Lecture one Introduction to parasitology

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Medical Parasitology
Chapters 1, 2, 13, 15, 20, 22
Ecological relationships Types of parasitism Parasite-host Relationships
updated 7 years ago by YCITLALIC
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Which do you think are the most common parasites that affect humans worldwide?
a. Protozoan Parasites (Giardia, Malaria)
b. Intestinal nematodes (roundworms, such as pinworms, whipworms)
c. Trematodes (flukes, such as blood or liver flukes)
d. Cestodes (tapeworms)

b. Intestinal nematodes (roundworms, such as pinworms, whipworms)


What makes an organism free living?

Not directly dependent on other organisms, not acquiring it's main nourishment by interacting with another organism.


Are most organisms free living?

No, most organisms are often dependent on other organisms for survival, for example parasitic organisms like flatworms or tapeworms. Evolved independently in nearly every animal phylum.


why are vampire bats consider parasitic?

they only feed on blood and consume 60% of their body weight every night in blood (have a highly specialized diet)


What are some examples vertebrate parasites?

-Brood parasites
-cuckoos & cowbirds
-vampire bats (feed on donkeys)


What is symbiosis?

Organism "living together"; not necessary a beneficial or harmful or mutual
-usually different species
-two organism living in close association
-one often lives in/on body of other

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How is Meadow pipet eggs & larger cuckoo egg that mimics host eggs a parasitic relationship?

Cuckoo is a brood parasite it lays its eggs on others species nest.
Cuckoo nestling are often much larger than their host.


What is commensalism?

-One member, usually he smaller, benefits from association
-other member neither benefits noris harmed
-members may share space, substrate, defense, shelter, transportation or food.


What relationship best describes an association between organisms often known as facultative (loosely bound) were a members doesn't dependent on relationship from survival?
a. Symbiosis
b. Commensalism
c. Mutualism
d. Parasitism

b. Commensalism

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What ecological relationship does a pea crab living inside an oyster have?
a. Symbiosis
b. Commensalism
c. Mutualism
d. Parasitism

b. Commensalism

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What ecological relationship does Entamoeba gingivalis grazing on dead cells, bacteria, food particles in the human mouth have?
a. Parasitic
b. Mutualism
c. Commensalism
d. Symbiosis

c. Commensalism

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What type of symbiotic interaction is this?

-Specialized form of commensalism (subset)
-Fairly loose association; no physical /biological dependence
-one organism, usually smaller (phoront), uses larger organism as transport
Dermatobia hominis (bot fly) eggs laid on abdomen of carrier host fly.
Phoretic mites on Nicrophorus spp. (burying beetle)

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What is mutualism?

-Association where both organism derive mutual benefit
-Relationship frequently intimate and obligatory (rather than facultative)
-Members are highly depend on relationships for survival.
Ex: Amphiprion perideraion resting in Heteractis magnifica; a typical clown fish-sea anemone relationship each other protects the other form predators.


Define Parasitism:

An organism living in or on another living organism, obtaining from it part or ALL it organic nutriment, usually detrimental to host.


What are the levels of parasitism?

-Obligate (most common) dependent on relationship with host for survival.
-Facultative normally non-parasitic organisms can become opportunistic parasites (transitions during life cycles)


Define Endoparasite and give an example?

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Live inside host
Ex: Trichinella spiralis in muscle tissue


Define Ectoparasite and give an example?

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Live on or close to the host surface
EX: Cattle louse; Haematopinus eurysternus


How is the jumping spider Evarcha culicivora and indirect parasite?

This is an unusual form of parasitism because no spiders can feed directly on human/animal blood, however it chooses to eat blood-fed female mosquitoes.


Another type of unusual parasitism is called Hyperparasitism:

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a parasite of a parasite and example is male Ornithodoros parkeri taking blood from a female.


Host specific:

-some parasites infect only a single host
-Other infect individuals across phyla


Definitive host:

Host in which parasite reaches sexual maturity


Intermediate host:

Required for parasite development, but does not reach sexual maturity in this host


Reservoir host:

-host in which parasite normally lives & multiplies
-Can serve as source of infection for other humans/anmials



Typically an invertebrate (usually an arthropod) that transmits an infectious agent (parasite) to vertebrate host


Direct LIfe Cycle

Organism is directly passed from one host to the next by aerosols , objects, feces, food/water, ect.


Indirect Life Cycle:

Organism develops and/or multiplies in a vector on intermediate host before being passed to the definite host.