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Lesson 9: Zoonotic Diseases May 2, 2006
ENV 150: Intro. to Environmental Health 1
ENV H 311: Lesson 9 1
Lesson 9. Vector Control
ZoonoticDiseases
Chuck TreserChuck TreserUniversity of WashingtonUniversity of Washington
Dept. of Environmental andDept. of Environmental and
Occupational Health SciencesOccupational Health Sciences
May 2, 2006May 2, 2006
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Lesson Overview
Definitions
The Problem
Causal Factors
Control Measures
Example
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Definitions
Pest: Serious or fatal disease (archaic)
Pestilence: Any, usually fatal, epidemicdisease
Zoonotic Disease: Diseases transmittedfrom vertebrate animals to humansthrough various routes
Pets
Livestock
Wildlife
Lesson 9: Zoonotic Diseases May 2, 2006
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ENV H 311: Lesson 9 4
Definitions Continued
Vector:
An arthropod which carries a pathogento a new host
Any organism which helps a pathogenreach a new host
An animate vehicle
Vectorborne Disease: Diseasestransmitted by a vector
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Zoonotic Diseases
Poultry 26
Rodents 32
Horse 35
Pig 42
Sheep/Goats 46
Cattle 50
Dog 65
Table 3.2 Number of Diseases that Human PopulationsShare with Domesticated Animals
Source: McNeil WH. Plagues and People, 1977
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Zoonotic Disease Transmission
Direct Contact
Transmission by Vectors
Lesson 9: Zoonotic Diseases May 2, 2006
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Direct Animal Contact
Disease agent found in saliva, blood,other body tissues
Bites, scratches
Contact with animal tissues or fluids(open cuts or on mucous membranes)
livestock - veterinarians, farmers
wildlife - handling dead or ill animals,field specimen collections
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Direct Animal Contact
Anthrax - Handling sheep, other animals
Plague - trappers skinning animals, blood or tissuecontact, also flea bites
Brucellosis - livestock tissue contact
Ringworm - fungal infection (young kittens,puppies)
Rabies - bites, scratches (virus found in saliva,salivary glands, nerve tissue only)
Rat bite fever - (Streptococcal bacterial infection)
Tularemia - rabbits, hares, rodents(also transmitted via other routes)
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For Example
~900 Salmonella cases reportedannually in Washington
Difficult to identify source of exposurefor every case
Most probably are foodborne
Unknown percentage due to animal contact
Some waterborne, some person-to person
Need good thorough investigations
Consider animal exposure
Lesson 9: Zoonotic Diseases May 2, 2006
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Salmonella Sources
High percentage of reptiles (snakes,lizards, turtles) naturally carry Salmonellawithout signs of illness
Serious cases in infants,immunocompromised, elderly
Any animal food product may harborSalmonella
Outbreaks: Denver Zoo, Oregon infantcases, petting zoos
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Transmission by Vectors
Ticks, mosquitoes, fleas, flies acquiredisease agent from animal reservoir andtransmit it to another host
Natural host is not affected by the agent
Accidental host may be severely ill or die
Washington - low incidence of reportedvector-borne diseases
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The Vector Problem
Nuisance
Property damageCrops
Structures
Goods
Human disease
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Nuisance
Each year . . .
American consumers spend$600,000,000 on pest control
60% is spent in the residential market
$2.9 Billion is spent on professionalpest control
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Economic Impact
Each year . . .
1/3 of the world’s crops are destroyedduring growth, harvesting and storage
25% of home gardener’s cropsdestroyed
$20 Billion in crop loss/damage
Residential damage = ???
