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Vectorborne Infectious Disease
Vector
• A living organism, usually an insect or other
arthropod, that can transmit a
communicable disease agent to a
susceptible host.
Vectorborne Disease Outbreak
(VBDO)
 The occurrence of two or more cases of a
vectorborne disease
 Risk increases with:
 Improper handling of waste water
 Inadequate drainage of rainwater
 Improper management of solid waste
Climate Sensitive Diseases
• Vectorborne Diseases:
– Malaria (Mosquito)
– Dengue Fever (Mosquito)
– Lyme Disease (Tick)
– Rocky Mountain Spotted Fever (Tick)
– Erlichiosis (Tick)
– Other vectorborne viruses
Vector Transmission
• mechanical transmission
the transfer of a pathogen from an infectious
source to a susceptible host by a vector without
any reproduction or developmental changes in the
pathogen
• biological transmission
the transfer of a pathogen to a susceptible host by
a vector, with the pathogen undergoing
reproduction, developmental changes, or both in
the vector
Insects as Vectors
• Man as Principal Host
– anthropophilic
species that usually feed on humans. "human loving“
– Ex. dengue, epidemic typhus, filariasis, malaria,
relapsing fever, yellow fever (urban)
• Man as Incidental Host
– zoonosis
diseases of animal transmissible to man
– Ex. African sleeping sickness, Chaga’s disease,
encephalitis, hemorrhagic fever, leishmaniasis, plague,
tularemia, yellow fever (jungle)
Orders of Insect Vectors
• Anoplura (anopl = unarmed; ura = tail)
the sucking lice, containing the human head and body lice.
• Diptera (di = two; ptera = wings)
the flies, gnats, midges, and mosquitoes.
• Hemiptera (hemi = half; ptera = wings)
the true bugs, including the conenose bugs (which transmit
Chagas' disease) and the bed bugs.
• Orthoptera (ortho = straight; ptera = wings)
the cockroaches, crickets, grasshoppers, katydids, mantids,
and walking sticks.
• Siphonaptera (siphon = tube; aptera = wingless)
the fleas.
• Acari
the ticks.
Anoplura (sucking lice)
• Pediculidae: includes the human head and
body louse (Pediculus humanus and
Pediculus capitis)
• Pthiridae: contains the human pubic louse
or crab louse (Pthirus pubis).
Diptera (The Flies and Mosquitoes)
• Culicidae: The mosquitoes
– 3000 species worldwide, 150 in North America
• Muscidae: the muscid flies
– Contain the house fly and the tsetse fly
• Simuliidae: the black flies
– 1000 species worldwide
• Pscyhodidae: sand flies
• Ceratopogonidae: the biting midges
• Tabanidae: the horse and deer flies
– 3000 species worldwide
Mosquitoes
Aedes spp. vectors of
dengue, yellow fever,
LaCrosse encephalitis,
filariasis, other viruses
Culex and Culiseta spp.
vectors of SLE, EEE, VEE,
WEE, WNV, RVF, filariasis,
Anopheles spp. vectors of
malaria, filariasis, heartworm
Mansonia spp. Vectors of
filariasis, RVF, WNV,
Sindbis, other viruses
Ochlerotatus spp. WNV,
JEE, other viruses
West Nile Virus 1999
West Nile Virus 2000
West Nile Virus 2001
West Nile Virus 2002
West Nile Virus 2003
West Nile Virus 2004
West Nile Virus 2005
West Nile Virus 2006
WNV Human Cases 2006
WNV Bird Cases 2006
WNV Veterinary Cases 2006
New Routes of Exposure
Muscid Flies
House fly (Musca spp.)- mechanical
vector of filth diseases (ex. Salmonella,
Cryptosporidium, E.coli, etc.)
Tsetse fly (Glossina spp.)- biological
vector of African Trypanosomiasis
Black Flies
Black flies (Simuliidae) are biting
flies that serve as vectors for
Onchocerciasis (River Blindness)
Onchocerciasis is caused by
Onchocerca volvulus, a parasitic
worm that lives for up to 14 years in
the human body
Sand Flies
Phlebotomine sand flies are
vectors of various pathogenic
agents responsible for diseases of
animals including man :
leishmaniases, bartonellosis and
various arboviroses
Leishmaniasis
• Parasitic disease caused by obligate intracellular protozoa
of the genus Leishmania spread by the bite of infected sand
flies
• Several different forms of leishmaniasis
– cutaneous (cue-TAY-knee-us) leishmaniasis, which causes skin
sores
– visceral (VIS-er-al) leishmaniasis, which affects some of the
internal organs of the body (for example, spleen, liver, bone
marrow).
Deer Flies
Deer flies (Chrysops spp.)
may serve as vectors for
Tularemia and Loa Loa
(loiasis)
Hemiptera (true bugs)
• Reduviidae - assassin
and conenose or
kissing bugs. About
2,500 species
worldwide (subfamily
Triatominae vectors
Chaga’s Disease)
• Cimicidae - bed bugs.
At least 75 species
worldwide.
