ZOOL 452 – March 4, 2014
Information on the midterm
• Practice doing conceptual analyses on Parasitology concepts.
• Think of the kinds of questions that would be asked
Tissuedwelling protozoan parasites
• Host Finding
o Through insect vectors. Passive transmission in that way
o Contaminated water sources. Oral ingestion.
Eg: Eimeria, Cryptosporidium, Toxoplasma (which can cause
o Deep French kissing. There are reports of individuals transmitting
intracellular parasites through kissing. This is rare.
• Establishment in the host
o Some parasites go to specific hosts. Some go to many different kinds of
o How do they go to specific cells? Receptor specificity and ligand
Going into a single cell type is an evolutionary disadvantage. This
makes it easier for the host to eliminate the parasite.
Eg: Plasmodium. Apicomplexans, in general, have the organelles
called rhoptries that are used to get into host cells.
Eg: Leishmania. Specific set of receptors that are used to get into
o Not all tissue specific parasites live inside cells. Eg: Trypanosomes.
o Most of the protozoans that live in the tissues are flagellates.
o Intracellular protozoans have to set up where they will live in the cell.
Plasmodium lives in a parasitophorous vacuole. Leishmania lives in the
T. cruzi just multiplies in the cytoplasm of individual cells; this is
why is it more of a generalist than a specialist, because it can live
both inside and outside of a cell.
o T. carassii ▯ extracellular protozoan. This parasite tries to control its
numbers so that its fish host will not die. Killing the fish is to the
disadvantage of the parasite.
very few fish will be killed, because the fish, if they are
immunocompetent, have the ability to eliminate the infection.
o Killing the host is NOT an option
The amount of time that is needed to transmit the parasite to
another host is reduced if the host is killed.
• Living in the host o Host cell is instructed to nourish them. Lots of evolutionary adaptations
have happened. Some parasites generate their own organelles within the
Eg: Hydrogenosome and glycosome
• Hydrogenosomes are membraneenclosed organelles of
some anaerobic ciliates and trichomonads that produce
molecular hydrogen, acetate, CO2, and ATP
• Glycosome = membraneenclosed organelle that performs
the function of glycolysis in Trypanosoma brucei,
Trypanosoma cruzi, and the Leishmania spp.
For the ones that live in the blood ▯nutrients are readily available.
Good quality food supply that is in the simplest form.
• Advantage: More stable environment than the gut.
Everything is kept the same.
• Advantage: There are no gradients in the blood. More
stable environment. Protozoan parasites of the blood do not
have to deal with changes in levels of stuff.
o Parasites that live in the epithelial cells (eg: Cryptosporidium) have to
develop very quickly, because the epithelial cells slough off every 4 days.
Some degree of urgency.
Most of them finish their development in 96 hours. Rapid
o Parasites leave the cell when the cell lyses. This happens through necrotic