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