BIO3850 Parasitology Module 3

Phylum of Liver Fluke

Platyhelminthes

Liver Fluke Class

Trematoda

Liver Fluke Subclass

Digenea

Oral Sucker

used for feeding

Urethral Sucker

Also known as acetabulum

Liver Fluke: Heterxenous or Monoxenous?

Heterxenous

Liver Fluke: First Intermediate Host

Mollusk (snail)

Liver Fluke Definitive Host

Vertebrate host

Fasciola hepatica

Sheep liver fluke

Fasciola hepatica: Etiological Agent of…

fascioliasis

Fascioliasis is found in…

sheep, cattle, rabbits, and humans

What is needed for Fasciola hepatica to become pathogenic?

semi-aquatic environment, sheep, and vegetation to become pathogenic

Liver Fluke Vegetation

Watercress grass

What is the first step in the liver fluke life cycle?

Eggs leave with feces.

What develops from the eggs in the liver fluke life cycle?

Miracidium.

What does the miracidium do after hatching?

Looks for a snail.

What happens when the miracidium encounters a snail in liver fluke?

It enters the snail's tissues.

What are the stages of development inside the snail in liver fluke?

Sporocyst -> redia -> more redia -> cercaria.

What does the cercaria do after leaving the snail?

It transforms into metacercaria on vegetation.

How does a sheep become infected with liver fluke?

By consuming metacercaria.

What happens to the metacercaria after being consumed by a sheep?

It becomes a juvenile and travels through the coelom to the liver.

Where does the juvenile liver fluke move after reaching the liver?

Into the parenchyma and then to the bile duct.

What does the juvenile liver fluke become in the bile duct?

An adult that starts to produce eggs.

How do the eggs of the liver fluke enter the small intestine?

Through the common bile duct.

What is the primary pathology caused by migrating juvenile liver flukes?

Damage to liver leading to anemia, edema, fibrosis, scarring, and reduced function.

What pathology do adult liver flukes cause in the bile duct?

Scarring and fibrosis in the bile duct leading to blockage.

What can result from blockage of the bile duct caused by adult liver flukes?

Toxicity and death.

Symptoms of Liver fluke

Anemia
Diarrhea
Enlarged liver
Abdominal pain- can last after treatment
Bottle jaw- in cattle and sheep

Liver Fluke Prevention

Pasture rotations- remove feces
Remove rabbits
Molluscicides- removes snails

Diagnosis and Treatment for Liver Fluke

Fecal smear
ELISA
Praziquantel- evidence of resistance
Albendazole
Triclabendazole

Fasciola gigantica

Found in south east asia, hawaii, Africa
75mm in length
Not common but possible in humans

Fascioloides magna

Definitive host: deer, moose, elk
Can be in sheep, cattle, goats, llamas, pigs
100mm
Not zoonotic

Clonorchis sinensis

Chinese liver fluke causing clonorchiasis.

Clonorchis sinensis is found in…

China, Korea, Taiwan, Japan
Range increases with fish exports

Definitive Host of Clonorchis

Includes dogs, cats, pigs, camels and humans.

intermediate hosts of clonorchis sinensis

1st intermediate: snails
2nd intermediate: fish

Transmission of Clonorchis sinensis

consumption of 2nd intermediate host

How do Clonorchis sinensis eggs leave the host?

Eggs leave with feces

What organism consumes the eggs of Clonorchis sinensis?

Snail consumes egg

What is the sequence of development stages for Clonorchis sinensis after the egg is consumed by a snail?

Miracidium hatches -> sporocyst -> redia -> daughter redia -> cercaria

What happens to C. sinensis cercaria after they leave the snail?

Cercaria leave snail and go into H2O

What happens when C. sinensis cercaria encounter fish?

Cercaria drops tail and burrows under scales -> metacercaria

How does the definitive host become infected with Clonorchis sinensis?

Definitive host consumes raw or undercooked fish

What occurs to C. sinensis metacercaria once ingested by the definitive host?

Metacercaria released in intestines -> juvenile

How do juvenile Clonorchis sinensis move to the liver?

Move to liver via common bile duct

Where do adult Clonorchis sinensis forms reside?

In the bile duct

How do adult Clonorchis sinensis release eggs?

Releases eggs into intestines via common bile duct

C. sinensis pathology

Eroded bile duct
Fibrotic tissue build up-> blocks up duct
Potential link to liver cancer
swelling

C. sinensis pathogenicity

Mixing fish and rice farming can increase pathogenicity

C. sinensis diagnosis and treatment

Fecal smear
Look for golden brown eggs
Praziquantel
Albendazole
Triclabendazole

Dicrocoelium dendriticum

Lancelet liver fluke

Dicrocoelium dendriticum is the etiological agent of…

Dicrocoeliasis

D. dendriticum infects

cattle, goats, sheep, rabbits, deer

What is the first step in the life cycle of Dicrocoelium dendriticum?

