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44 Cards in this Set

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  • Back
Define arbovirus
Arthropod borne virus with complex interactions between vector, host & reservoir in a biotic/abiotic environment.
Define biotic
Associated with or derived from living organisms. The biotic factors in an environment include the organisms themselves as well as such items as predation, competition for food resources, and symbiotic relationships.
Define abiotic
Not associated with or derived from living organisms. Abiotic factors in an environment include such items as sunlight, temperature, wind patterns, and precipitation.
Define surveillance
Ongoing systematic collection, collation, analysis of data, and dissemination
Describe the transmission cycle process of arboviruses
Natural cycle maintained by hematophagous arthropods. After ingesting viremic blood, TOT/venereal/vertical transmission.
What is it about TOT that allows transmission of arbovirus to egg?
Follicles are permissive
Maintenance is....?
Increase in disease via long term survival and prolonged infection of reservoir or vector.
More infected hosts & vectors
More transmission
Responsible for epidemics
Modify feeding behaviors
How many arboviruses are there?
3 types of arboviral infection and mode of infection (RAP)
Refractive - block entry/infection
Abortive - permit entry, block replication
Productive - infects permissive cell
Arbovirus genome is usually___.
small RNA
6 stages of arboviral replication
Maturation & Budding
Where do arboviruses infect and replicate in mosquito?
midgut cuboidal epithelial cells
After arbovirus infects the mosquito and replicates, how does it disseminate to infect secondary organs?
via tracheoles and hemolymph
Define poikilotherm
An organism that regulates its body temperature largely by exchanging heat with its surroundings
What does poikilotherm have to do with mosquitos?
Environmental temp determines how quickly virus is transmitted.
4 aspects of arboviral development
Infect & replicate
Disseminates & infects 2ndary organs
Lifelong infection
Temp dependant
4 challenges to being an arbovirus
1. They infect vert and invert hosts, which are phylogenetically different organism, with mammalian and insect cells.
2. There are biochemical, physiological & temp differences. For example, the mosquito miguts pH is 9.5-10.1
3. Lot of TOLL receptors recognize it (dsRNA potent IFN-y stimulator)
4. Pressure from humans, but still successful (M&M)
2 things that make an arbovirus happy.
1. To cause high-titered infections in the host that are of long duration but not virulent
2. To infect and replicate in the vector such that the virus is not detrimental.
What are secondary effects that increase transmission from mosquito to vertebrate?
1.Salivary inhibitors which allow sufficient probing & engorgement time.
2.Chitinase as an example in Leish. It destroys the internal mouthparts of the sandfly.
3.Study of saliva is wave of future.
4.Leaky midgut phenomenon
Why can the mosquito midgut be an impediment to arboviral infection?
1.Doesn't allow for dissemination
2.Virus gets trapped within cells
3.Defense mechanisms such as encapsulation, anti-microbial peptides, serine protease cascade causing melanization
What can inactivate an arbovirus?
midgut enzymes
3 things that can prevent transmission of arbovirus from mosquito to vertebrate.
1. Midgut impedes transmission
2. Virus is inactivated by midgut enzymes
3. Species specific dose phenomenon (titer where 5% vectors infected)
What is vectorial capacity?
Ability of species to transmit a pathogen in a given location at a specific time. Depends on the number of infectious bites a person receives daily.
6 variables in vectorial capacity
Population size
Length & # gonadotropic cycles
Feeding behavior
Diel activity
What is diel?
24 hour cycle/behavior
What is vector competence?
Vector's intrinsic ability to biologically transmit disease.
What are 4 variables that determine vector competence?
1.Susceptibility to infections
3.Duration of extrinsic incubation (10-14 d Bunya/Flavi, 7 d. Alpha)
4.Transmission efficiency
Incrimination of Vectors - Koch?
4 points
1.Vector must associate with and feed on vert host in field
2.Naturally infected mosq's must be recovered
3.Vector must become infected by feeding on viremic host
4.Ability of infected vector to transmit path to a naive host must be confirmed under controlled conditions
4 place to isolate virus in order to incriminate vector? bloodmeal
2.migut only hemocoel but not salivary glands salivary glands (if in legs, usually able to transmit)
what 6 things affect biological transmission of arboviruses?
1.vector has a low infection threshold (virus doesn't lower fitness, and replicates in midgut & salivary glands)
2.spatial/temporal assoc w/host
3.diel activity
4.feeding preference (does host preference change? Bridge vector)
Vertebrate considerations for transmissibility of arbovirus.
Is the virus a high titered one, how long does the vertebrate live (will develop immunity at some point), is there an annual generation of susceptible members, and is the virus transmissible tangentially (through close feeding association). There is sometimes mosq to mosq transmission if they're feeding close enough together.
Characteristics of vertebrates that make them good hosts
1.Susceptible to infection (role of sentinel flocks/138 sp birds were WNV +)
2.Develop viremia sufficient to infect vectors
3.Share time & space with vector
4.Stereotypical behavior (return to water hole or mow lawn near trash pile? Does host have a/c & TV?)
5.Poor defensive behavior (young exhibit - nestling amplifiers. If good, interrupt vector feeding (budgies)
6.migration/immigration undue mortality (SA monkeys & YF)
How is a bird inoculated with WNV?
1.bite from infected mosq
2.eats carrion infected with WNV
3.eats infectious mosq behavior (preening & saliva, common water source/feces)
2 types of cycling & locations
epidemic - urban
endemic - sylavatic
Urban vectors are ____.
anthropophagic (I believe he means "feeds on humans"
Sylvatic vectors are ____.
Hemagogous. Feed on monkeys and humans.
What occurs in LaCrosse infection because of TOT?
Male Aedes are born infected
Where does LaCrosse virus come from?
Midwest. Now increasing in Atlantic.
Why is LaCross spreading?
Intrusion of humans into sylvatic areas of virus cycling, possible introduction of new vectors. We also have better surveillance and medical care.
During seasonal changes, where does the virus go?
1.Overwintering causes inactivity during the winter (diapause choice).
2.Persistence/reintroduction into environment (WNV+ mosq's are in sewers, eggs (TOT) in LAC & RVF,
migrating birds carry it, hibernating reptiles/mammals maintain it.
How does global travel impact the ability of arboviruses to get around?
500M travelers cross int'l boundaries each year. In 1961, 20.692 mosq's were recovered from aircraft. 75M tons of cargo is shipped, including tired and bamboo plants.
When was A.aegypti imported to New World? How was C. pipiens & quinquefasciatus imported?
Early sailing ships
Take advantage of man (waste...)
What are the antinflammatory effects of cortisol?
kills T-cells and eosinophils
inhibit macrophage migration
inhibits phospholipase-A
stabilizes endothelium
stabilizes mast cells