Helminths Flashcards
Genus (genera)
always capitalized and italicized/underlined
Species
always in lowercase
Taxonomic ranks
domain
kingdom
phylum
class
order
family
genus
species
3 main groups of helminth worms
Trematodes (flukes), cestodes (tapeworms), nematodes (roundworms)
3 life cycle stages of a helminth
egg, larvae, adult
Trematodes (flukes)
ovoid body shape
Clonorchis sinensis
oriental liver fluke (china, japan, korea, vietnam, & taiwan) contracted from undercooked, infected fish
causes clonorchiasis & liver disease
mostly asymptomatic
Schistosoma mansoni
blood fluke
causes schistosomiasis
snails are intermediate host
contracted from fecally contaminated water containing juveniles
Schistosoma mansoni route of infection
juveniles penetrate skin, enter circulation, develop in intestinal walls
eggs penetrate intestinal wall & are passed in the feces
Schistosoma mansoni symptoms
bloody diarrhea, abdominal pain, fever, & lethargy
Paragonimus westermani
lung fluke
causes paragonimiasis
spread thru undercooked crabs & crayfish infected w/ cysts
Paragonimus westermani
causes paragonimiasis
spread thru undercooked crabs & crayfish infected w/ cysts
Paragonimus westermani route of infection
hatch in duodenum, penetrate intestinal wall & diaphragm, travel to lungs, eggs released into bronchioles, passed thru sputum or feces
Cestodes (tapeworms)
adult body divided into segments called proglottids (sexual reproduction)
scolex (head/attachment)
Taenia saginata
beef tapeworm
cattle intermediate host
mild nausea, diarrhea, abdominal pain, & headache
Taenia solium
pork tapeworm
Taenia pisiformis
dog tapeworm
hares & rabbits are intermediate hosts
Nematodes (roundworms)
literally worms
Ascaris lumbricoides
Roundworm
causes ascariases
consumption of fecally contaminated soil or food
juveniles emerge in intestines, penetrate walls, and migrate to lungs & other tissues
symptoms depend on tissue infected (mostly asymptomatic)
dx. eggs in feces
Enterobius vermicularis
pinworm
causes enterobiasis
fecal-oral transmission often in orphanages and MH’s
females emerge at night to lay eggs in perianal region
dx. eggs collected on cellophane tape
Necator americanus
hookworm
juveniles penetrate skin, enter blood, travel to lungs
bloody diarrhea, iron deficiency anemia
Trichinella spiralis
roundworm
causes trichinosis
ingesting raw/undercooked pork or wild game infected with larvae
nausea, dyspepsia, diarrhea, muscle pain, fever, weakness
Identify top & bottom specimens
Trematodes (flukes)
Top: Clonorchis sinensis egg
Bottom: Schistosoma mansoni egg
Identify top & bottom specimens
Cestodes (tapeworms)
Top: Taenia pisiformis egg
Bottom: Taenia solium scolex
Identify specimen
Cestodes (tapeworms)
Taenia pisiformis proglottid
Identify specimens
Nematodes (roundworms)
Top: Enterobius vermicularis egg
Middle: Necator americanus egg
Bottom: Ascaris lumbricoides egg
Schistosoma mansoni lifecycle
-1. eggs in feces (dx stage)
-2. eggs hatch in water, releasing miracidia
-3. miracidia penetrate snail tissue
-4. develop into sporocysts in snail
-5.cercariae released into water
-6. penetrate skin
-7. lose tails (penetration) & become schistosomulae
-8. circulation
-9. migrate to portal blood in liver & mature into adults
-10. adult worms pair & migrate to mesenteric venues of bowel/rectum to lay eggs
