Helminthes- lung flukes & liver flukes

Question 1

Which is the most common and widely distributed lung fluke?

Answer 1

Paragonimus westermani

Question 2

What are the third intermediate hosts for lung flukes?

Answer 2

fresh-water crabs and rover crayfish infected with metacercariae

Question 3

How do carnivores and humans get the parasite?

Answer 3

by eating the definitive host

Question 4

Where does the parasite excyst?

Answer 4

in the duodenum

Question 5

Where do the adult worms reside and how are the eggs spread?

Answer 5

adults are in the lungs and eggs spread through sputum. if sputum is swallowed, the eggs can be in the feces

Question 6

Describe the lung fluke life cycle

Answer 6

in water, eggs become miracidia and penetrate the snail. cercaria leave the snail 3-5 months later and penetrate crabs to develop into metacercaria

Question 7

Describe the pathology of lung flukes

Answer 7

metacercaria excyst in the duodenum -> penetrate the intestinal wall into peritoneal cavity -> through the abdominal wall and diaphragm -> into lungs and develop into adults

Question 8

What other tissues can the worms infect?

Answer 8

the brain and striated muscles. cannot complete the life cycle in these tissues because eggs cannot migrate

Question 9

What are symptoms of the acute phase of lung fluke infection?

Answer 9

adbominal pain, fever, cough, urticaria, hepatosplenomegaly, pulmonary abnormalities

Question 10

What are symptoms of the chronic phase of lung fluke infection?

Answer 10

cough, expectoration of discoloured sputum, chest radiograph abnormalities

Question 11

How can lung fluke infection be diagnosed?

Answer 11

presence of eggs in stool or sputum (not present until 2-3 months post infection) or biopsy recovery of adult worms

Question 12

What drug is used to treat lung fluke infection?

Answer 12

praziquantel

Question 13

Where are liver flukes found in the body?

Answer 13

in the bile capillary and ducts of the liver

Question 14

What effect do liver flukes have on humans?

Answer 14

not much, interfere with health

Question 15

What effect do liver flukes have on agriculture?

Answer 15

cause livestock to not gain weight and reduce production

Question 16

Which area is very affected by liver flukes affecting livestock?

Answer 16

the Gulf coast because it is near a lot of water

Question 17

What is the primary pathology of liver flukes?

Answer 17

many worms clog up bile ducts. bile cannot get out of liver cells, which die. calcium deposits cause fibrosis (scarring) and ducts becoming useless

Question 18

What is the secondary pathology of liver flukes?

Answer 18

metacercariae penetrate intestine and move through body cavities to get to liver from the outside. some won’t make it to liver and will cause other problems (seizures in brain)

Question 19

What are the symptoms of liver fluke infection?

Answer 19

anemia (from sucking blood), diarrhea, edema, enlarged liver

Question 20

What is bottle jaw?

Answer 20

a soft swelling beneath the jaw caused by hypoproteinemia (low blood protein). often caused by liver flukes

Question 21

What drugs are used to treat liver flukes?

Answer 21

• Fasciola hepatica infections may not respond to praziquantel so triclabendazole is used
• For Dicrocoelium dendriticum, praziquantel
• For Clonorchis sinensis, praziquantel or albendazole

Question 22

Which species of large liver flukes affect ruminants and humans?

Answer 22

Fasciola hepatica, fasciola gigantica, fasciola magna

Question 23

Which hosts can fasciola hepatica infect?

Answer 23

definitive host is sheep, but can also sometimes infect cattle (when sheep are not present) and humans

cosmopolitan distribution found in agricultural animals in North and South America

Question 24

Which hosts can fasciola gigantica infect?

Answer 24

equivalent of fasciola hepatica but in Southeast Asia, Hawaii and Africa, but slightly bigger

infects cattle and buffalo, but sometimes goats, sheep, and donkeys

Question 25

Which hosts can fasciola magna infect?

Answer 25

deer, moose, elk mostly
sometimes cattle, bison, sheep, goats, pigs
NEVER found in people
RARE: domestic ruminants

common in North America: Gulf coast + Great Lakes

Question 26

Which family of snails is the intermediate host for ruminant liver flukes?

Answer 26

from the family Lymnaeidae, which are aquatic and semi aquatic snails

Question 27

Describe the life cycle of fasciola hepatica

Answer 27

eggs: indistinct operculum, non-embryonated
miracidia: develop in egg in the external environment. hatch and infect a snail
snail: develop 2 sporocysts, 2 redia generations, cercaria released into aquatic environment
cercaria: encyst as metacercaria on aquatic vegetation. grass and water cress are 2nd intermediate host

Question 28

What are the hosts of the small liver fluke Clonorchis sinensis?

Answer 28

definitive: carnivores, including humans
also pigs, rats, camels
intermediate: snail (1st) and fish (2nd)

Question 29

What is the habitat of Clonorchis sinensis?

Answer 29

freshwater

Question 30

What are the hosts of the small liver fluke Dicrocoelium dendriticum?

Answer 30

definitive: sheep, goats, deer, cattle, rabbits, groundhogs (usually ruminants)
sometimes humans
intermediate: land snail (1st) and ant (2nd)

cosmopolitan distribution but mostly Eastern Europe

Question 31

How does Dicrocoelium dendriticum manipulate its host?

Answer 31

one cercaria in the ant will infect the sub-esophageal ganglion and will alter the ant’s behaviour such that every night, the ant moves to the top of a grass blade to increase its chances of being ingested by a ruminant. the ant will leave the blade during the day to avoid dying of heat

Question 32

What are the hosts of the GI tract fluke Euhaplorchis californiensis and where does it live?

Answer 32

in california
1st intermediate is the California Horn snail
2nd intermediate is the California killifish
definitive host can be a variety of fish eating shore birds

Question 33

How does Euhaplorchis californiensis manipulate its host?

Answer 33

when in the fish, the parasite sits on the brain and blocks the production of serotonin, which normally reduces aggression. parasite also increases dopamine levels, which make the fish more restless
because of this, the fish flashes its belly an moves to the surface a lot more often than usually and is much more likely to be eaten by a bird