Definitions relevant to Parasitology

PARASITE: An organism which derives sustenance or benefit at the expense of its host.

ENDOPARASITE = internal

ECTOPARASITE = external

OBLIGATE: Parasite stage necessary for completion of life cycle.

e.g., Trichuris trichiura, Entamoeba histolytica.

FACULTATIVE: Normally free-living, but can exist as a parasite.

e.g., Strongyloides stercoralis.

ACCIDENTAL: A parasite found in an abnormal host.

e.g., Naegleria fowleri.

HOST: That organism which is necessary for the development of a parasite.

DEFINITIVE: Parasite reaches sexual maturity.

e.g., Humans for Clonorchis sinensis

INTERMEDIATE: Necessary for development, but parasite does not reach sexual maturity.

e.g., cyprinid fishes for Clonorchis sinensis

PARATENIC: A host which is not necessary for the physiological development of the parasite, but which facilitates transferral from the intermediate host to the definitive host to the definitive host.

VECTOR: Any agent, e.g. insect, that transmits a disease organism.

HYPERPARASITISM: Parasite serving as a host for another parasitic species.

For Protozoa:

TROPHOZOITE: Metabolically active form of protozoan parasites,

within the apppropriate organ of the host.

CYST: Metabolically inactive form of protozoan parasites,

adapted for transmission.