What is the traditional definition of a parasite?
An organism that lives in or on a host of another species and requires the host for nutrition and reproduction.
Which types of organisms can act as parasites?
Protozoa, nematodes (roundworms), and flatworms.
What protozoan parasite causes malaria?
Plasmodium falciparum.
How is malaria transmitted?
Mosquito-borne transmission.
Which region accounts for 90% of malaria cases?
Sub-Saharan Africa.
How many deaths per year does malaria cause?
Up to 1 million deaths per year.
What is the mechanism of action of chloroquine?
Becomes protonated and trapped in acidic lysosome, preventing hemoglobin digestion.
Why does chloroquine resistance occur?
Mutations enhance drug efflux from parasite vesicles via transporter proteins.
What is the mechanism of quinine?
Inhibits heme polymerase → toxic free heme accumulates.
Why is quinine widely used today?
Chloroquine resistance.
Pyrimethamine acts as an antagonist to which metabolic pathway?
Folate metabolism (inhibits dihydrofolate reductase).
Why does pyrimethamine selectively target parasites?
It has higher affinity for parasite DHFR than human.
How does resistance to pyrimethamine occur?
Single point mutation in DHFR enzyme.
Which helminth groups commonly infect humans?
Cestodes, intestinal nematodes, tissue nematodes, trematodes.
Praziquantel is the drug of choice for which infection?
All species of schistosomes.
What is the mechanism of action of praziquantel?
Activates Ca2+ channels causing paralysis and enhances immune susceptibility.
What is the mechanism of action of piperazine?
GABA receptor agonist on parasite muscles → paralysis.
Which worms does piperazine treat?
A. lumbricoides (roundworm) and E. vermicularis (threadworm).
What is levamisole’s mechanism?
Nicotinic acetylcholine receptor agonist causing NMJ stimulation then blockade.
Ivermectin is the drug of choice for which disease?
Onchocerciasis (river blindness).
What is ivermectin’s mechanism?
Opens glutamate-gated chloride channels → paralysis.
Where are glutamate-gated chloride channels found?
In invertebrates only.
What happens when glutamate-gated chloride channels open?
Chloride influx → hyperpolarization → paralysis.
What organism is used experimentally to express parasitic glutamate-gated chloride channels?
Xenopus oocytes (frog oocytes).
