Epidemiology and Transmission Ecology Flashcards
What does a complete understanding of disease transmission require the study of (both)
Macroepidemiology and microepidemiology
- large-scale problems of disease distribution
- demographic and cultural factors affecting transmission
- illness and death rates
- economic impacts
- requires substantial funding, institutions, trained personnel, and government policies allowing for data collection
macroepidemiology
- small-scale problems
- looks at how disease distribution affects individual host-parasite interactions, parasite strains, host genetic variation, immunity
microepidemiology
Which institution monitors national health statistics, issues weekly morbidity and mortality reports, responds to situations to learn more about origin/transmission dynamics, and provides electronic health statistics?
The Centers for Disease Control and Prevention (CDC)
What organization is global in scale and provides information about many health issues?
The World Health Organization (WHO)
Name four things the distribution of a parasite is influenced by WITHIN POPULATIONS:
1) host age
2) sex
3) social and economic status
4) diet and ecological conditions that factor completion of life cycles
How are pinworms an example of how a parasite is distributed?
Influenced by age – children are a source of parasites for the entire family
How is leishmania an example of how parasites are distributed?
Infections often occur in agricultural workers (shows how occupation plays a role in health)
Vehicles by which infections are transmitted from one host to another – provide two examples
Vectors; snails and blood-sucking arthropods
What are the two most medically important vectors and what do they carry?
- mosquitos (malaria)
- snails (blood flukes/schistosomes)
How does malaria illustrate the need to understand vector biology as a means of control?
Standing water is a good breeding ground for mosquitos – difficult to eliminate as this may be the only available source of water for drinking/bathing
How does Egyptian agricultural practices illustrate the need to understand vector biology?
Irrigation ditches are the ideal environments for snails, which are intermediate hosts for schistosomes
- a natural set of conditions under which it is predicted for a disease to occur
- a landmark of parasitology (scientists could recognize and predict where diseases could occur and could thus be controlled)
A natural “nidus” or focus (part of landscape epidemiology)
Name four knowledge factors influencing landscape epidemiology within the nidus:
- Climate
- Plant and animal population densities
- Geological conditions
- Human activities
What type of mapping can be used to reveal vegetation and land-use patterns?
Geographic information systems
Name two diagnostic groups that have been helpful
- IsoCode STIX (allows samples to be collected and transported for processing)
- Human Genome Project (opened opportunities for epidemiologists to address public health problems)
What type of descriptors are the the following
- numbers of parasites
- reproductive success/fitness
quantitative descriptors
when talking about parasite communities, what two terms are used?
mean intensity and prevalence (can also include density, abundance, etc.)
large parasites that do not multiply in or on a host, occur in aggregated populations, most hosts uninfected or lightly infected
provide examples
macroparasites; adult tapeworms, trematodes, nematodes, arthropods
small parasites that do multiply within a host
provide examples
microparasites; trypanosomes, apicomplexans, amoebas
List four things a complete quantitative description of parasitic populations might include
- counts
- measurements
- determination of sexes
- determination of maturity
when a single host can harbor many species
parasite community
are parasites autotrophic or heterotrophic and what does this mean?
heterotrophic; they can only obtain energy from other sources (existing organic mcs, nitrogen, and amino acids)
how to tapeworms and acanthocephalans feed without a digestive tract?
they absorb sugars and amino acids across their surface/through uptake sites on their plasma membrane
what does tick saliva contain?
an anticoagulant
True or false: parasites always live at higher trophic levels than their hosts
False; parasites make up a substantial fraction of biomass/can be important indicators of biodiversity bc tells which intermediate hosts are present and larval stages indicate habitat
In terms of parental care and reproductive success, how do parasites function?
- little parental care
- low reproductive success leads to high reproductive potential –> heavy energy investment to counteract low probability of offspring success
how can parasites increase their reproductive potential?
- asexual reproduction/hermaphroditism
- helpful because they do not have to find another member of their species to reproduce
- high egg production
- the nucleus divides multiple times before cytokinesis
- simultaneous production of multiple daughter cells
- leads to millions of offspring in very few days
schizogony/multiple fission
what is the life cycle of coccidia
schizogony (asexual) –> gametes –> cyst form outside of host
what is binary fission most common among?
free-living protozoa
provide examples of asexual reproduction during immature stages
- metacestodes of tapeworms
- cysticerci of taenia
- hydatid cysts of echinococcus
- when embryo generations are produced within the body of prior generations
- many embryos develop from a single zygote
who is this exhibited by
polyembryony; flukes/trematodes
life cycle of a fluke/trematode
eggs –> miracidia –> sporocysts give rise to daughter sporocysts that each produce rediae –> cercariae
when a parasite can fertilize its own eggs, does not produce unusual genetic recombinations (does guarantee offspring)
hermaphroditism
what is the continual asexual reproduction in tapeworms known as (leads to the production of proglottids)
strobilization
how do leucochloridium change their behavior to enhance the likelihood of a host encounter
- pigement in sporocysts move into snail tentacles and pulsate to look like caterpillars
- goal to get land snails eaten by insectivorous birds
how to acanthacephalans alter their behavior?
change the color of amphipod, leads to photactic behavior where the IH swims to the water’s surface
the study of relationships between organisms and their environments
ecology
when the host is the parasite’s environment, what four things need to be considered
- taxonomy
- transmission
- population dynamics
- evolutionary history
what two things make the host as an environment ideal?
- hosts are nutrient dense
- they can regulate body temperature
why do adaptation often come about?
- so the life stage can better survive the abiotic conditions existing between hosts
- because hosts can defend themselves (immune response)
which step do parasite control strategies often target
reducing probability of host-parasite encounter
what is niche often determined by?
host diet, physiological condition, and the presence of other parasites
how do nematodes in testudo graeca demonstrate how parasites occupy different niches?
they live in the large intestine but are restricted radially from the center to the mucosa
when an organism inhabits a cavity of an animal’s body; when an organism lives in the tissues of a host
coelozoic; histozoic
where do most endoparasites live?
in the GI tract
what provides evidence of parasite adaptation to a habitat within a host
site specificity
what is an example of site specificity
toxoplasma gondii in the retina vs. taenia in the chamber
there is evidence for many ——— within a host
microenvironments
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