CDPH VCT Exams Category C

Epidemiology

the study of human disease patterns.
ex: malaria, plague, typhus

Vector

any animal capable of transmitting the causative agent of human disease or capable of producing human discomfort or injury, including but not limited to, mosquitoes, flies, other insects, mites, and rats

Vector borne diseases

infectious diseases in which the microorganisms that cause the symptoms are transmitted by insects or other arthropods

epidemic

an unusually large number of cases of a disease in humans occurring within a short period

epizootic

an outbreak of a disease in animals other than humans

endemic disease

the constant occurrence of an infectious or disease causing agent in a given geographic area in humans

Arthroponoses

infectious diseases carried by people and transferred to animals ex: Tb and the flu

zoonosis

an infectious disease of non human vertebrates that is secondarily transmissible to humans

What are the three components to the life cycle of vector borne diseases?

host, pathogen, vector

parasite

an organism that lives at the expense of another organism

endoparasites

when a parasite lives inside the host

ectoparasites

when a parasite lives on the skin of the host

pathogenicity

the proportion of hosts that develop symptoms among those infected by a particular strain of pathogen

virulence

refers to the proportions of cases of infection that develop severe symptoms

-emia

When an epidemiologic term refers to the presence of pathogens in the blood stream of infected hosts, what are the ending letters?

Mechanical transmission

when the pathogen adheres to the body hairs, spines, sticky pads or other structures of insects. This form of transmission can be through regurgitation or defecation

Nearly all mechanically transmitted diseases can also be transmitted in other ways (T/F)

True

Propagative Transmission

One of the three forms of biological transmission:
-the pathogen multiplies within the body of the vector BUT does not undergo any changes in form
-most of our viral diseases fall into this category
ex: plague

Cyclical transmission

One of the three forms of biological transmission:
-Parasites undergo several molts in the body of the vector. They start out as a microfilariae and develop into an infectious larvae
-No multiplication occurs in the vector
-only the pathogens that are transmitted this way are filarial nematodes

Propagative and Cyclical transmission

One of the three forms of biological transmission:
-BOTH multiplication and changes in the life form of the pathogen occur within the vector
Ex: malaria, leishmaniasis

Horizontal transmission

involved the pathogen being transmitted by a vector to a host in a cyclical pattern

Vertical transmission

more direct mode of disease transmission that does not involve a host, but occurs directly from infected mother to offspring

vector incrimination

the process of knowing which species of arthropod is serving as a vector of a particular disease
Must meet the following criteria:
-Identifying contact between arthropod and host
-having a biological association in time
-repeated demonstration of disease between arthropod and host
-replicable under experimental conditions

vectoral capacity

the potential of a group of arthropods to transmit a given pathogen. There are 6 main determinants
-abundance
-host preference and host feeding patterns
-longevity
-dispersal
-vector competence

The number of insect species found in North America is currently estimated at about _____ with new species being continuously added.

90,000

Insect

a highly specialized invertebrate with:

-An impervious exoskeleton composed of chitin

– A body with internally attached muscles

– A segmented body movable only at the joints

– A body that is differentiated into a head, a thorax, and an abdomen

Molting

when an insect must shed its exoskeleton

-After molting, the new exoskeleton is soft and pliable, allowing the insect to expand its body (grow)

3 Types of Metamorphasis

-No metamorphosis: egg>adult

-Incomplete metamorphosis: egg>nymph>adult 

-Complete metamorphosis: egg>larvae>pupae>adult

Cockroach biology

-lives and breeds indoors

-simple metamorphosis

-can develop anywhere there is moderate temperature and humidity and adequate food and water

-semi-social insects, aggregate in clusters guided by pheromones

-emerge at night, like dark spaces

-indoor (domestic) and outdoor

-nymphs go through 5-7 instars

-presence usually indicative of poor sanitation, construction
-removal with a high velocity vacuum cleaner equipped with HEPA filter is becoming increasingly popula

German Cockroach (Blattella germanica)

The most widespread pest species

-exclusively indoors

-prefer dark moist conditions near 84 degrees and near food and waste

-small, 1.5 cm long

-tawny brown, and have two longitudinal, parallel dark streaks

Brownbanded cockroach (Supella longipalpa)

-exclusively indoors

-Found near the ceiling or in the upper rooms of multistory buildings where the temperature is usually warmer

-similar to german cockroaches, but more colorful with two transverse bands

Oriental cockroach (Blatta orientalis)

-1-1.25 in long (larger)

-primarily found outdoors

-females are wingless

-prefer cool moist and dark environments with vegetation
-CANNOT CLIMB SMOOTH SURFACES

American Cockroach (Periplaneta americana)

-Prefer dark warm areas with high humidity
-Most common domestic species associated with sewer systems (+steam, subways)

-Large in size with reddish brown wings and paler area around the pronotum

-Adults are 1.5-2 in

-long lived

Smokybrown cockroach (Periplaneta fuliginosa)

-Lives primarily outdoors in trees or dense vegetation

-When infesting indoors they tend to be in an area that is usually heated

-uniform dark brown color, slightly smaller than American cockroach