Parasitology Exam 2: Platyhelminthes

Are Platyhelminthes segmented?

NO! tapeworms are Strobilated

Platyhelminth coelum

acoelomates

Parenchyma

the “packing peanuts” for acoelomates that holds organs in place

Osmoregulation organ in Platyhelminthes

protonephridia

Platyhelminth digestive system

incomplete gut (lost gut in tapeworms)

Platyhelminth muscular system

circular & longitudinal muscles

Digenea

endoparasitic flukes of vertebrates in the adult stage of their life cycle

Platyhelminth Classes

Turbellaria, Trematorda, Monogenea, Cestoidea

Syndesmis

parasitic Turbellarian of sea urchins and sand dollars

Turbellaria

class of Platyhelminthes that are mostly free-living

Trematoda

class of Platyhelminthes: the parasitic flukes

flukes class

Trematoda

Tegument

mass of protoplasm without division of cells on the outside of the trematoda and cestoideas.
used for inhibiting digestive enzymes, nutrition uptake and anchoring with actin spines

actin spines

on the tegument, used for anchoring self to hold

Aspidobothrea

Trematoda that are endoparasites of molluscs

Opisthaptor

body part used for attachment to host

Protonephridia

“flame cell” used for excretion of NH3

Fluke digestive system

incomplete (one opening- oral sucker)

Operculum

lid on fluke egg

Acetabulum

a sucker on a fluke use for attachment (central of body)

Fluke reproduction

all monecious, EXCEPT Schistosoma-dioecious

cirrus

male copulatory organ on flukes

Fluke Life Cycle (body forms)

Egg —> Miracidium —> Sporocyst —> Redia/daughter sporocyst —> cercaria —> encysts on/in host (Schistosoma skips this) —> metacercariae/adult

What life stage is used for fluke diagnoses?

egg

Miracidium

fluke: “hairy peanut” non-feeding, swimming body form that emerges from the egg and is finding its first host

Sporocyst/Redia

fluke: life stages in 1st host (snail) -non-feeding, begins proliferation (asexual), makes germ balls that give rise to cercaria

Cercaria

fluke: life stage leaves the snail host and is looking for the next host, non-feeding stage, swimming stage, has a tail (split tail= Schistosoma)

Encysted metacercaria

fluke: infective stage, encysted in or on 2nd host (except Schistosoma-skips this step), can survive stomach acid: excysts in small intestine

Metacercariae

fluke: adult form: in the vertebrate host (definitive), sexually mature

Fluke growth & metamorphosis stages

egg, miracidium, sporocyst

Fluke proliferation stages

daughter sporocyst, redia, cercaria

infective stage of most flukes

encysted metacercaria (except Schistosoma)

Alaria americana

Fluke of canids (dogs, fox, etc)

Alaria americana hosts

Snail (intermediate 1)—> tadpole (intermediate 2)—> snake (paratenic) —> canid (definitive)

How can humans get infected with Alaria americana?

eating frog legs- becomes ectopic in lungs, stomach, brain- fatal

miracidium always penetrates a _____ host

snail (1st intermediate host)

heart lung migration purpose

mimics an additional host

Alaria americana transmission

Trophic- fox eats infected snake (or frog)

Bilharzia disease is caused by…

Schistosoma spp.

Blood flukes

Schistosoma spp.

How are Schistosomes different from other flukes?

diecious, skips encystment stage, in blood

Schistosoma japonicum where in the body does the female release eggs?

mesenteric veins of the small intestines (released via feces)

Schistosoma mansoni where in the body does the female release eggs?

mesenteric veins of the large intestines (released via feces)

Schistosoma haematobium where in the body does the female release eggs?

venus plexus near urinary bladder and ureters (released via urine)

Schistosoma world locations

Egypt, China, AfJorica, S. America, Caribbean

Joshua’s curse on Jericho parasite

Schistosomes

What parasite is common in the Nile River (Egypt)?

Schistosomes

Schistosoma hosts

snail —> humans

Schistosoma mansoni egg

Schistosoma haematobium egg

Life cycle of Schistosomes (starting at egg)

1. eggs released in human feces or urine

2. egg hatches into miracidium when in freshwaters

3. miracidium swims to find snail host

4. miracidium penetrates snail

5. develops into cercaria in snail

6. cercaria released from snail

7. cercaria swims to find definitive host

8. cercaria penetrates through the skin of human & loses tail

9. covers itself in host antigens

10. migrates to liver to feed & mature

11. develops into adults

12. sexual reproduction in mesenteric veins of intestine or bladder

13. male dies, female migrates to specific host site

14. female releases eggs with stool or urine

What is unique about the Schistosome cercaria

forked/split tail

Schistosome symptoms

• localized dermatitis (where penetrated skin)

• fever & congestions during migratory phase (or asymptomatic)

• chills, fever, fatigue, headache, malaise (acute phase/egg production)

• for S. haematobium: hematuria, pain with urination, loss of bladder function

• Ascites- build up of fluid

Where in the world is Schistosoma mansoni?