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Important Zoonotic &Vectorborne Diseases
ArboviralEncephalitides
Dengue
Hantavirus
Lyme Disease
Malaria
Plague
Rabies
RMSF
Tularemia
Typhus (Epidemic)
Typhus (Murine)
Yellow Fever
Lesson 9: Zoonotic Diseases May 2, 2006
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On the web…
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United States, Selected Years 1990 - 2002
Vectorborne Disease
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Vectorborne Disease
Lesson 9: Zoonotic Diseases May 2, 2006
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Vectorborne Disease
WNV
Total
US Cases,
2003
9,862
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Vectorborne Disease
WNV
Total
US Cases,
2004
2231
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Generalized Vector Cycle
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Vectorborne Disease Ecology
The agent becomes established in ananimal population
The animal population comes intocontact with man
(one or the other, or both, move)
The vector must be able to transmitthe agent to humans
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Disease Ecology Continued
Epizootic conditions prevailSufficient numbers of infective vectors
Appropriate climatic conditions existTemperature range
Humidity
Rainfall
Confluence of all of these factors isnecessary
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Important Vectors
ArthropodsMosquitoes
Other flies
Fleas
Ticks
Lice
Mites
Other Animals
Rats
Mice
Bats
Birds
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Transmission
Mechanical
Biological
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Tickborne Diseases
Lyme disease
Relapsing fever
Tularemia
Ehrlichiosis
Babesiosis
Rocky Mountain Spotted fever
Tick paralysis (intoxication)
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Rocky Mountain Spotted Fever
Lesson 9: Zoonotic Diseases May 2, 2006
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Rocky Mountain Spotted Fever
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Rocky Mountain Spotted Fever
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Rocky Mountain Spotted Fever
Rocky Mountain Spotted Fever in Washington
0
1
2
3
4
5
6
7
8
9
10
1920
1923
1926
1929
1932
1935
1938
1941
1944
1947
1950
1953
1956
1959
1962
1965
1968
1971
1974
1977
1980
1983
1986
1989
1992
1995
1998
reported cases
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Diseases Transmitted by
Flies
Tularemia - deer fly bites
Mechanical transmission of entericbacteria (Salmonella, Shigella,Campylobacter)
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Tularemia
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Tularemia
1990-2000
• 1,368 cases of
• from 44 states
• ~ 124 cases/year
• Range = 86-193
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Tularemia
Tularemia in Washington
0
1
2
3
4
5
6
7
8
9
1929
1931
1933
1935
1937
1939
1941
1943
1945
1947
1949
1951
1953
1955
1957
1959
1961
1963
1965
1967
1969
1971
1973
1975
1977
1978
1981
1983
1985
1987
1989
1991
1993
1995
1997
1999
2001
reported cases
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Fleaborne Diseases
Bartonellosis -formerly cat scratch fever
Tapeworms
Plague - (1984) one human case inWashington
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Plague
Early 1330san outbreak ofbubonic plagueoccurred in China
Spread to westernAsia and Europe
Sicily, October of1347
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Plague
1348: spread as farnorth as England
25 million peopledied in 5 years
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Plague
Estimated popu-lation of Europefrom 1000 to1352:
1000 ~ 38 million
1100 ~ 48 million
1200 ~ 59 million
1300 ~ 70 million
1347 ~ 75 million
1352 ~ 50 million
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London, 1665-1666
Disappeared after1352
Until the mid-17thcentury
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Plague in the U.S.
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So What?
Historically interesting
But things are differenttoday, right?
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Plague: Distribution
Countries reporting plague: 1970 - 1995
Probable foci
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Plague in the U.S.
Reported humanplague cases bycounty
1970 - 1997.
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Plague: Incidence
Number of Human Plague CasesUnited States, 1970 - 1995
No
. o
f C
ase
s
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Plague Incidence
MT OK WA WY ID TX NV UT OR CA CO AR NM
1944-53
1954-63
1964-73
1974-83
1984-93
0
20
40
60
80
100
120
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Plague
Agent: Yersinina pestis (bacterium)
Vector: Xenopsylla cheopis(Oriental Rat Flea)
Reservoir: Rattus Norvegicus andRattus rattus (Norway and Roof Rats)
Onset: 2 -6 days after being bitten
Disease: Bubonic, Pneumonic &Septicemic
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Bubonic Plague
High Fever
Toxemia
Petechiae
Shock
Buboes
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Plague: Agent
Yersinia pestis
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Plague: Transmission
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Plague: Vectors
Oriental Rat Flea
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Plague: Vectors - Cont’d.
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Plague: Vectors - Cont’d.
Life cycle of the flea
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Reservoir
UrbanUrban
RuralRural
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Mosquitoborne Diseases
Western equine encephalitis virus
St. Louis encephalitis virus
Both have occurred in Washington but noreported cases since early 1980’s
West Nile virusdetected in 1999 in New York City
human and horse deaths, dead birds
progressing to other states in 2000
Planned surveillance effort in Washington
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Malaria
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Malaria
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Malaria
Malaria Incidence in Washington
0
10
20
30
40
50
60
70
1947
1949
1951
1953
1955
1957
1959
1961
1963
1965
1967
1969
1971
1973
1975
1977
1978
1981
1983
1985
1987
reported cases
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West Nile Virus
Incidental
infections
Bird
reservoir
hosts
Incidental infections
Mosquito vector
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1
10
100
1000
10000
1964
1966
1968
1970
1972
1974
1976
1978
1980
1982
1984
1986
1988
1990
1992
1994
1996
Y e a r
No
.of
Cases
EEE
Cal
SLE
WEE
Arboviral DiseasesUnited States 1964 - 1996
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66-7071-75
76-8081-85
86-9091-95
96-97
EEE
Cal
SLE
WEE
0
500
1000
1500
2000
2500
No.
