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CAPT Michael E. Herring, REHS, MPHSenior Environmental Health Scientist
CDC National Center for Environmental Health
Environmental Health Services Branch
Vector-Borne Diseases
National Center for Environmental Health
Division of Emergency and Environmental Health Services
The Critical Role of Environmental Healthin Vector Control and Disease Prevention
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 TickRhipicephalus sanguineus
VectorTransmitters of disease-causing
organisms that carry a pathogen from one host to
another
Vector-Borne Disease TransmissionBiological
• 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 Total Cases in U.S. 1999-2009
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
10
100
1000
10000
Reported Human Cases ReportedAverage = 2891/yr; range = 21-
9862
Nu
mb
er
of
Cases (
log
scale
)
Year
Reported WNND Cases, United States, 1999-2009*
YearTotal
WNND
1999-
2002
3,088
2003 2,866
2004 1,148
2005 1,309
2006 1,495
2007 1,227
2008 689
2009*
366
Total
12,188
* Reported as of 2/4/2010
12,188 WNND Cases
X 28 WNF/WNND
~341,000 WNF Cases12,188 WNND Cases
x 140 infections/WNND
~ 1.7 Million Infections
WN Fever ~17%
Asymptomatic ~82%
WNV: The “Iceberg” WNND <1%
1 WNND : 28 WNF1 WNND : 140 Total Infections
WN LAC SLE EEE POW WEE 0
200
400
600
800
1000
1200 1108
8919 8 1.5 0.01
Avg
. N
um
ber
of
Cases
Arboviral Nuroinvasive Disease
Annual average Cases 1999-2009 in the USA
119 Cases per year combined
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 post-infection
*# Sejvar et al., J Neuropsychol 2008; ^Greenberg et al., EID 2005;
>300 Bird Species Killed by WNV Since 1999
American Crow Carolina Wren Gray Catbird Northern Goshawk Scissor-tailed FlycatcherAmerican Goldfinch Cedar Waxwing Gray-cheeked Thrush Northern Harrier Sharp-shinned HawkAmerican Kestrel Chilean Flamingo Great Black-backed Gull Northern Mockingbird Short-eared OwlAmerican Robin Chimney Swift Great Blue Heron Northern Parula Snowy OwlAmerican White Pelican Cockatiel Great Egret Northern Saw-whet Owl Song SparrowBald Eagle Cockatoo Great Horned Owl Northern Waterthrush Steller's JayBaltimore Oriole Common Grackle Great-tailed Grackle Osprey Swainson's HawkBarn Owl Common Ground-Dove Green Heron Ovenbird Swainson's ThrushBarn Swallow Common Loon Guanay Cormorant Pied-billed Grebe Swallow-tailed KiteBarred Owl Common Nighthawk Harris' Hawk Prairie Falcon Traill's FlycatcherBelted Kingfisher Common Raven Hermit Thrush Purple Finch Tufted TitmouseBlack Skimmer Common Yellowthroat Herring Gull Purple Martin Tundra SwanBlack Vulture Cooper's Hawk Hooded Warbler Red-crowned Parrot Turkey VultureBlack-billed Magpie Dickcissel House Finch Red-eyed Vireo Varied TitBlack-capped Chickadee Domestic Chicken House Sparrow Red-headed Woodpecker VeeryBlack-crowned Night Heron Double-crested Cormorant Impeyan Pheasant Red-shouldered Hawk Virginia RailBlackpoll Warbler Downy Woodpecker Kentucky Warbler Red-tailed Hawk Warbling VireoBlack-throated Blue Warbler Eastern Bluebird Killdeer Red-winged Blackbird Western Scrub-JayBlack-whiskered Vireo Eastern Kingbird Laughing Gull Ring-billed Gull White-breasted NuthatchBlue Jay Eastern Phoebe Least Bittern Ring-necked Pheasant White-crowned PigeonBlythe's Tragopan Eastern Screech-Owl Loggerhead Shrike Rock Dove White-winged DoveBoat-tailed Grackle Eastern Towhee Lorikeet species Rose-breasted Grosbeak Wild TurkeyBrewer's Blackbird Emu Macaw Rough-legged Hawk Winter WrenBroad-winged Hawk Eurasian Collared-Dove Mallard Ruby-throated Hummingbird Wood DuckBronze-winged Duck Eurasian Wigeon Merlin Ruddy Duck Wood ThrushBrown Thrasher European Goldfinch Mississippi Kite Ruddy Turnstone Yellow WarblerBrown-headed Cowbird European Starling Mourning Dove Ruffed Grouse Yellow-bellied SapsuckerBudgerigar Evening Grosbeak Mute Swan Rusty Blackbird Yellow-billed CuckooCanada Goose Field Sparrow Nashville Warbler Sandhill Crane Yellow-crowned Night-HeronCanada Warbler Fish Crow Northern Bobwhite Savannah Sparrow Yellow-rumped WarblerCanvasback Fox Sparrow Northern Cardinal Scarlet Ibis Zebra FinchCarolina Chickadee Golden Eagle
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 DiseaseUnited States, 2009
Range of Ixodes pacificus(Western black-legged tick)
Rocky MountainSpotted 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 Scrub typhus• Hantavirus 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 travelLack of knowledge regarding control of bed bugs due to their prolonged absenceIncreased resistance to available pesticidesThe 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 Survey2010 2011
College dorms 35 54Hotels/motels 67 80Nursing homes 25 46Office buildings 18 38Schools /day care centers 10 36Hospitals 12 31Transportation (train/bus/taxi) 9 18Movie theaters 5 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 NeedsAssessment Summary
2007
State Public Health Vector Control Conference:
Workforce and Disease Priorities NeedsAssessment Summary
********************************************Seventy-four percent of SPHVCC
survey respondents reported they didnot have a sufficient number of
public health workers to effectivelystaff 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 NeedsAssessment 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.orgCDC Sponsored Programs
Environmental Public Health Online Courses (EPHOC)
http://www.southcentralpartnership.org/ephoc
- General Environmental Health - Radiation Protection- Statutes and Regulations - Occupational Safety and Health- Food Protection - Air Quality/Environmental Noise- Potable Water - Housing Safety and Sanitation- Wastewater - Institutions and Licensed- Solid and Hazardous Waste Establishments- Hazardous Materials - Swimming Pools and -Zoonoses, Vectors and Pests Recreational Facilities-- Disaster Sanitation
Training/Reference Material
www.cdc.gov/nceh/ehs/default.htm