Transcript Zoonoses - USAID Natural Resource Management and

Emerging Infectious Disease,
Zoonoses and the HumanLivestock-Wildlife Health
Interface
A Primer for Conservationists
College of African Wildlife Management
Mweka, Tanzania
July 2008
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)
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)
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)
Emerging Infectious Disease
• Approximately 75% of recent emerging
infectious diseases have been zoonoses
Avian Influenza Virus
Ebola Virus
Anthrax
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
Nature Study
•EID events: 1940 - 2004
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 nonwildlife, (c) drug-resistant pathogens, (d) vector borne pathogens
Human-Livestock-Wildlife
Interface
• Food Security
• Public Health
• Conservation
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
Human-Livestock-Wildlife
Interface
• Bush Meat Trade
N. Wolfe
Human-Livestock-Wildlife
Interface
• Logging, Agricultural Encroachment, and
Wildlife Habitat Loss
NGS
Human-Livestock-Wildlife
Interface
• Wet Markets
Public Health Challenges in
Africa
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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
Zoonotic Disease
Impacts in Africa
• 70% of continent’s 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
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
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
Zoonoses
Case Studies
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Avian Influenza (H5N1)
West Nile Virus
Nipah Virus
Rift Valley Fever
Avian Influenza
• 20th century pandemics:
– 1918 (~50 million deaths globally)
– 1957 (~1 million)
– 1968 (~750,000)
• 1997: currently circulating H5N1 strain
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
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)
Vaccination
Cull
(FAO)
(FAO)
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%
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
West Nile
• Flavivirus
• Initially identified West Nile district of
Uganda 1937
• Transmission via infected mosquito
• Primary reservoir in birds
• Dead end hosts: humans, horses
West Nile
ERAP/Cornell
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
West Nile
• National
Cumulative
2007 Human
Disease Cases:
3623
USGS/CDC
The Nipah Story
• Nipah virus
– Malaysia 1999
– Paramyxovirus
– 265 people exposed on pig farms and at
slaughterhouses
– Case fatality rate of 40%
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
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
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
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
CCM
Wildlife Reservoirs
• Bats potential or proven reservoirs for:
– Rabies virus
– Ebola virus
– Lassavirus
- Nipah virus
- Rift Valley fever
- West Nile virus
• Rodents (hantaviruses, coronaviruses)
• Japanese wild boars (hepatitis E virus)
• Non-human primates (SFV, SIV)
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
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
Rift Valley Fever
• Livestock Clinical Signs:
– Fever
– Abortion
– Death (lambs/kids/calves)
• Human Clinical Signs:
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Fever
Headache
Bleeding
Malaise
USDA
CDC
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
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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
Rift Valley Fever
CDC
Rift Valley Fever
CDC
Rift Valley Fever
• Control Measures:
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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
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
Rift Valley Fever
• Interdisciplinary coordination for surveillance
and response
NGO/CBO
Government/Ministries
Tools:
Community 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
Tools:
Outbreak Control and Response
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Confirmatory Diagnosis
Case Identification
Quarantine and perimeter control
Livestock culls and destruction of contaminated
livestock products
• Compensation
• Disinfection of premises
• Vaccination Decisions
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
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