Trematodes & Cestodes - Laboratory Procedures for Veterinary Technicians

Vocabulary flashcards covering trematode and cestode morphology, diagnostic characteristics, life cycles, and clinical identification for veterinary technician laboratory procedures.

Trematodes

Flat, unsegmented parasitic flatworms (commonly referred to as flukes); most species are hermaphroditic, having both male and female reproductive organs in a single worm.

Operculum

A lid-like cap or opening situated at one pole of many oval fluke eggs through which the larva hatches.

Fecal sedimentation

A concentration technique particularly useful for detecting trematode eggs that are too heavy or dense to float in routine flotation solutions.

First intermediate host of trematodes

A snail, which is typically required in the indirect life cycle of flukes.

Paragonimus kellicotti

The lung fluke of dogs and cats; adult worms reside and produce eggs inside cystic cavities in the host's lung tissue.

Prepatent period of Paragonimus kellicotti

Approximately $5\text{–}7\,\text{weeks}$ in cats, though exact timing may vary.

Second intermediate host of Paragonimus kellicotti

Crayfish (freshwater crustaceans), in which infective metacercariae develop.

Miracidium

The ciliated larval stage of a fluke that hatches from an egg in fresh water and penetrates the first intermediate host (a snail).

Cercaria

The free-swimming larval stage of a fluke that emerges from the snail intermediate host to seek out and penetrate the secondary intermediate host (such as a crayfish).

Cestodes

Parasitic flatworms commonly known as tapeworms, characterized by an attachment head (scolex) and a segmented body composed of proglottids.

Scolex

The specialized head or organ of attachment in tapeworms, typically featuring four muscular suckers and sometimes an apical rostellum with hooks.

Rostellum

The projection on the apical surface of the scolex of certain tapeworms that bears anchor-like hooks.

Proglottid

An individual body segment of a cestode; mature segments possess functional male and female reproductive systems, while gravid segments become packed with eggs.

Oncosphere

The six-hooked (hexacanth) embryo found inside a viable cestode egg.

Dipylidium caninum

The flea tapeworm (also known as the double-pored or cucumber-seed tapeworm) of dogs and cats; adults inhabit the small intestine.

Egg packet of Dipylidium caninum

A diagnostic microscopic envelope containing variable clusters of eggs, each egg holding a six-hooked hexacanth embryo.

Dipylidium caninum proglottid

A tapeworm segment featuring two genital pores (one on each lateral margin) that resembles a cucumber seed when fresh or mobile, and an uncooked grain of rice when dried.

Intermediate hosts of Dipylidium caninum

Fleas (the usual intermediate host, where flea larvae ingest eggs and develop into cysticercoids) and chewing lice.

Taenia pisiformis

A tapeworm of dogs whose intermediate hosts are lagomorphs (rabbits and hares); adults reside in the small intestine.

Hydatigera taeniaeformis

A feline tapeworm (formerly called Taenia taeniaeformis) whose intermediate hosts are rodents; adults inhabit the feline small intestine.

Taeniid-type egg

A spherical to subspherical cestode egg with a thick, radially striated embryophore enclosing an oncosphere with three pairs of hooks; cannot be differentiated to the species level by routine light microscopy.

Taenia proglottid

A rectangular tapeworm segment possessing a single lateral genital pore.

Echinococcus granulosus sensu lato

A small taeniid tapeworm involved in canid–livestock/ungulate life cycles that causes cystic echinococcosis (hydatid disease) in intermediate hosts, including humans.

Echinococcus multilocularis

A small taeniid tapeworm involved in canid–rodent cycles that causes highly destructive alveolar echinococcosis in intermediate hosts.

Adult Echinococcus morphology

Minute adult tapeworms measuring only a few millimeters in length and consisting of a scolex and very few proglottids.

Cystic echinococcosis

A zoonotic larval infection caused by Echinococcus granulosus sensu lato where fluid-filled hydatid cysts develop in visceral organs (primarily liver and lungs) of intermediate hosts after ingesting eggs.

Alveolar echinococcosis

An invasive, tumor-like larval tapeworm infection in intermediate hosts and humans caused by Echinococcus multilocularis.