New & Old World (Brazil, Caribbean, Africa)

Where in the world is Schistosoma haematobium?

Old World (Africa)

Where in the world is Schistosoma japonicum

Old World (China, Japan)

Chronobiology

the release of cercariae at a specific time of day when definitive host is most active

Reservoir host of Schistosoma japonicum

dog/cat

Schistosome treatment

Praziquantel

Swimmer’s Itch

Cercarial dermatitis

schistosomes that are in the wrong host (usually a bird)

very common in the great lakes

Swimmers Itch symptoms

• tingling after emerging from water

• red spots form

• intense itching for several days

How to avoid swimmer’s itch?

towel off when you exit water
swim away from shallow areas
apply sunscreen

If there are schistosomes in the water, does that make it polluted?

No! natural lake conditions with lots of diversity

Eosinophilia

high eosinophil count- associated with helminth infection

Echinostoma

• fluke parasite of birds, mammals, crustaceans and amphibians

  • common in frogs- inhibit tadpole growth-legs

• “spiney head”

• non-host specific

Fasciola hepatica common name

Sheep Liver Fluke

Fasciola hepatica transmission

trophic

Fasciola hepatica hosts

definitive: sheep, cattle, goats

intermediate: snail

encysts ON aquatic plants

Where in the mammal body is Fasciola hepatica?

bile ducts, gallbladder and liver

Fasciola hepatica life cycle (start at egg)

1. egg passed through sheep feces

2. miracidium hatches in water

3. miracidium swims to find and penetrate snail host

4. develops into sporocyst —> redia —> cercaria

5. leaves snail and swims to encyst on aquatic plant

6. plant and cyst ingested by mammal

7. develops into metacercaria

8. migrates to bile ducts/liver & sexual reproduction

9. eggs released in the feces

acute phase Fasciola symptoms

• migratory phase of the larvae that can last for weeks

• diarrhea

• fever

• nausea

• stomach ache

• vomiting

• eosinophilia

Fasciola chronic phase symptoms

• adults are in the large biliary ducts

• liver inflammation

• bile fluid obstruction

Fasciola eggs

oval shape with an operculum

Dicrocoelium dentriticum

parasite of sheep, cattle, goats and pigs

causes behavior change in the intermediate host (ant) where they climb to the top of a blade of grass, increasing odds of getting eaten by determinate host

Paragonimus westermani common name

lung fluke

Paragonimus westermani life cycle starting at egg

1. eggs passed via feces or coughed up with sputum

2. miracidium develops in eggs when in freshwater

3. miracidium hatches and swims to penetrate snail

4. miracidium —> sporocyst —> redia —> cercaria

5. cercaria shed into water

6. cercaria swim ot find and penetrate crustacean

7. encysts as metacercaria in crustacean tissues

8. crustacean ingested by human

9. excysts in human gut

10. migrates to peritoneal cavity

11. develops into adult & migrates to lungs in pairs

How do humans get Paragonimus westermani?

eating undercooked crabs or crayfish

-used in traditional medicine in Korea, Japan & Africa

-consumed raw or prepared only in vinegar or wine w/o actually cooking it

Zone of Immune Privilege which species?

Paragonimus westermani

secretes enzymes around self that are able to digest host antibodies

Clonorchis sinensis common name

Chinses liver fluke

Clonorchis sinensis life cycle starting at egg

1. egg released in feces

2. egg ingested by snail

3. miracidium —> sporocyst —> redia —> cercaria

4. cercaria leaves snails

5. cercaria swims to find and penetrate fish

6. encyst inside fish muscle into metacercaria

7. human consumes undercooked fish

8. excyst metacercaria in duodenum

9. migrate to bile duct/liver

10. mature into adults & sexual reproduction

Paragonimus westermani transmission type (to human)

trophic (eating)

Clonorchis sinensis egg

flask shape, narrowing at operculum

Clonorchis sinensis transmission type (to human)

trophic: human eating undercooked fish

Heterophyes heterophyes

intestinal fish fluke

Heterophyes heterophyes hosts

snail —> fish —> fish eating mammals

How many suckers does Heterophyes heterophyes have

3: oral, acetabulum (ventral) & gonodyl (genital)

Ribeiroia ondatrae

causes limb deformities in frogs (easier for bird predators to eat frog)

Ribeiroia ondatrae hosts

snail —> tadpole —> bird

Glochidia

parasitic life stage of a freshwater bivalve that is an obligate parasite of fish gills/fins (used for transportation of larvae)

opisthaptor

sucker or claws/hooks for attachment of monogenean to host

Gyrodactylus

monogenean parasite of fish that is viviparous

Polystoma

monogenan parasite of fish that is ovoviparous

viviparous

gives birth to live young

oviparous

lays eggs (not live birth)

polyembryony

• Gyrodactylus

• splitting of one sexually produced embryo into many

Cestoidea

• tapeworms

• all parasitic

tapeworm gut

no digestive tract

Cestoidea reproduction

• duplication of reproductive systems as each proglottid has its own set (monecious)

What does “armed scolex” mean?

the scolex has spikes (for attachement)