Protozoa and Helminths Lecture Review

Practice flashcards covering the characteristics, classifications, and medical importance of protozoa and helminths based on lecture notes.

Trophozoites

The feeding and growth part of the protozoan life cycle (active form).

Cyst

A cell with a protective wall that allows survival when food, moisture, or oxygen are lacking, or when toxic chemicals are present.

Encystment

The process by which a trophozoite becomes a cyst.

Cytostomes

Oral grooves lined with hair-like cilia used by some protozoans to sweep in food particles.

Holozoic

Heterotrophic protozoans that ingest whole food particles through phagocytosis.

Saprozoic

Heterotrophic protozoans that ingest small, soluble food molecules.

Contractile vacuoles

Organelles used to move water out of the cell for osmotic regulation (salt and water balance).

Giardia intestinalis

Also known as $G.\text{ lambia}$ or $G.\text{ duodenalis}$, this flagellate has cysts excreted in feces and causes severe diarrhea.

Trichomonas vaginalis

A flagellate with an undulating membrane that causes urinary and genital tract infections; it lacks an infectious cyst phase and must be transferred host to host.

Euglenozoa

Flagellated autotrophs with disk-shaped mitochondria and a red eyespot for light direction; they lack sexual reproduction.

Trypanosoma brucei

The hemoflagellate that causes African sleeping sickness and is transmitted via the bite of a tsetse fly.

Trypanosoma cruzi

The pathogen that causes American sleeping sickness (Chagas disease), transmitted by the kissing bug (triatomine bug).

Entamoeba histolytica

A pathogenic amebae that causes bloody fatty stool and is transmitted through the ingestion of cysts in feces.

Acanthamoeba

An amebae found in fresh water that causes eye infections (keratitis) and can disseminate to the brain.

Naegleria fowleri

An amebae found in warm fresh water that enters through the nasal mucosa and migrates to the brain, causing primary amebic meningoencephalitis (PAM).

Apicomplexa

A phylum of non-motile, obligate parasites with complex life cycles, typically involving intermediate hosts and vectors.

Toxoplasma gondii

An apicomplexan that is a leading cause of death from foodborne illness in the US; it is particularly dangerous to unborn children and the immunocompromised.

Definitive host

The host in which sexual reproduction of a parasite occurs (e.g., the Anopheles mosquito for Plasmodium).

Intermediate host

The host in which asexual reproduction or larval development occurs (e.g., humans for Plasmodium).

Plasmodium spp.

Apicomplexans that cause malaria; humans harbor sporozoites which divide in the liver to release merozoites.

Cryptosporidium

Often called 'crypto,' this parasite causes GI infections that are usually self-limiting and can be stained with carbolfuchsin.

Balantidium coli

The only member of the ciliate phylum known to be pathogenic to humans; it originates from fecal contamination and causes mucoid bloody stool.

Dioecious

Organisms that have separate male and female individuals.

Monoecious (hermaphroditic)

Organisms that possess both male and female reproductive systems in one animal.

Trematodes

Also known as flukes; leaf-shaped platyhelminths with ventral and oral suckers that absorb food through a cuticle covering.

Cestodes

Tapeworms that use a scolex for attachment and consist of body segments called proglottids.

Scolex

The head of a tapeworm equipped with suckers (and sometimes hooks) for attachment to the host.

Proglottids

Body segments of a tapeworm that contain both male and female reproductive organs.

Nematodes

Roundworms that are cylindrical with complete digestive systems; includes species like Ascaris lumbricoides and Enterobius vermicularis.

Dirofilaria immitis

A nematode spread by mosquitoes that causes heartworm.

Biological transmission

Vector transmission where the pathogen multiplies in the vector and the vector acts as the definitive host for sexual reproduction.