trematoda (C. sinensis, F. hepatica, P. westermani)

clonorchis sinensis, fasciola hepatica, paragonimus westermani

provide basic info about the Trematoda

-most species are hermophroditic (has both male and female reproductive organs)

-two-way gut: mouth to esophagus. no anus, so food goes right back to mouth

-adults are endoparasites of vertebrates

-have oral and ventral suckers

describe the trematode life cycles

type of life cycle

how many hosts

what do the eggs require

what hatches from egg, provide some details of conditions in some

-indirect life cycle

-at least 2 hosts:

→Intermediate almost always snails.

→Definitive host always a vertebrate

-eggs may require time in environment for embryonation

-miracidium hatches from egg:

→free swimming (life stage to find snail host in most)

→limited sesory capability

→some dont hatch until ingested

what is the diagnostic stage of trematodes

the egg

what does the miracidia do to the intermediate host (all tremadoes have this stage)

penetration galnd will penetrate foot of snail

what hosts does asexual and sexual reproduction occur

-sexual reproduction happens in definitive host

-asexual reproduction happens in intermediate host

provide details about sporocyst (‘optional’ stage, depends on trematode species)

what does it lack, what can u infer from that

what does sporocyst make and from where

what about the next generation

what doe some have

-miracidia metamorphose

-lacks mouth/digestive system. thus not a feeding stage

-embryos in sporocyst from germinal sac. produces next larval stage by asexual reproduction

-what the next generation will be depends on species

-some have daughter sporocysts

-sac full of embryos

provide details about Redia (kinda optional, depends on species)

where does it exit from

where does it migrate

why is it more active than sporocysts

what type of digestive system

what do embryos develop into

-exits sporocyst: bursts out and exits through birth pore

-migration within mollusc/snail host

-more active than sporocysts: b/c theyre the feeding stage

-rudimentary/simple digestive system

-embryos develop into daughter redia or cercaria depneding on species

-can have 2nd generation

what can happen to the Redia in the intermediate snail host in trematodes

redia may eat another redia bc of competition

define polyembryony

how does this correlate with miracidium

definition: process where a single egg asexually reproduction/divides to produce multiple, genetically identical larvae inside intermediate snail host.

-a single miracidium can produce hundreds of cercaria. (doesnt mean high reproduce success, not all miracidium find a snail within 24hrs and will die)

provide details about Cercaria in trematode (all tremadoes have this stage)

-free swimming/ free living stage (depends on species, in water or land)

-Emerge through birth pore

-Most have tail

-stage that exits the snail

Why could the penetration glands be important to cercaria?

-how does this correlate with cercaria being the infective stage in either the 2nd intermediate host or definitive host

most have penetration glands near anterior end. indicates cercaria is the stage that has to find the next host.

-Stage infective to 2nd intermediate host (if there is a 2nd int. host)

if there isnt a 2nd intermediat host: then cercaria stage is infective to definitive host

provide details about Metacercaria in trematode

what host does this occur in and why

what type of stage is this

what happens in 2nd intermediate host

where is it present in

what happens in appropiate definitive host

-IF there is a 2nd intermediate host, then the metacercaria is the stage that occurs in the 2nd int host.

-Quiescent stage: non-feeding. non active

-In 2nd intermediate host

→Tail drops off of cercaria and Secretes cyst wall

-Present in: aquatic vegetation, sticks, rocks, etc.

-In appropriate definitive host:

→Trematode excysts

→Migrates to organ/tissue

→Matures to adult

Define Quiescent stage

A resting/inactive period for metacercaria. Protects parasite while it waits inside an intermediate host to be eaten by the final host to continue its development

There is considerable variation in the life cycle of trematodes but the basic pattern is

egg → miracidium → sporocyst → redia → cercaria → metacercaria → adult

What stages do all trematodes have

Egg, miracidium, cercaria

what stage depends on the trematode species for it to occur

sporocysts, redia, metacercaria

Where is Clonorchis sinesis found in the map

what is the adult morphology

- most prevalent in china/asia

-Morphology: Inside bile duct in liver, produces up to 4,000 eggs

Provide life cycle of Clonorchis sinensis

1. Human passes embryonated eggs through feces (diagnostic stage)

2. Eggs are ingested by the Parafossarulus manchouricus snail. Eggs must be ingested by intermediate host to hatch. Eggs release miracidia, which develops into sporocysts → Rediae → Cercariae

3. Cercariae exit snail host into water, where they penetrate flesh of fish and encyst as metacercariae.

4. Metacercariae in skeletal muscle of undercooked fish is ingested by definitive human host (infective stage)

5. After ingestion, metacercariae excyst in duodenum

6. Adults in biliary duct, repeat cycle

Clonorchis sinensis Pathology and symptoms

Symptoms: (mostly asymptomatic).

