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 Man as Incidental 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: Transmission from Rodents via flea 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

Hantavirus Pulmonary Syndrome Cases by State of Exposure United States – September 19, 2006 Total Cases (N=453 in 30 States) 0 Cases >=10 Cases 5-9 Cases 1-4 Cases 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 3. Characteristics of Hantaviruses: Hantaviruses are unique among Bunyaviridae genera in that they are not associated with an arthropod vector. In general, a distinct rodent species is the reservoir for each hantavirus. Transmission of hantaviruses to humans most often occurs via inhalation of aerosolized, virus-laden rodent excreta.

Transmission of Hantaviruses Chronically infected rodent Horizontal transmission of infection by intraspecific aggressive behavior Virus also present in throat swab and feces Virus is present in aerosolized excreta, particularly urine 4. Transmission of Hantaviruses: The virus is horizontally transmitted between rodents through intraspecific aggressive behaviors, such as biting. The virus is transmitted to humans from aerosolized rodent excreta, particularly urine. Transmission to humans also can occur from inhalation of secondary aerosols, and from rodent bites or other direct contact of infectious material with mucous membranes or broken skin. Secondary aerosols, mucous membrane contact, and skin breaches are also sources of infection

Peromyscus maniculatus 12. Deer Mouse (Peromyscus maniculatus) and Cotton Rat (Sigmodon hispidus): The deer mouse is the primary rodent host for Sin Nombre virus, the main etiologic agent of HPS in North America. The cotton rat is the primary rodent host for the Black Creek Canal virus. Infected rodents show no visible evidence of acute or chronic infection. Peromyscus maniculatus Deer mouse Sigmodon hispidus Cotton rat

Sin Nombre Virus Characteristics Family Transmission Viral particles Structural proteins Genome Bunyaviridae vertebrate hosts, no arthropod vectors spherical, 80-120 nm Glycoproteins: G1, G2 nucleoprotein: N ss-RNA, trisegmented, negative polarity 13. Characteristics of Sin Nombre Virus: Sin Nombre virus belongs to the family Bunyaviradae and contains three genomic RNA segments of negative polarity. The virion of Sin Nombre virus is spherical and is 80-120nm in diameter. The virion contains two glycoproteins, G1 and G2, located on the outer surface, which are the nucleoprotein and the viral polymerase.

Rodent Exposure 70 confirmed HPS cases Peridomestic exposure Peridomestic & occupational exposure Peridomestic & recreational exposure Occupational exposure Entering/cleaning rodent-infested structures 69% (48/70) 19% (13/70) 9% (6/70) 4% (3/70) 26. Rodent Exposure Data from 70 confirmed HPS Cases: A review of confirmed HPS cases was conducted to characterize rodent exposure. Of 70 confirmed HPS cases, 69% had peridomestic exposure; 19% had both peridomestic and occupational exposure; 9% had peridomestic and recreational exposure; 4% had occupational exposure; and 9% had rodent exposure while entering and cleaning rodent-infested structures. Armstrong, L.R. et al., JID 1995; 172 (October)

Prevalence of SNV IgG Antibodies in Select U.S. Populations Risk group Forest workers1 Health care workers2 Prodromal HPS3 Contacts4 Rural OCC5 Rodent workers6 Total Postive/tested (%) 0/143 0/396 3/299 (1.0%) 3/239 (1.3%) 1/522 (0.2%) 8/932 (0.9%) 15/2531 (0.6%) Location/time SW US, 1993 SW US, 1994 US, 1994 27. Seroprevalence of SNV IgG Antibodies in Select U.S. Populations: Studies focusing on select high-risk groups showed a total prevalence of SNV antibodies of 0.6% (15/2531). Antibody prevalence was 0% (0/143) for forest workers; 0% (0/396) for health care workers; 1% (3/299) for prodromal HPS patients during initial 1993 outbreak; 1.3% (3/239) for contacts of HPS patients; 0.2% (1/522) for rural OCC; and .9% (8/932) for rodent workers. 1. Vitek et al, 1996 2. Vitek et al, 1996 3. Simonsen et al, 1995 4. Zeitz et al, 1995 5. Zeitz et al, 1995 6. Armstrong et al, 1995

HPS Prevention Control Mice Inside Control Mice Outside 29. HPS Prevention: Overview Slide. The best method to prevent HPS is to limit human-rodent contact. Mice should be controlled inside and outside of the home. Safety precautions should be used when cleaning in areas with evidence of rodent infestation. Use Safety Precautions