Vector-Borne Diseases
The Critical Role of Environmental Health
in Vector Control and Disease Prevention
CAPT Michael E. Herring, REHS, MPH
Senior Environmental Health Scientist
CDC National Center for Environmental Health
Environmental Health Services Branch
National Center for Environmental Health
Division of Emergency and Environmental Health Services
Brain Teaser –
What percentage of all diseases known to
affect human-kind throughout history are
zoonotic (of animal origin) and often
transmitted by a vector?
60 Percent!
Brain Teaser – 2
What percentage of all new or emerging
diseases that threaten human health
today are zoonotic or vector-borne
illnesses?
75 Percent!
What animals are responsible
for more human illness and death
than any other group of mammals?
Rats and Mice
How many human
diseases can be
transmitted by
rodents?
61
Based on CDC projections, how many West
Nile virus infections have occurred in the U.S.
since the virus was first identified here in
1999?
1.8 Million!!!
What disease vector ranks #1
in pathogen diversity?
Ticks
What type of tick is the likely the
most common in the world?
The Brown Dog Tick
Rhipicephalus sanguineus
Vector
Transmitters of disease-causing
organisms that carry a pathogen
from one host to another
Vector-Borne Disease Transmission
Biological
• Most significant mode of transmission
- Arthropod ingests a pathogen while taking a blood meal
from an infected host
- Pathogen multiplies within the arthropod (reservoir)
- Pathogen is transmitted to another host when
arthropod takes another blood meal
Mechanical
• Vector physically carries pathogens from one
place or host to another, usually on body parts or
through the gastrointestinal tract
Vector-Borne Disease Transmission
• Transovarian transmission - Infectious
agent is passed vertically to succeeding
generations
• Transstadial transmission – infectious
agent is passed from one stage of life cycle
to another, as nymph to adult
Emergence/Resurgence of Vector-Borne
Diseases
• Pesticide resistance
• Decreased resources for surveillance, prevention
and control
• Deterioration of public health infrastructure
• Unprecedented population growth
• Uncontrolled urbanization
• Changes in agricultural practices
• Deforestation
• Increased travel
*Encyclopedia of Public
Health
What’s going on out there?
Mosquito-Borne Disease
West Nile Virus
Number of Cases (log scale)
Total Cases in U.S. 1999-2009
10000
1000
100
10
1
Year
Reported Human Cases Reported
Average = 2891/yr; range = 21-9862
Reported WNND Cases, United States,
1999-2009*
Total
WNND
12,188 WNND Cases
19992002
3,088
X 28 WNF/WNND
2003
2,866
~341,000 WNF Cases
2004
1,148
2005
1,309
2006
1,495
2007
1,227
2008
689
2009*
366
Year
Total 12,188
* Reported as of 2/4/2010
12,188 WNND Cases
x 140 infections/WNND
~ 1.7 Million Infections
WNV: The “Iceberg”
WNND <1%
WN Fever ~17%
Asymptomatic ~82%
1 WNND : 28 WNF
1 WNND : 140 Total Infections
Arboviral Nuroinvasive Disease
Annual average Cases 1999-2009 in the USA
Avg. Number of Cases
1200
1108
1000
800
600
119 Cases per year combined
400
200
89
19
8
1.5
0.01
SLE
EEE
POW
WEE
0
WN
LAC
WNV: Long-Term Outcomes
• WN Encephalitis and WN Fever
– Persistent disabling neurologic sequelae
common
– Tremors, movement disorders, cognitive
problems in >50%
– 8 published studies show complaints frequently
persist >1 year post infection (Some > 3 years)
– Fatigue, pain, subjective memory / concentration
problems
– Higher all-cause mortality rates >1 year postinfection