→inflammation, obstruction of biliary ducts, abdominal pain, anemia

Pathology

→Erosion of epithelial lining of bile ducts (depends on how many worms you have)

→Depends on intensity of infection (can thicken bile duct and make harder tissue)

-Feeds on lining of bile duct, physical damage to bile duct.

Clonorchis sinensis diagnosis and treatment

-Diagnosis: Eggs in feces

-Treatment: Praziquantel

Clonorchis sinensis Epidemiology

-method and manner of human waste disposal

-very common where raw fish is eaten regularly

-human feces used to fertilize fish ponds, b/c theyre algae eaters

-dogs and cats are good reseivor hosts

-rice farms can be contaminated by water or feces

Fasciola hepatica

-who is not their primary host

-where are they located in map

-humans are not their primary host

-occurs in the U.S and 70 different countries. Europe, northern africa, south america, texas. Oregon, washington

-associated with sheep ranching

Where is adult found for Fasciola hepatica

mainly in liver biopsy

largest trematode in humans

Describe the Fasciola hepatica life cycle

1. Unembroynated eggs passed in feces

2. Eggs become embryonated in freshwater over ~2 weeks

3. Embryonated eggs release miracidia and penetrates Lymnaeidae Stagnicola bulimoides snail host

4. In the snail, parasites develop into sporocysts → rediae → cercariae. Cercariae exit the snail

5. Cercariae encyst as metacercariae on aquatic vegetation.

6. Metacercariae on vegetation is ingested by humans and other mammals like sheep

7. after ingestion, the metacercariae excyst in duodenum, penetrating intestinal wall.

8. Immature flukes migrate through the liver into biliary ducts and mature into adult flukes (2-3 months) and produce eggs. Feed on lining of bile duct, sexual reproduction. Repeat cycle

Epidemiology of Fasciola hepatica

-By eating aquatic vegitation with metacercariae

-human infection is rare in the U.S

-high prevalence in children of Bolivia

-sometimes drinking ‘nature’ water without boiling it first

Course of infection in trematodes Question

how do u answer

what happens in humans

starts when you ingest metacercaria. ends when you poop out eggs

Go in detail about veterinary Fascioliasis

what does it reduce

in what age is higher mortality

treatment?

-major problem, higher mortality in young animals

-reduces milk production

-same treatment as humans (Triclabendazole)

Fasciola hepatica pathology and symptoms

-pathology: juveniles wandering through the liver. Anemia in heavy infections

-symptoms: Adults in bile ducts results in inflammation and edema. Cirrhosis/jaundice. takes a lot of worms to block bile ducts

Fasciola hepatica diagnosis and treatment

-diagnosis: eggs in feces

-treatment (in animals and humans): Triclabendazole

Paragonimus westermani

-who is not their normal host

-who is their definitive host

-where is it located on the map

-humans are not their normal host

-lions, tigers, cats, dogs, pigs are definitive host

-Most present in asia: Japan, Korea, China, Philipines

Paragonimus westermani life cycle

1. Human passes unembryonated eggs through feces or coughing them out

2. Eggs become embryonated in water (16 days to weeks)

3. Miracidia hatch and penetrate Thieridae stream snail

4. In the snail, develops into sporocysts → rediae → cercariae (cercariae dont have tails b/c they sink in a stream and eaten by 2nd intermediate host, crustacean)

5. In cruscacean, cercariae encyst into metacercariae. Infective stage for mammalian host. 

6. Human infected by eating undercooked crab/crayfish with metacercariae

7. Metacercariae excyst in duodenum, penetrating through intestinal wall, then to abdominal wall and diaphram into the lungs. In lungs, they become encapsulated and develop into adults

8. Adults in cystic cavities in lungs lay eggs which are excreted in sputum (coughed out) or eggs are swallowed and pass through the stool.

In Paragonimus westermani,

what happens if the worms reach other organs and tissue

how long can infection persist in humans

what happens if juvenile worms get lost

-worms may reach brain and striated muscles. however, when this takes place completion of the life cycles is not achieved bc eggs cannot exit these sites.

-some juvenile worms get lost, causing damage in diaphragm. Breathing is painful and difficult, inflammation of brachioles in lungs.

-infection may persist for 20 years in humans

Paragonimus westermani epidemiology

who are the natural definitive host

paragonomiosis

exposure types

natural definitive host: carnivores

can use rodents, dogs, pigs

paragonomiosis: when humans eat raw crustaceans

exposure can occur by contaminated utensils during kitchen food preparation

method and manner of human and waste disposal

Paragonimus westermani pathology and symptoms

-pathology: results from adults in the lungs

→ inflammatory response and encapsulation

→ chest pain and breathing difficulty

→ spinal cord (paralysis) and heart (fatal)

Paragonimus westermani diagnosis and treatment

-diagnosis: eggs in sputum, feces;

→or pleural fluid (in chronic heavy infections, not in spit or feces)

-treatment: praziquantel