of
Cases
Y e a r s
EEE
Cal
SLE
WEE
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EEE Cases
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WEE Cases
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LaCrosse Cases
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SLE Cases
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SLE Cases
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Causal Factors
A “good” vector must:
Be able to harbor the agent
Be able to spread the agent
Be mobile
Survive long enough to:Reproduce
Disseminate the agent
Have wide zonal tolerances
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Emerging Diseases
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Protecting the Public’s Health
Surveillance
Personal Protection and Education
Vector Control
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Zoonotic Disease Program
Education/technical assistanceprevention information
Case investigation (human andanimal)
SurveillanceHuman and animal cases
Animal reservoir, arthropod vectors
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Personal Protection
Wear long sleeves & pants in mosquito-infested areas
Use repellant containing DEET (N,N-diethyl-3-methylbenzamide) and followdirections carefully
Limit outdoor activities at dawn and earlyevening
Repair holes in door & window screens
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Control
Usually involves controlling thevector
Habitat reduction / modification
Sanitation
Larvaciding
Adulticiding
Integrated Pest Management (IPM)
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To Control Vectors
Deny them:
Water
Food
Harborage
Warmth
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Surveillance
What does it mean?
Human and animal caseswho, when, where, how
Prevalence studies
reservoir animals
arthropods (ticks, mosquitoes)
Population monitoring
Species distribution
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For Example
WNV Surveillance:
Dead birdsEspecially crows, jays, magpies
Mosquitoes
Captive sentinels (e.g. chickens)
Veterinary surveillance
Human surveillance
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Estimated Sensitivityof WNV Surveillance Methods
Human cases
Veterinary cases
Mosquitoes
Dead birds
Time
Dis
ease A
cti
vit
y
Sentinel hosts
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Packed with
dry ice in
preparation for
trapping.
EVS Mosquito Traps
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Setting the
trap in proper
location.
EVS Mosquito Traps
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In operation.
EVS Mosquito Traps
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WNV Mosquitoesin Washington
1Ochlerotatus japonicus
5Ochlerotatus canadensis
10Coquilletidia perturbans
26Anopheles punctipennis
35Culex tarsalis
1Culex restuans
28Culex pipiens
27Aedes vexans
29Aedes cinereus
Counties (39)Mosquito species
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Tick Surveillance
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Rodent Surveillance
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Rodent Surveillance
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Control Measures
Appropriate for pest
Acceptable to community
IPM approach
Good records
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Control Measures Continued
Arthropods
Sanitation
Environmental modifications
Pesticides
Larvicides
Adulticides
Repellants
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Control Measures Continued
Rodents
Sanitation
Environmental modificationsRodent proofing
Trapping
Rodenticides
Lesson 9: Zoonotic Diseases May 2, 2006
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Integrated Pest Management(IPM)
Physical Control
Mechanical Control
Biological Control
Chemical Control
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IPM
Physical Control
Sanitation
Environmental modification
Mechanical Control
Trapping
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Habitat Reduction
Eliminate standing water (flower pots; tires;wheelbarrows; wading pools)
Change the water in birdbaths at least weekly
Aerate and chlorinate swimming pools and hottubs; cover if possible
Consider mosquito-eating fish for your pond
Keep gutters clean to prevent standing water
Spread the word: educate your friends andneighbors
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IPM Continued
Biological Control
Use resistant species
Natural enemies
Sterile males
Biological insecticidesInsect Pheromone
Bacteria
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IPM Continued
Chemical Control
By ApplicationLarvacides
Adulticides
By Mode of Action
Stomach poisons
Contact poisons
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IPM Continued
Chemical Control Continued
By Chemistry Inorganics
Orgonchlorine compounds
Organophosphate compounds
Carbamate compounds
Pyrethrins & Pyrethroids
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Cooperation / Coordination
Federal
State
Local
Private sector(PCOs)
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Questions
??
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Summary
Historically vectorborne diseaseshave been a major threat
Well controlled in industrializedworld since WW/II
Remains a problem in developingworld
Emerging problem for the entireworld
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Next Lesson
FoodFoodProtectionProtection
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Resources
Web Resources:http://www.cdc.gov/ncidod/dvbid/index.htm
Dengue Fever
Lyme Disease
Plagues
Arboviral Encephalitides
West Nile Virus
Japanese Encephalitis
Yellow Fever
Tularemia
www.doh.wa.gov/WNV