*# Sejvar et al., J Neuropsychol 2008; ^Greenberg et al., EID 2005
>300 Bird Species Killed by WNV
Since 1999
American Crow
American Goldfinch
American Kestrel
American Robin
American White Pelican
Bald Eagle
Baltimore Oriole
Barn Owl
Barn Swallow
Barred Owl
Belted Kingfisher
Black Skimmer
Black Vulture
Black-billed Magpie
Black-capped Chickadee
Black-crowned Night Heron
Blackpoll Warbler
Black-throated Blue Warbler
Black-whiskered Vireo
Blue Jay
Blythe's Tragopan
Boat-tailed Grackle
Brewer's Blackbird
Broad-winged Hawk
Bronze-winged Duck
Brown Thrasher
Brown-headed Cowbird
Budgerigar
Canada Goose
Canada Warbler
Canvasback
Carolina Chickadee
Carolina Wren
Cedar Waxwing
Chilean Flamingo
Chimney Swift
Cockatiel
Cockatoo
Common Grackle
Common Ground-Dove
Common Loon
Common Nighthawk
Common Raven
Common Yellowthroat
Cooper's Hawk
Dickcissel
Domestic Chicken
Double-crested Cormorant
Downy Woodpecker
Eastern Bluebird
Eastern Kingbird
Eastern Phoebe
Eastern Screech-Owl
Eastern Towhee
Emu
Eurasian Collared-Dove
Eurasian Wigeon
European Goldfinch
European Starling
Evening Grosbeak
Field Sparrow
Fish Crow
Fox Sparrow
Golden Eagle
Gray Catbird
Gray-cheeked Thrush
Great Black-backed Gull
Great Blue Heron
Great Egret
Great Horned Owl
Great-tailed Grackle
Green Heron
Guanay Cormorant
Harris' Hawk
Hermit Thrush
Herring Gull
Hooded Warbler
House Finch
House Sparrow
Impeyan Pheasant
Kentucky Warbler
Killdeer
Laughing Gull
Least Bittern
Loggerhead Shrike
Lorikeet species
Macaw
Mallard
Merlin
Mississippi Kite
Mourning Dove
Mute Swan
Nashville Warbler
Northern Bobwhite
Northern Cardinal
Northern Goshawk
Northern Harrier
Northern Mockingbird
Northern Parula
Northern Saw-whet Owl
Northern Waterthrush
Osprey
Ovenbird
Pied-billed Grebe
Prairie Falcon
Purple Finch
Purple Martin
Red-crowned Parrot
Red-eyed Vireo
Red-headed Woodpecker
Red-shouldered Hawk
Red-tailed Hawk
Red-winged Blackbird
Ring-billed Gull
Ring-necked Pheasant
Rock Dove
Rose-breasted Grosbeak
Rough-legged Hawk
Ruby-throated Hummingbird
Ruddy Duck
Ruddy Turnstone
Ruffed Grouse
Rusty Blackbird
Sandhill Crane
Savannah Sparrow
Scarlet Ibis
Scissor-tailed Flycatcher
Sharp-shinned Hawk
Short-eared Owl
Snowy Owl
Song Sparrow
Steller's Jay
Swainson's Hawk
Swainson's Thrush
Swallow-tailed Kite
Traill's Flycatcher
Tufted Titmouse
Tundra Swan
Turkey Vulture
Varied Tit
Veery
Virginia Rail
Warbling Vireo
Western Scrub-Jay
White-breasted Nuthatch
White-crowned Pigeon
White-winged Dove
Wild Turkey
Winter Wren
Wood Duck
Wood Thrush
Yellow Warbler
Yellow-bellied Sapsucker
Yellow-billed Cuckoo
Yellow-crowned Night-Heron
Yellow-rumped Warbler
Zebra Finch
Mammals killed by
WNV in the USA
•
•
•
•
•
Horse
Squirrel
Dog
Cat
Sheep
•
•
•
•
•
Domestic rabbit
Eastern Chipmunk
Striped Skunk
Bat
Raccoon
Dengue
• Dengue is transmitted between people by Aedes
aegypti and Aedes albopictus
• More than one-third of the world’s population living
in areas at risk for transmission
• Over 100 million people are infected yearly
• No vaccine and no specific treatment.
Dengue
• Dengue fever - high fever, severe headache,
severe pain behind the eyes, joint pain, muscle
and bone pain (“break-bone fever), rash, and mild
bleeding
• Dengue hemorrhagic fever – 2 to 7 days of high
fever followed by persistent vomiting, severe
abdominal pain and difficulty breathing. Next
phase is a 24- to 48-hour period when capillaries
become “leaky” leading to pleural effusions. May
lead to circulatory system failure and shock,
followed by death, if not treated.
