Parasitology Lecture 8 Flashcards
Introduction to Parasitology
Definition of parasite
an organism that lives on or in a host organism and gets its food from or at the expense of its host
True or false: viruses, bacteria, and fungi can be considered parasites
True (although it depends on who you’re talking to)
Medical parasites are considered as ____ ____
eukaryotic pathogens
How many species of protozoans are known to be human parasites?
70
How many species of helminths are known to be human parasites?
300
True or false: there are thousands of parasites known to exist, but only a small subset affect humans
True
The number of parasites is growing due to:
sequencing
True or false: some parasites are insects or arachnid ectoparasites
True
Since we’re considering eukaryotic parasites, some key features they have are: (2)
membrane-bound organelles, nucleus
True or false: there isn’t much diversity regarding the parasites that infect livestock
False - huge diversity (there are some overlaps)
True or false: some parasites infect plants
True
What are 3 classes of human parasites?
- Protozoa
- Helminths
- Ectoparasites
Depending on life cycle, protozoa may be __-___ or ____
free-living or parasitic
True or false: pathogenic protozoa don’t usually multiply in humans, whereas worms can multiply in humans
False - worms usually don’t multiply in humans but protozoa do
Common modes of transmission of protozoa include: (2)
- fecal-oral route (GI inhabitant)
2. arthropod vector (blood/tissue inhabitant)
Name the 4 categories of pathogenic protozoa based on mode of movement
- Amoebozoa (pseudopods)
- Mastigophora (flagellates)
- Ciliophora (ciliates)
- Sporozoa (not motile in adult stage)
Example of Amoebozoa
Entamoeba
Example of Mastigophora
Giardia, Leishmania
Example of Ciliophora
Balantidium
Example of Sporozoa
Plasmodium
Which of the following classes of Protozoa reproduces via schizogony? A. Amebas B. Ciliates C. Sporozoa D. Flagellates
C. Sporozoa
Binary fission
Cell contents double and are halved into 2 daughter cells
Schizogony
Huge amplification process within a host cell to increase progeny, after a certain amount of time the nuclei acid material splits up and is released
Entamoeba histolytica lives in the ___ and causes:
gut; dissolves tissue
True or false: Plasmodium falciparum is the most deadly of the malaria parasites
True
Trypanosoma cruzi appearance in blood smear:
stain purple, extracellular (not found inside RBC), large kinetoplast, centrally located nucleus
Leishmania donovani is usually found within ___ ____
bone marrow
Helminth parasites are ___, ___-____ organisms
large, multi-cellular
True or false: helminths are usually visible to the naked eye as adults
True
True or false: helminths can be free-living or parasitic
True
Three main groups of helminths:
- flatworms (trematodes)
- Cestodes (tapeworms)
- Roundworms (nematodes)
True or false: thorny-headed worms are common parasites that infect humans
False - rare
3 characteristics used to categorize helminths
morphology, sex, GI tract
Roundworm morphology
Earthworm shaped (or spindle)
True or false: Roundworms are hermaphroditic
False - separate sexes
Roundworm GI tract
tubular
Tapeworm morphology
head with segmented body
Tapeworm GI tract
none - each segment absorbs nutrients/excretes waste
Fluke morphology
leaf shape with oral/ventral suckers (to attach to lumen)
Both tapeworms and flukes are ______
hermaphroditic
Schistosoma parasites cause disease in:
GI tract and bladder
Ectoparasites are:
ticks, fleas, lice, and mites that attach or burrow into the skin and remain there for relatively long periods of time
Ectoparasites effects on host (2)
- directly cause disease
2. transmit pathogens (most)
True or false: blood-sucking arthropods like mosquitoes may be considered as ectoparasites
True
Examples of important intestinal parasites in the US
Enterobius vermicularis, Giardia lamblia, Entamoeba histolytica
Historically, what types of people are at the highest risk for parasitic infection?
Minorities, immigrants, and poor/disadvantaged people (those w/o access to healthcare)
Why is it important to know the geography and host range of parasites?
Often can be a defining factor or help us diagnose if we know where Pt has been or where they are
Definitive host
organism where sexual cycle of parasite occurs
Intermediate host
organism that harbors parasite for transition period, often where asexual cycle occurs
Accidental host
Non-natural host but may cause infection if there’s contact
Dead end host
intermediate host that can’t transmit the infection to the definitive host
Delusional parasitosis
rare psychiatric disorder in which Pt has a fixed, false belief that they’re infested with parasites
(often reject psychiatric intervention but treated with antipsychotic meds/counseling)
Examples of structures that can be mistaken for parasitic material
Plant material, pollen, vegetable cells, weird looking platelets, Charcot-Leyden crystals, nucleated RBC, Howell-Jolly bodies
