Helminthes- lung flukes & liver flukes Flashcards
Which is the most common and widely distributed lung fluke?
Paragonimus westermani
What are the third intermediate hosts for lung flukes?
fresh-water crabs and rover crayfish infected with metacercariae
How do carnivores and humans get the parasite?
by eating the definitive host
Where does the parasite excyst?
in the duodenum
Where do the adult worms reside and how are the eggs spread?
adults are in the lungs and eggs spread through sputum. if sputum is swallowed, the eggs can be in the feces
Describe the lung fluke life cycle
in water, eggs become miracidia and penetrate the snail. cercaria leave the snail 3-5 months later and penetrate crabs to develop into metacercaria
Describe the pathology of lung flukes
metacercaria excyst in the duodenum -> penetrate the intestinal wall into peritoneal cavity -> through the abdominal wall and diaphragm -> into lungs and develop into adults
What other tissues can the worms infect?
the brain and striated muscles. cannot complete the life cycle in these tissues because eggs cannot migrate
What are symptoms of the acute phase of lung fluke infection?
adbominal pain, fever, cough, urticaria, hepatosplenomegaly, pulmonary abnormalities
What are symptoms of the chronic phase of lung fluke infection?
cough, expectoration of discoloured sputum, chest radiograph abnormalities
How can lung fluke infection be diagnosed?
presence of eggs in stool or sputum (not present until 2-3 months post infection) or biopsy recovery of adult worms
What drug is used to treat lung fluke infection?
praziquantel
Where are liver flukes found in the body?
in the bile capillary and ducts of the liver
What effect do liver flukes have on humans?
not much, interfere with health
What effect do liver flukes have on agriculture?
cause livestock to not gain weight and reduce production
Which area is very affected by liver flukes affecting livestock?
the Gulf coast because it is near a lot of water
What is the primary pathology of liver flukes?
many worms clog up bile ducts. bile cannot get out of liver cells, which die. calcium deposits cause fibrosis (scarring) and ducts becoming useless
What is the secondary pathology of liver flukes?
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)
What are the symptoms of liver fluke infection?
anemia (from sucking blood), diarrhea, edema, enlarged liver
What is bottle jaw?
a soft swelling beneath the jaw caused by hypoproteinemia (low blood protein). often caused by liver flukes
What drugs are used to treat liver flukes?
- Fasciola hepatica infections may not respond to praziquantel so triclabendazole is used
- For Dicrocoelium dendriticum, praziquantel
- For Clonorchis sinensis, praziquantel or albendazole
Which species of large liver flukes affect ruminants and humans?
Fasciola hepatica, fasciola gigantica, fasciola magna
Which hosts can fasciola hepatica infect?
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
Which hosts can fasciola gigantica infect?
equivalent of fasciola hepatica but in Southeast Asia, Hawaii and Africa, but slightly bigger
infects cattle and buffalo, but sometimes goats, sheep, and donkeys
Which hosts can fasciola magna infect?
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
Which family of snails is the intermediate host for ruminant liver flukes?
from the family Lymnaeidae, which are aquatic and semi aquatic snails
Describe the life cycle of fasciola hepatica
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
What are the hosts of the small liver fluke Clonorchis sinensis?
definitive: carnivores, including humans
also pigs, rats, camels
intermediate: snail (1st) and fish (2nd)
What is the habitat of Clonorchis sinensis?
freshwater
What are the hosts of the small liver fluke Dicrocoelium dendriticum?
definitive: sheep, goats, deer, cattle, rabbits, groundhogs (usually ruminants)
sometimes humans
intermediate: land snail (1st) and ant (2nd)
cosmopolitan distribution but mostly Eastern Europe
How does Dicrocoelium dendriticum manipulate its host?
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
What are the hosts of the GI tract fluke Euhaplorchis californiensis and where does it live?
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
How does Euhaplorchis californiensis manipulate its host?
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