Eggs in environment consumed by snail

What happens after the eggs are consumed by the snail in the life cycle of Dicrocoelium dendriticum?

Miracidum hatch and undergo polyembryony to get cercaria

What is a 'snot ball' in the life cycle of Dicrocoelium dendriticum?

A structure containing cercaria pushed out of the snail

What happens to the snot ball containing cercaria in the life cycle of Dicrocoelium dendriticum?

It is eaten by an ant

What occurs when cercaria reach the brain of the ant in the life cycle of Dicrocoelium dendriticum?

Some cercaria go to the abdomen and encyst

What behavior does an infected ant exhibit in the life cycle of Dicrocoelium dendriticum?

It clamps to the top of a tree and is eaten by a cow

What is released in the abdomen of the cow after it eats the infected ant?

Metacercaria

Where do juvenile Dicrocoelium dendriticum go after being released in the cow's abdomen?

To the liver

Where do adult Dicrocoelium dendriticum reside in the cow?

In the bile duct

What do adult Dicrocoelium dendriticum produce?

Eggs

How are eggs of Dicrocoelium dendriticum released into the environment?

They go to the intestines and are released with feces

Echinostoma

Genus of gut flukes infecting birds and mammals.

Definitive host of Echinostoma revolutum

birds and mammals and few reptiles

Echinostoma revolutum intermediate host

1st intermediate: snail
2nd intermediate: mollusk, planaria, fish, and frog/toad

What is the first step in the life cycle of Echinostoma revolutum?

Eggs are released with feces.

What happens to the eggs of Echinostoma revolutum after they are released?

Miracidium hatch in water and then find and burrow into a snail.

What is the process that occurs after the E. revolutum miracidium burrows into the snail?

Polyembryony occurs, leading to the formation of cercaria.

What do cercaria do after leaving the snail in the life cycle of Echinostoma revolutum?

They find a second intermediate host and develop into metacercaria.

What happens when the definitive host consumes the second intermediate host of E. revolutum?

Echinostoma revolutum becomes an adult in the small intestines and releases eggs.

Nanophytes salmincola

Gut fluke affecting canids, humans, birds, racoons, and skunks

where does Nanophytes salmincola have high pathogenicity

dogs- 9/10 will not survive

Neorickettsia helmithocea

Intracellular rickettsia causing salmon poisoning.

Nanophytes salmincola life cycle

Nanophytes salmincola dog pathology

Transmission: consumption of raw or undercooked fish
Fever, edema of face, vomiting and diarrhea
Results in death in 10 days - 2 weeks

Alaria spp.

Found in small intestine of carnivores
Has 3 suckers

What happens to Alaria spp. eggs?

Eggs leave with feces.

How long does it take for Alaria Miracidium to hatch?

Miracidium hatches in 2 weeks.

What does Alaria Miracidium do after hatching?

Miracidium enters a snail and undergoes polyembryony to cercaria.

What happens to Alaria cercaria after it leaves the snail?

Cercaria leaves the snail into the water column and finds and enters a tadpole.

What stage does Alaria cercaria become after entering a tadpole?

Becomes mesocercaria.

What happens to Alaria mesocercaria when consumed by a second intermediate host?

Mesocercaria burrows into tissues.

What is the next step after a paratenic or tadpole host with alaria is consumed by the definitive host?

Mesocercaria burrows out of the intestines.

Where does Alaria mesocercaria go after leaving the intestines?

Goes to the lungs.

How long does it take for Alaria mesocercaria to become metacercaria?

Metacercaria forms in 5 weeks.

What does the juvenile Alaria spp. do after developing?

Crawls up the trachea to go into the esophagus.

What is the final stage of Alaria spp. life cycle?

Adult produces and releases eggs.

Genus of Lung flukes

Paragonimus

3 foci of lung fluke

Asia, west Sub Saharan Africa, Central and South America

Definitive host of Lung fluke

weasels, felics, canids, pigs, raccoons, fox, opposums, humans

Parotenic host for lung fluke

birds and mammals

Intermediate host of lung flukes

1st intermediate: snails
2nd intermediate: arthropod (crabs and crayfish)

What is the first stage of the lung fluke life cycle?

Egg leaves with feces

What hatches from the lung fluke egg in water?

Miracidia

What does the lung fluke miracidia find and burrow into?

Snail tissues

What are the stages of development inside the snail for lung flukes?

Sporocyst -> redia -> daughter redia -> cercaria

What type of cercaria leaves the snail for lung fluke?

Microcerous cercaria

What does the lung fluke cercaria find after leaving the snail?

Second intermediate host