ICL 3.2: Trematodes Flashcards
what’s the common name for trematodes?
flukes
they’re a type of helminths –> platyhelminths specifically = flatworms
which trematodes are transmitted by ingestion and cause tissue infection?
- fasciola hepatica
2. paragonimus westermani
which trematodes are transmitted by contact and cause tissue infection?
- schistosoma japonicum
- schistosoma mansoni
- schistosoma haematobium
what kind of infection do trematodes cause?
tramatodes are transmitted by either ingestion or contact
but they ALL always lead to tissue infection
which groups are at risk for trematode infection?
- immigrants
- tourism/foreign travel
- military
major contributor to morbidity in developing countries
how do humans get schistosomiasis?
humans get infected by contact through the skin by cercariae
infection is by water-born cercaria – hyaluronidase helps in skin penetration
cercariae = a free-swimming larval stage in which a parasitic fluke passes from an intermediate host (typically a snail) to another intermediate host or to the final vertebrate host
which 3 parsites cause schistosomiasis in humans?
- Schistosoma mansoni (mesenteric veins)
- S. japonicum (mesenteric veins)
- S. haematobium (veins of the bladder)
they are all transmitted by contact and cause tissue infection
what is the life of schistosomes?
- bacteria in the feces or urine
- eggs hatch releasing miracidia
- miracidia penetrate snail tissue
- sporocysts in snail
- cercariae released by snail into water and free swimming
- cercariae penetrate human skin (definitive host)
- cercariae lose tails during penetration and become schistosomulae
- circulation
- migrate to portal blood in liver and mature into adults
- paired adult worms migrate to mesenteric venules of bowel/rectum and venous plexus of bladder where they are shed in stools and urine
what are the key points in the schistosome life cycle?
adults live 2-30 years inside the body!!!
100s-1000s eggs are released each day and migrate into intestinal lumen or bladder – eggs produce proteases allowing for this tissue migration
however ~50% “eggs” die within host tissue and account for most pathology = inflammatory response
which enzyme helps schistosomes penetrate human skin?
hyaluronidase
which tissue does schistosoma mansoni infect?
mesenteric veins
which tissue does schistosoma japonicum infect?
mesenteric veins
which tissue does schistosoma haematobium infect?
veins of the bladder
what are the effects on the body caused by S. mansoni and S. japonicum?
- portal hypertension
- ascites** (like swollen african kid stomach)
- esophageal varicose veins
- liver fibrosis
what is pipestem fibrosis? which parasite is it caused by?
Longitudinal sections of portal canals in which there is a great increase in the amount of fibrous tissue around the vessels and bile ducts - due to large numbers of schistosome eggs
caused by S. mansoni and S. japonicum
what are the effects on the body caused by schistosoma haematobium?
- hematuria in early disease
- eventual fibrosis of bladder and obstructive uropathy
- rarely renal failure and hydronephrosis
- rarely bladder carcinoma
how do you diagnose a schistosome infection?
- eggs in feces or urine are characteristic and diagnostic
S. mansoni = big lateral spine sticking out from the long side of the body
S. japonicum = small lateral spine
S. haematobium = terminal spine sticking out from one of the ends
- immunodiagnosis = ELISA, IFAT, RIA, IHA
how do you treat a schistosome infection?
praziquantel (PZQ) and oxamniquine (OXQ)
effective, but resistance increasing
how do you prevent schistosome infection?
- avoid swimming or wading in freshwater when you are in countries in which schistosomiasis occurs –> swimming in the ocean and in chlorinated swimming pools is safe
- drink safe (boiled / filtered) water
- sanitation = avoid excretion into open water where snails live
- education
- snail reduction using molluscicides, biological control
what’s the common name for paradonimus westermani?
lung fluke
so it’s a trematodes
what is the life cycle of paradonimus westermani?
- unembryonated eggs are released in sputum or in feces
- embryonated eggs
- miracidiae hatch and penetrate snail
- snail: sporocysts –> rediae –> cercariae
- cercariae invade the crustacean and encyst into metacercariae
- humans ingest inadequately cooked or picked crustaceans containing metacercariae
- excyst in duodenum
- adults in cystic cavities in lungs lay eggs which are excreted in sputum; alternately eggs are swallowed and passed with stool
how is paradonimus westermani transmitted?
consumption of raw/undercooked seafood
Asia/South America, imports??
where is paradonimus westermani found in the world?
paragonimus spp. are distributed throughout the Americas, Africa and southeast Asia
paragonimus westermani is distributed in southeast Asia and Japan
what are the symptoms of paradonimus westermani infection?
acute = diarrhea, abdominal pain, fever cough, pulmonary abnormalities, eosinophilia
chronic = pulmonary manifestations: cough discolored sputum, expectorated clusters of reddish brown eggs, not blood, radiographic abnormalities (pseudeotubercules)
