Overview Flashcards
obligate parasite
cannot exist without the host
facultative
parasite which can live in the environment on its own but also infect the host
endo-
internal parasites
ecto-
external parasites
spurious parasites
not a true parasite, at least in the host in which it is found; “false” parasite
example of a spurious parasite
something found on
fecal examination that is from a source outside of the individual and is
not related to an infection of the individual being examined; often
derived from eating part of a host infected with a parasite
zoonotic parasite
parasite that typically infects animals but have ability to infect humans
host
organism which harbors and nourishes the parasite
host-specific parasites
can only infect and cause disease in a particular host
definitive host
host in which parasite undergoes sexual reproduction
intermediate host
no sexual reproduction of parasite, but can replicate via binary fission
vector host
living organism which carries a parasite from host to host; can undergo both sexual reproduction and binary fission in vector
reservoir host
host in which the parasite lives and develops but does not cause disease and is available for transmission
paratenic (transfer) host
atypical (substitute) intermediate host that
ingests & harbors infective parasite stage which remains active and unchanged (a collector or storage host)
What happens if something ingests a paratenic host?
parasite will undergo its typical development and cause disease
Steps for Parasite to Complete Life Cycle
Find host
Reach development site in/on host
Survive in/on host
Evade host immune system
Feed & reproduce
Release eggs or larvae out of host
Survive in external environment
development site
area within/on the host for parasites to target, which is usually one specific site within the host (like lungs or intestines)
Is the parasite-host relationship typically short or long term?
long term
4 Modes of Parasite Transmission
- Free-living Passive (accidental ingestion)
- Free-living Active (accidental penetration)
- Infected intermediate host ingested by definitive host
- Vector transmission
5 Main Categories of Parasites
- Protozoa
- Platyhelminths
- Nematodes
- Acanthocephala
- Arthropods
Direct Effects of Parasite on Host
feeding and destroying tissues, production of toxins, mechanical interference
Indirect Effects of Parasite on Host
host allergic responses, secondary infections, manipulate the host via behavioral changes (competition/predation)
Do larger parasites have a larger effect?
not necessarily - some small parasites are much more pathogenic than larger ones
Costs and Benefits of Host Specificity
host finding, adaptation to host, avoidance of host response
Limits of Narrow Specificity
limits distribution of the parasite and improves the probability of synchronization or parasite and host life cycles
Can parasites end up in the wrong place, or even host?
apparently yes
Protozoa
single cell eukaryotes classified based on morphology and means of locomotion
Trichomonas
mucoflagellate protozoa with multiple flagella, a tail-like flagella at the opposite end, and a single nucleus
Giardia
mucoflagellate protozoa with multiple flagella and two nuclei
Difference Morphologically between Trichomonas and Giardia?
number of nuclei - trich has one, giardia has two
Trypanosoma
hemoflagellate, little flagella (one) will keep it moving, can be seen on blood smears?
Babesia
hemosporidian protozoa - pear shaped and found within RBC
2 Forms of Leishmania
- Insect Stage
- Mammalian (Intracellular) Stage
Coccidia Protozoa
crescent shaped with elaborate organelles
Protozoas in Phylum Metamonada
Giardia
Protozoas in Phylum Amoebozoa
Entamoeba
Protozoas in Phylum Ciliophora
Balantidium
Protozoas in Phylum Parabasalia
Trichomonas, Tritrichomonas
Protozoas in Phylum Euglenozoa
Leishmania, Trypanosoma
Protozoas in Phylum Apicomplexa
Babesia, Cryptosporidium, Eimeria, Cytauxzoon, Neospora, Isospora, Toxoplasma, Theileria, Hammondia, Sarcocystis
2 Classes of Platyhelminths (or 4)
- Trematodes
- Cestodes
(3. Turbellaria
(4. Monogenea)
Trematodes (class Trematoda)
flukes (large flatworms)
have a reproductive system (eggs)
can be found in many different organ systems and cause a variety of disease
Digenia
subclass of trematodes that contains many parasites of veterinary importance
Turbellaria and Monogenea
classes of flatworms that are parasites of fish and aquatic organisms, respectively
Cestodes (class Cestoda)
multi-segmented worms with complex life cycles
have hooks to dig into animal tissue and suckers to help attach to tissue so it doesn’t get flushed out; also proglottids
Cestodaria
subclass of cestodes which are non-segmented parasites of marine fish
rostellum
aka mouth (at least on tapeworms)
proglottid
one segment of a tapeworm which have both male and female reproductive tracts (usually full of eggs); one can break off the entire worm and be enough to cause infection
Eucestoda
the other subclass of Cestoda (majority here versus Cestodaria)
Nematodes (phylum Nematoda)
unsegmented roundworms, vary in length, can be free-living or parasitic, most are dimorphic
Difference between Male and Female Nematodes
males are smaller than females and have a bent tail for holding the female for copulation
Acanthocephala
“discrete” phylum
thorny headed worms (for digging into animal tissue) or which there are several important species in swine and wildlife (but overall not super common)
Arthropods (phylum Arthropoda)
includes subphylum Hexapoda and class Arachnida
Hexapods (Insects)
mosquitoes, lice, fleas
Arachnids
ticks and mites
