platyhelminths full breakdown

Platyhelminths

Phylum of flatworms containing two groups: cestodes (tapeworms) and trematodes (flukes)

Cestodes

Tapeworms; segmented, adults live in the small intestine and shed gravid segments

Cestode adult location

Small intestine

Cestode larval stage

Metacestode

Cestode prevalence

Very common; found in almost every vertebrate

Cestode egg diagnosis

Eggs can’t be seen on fecal; look for segments instead

Cestode nutrient absorption

Adults absorb nutrients through their skin (tegument)

Proglottid

A tapeworm segment, each with 1 set of male and female reproductive organs

Gravid segments

Egg-filled proglottids that are shed by the adult tapeworm

Cestode life cycle

Eggs eaten by IH, metacestode in IH is eaten by DH, eggs are passed into the environment

Metacestode type: 1 larva = 1 adult

Cysticercus (one larva produces one adult)

Metacestode type: 1 larva = thousands of adults

Hydatid cyst (one larva produces thousands of adults)

Taeniidae

Cestode family with square and rectangular segments; DH = predator mammal, IH = prey herbivore or mammal

Taeniidae DH

Predator mammal

Taeniidae IH

Prey herbivore or mammal

Taeniidae segment shape

Square and rectangular

Echinococcus multilocularis

Taeniid tapeworm; worm is only three segments long

Echinococcus multilocularis metacestode

Hydatid = alveolar cyst

Echinococcus multilocularis DH

Fox, dog, maybe cat

Echinococcus multilocularis IH

Small rodents

Echinococcus multilocularis accidental IHs

Humans and other animals

Echinococcus multilocularis adult size

Only three segments long

Alveolar echinococcosis

Disease caused by E. multilocularis; cysts form due to larvae, happens only in intermediate hosts

Taenia taeniaeformis

Most common tapeworm of hunting cats; DH = cats, IH = rodents

Taenia taeniaeformis DH

Cats

Taenia taeniaeformis IH

Rodents

Taenia pisciformis

Taeniid tapeworm; DH = dogs and wild canids, IH = rabbits

Taenia pisciformis DH

Dogs and wild canids

Taenia pisciformis IH

Rabbits

Non-taeniid cestodes

Cestodes whose IH = arthropods and whose metacestode = cysticercoid

Non-taeniid IH

Arthropods

Non-taeniid metacestode

Cysticercoid

Invaginated scolex

Scolex feature of non-taeniid cestodes

Dipylidium caninum

Non-taeniid tapeworm; zoonotic; IH = fleas

Dipylidium caninum zoonotic?

Yes, zoonotic

Dipylidium caninum IH

Fleas

Dipylidium caninum PPP

3 weeks

Dipylidium caninum diagnosis

Egg segments (proglottids) around feces and in areas of sleep

Dipylidium caninum life cycle

Flea larvae ingest eggs, cysticercoid forms, DH is infected by eating adult fleas

Dipylidium caninum infection route

DH eats adult fleas containing the cysticercoid

Anoplocephala

Equine tapeworms; difficult to diagnose and prevent

Anoplocephala host

Equine (horses)

Anoplocephala diagnosis and prevention

Difficult to diagnose and prevent

Anoplocephala pathogenicity

Non-pathogenic UNLESS they build up at the ileocecal junction and cause colic

Anoplocephala life cycle

Eggs ingested by mites, cysticercoid forms in mites, DH ingests mites in pasture

Anoplocephala IH

Mites

Moniezia

Ruminant tapeworm; dramatic but not harmful

Moniezia host

Ruminants

Moniezia pathogenicity

Dramatic looking but not harmful

Trematodes

Flukes; leaf-shaped parasites

Trematode shape

Leaf-shaped

Digenetic flukes

Flukes with 2 intermediate hosts

Digenetic fluke number of IHs

2 intermediate hosts

Digenetic fluke first IH

ALWAYS a snail

Digenetic fluke diagnostic test

Sedimentation, because the eggs are heavy

Digenetic fluke egg release

Adult in DH releases eggs that hatch in the water

Miracidium

Fluke larva that swims to the snail host

Metacercaria

Infective larval stage for the DH

Liver flukes PPP

3-4 months

Liver fluke migration

A few weeks after ingesting metacercariae, larvae migrate to the liver, then to the bile ducts and mature

Fasciola hepatica

Liver fluke; hosts = ruminants, rabbits, humans, dogs

Fasciola hepatica hosts

Ruminants, rabbits, humans, dogs

Fascioloides magna

Liver fluke; host = white-tailed deer

Fascioloides magna host

White-tailed deer

Nanophyetus salmincola

Carnivore intestinal fluke; second IH = fish

Nanophyetus salmincola type

Carnivore fluke, intestinal fluke

Nanophyetus salmincola second IH

Fish

Salmon poisoning disease

Disease in dogs caused by Rickettsia (bacteria) carried by Nanophyetus salmincola

Salmon poisoning agent

Rickettsia, a bacteria that causes salmon poisoning in dogs