoes
• Direct exposure to infected tissues
• Outbreaks typically follow heavy rainfall

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Rift Valley Fever
CDC
Countries with endemic disease and substantial
outbreaks of RVF
Countries known to have some cases, periodic
isolation of virus, or serologic evidence of RVF
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Rift Valley Fever

• Livestock Clinical Signs
• Fever
• Abortion
• Death (lambs/kids/calves)
• Human Clinical Signs
• Fever
• Headache
• Bleeding
• Malaise

USDA
CDC
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Rift Valley Fever

• Prior outbreak Kenya 1997-1998
• Associated with heavy rains/flooding
• 89,000 people infected (seroprevalence survey)
• 478 deaths
• Kenya outbreak November 2006-January 2007
• Followed unusually heavy rains (3x national
  average)
• Human cases 404
• Deaths 118
• Case fatality rate 29
• Greatest risk factor for human infection was
  interaction with livestock

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Rift Valley Fever
CDC
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Rift Valley Fever
CDC
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Rift Valley Fever

• Control Measures
• Movement restrictions/quarantine
• Slaughter ban/meat inspection
• Livestock vaccination
• Public outreach/education/radio
• Impacts
• Loss of livelihoods/income (markets closed)
• Nutritional/dietary (slaughter ban/? meat price
  leading to ? bush meat consumption)
• Broader Economy (trade restrictions/control
  costs)
• Wildlife health (impacts on wild ruminants
  unknown)

BBC
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Rift Valley Fever

• Proactive Solutions
• Climate forecasting to predict where heavy rains
  may predispose to RVF outbreak
• Rainfall predictions coupled with livestock
  disease surveillance may provide a functional
  early warning system
• Education of high risk populations
• Use of mosquito nets/repellent
• Avoiding contact with suspect animals/animal
  tissues
• Thorough cooking of meat/dairy products

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Rift Valley Fever

• Interdisciplinary coordination for surveillance
  and response

NGO/CBO
Government/Ministries
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ToolsCommunity Based Surveillance

• Train community members to detect and report
  cases using standard diagnostic criteria
• Strengths
• Improves diagnostic sensitivity
• Allows real-time ongoing monitoring with minimal
  resources at minimal cost
• Fosters community education and awareness
• Weaknesses
• First stage in outbreak detection laboratory or
  health worker confirmation needed
• Requires good communication/chain-of-command

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ToolsOutbreak Control and Response

• Confirmatory Diagnosis
• Case Identification
• Quarantine and perimeter control
• Livestock culls and destruction of contaminated
  livestock products
• Compensation
• Disinfection of premises
• Vaccination Decisions

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The Way Forward

• Understanding the complex factors that lead to
  disease emergence
• Social (poverty instability)
• Economic (livestock wildlife trade)
• Environmental (ecosystem degradation climate
  change)
• Improve data collection/analysis/sharing
• Empower communities to proactively monitor and
  rapidly respond
• Multi-disciplinary approach

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Additional Resources

• ProMED Mail www.promedmail.org
• World Organization for Animal Health (OIE)
  www.oie.int
• Centers for Disease Control and Prevention
  www.cdc.gov
• Google Predict and Prevent Initiative
  www.google.org
• HealthMap www.healthmap.org/en
• Consortium for Conservation Medicine
  www.conservationmedicine.org