Helpful Definitions

Predation

attack and frequently kill

Scavenge

already dead

Symbiosis

a close association

Commensalism

• Type of Symbiosis

• “Eating at same table”/ Mutualism

Parasitism

• Type of Symbiosis

• Some degree of harm

• Close/prolonged contact

Infective stage

Form/stage of parasite ingested by or introduced to host, causing parasitism

Diagnostic stage

Specific form/stage of parasite (often microscopic) that contributes to identification of parasite

Intermediate host

Required host in life cycle in which larval development must take place

Paratenic host

host in which parasite survives w/out maturation (Summerfest shuttle)

Definitive host

Host in which sexual reproduction occurs

Rhabditiform larvae

Early development stage of larvae (L1 larvae)

Filariform larvae

infective third-stage larvae (L3 larvae)

Larva migrans

larval helminth (typically a nematode) that wanders in host tissues (cutaneous, visceral, ocular) because it cannot mature into adult

Soil-transmitted helminth (3)

• affects 1.5 billion worldwide

• Roundworm, hookworm, whipworm

• periodic deworming of children in areas of ≥ 20% prevalence

Oviposition

laying eggs

Parthenogenesis

form of sexual reproduction in which organism develops without fertilization by male (threadworm)

Autoinfection (2)

• infection by a pathogenic agent already within body

• infection transferred from one part of body to another

Buccal cavity

space between the oral opening and the beginning of the esophagus in roundworms (rhabditiform larvae)

Genital primordium

ovoid clump of cells that becomes the reproductive system (rhabditiform larvae)

Scolex

anterior end of a tapeworm, bearing suckers or hooks for attachment

Proglottid

segment of a tapeworm, containing both male and female reproductive organs (hermaphrodite)

Oncosphere

spherical, six-hooked tapeworm larva inside eggshell

Operculum

trapdoor; lid-like structure at one end of eggshell though which larva escapes

Aboperculum

end of egg opposite of opercular end

Hydatid cyst

stage of Echinococcus tapeworm; large bladder in which daughter cysts and scolices develop

Cysticercus

stage of Taenia solium tapeworm in which single scolex is invaginated into a fluid-filled bladder

Charcot-Leyden crystals (3)

• slender crystals (double, elongated pyramids with pointed ends) that are formed from the breakdown products of eosinophils

• can be found in feces, sputum, and tissue

• indicative of immune response to a parasitic infection

Miracidium

free-living, ciliated larva released from trematode egg and infective for mollusk intermediate host

Cercaria

free-living, tailed larval stage of trematode; can penetrate human skin OR encyst (vegetation, vertebrates)

Metacercaria

infective, encysted larval stage of trematode

Hermaphrodite

both female and male reproductive organs in same parasite (cestodes; most trematodes)

Trophozoite

feeding, motile stage of protozoa

Cyst

resting stage of protozoa

Karyosome

concentrated clumps of chromatin material within nucleus; position and morphology often used to differentiate intestinal protozoa

Chromatin

deep-staining DNA-containing portion of nucleus (protozoa)

Chromatoidal bar

deep-staining, bar-shaped, round or splinter inclusions found in cytoplasm of certain amoebae (Entamoeba spp.)

Sporogony

stage in sexual cycle of Plasmodium spp. that occurs within mosquito, with eventual production of infective sporozoites

Schizogony

stage in asexual cycle of Plasmodium spp. that occurs within erythrocyte, with eventual production of merozoites

Merozoite

product of schizogonic cycle in malaria produced in liver (pre-erythrocytic cycle) produced in erythrocytes (erythrocytic cycle)

Amastigote

small, round, intracellular stage of Leishmania spp. and Trypanosoma cruzi in which base of flagellum is anterior to nucleus (but no external flagellum)

Promastigote

extracellular stage of Leishmania and Trypanosoma; base of flagellum continues anterior to nucleus, free flagellar portion is short

Epimastigote

extracellular stage of Trypanosoma spp.; base of flagellum continues anterior to nucleus, flagellum passes through body and attached by undulating membrane

Trypomastigote

extracellular stage of Trypanosoma spp.; flagellum is now posterior to nucleus