Chaga’s Disease
• American Trypanosomiasis caused by Trypanosoma cruzi
Acute:
• Acute symptoms only occur in about 1% of cases. swelling of the eye
on one side of the face, fatigue, fever, enlarged liver or spleen, and
swollen lymph glands. Sometimes, a rash, loss of appetite, diarrhea,
and vomiting occur. In infants and in very young children with acute
Chagas disease, swelling of the brain can develop in acute
Indeterminate:
• Eight to 10 weeks after infection, the indeterminate stage begins.
During this stage, people do not have symptoms.
Chronic:
• Ten to 20 years after infection, people may develop the most serious
symptoms of Chagas disease. Cardiac problems, including an enlarged
heart, altered heart rate or rhythm, heart failure, or cardiac arrest are
symptoms of chronic disease. Chagas disease can also lead to
enlargement of parts of the digestive tract, which result in severe
constipation or problems with swallowing. Not everyone will develop
the chronic symptoms of Chagas disease.
Orthoptera (roaches)
• Mechanical vectors
• Several families
– Most important include:
• Periplaneta (American
cockroach)
• Blatella (German and Oriental
cockroaches)
Siphonaptera (the fleas)
• Ceratophyllidae - mainly associated with
rodents
• Leptopsyllidae
• Pulicidae - several species of human pests
• Tungidae - chigoe fleas
Plague
• Yersinia pestis
• Two forms:
– Bubonic
– Pneumonic
• Transmission
from Rodents via
flea
Acari (the mites and ticks)
• Ixoididae
– Ixodes and
Dermacentor (hard
ticks)
• Argasidae
– Orithodoros (soft ticks)
Lyme’s Disease
• Borrelia burgdorferi
• red, slowly expanding rash
(called erythema migrans or
EM)
• Neurologic and muscular
symptomology, arthritis
• Named after cluster of cases
in Lyme, CT in 1970’s
• First observed in early 20th
century
Rocky Mountain Spotted Fever
• Rickettsia rickettsii
• Clinical description
– A tickborne febrile illness
most commonly
characterized by acute
onset and usually
accompanied by myalgia,
headache, and petechial
rash (on the palms and
soles in two thirds of the
cases).
Vertebrate Vectors
•
•
•
•
•
•
Dogs
Cats
Raccoons
Bats
Mice
Etc.
Rabies
• Rhabdoviridaenonsegmented,
negative-stranded
RNA genomes
• Illness is acute
encephalitis in all
warm-blooded hosts,
including humans, and
the outcome is almost
always fatal
Hantavirus Pulmonary Syndrome Cases
by State of Exposure United States – September 19, 2006
Total Cases (N=453 in 30 States)
33
8
25
8
1
15
2
7
16
38
3
5
7
25
3
1
10
2
47
2
3
1
13
1
2
46
0 Cases
1-4 Cases
5-9 Cases
>=10 Cases
70
29
2
1
Twenty-seven cases were reported with unknown state of
exposure.
•
Characteristics of
Hantaviruses
No arthropod vector established
Unique among genera of
Bunyaviridae
•
Rodent hosts
Genus and possibly species
specific
•
Transmission
Aerosolization of rodent excreta
Transmission of Hantaviruses
Chronically infected
rodent
Horizontal transmission of
infection by intraspecific
aggressive behavior
Virus also present in
Virus is present in
throat swab and feces
aerosolized excreta,
particularly urine
Secondary aerosols, mucous
membrane contact, and skin
breaches are also sources of
infection
Peromyscus maniculatus
Deer mouse
Sigmodon hispidus
Cotton rat
Sin Nombre Virus
Characteristics
Family
Bunyaviridae
Transmission vertebrate hosts,
no arthropod vectors
Viral particles spherical, 80-120 nm
Structural
proteins
Glycoproteins: G1, G2
nucleoprotein: N
Genome
ss-RNA, trisegmented,
negative polarity
Rodent Exposure
70 confirmed HPS
cases
Peridomestic exposure
69% (48/70)
Peridomestic & occupational exposure 19% (13/70)
Peridomestic & recreational exposure
9% (6/70)
Occupational exposure
4% (3/70)
Entering/cleaning rodent-infested
structures
9% (6/70)
Armstrong, L.R. et al., JID 1995; 172 (October)
Prevalence of SNV IgG Antibodies
in Select U.S. Populations
Risk group
Postive/tested (%)
Location/time
Forest workers1
Health care workers2
Prodromal HPS3
Contacts4
Rural OCC5
Rodent workers6
0/143
0/396
3/299 (1.0%)
3/239 (1.3%)
1/522 (0.2%)
8/932 (0.9%)
SW US, 1993
SW US, 1993
SW US, 1993
SW US, 1993
SW US, 1994
US, 1994
Total
15/2531 (0.6%)
1. Vitek et al, 1996
4. Zeitz et al, 1995
2. Vitek et al, 1996
5. Zeitz et al, 1995
3. Simonsen et al, 1995
6. Armstrong et al, 1995
HPS Prevention
Control Mice Inside
Control Mice Outside
Use Safety Precautions