Helminthic Infections Flashcards
Another name for roundworm
nematode
Morphology of nematode
elongated cylindrical body that tapers at either end; covered by multi-layered cuticle (not recognized as foreign); separate sexes
Life cycle of nematodes
eggs –> larvae (in environment) –> adults (in host)
Reinfection of nematodes
rare; eggs need to be in environment for days-weeks to be contagious; Exception: PINWORM (short duration, reinfection)
Pinworm name
Enterobius vermicularis
Enterobiasis cause
pinworm (enterobius vermicularis)
Most common helminth disease
pinworm (enterobiasis)
Characteristic of pinworm
small, whitish;
short life cycle for eggs (reinfection)
transmitted person to person or indirectly from environment;
children (most common)
Life cycle of enterobiasis
eggs deposited on perianal –> infective eggs are ingested and larvae hatch in small intestine –> adult establish and mature in colon (~2 mo) –> Gravid female migrates at night to perianal to deposit eggs –> eggs infectious in 4-6 hours (survive indoors 2-3 weeks)
Sx of pinworm
mainly asymptomatic
PRURITUS ANI
bacterial infection, disturbed sleep, abdominal pain
infection of female genital tract
Dx of pinworm
tape method- eggs on perianal skin (2-3 hrs after goes to sleep, first in morning, 3 consec days, fingernails)
NO PCR or SERO TESTS or STOOL
Tx for pinworm
mebendazole/albendazole
all members in household should be treated at same time!;
HANDWASHING to minimize spread
Acquired through soil ingestioin
Ascaris lumbricoides (large intestinal roundworm) & Trichuris trichiura (whipworm)
Cause of ascariasis
Ascaris lumbricoides
Life cycle of Ascaris
infective eggs ingested –> larvae released into duodenum –> larvae penetrate mucosa and travel in bloodstream to lungs –> larvae penetrate alveoli and travel up trachea to oropharynx –> larvae swalloed and mature in duodenum –> adult worms produce eggs which can become infective in soil (18 days - several weeks) –> adult worms live ~2 years
Sx of ascariasis
asymptomatic
depends on worm burden: blockage, Pulmonary-Loeffler’s syndrome, ab pain, obstruction
Dx of ascariasis
Microscopic detection of eggs in stool
Tx: mebend/alben
Trichuris trichiura aka
whipworm
Cause of trichuriasis
trichuris thrichiura
Characterists of trichuris
small worm with whiplike morphology; “egg capsules” (pinched capsule at each end)
Epidemiology of trichuris
ingestion of contaminated soil; prevalent in children; worldwide
Life cycle of trichuris
infective (embryonated) eggs are ingest and larvae release in duodenum –> matures in colon –> released eggs mature in soil
Sx of trichuris
determined by worm burden most asymptomatic (light) heavy: frequent painful passage of stool (mucus, water and blood!); rectal prolapse, children: growth retardation and anemia
Dx of trichuris
eggs in stool (Egg capsules)
Hookworm kinds
necator americanus and ancylostoma duodenale
Characteristics of hookworms
feed on blood from intestinal mucosa
small
Epidemiology of hookworm
inadequate disposal of human feces
eggs reach infectivity and hatch in soil
larvae can PENETRATE SKIN
Life cycle of hookworm
infective egg hatch in soil —> infective stage larvae (filariform) penetrate skin and travels in blood stream to lungs –> penetrate alveoli and go to oropharynx –> swallowed and mature in duodenum –> produce eggs which mature and hatch in soil
filariform
infective larvae of hookworms
Sx of hookworm
blood-filled, pruritic lesions at site of penetration (“ground itch”), blood loss due to feeding (anemia)
Dx of hookworm
eggs in stool
Causes strongyloidiasis
strongyloides stercoralis
Characteristics of stronglyoids stercoralis
“threadworms”; small
2 multiplication cycles: in host (parasitic) or in soil (free living)
tropical/subtropical areas
related to POOR SANITATION
Life cycle of strongyloides
infective larvae in soil penetrate skin –> travel to blood stream, to lungs, penetrate alveioli, travel to oropharynx –> swallowed and mature in duodenum –> following reproduction, the adult female releases larvae in the feces –> free living multiplication cycle in soil
Sx of stronglyoides
diarrhea, pain, constipation, malabsorption
Tracks due to migration
Autoinfection! - chronic infection for years
life threatening in patients w/ defect in cell mediated immunity
Dx of strongyloidiasis
larvae in stool or duodenal aspirate
sputum of hyperinfected patient may contain larvae
Trematode aka
fluke
Characteristics of trematodes
2 intermediate hosts, 1 definitive host;
flattened, leaflike body
presence of suckers
hermaphroditic
Chinese liver fluke
clonorchis sinensis
cause of clonorchoriasis
chlonorchis sinensis
Characteristics of clonorchis sinensis
small, adults live in biliary ducts!!!
Far East
transmission via ingestion of raw, smoke, pickled, salt-cured and dried FISH
life cycle of clonorchis
fish containing larvae (metacercariae) are eaten –> excystation in duodenum and larvae pass directly to bile ducts where they mature –> eggs released in feces –> eggs eaten by snails –> following development, larvae (cercariae) are released –> cercariae encyst under the scales or in the flesh of fish (metacercariae again)
Metacercariae
encysted clonorchis in FISH
Cercariae
develop and are released by snails
Sx of clonorchis
most asymptomatic
chronic disease develops late and related to worm burden
Dx of clonorchis
eggs in stool (geographic history)
Tape worm types
Taenia solium (pork) Taenia saginata (beef) Agents of Taeniasis
taenia =
tapeworm
Characteristics of tapeworm
large worms (3-8 m) possess scolex (head structure) eggs released in proglottids are immediately infectious Definitive host = humans worldwide
Life cycle of taenia
infective age ingested by cattle (saginata) or pigs (solium) –> hatch in duodenum and released larvae penetrate wall –> cysticerci (larvae) develop in muscle –> poorly cooked meat ingested by human releases cysticercus which develop into adult tapeworm in jejunum –> proglottids (segments) released in feces contain infectious eggs –> Cysticercosis can develop if infective eggs are ingested by a human (SOLIUM)
Cysticercosis
due to T. solium; can cause blindness, seizures
Sx of taenia
most asymptomatic;
mild GI
cysticerosis (Solium)
Dx of taenia
eggs or proglottids in stool
lesions demonstrated by CT for cysticercosis
Definitive: histologic demonstration
Fish tapeworm
diphyllobothrium latum
Cause of diphyllobothriasis
Diphyllobothrium latum (fish tapeworm)
Characteristics of diphyllobothrium
very long (12 m), thousands of proglottids
eggs released singly, not in proglottids (not as bad of infection as taenia)
eggs develop and hatch in WATER and series of host passages are required for life cycle
wide spread: Great Lakes and Alaska
Humans and other fish heating mammals harbor adult worms
Life cycle of diphyllobothrium
infective larvae in mm. of fish –> poor cooked fish ingested by a human release larvae in duodenum –> adult worm develops in jejunum and eggs released to feces –> eggs hatch in water and larval forms ingested by crustaceans –> infected crustacean ingested by small fish –> small fish ingested by larger fish…
Due to ingestion of poorly cooked fish
Clonorchis (chinese liver fluke) & diphyllobothrium (fish tapeworm)
Sx of diphyllobotrium
most asymptomatic
adult worm competes for VITAMIN B12
Dx of diphyllobotrium
Anemia + positive histories
eggs in stool
ID of adult worm