Tick-Borne Disease
Lyme Disease
•
•
•
•
Caused by the bacterium Borrelia burgdorferi
Transmited to humans through the bite of
infected blacklegged ticks
The deer tick, (Ixodes scapularis) spreads the disease in
the northeastern, mid-Atlantic, and north-central United
States, and the western blacklegged tick (Ixodes pacificus)
spreads the disease on the Pacific Coast.
• Symptoms - fever, headache, fatigue, and a characteristic
skin rash called erythema migrans (70 - 80% of infections)
• If left untreated, infection can spread to joints, the heart,
and the nervous system
• #1 reportable vector-borne disease in the U.S. and the #5
most reported disease overall.
Reported Cases of Lyme Disease by
Year, United States, 1995-2009
Reported Cases of Lyme Disease
United States, 2009
Range of Ixodes pacificus
(Western black-legged tick)
Rocky Mountain
Spotted Fever
• Caused by the bacterium Rickettsia rickettsii
• Transmitted in the U.S. by the American dog tick
(Dermacentor variabilis, Rocky Mountain wood tick
(Dermacentor andersoni), Lone Star tick (Amblyomma
americanum) and brown dog tick (Rhipicephalus
sanguineus)
• Symptoms - fever, headache, abdominal pain, vomiting,
and muscle pain. A rash may develop, but is often absent
in the first few days, and in some patients, never develops
• RMSF is a serious illness that can be fatal in the first eight
days of symptoms if not treated correctly (doxycycline
within 5 days)
Tularemia
• Caused by the bacterium Francisella tularensis.
• Transmitted to humans by the dog tick (Dermacentor
variabilis), the wood tick (Dermacentor andersoni), and the
lone star tick (Amblyomma americanum).
• Deer flies (Chrysops spp.) have been shown to transmit
tularemia in the western U.S.
• Highly infectious. A small number (10-50 or so organisms)
can cause disease.
• Potential bio-terror weapon. Commonly occurs in nature.
People who inhale an infectious aerosol would experience
severe respiratory illness, including life-threatening
pneumonia and systemic infection.
Tularemia
• Ulceroglandular - Occurs following a tick or deer fly bite or after
handing of an infected animal. Skin ulcer appears where the
organism entered the body (most common form).
• Glandular - Similar to ulceroglandular but without an ulcer.
• Oculoglandular - Bacteria enter through the eye. Can occur
when touching the eyes while butchering an infected animal.
• Oropharyngeal - From eating or drinking contaminated food or
water (sore throat, mouth ulcers, tonsillitis, and swelling of lymph
glands in the neck.)
• Pneumonic - Most serious form. Symptoms include cough,
chest pain, and difficulty breathing. Results from breathing dusts
or aerosols containing the organism.
Reported cases of Tularemia, United States
2001-2010
Flea-Borne Disease
Plague
• Caused by the bacterium Yersinia pestis.
• Usually transmitted by the bite of an infected
rodent flea or by handling an infected animal
• The last U.S. urban plague epidemic occurred in
Los Angeles in 1924-25
• Most human cases in the United States occur in
two regions: 1) northern New Mexico, northern
Arizona, and southern Colorado; and 2) California,
southern Oregon, and far western Nevada
Plague
• Bubonic plague: enlarged, tender lymph nodes,
fever, chills and prostration (total
exhaustion/collapse)
• Septicemic plague: fever, chills, prostration,
abdominal pain, shock and bleeding into skin and
other organs
• Pneumonic plague: fever, chills, cough and
difficulty breathing; rapid shock and death if not
treated early
RATS!!!
ECONOMIC IMPORTANCE
• Rats in the human environment cause
enormous economic loss
- Consume and contaminate vast
quantities of food
- Cause fires by gnawing the insulation
from electric wires
• Commensal rodents cost billions of
dollars each year in the United States.
- Internal destruction to computers and
other sensitive equipment
- Structural damage to homes and
businesses
Human Health Impact
RODENT-BORNE DISEASES
• Rats and mice spread diseases in two
distinct ways.
