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 transmissionthe 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 transmissionthe 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
Phlebotomine sand flies are vectors of various pathogenic agents responsible for diseases of animals including man : leishmaniases, bartonellosis and various arboviroses
Sand Flies
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 cruziAcute:• 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
• Rhabdoviridae-nonsegmented, negative-stranded RNA genomes
• Illness is acute encephalitis in all warm-blooded hosts, including humans, and the outcome is almost always fatal
2
3
0
46
38 47
1
15
2
5
13
2
25
716
70
3
1
8
2
8
10
29
25
1
1
33
3
1
7
Hantavirus Pulmonary Syndrome Casesby State of Exposure United States – September 19, 2006
Total Cases (N=453 in 30 States)
0 Cases
>=10 Cases5-9 Cases1-4 Cases
Twenty-seven cases were reported with unknown state of exposure.
• No arthropod vector establishedNo arthropod vector establishedUnique among genera of Unique among genera of
BunyaviridaeBunyaviridae
• Rodent hostsRodent hosts Genus and possibly species Genus and possibly species specificspecific
• TransmissionTransmission Aerosolization of rodent excretaAerosolization of rodent excreta
Characteristics of Characteristics of HantavirusesHantaviruses
Chronically infected Chronically infected rodentrodent
Virus is present in Virus is present in aerosolized excreta, aerosolized excreta,
particularly urineparticularly urine
Horizontal transmission of Horizontal transmission of infection by intraspecific infection by intraspecific
aggressive behavioraggressive behavior
Virus also present in Virus also present in throat swab and fecesthroat swab and feces
Secondary aerosols, mucous Secondary aerosols, mucous membrane contact, and skin membrane contact, and skin breaches are also sources of breaches are also sources of
infectioninfection
Transmission of HantavirusesTransmission of Hantaviruses
Peromyscus maniculatusDeer mouse
Sigmodon hispidusCotton rat
FamilyFamily
TransmissionTransmission
Viral particlesViral particles
Structural Structural proteinsproteins
Genome Genome
BunyaviridaeBunyaviridae
vertebrate hosts,vertebrate hosts,no arthropod vectorsno arthropod vectors
spherical, 80-120 nmspherical, 80-120 nm
Glycoproteins: G1, G2Glycoproteins: G1, G2nucleoprotein: Nnucleoprotein: N
ss-RNA, trisegmented,ss-RNA, trisegmented,negative polarity negative polarity
Sin Nombre Virus Sin Nombre Virus CharacteristicsCharacteristics
Peridomestic exposurePeridomestic exposure
Peridomestic & occupationalPeridomestic & occupational exposureexposure
Peridomestic & recreational exposurePeridomestic & recreational exposure
Occupational exposure Occupational exposure
Entering/cleaning rodent-infested Entering/cleaning rodent-infested structuresstructures
Armstrong, L.R. et al., JID 1995; 172 (October)Armstrong, L.R. et al., JID 1995; 172 (October)
69% (48/70)69% (48/70)
19% (13/70)19% (13/70)
9% (6/70)9% (6/70)
4% (3/70)4% (3/70)
9% (6/70)9% (6/70)
Rodent ExposureRodent Exposure70 confirmed HPS 70 confirmed HPS
casescases
Risk groupRisk groupForest workersForest workers11
Health care workersHealth care workers22
Prodromal HPSProdromal HPS33
ContactsContacts44
Rural OCCRural OCC55
Rodent workersRodent workers66
TotalTotal
Location/timeLocation/timeSW US, 1993SW US, 1993SW US, 1993SW US, 1993SW US, 1993SW US, 1993SW US, 1993SW US, 1993SW US, 1994SW US, 1994US, 1994US, 1994
Postive/tested (%)Postive/tested (%)0/1430/1430/3960/3963/299 (1.0%)3/299 (1.0%)3/239 (1.3%)3/239 (1.3%)1/522 (0.2%)1/522 (0.2%)8/932 (0.9%)8/932 (0.9%)
15/2531 (0.6%)15/2531 (0.6%)
1. Vitek et al, 19961. Vitek et al, 1996 2. Vitek et al, 19962. Vitek et al, 1996 3. Simonsen et al, 19953. Simonsen et al, 19954. Zeitz et al, 19954. Zeitz et al, 1995 5. Zeitz et al, 19955. Zeitz et al, 1995 6. Armstrong et al, 19956. Armstrong et al, 1995
Prevalence of SNV IgG Antibodies Prevalence of SNV IgG Antibodies in Select U.S. Populationsin Select U.S. Populations
Control Mice InsideControl Mice Inside
Control Mice OutsideControl Mice Outside
Use Safety PrecautionsUse Safety Precautions
HPS PreventionHPS Prevention