Parasitology: The Parasite's Way of Life

Vocabulary flashcards covering key terms, life cycle definitions, host classifications, transmission routes, and parasitic adaptations from Chapter 3.

Direct Life Cycle

A parasite life cycle that utilizes only a single host species to complete development.

Indirect Life Cycle

A parasite life cycle that requires two or more host species to complete development.

Definitive Host

The host organism in which a parasite undergoes sexual reproduction.

Intermediate Host

The host organism in which a parasite undergoes larval development or asexual reproduction.

Paratenic Host

A nonessential host in a parasite life cycle that does not undergo developmental changes but increases the likelihood of transmission to a definitive host.

Feco-Oral Transmission

A transmission pathway where infective parasite cysts or eggs passed in stool are ingested through contaminated food, water, or fomites.

Trophozoite

The active, motile, feeding, and reproducing stage of a protozoan parasite, such as Giardia lamblia.

Cyst

The metabolically inactive, resistant, and infective form of a protozoan parasite capable of surviving outside the host.

Trophic Transmission

A transmission strategy where a parasite utilizes predator-prey relationships across trophic levels to move from an intermediate host to a definitive host.

Vector Competence

The intrinsic ability of a specific vector type to become infected with, support development of, and transmit a specific pathogen.

Primary Vector

A vector species capable of maintaining a parasite transmission cycle independently in the absence of other vector species.

Secondary Vector

A vector with lower transmission capacity that can transmit a parasite but cannot maintain the transmission cycle on its own.

Vertical Transmission

Transmission of a parasite directly from mother to offspring via trans-placental routes, breast milk, or infected gametes.

Polyembryony

A form of asexual reproduction in digenetic trematodes where a single embryo produces multiple offspring within an intermediate host.

Tachyzoites

The rapidly replicating form of Toxoplasma gondii responsible for acute tissue infection and cellular invasion.

Bradyzoites

The slowly replicating form of Toxoplasma gondii contained within tissue cysts during chronic infection.

Cutaneous Larval Migrans

A creeping skin condition in humans caused when larvae of non-human hookworms, such as Ancylostoma braziliense, penetrate and migrate through skin epithelium without invading deeper tissue layers.

Allee Effect

A phenomenon where individual fitness increases as population density increases, helping dioecious parasites locate sexual partners within a host.

Genome Reduction

The evolutionary reduction in genome size and protein-encoding gene count in eukaryotic parasites adapted to stable, host-provided environments.

Portal of Exit

The anatomical structure or route through which a parasite propagule leaves the host body.

Stumpy Induction Factor (SIF)

A density-dependent chemical signal produced by long slender forms of Trypanosoma brucei that triggers differentiation into short stumpy forms for vector transmission.

Dracunculus medinensis

A parasitic nematode (Guinea worm) historically extracted by winding the worm around a stick.