– Directly - by contamination of food, water and air with
their urine and feces
– Indirectly – by way of rodent fleas, ticks and mites
Direct
Indirect
• Rat bite fever
Plague
• Salmonellosis
Murine typhus
• Leptospirosis
• Hantavirus
Scrub typhus
Tularemia
Bed Bugs
• Resurgence of a pest health departments
have not dealt with in over 50 years.
Why are they back?
Greater
international and domestic travel
Lack of knowledge regarding control of
bed bugs due to their prolonged absence
Increased resistance to available
pesticides
The continuing decline or elimination of
effective vector/pest control programs at
state and local public health agencies.
Photo courtesy of Dr. Harold Harlan, Armed Forces Pest
Management Board Image Library (http://www.afpmb.org)
2011 NPMA Bed Bug Survey
College dorms
Hotels/motels
Nursing homes
Office buildings
Schools /day care centers
Hospitals
Transportation (train/bus/taxi)
Movie theaters
•
2010
2011
35
67
25
18
10
12
9
5
54
80
46
38
36
31
18
17
Survey respondents also report finding bed bugs in retail stores,
laundromats, libraries, restaurants and airplanes.
State Public Health Vector Control
Conference:
Workforce and Disease Priorities Needs
Assessment Summary
2007
State Public Health Vector Control Conference:
Workforce and Disease Priorities Needs
Assessment Summary
********************************************
Seventy-four percent of SPHVCC
survey respondents reported they did
not have a sufficient number of
public health workers to effectively
staff their vector control units.
*******************************************
State Public Health Vector Control
Conference:
Workforce and Disease Priorities Needs
Assessment Summary
• 66% of respondents said they lacked capacity for
field-based surveillance and control teams
• 41% lacked medical entomologists
• 41% lacked specialists in public health promotion
and education
• 38% lacked tick control and disease specialists
• 25% lacked epidemiological surveillance capacity
State Public Health Vector Control Conference:
Workforce and Disease Priorities Needs
Assessment Summary
***************************************
Eighty percent (80%) of respondents said that
their agencies had undertaken no activity in
regards to preparing for climate change and its
effect on vector-borne diseases.
********************************************
(Note: The remaining 20% stated their agencies had
undertaken “limited” activities.)
So what is CDC doing to
confront these challenges?
CDC Activities




Collaboration (e.g. Federal Bed Bug Work
Group, Public Health Pesticide Consortium)
Education/information dissemination
Environmental health workforce
development/training
Resource for basic entomology, pesticide
resistance and IPM
Integrated Pest Management
Integrated Pest Management (IPM) is the
coordinated use of pest and environmental
information with available pest control
methods to prevent unacceptable levels of
pest damage by the most economical means
and with the least possible hazard to people,
property, and the environment.
Biology and Control of Vectors and Public Health
Pests: The Importance of IPM
Biology and Control of Vectors and Public Health
Pests
• Training focal areas –
–
–
–
–
–
–
–
–
–
–
–
–
Integrated Pest Management (IPM)
Vectorborne Diseases
Rodent Control
Mosquito Control
Tick Control
Bed Bug Control and Interactive Inspection
Bio-terror Agents
Pesticides/”Green” Pest Control
Housing and Lodging Pests
Food Service Pests (including “kitchen crawls”)
School IPM
Global Climate Change
• Biology and Control of Insects and Rodents
• Biology and Control of Vectors and Public
Health Pests: IPM
• Environmental Health Training in Emergency
Response (EHTER)
• Environmental Health Performance Standards
www.nehacert.org
CDC Sponsored Programs
Environmental Public Health
Online Courses (EPHOC)
http://www.southcentralpartnership.org/ephoc
- General Environmental Health
- Statutes and Regulations
and Health
- Food Protection
Quality/Environmental Noise
- Potable Water
- Wastewater
- Solid and Hazardous Waste
- Hazardous Materials
-Zoonoses, Vectors and Pests
-- Disaster Sanitation
- Radiation Protection
- Occupational Safety
- Air
- Housing Safety and Sanitation
- Institutions and Licensed
Establishments
- Swimming Pools and
Recreational Facilities
Training/Reference Material
www.cdc.gov/nceh/ehs/default.htm