Parasitology: Types of Parasites

Study Notes

A parasite is an organism that lives in or on another organism (host) and causes harm.
Accidental parasite: a parasite that attacks an unnatural host and survives (e.g., Hymenolepis diminuta, a rat tapeworm).
Intermittent parasite: arthropodes, such as mosquitoes, which periodically feed on larger organisms.
Monoxen parasite: a parasite that completes its life cycle in or on one host.
Heteroxen parasite: a parasite that completes its life cycle in or on more than one host.

Definitive host: the host in which the sexual or adult form of the parasite is found.
Intermediate host: the host in which the asexual or immature, or larval form of the parasite is found.
Patient: a person who has parasites in their body and shows clinical symptoms.
Carrier: a person who has parasites in their body but does not show symptoms.
Reservoir host: an animal that harbors the same species of parasites as humans.

Non-pathogenic parasites: live in/on the body of the host and do not cause disease.
Pathogenic parasites: are disease-causing parasites.
Opportunistic parasites: do not generally produce disease in healthy individuals but cause illness in individuals with impaired immunity.

Infection: the presence of a parasite in or on the tissues of the host.
Infestation: the presence of arthropods on the skin of the host.
Transmission: human-to-human, animal-to-human, food-borne, water-borne, blood-borne, vector-borne, and sexual transmission.

A) Syngamy: sexually different cells unite to form a zygote.
B) Conjugation: 2 cells attach to each other, and the exchange of nuclear material occurs.

Nematodes (Roundworms): multicellular, macroscopic adult forms, microscopic eggs, complex life cycle.
Trematodes (Flukes): multicellular, macroscopic adult forms, microscopic eggs, complex life cycle.
Cestodes (Tapeworms): multicellular, macroscopic adult forms, microscopic eggs, complex life cycle.

Unsegmented body tapered at each end, body covered by tough cuticle that resists drying and crushing.
Possess developed digestive and excretory organs.

A type of protozoa that has an apical complex that helps the organism enter the host cell.
No locomotion organelles.

Small, microscopic, eukaryotes, unicellular organisms, wide range of sizes and shapes.
Contain nucleus and functional organelles.
Reproduce quickly, may have asexual and/or sexual phase in the host and/or vector.