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79 Cards in this Set

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Three major parts of adult tapeworms
Scolex (head), neck, proglottids
Segment of adult tapeworm involved in egg formation. They grow from the neck so the most mature ones are found distally, immature ones proximal to the neck
This part of the tapeworm features specialized structures for attachment to intestinal mucosa
Scolex (head), which features suckers
Features of the mature proglottid of tapeworms
Testis, uterus, ovary, York reservoir, genital pore
This is how adult tapeworms feed
Absorb contents of intestinal lumen through the entire surface of the worm
Latin binomial of beef tapeworm
Taenia saginata
Latin binomial of pork tapeworm
Taenia solium
Latin binomial of fish tapeworm
Diphyllobothrium latum
Treatment of tapeworms
Definitive host of taenia saginata (beef tapeworm)
Infective stage of taenia saginata
Cysticercus in raw or under-cooked beef
Encysted larvae of Taenia spp. (beef and pork tapeworms)
Length of Taenia spp. (pork and beef tapeworms)
12 to 30 feet, adult length reached over the course of several months
Diagnostic stage of Taenia saginata
Gravid proglottid (containing 50,000 to 10,000 eggs) in feces or environment (may exit when patient is not defecating). Free eggs may also be seen
Intermediate host of Taenia saginata
Appearance of Taenia saginata and solium eggs
Radial striations on yellow-brown egg shell
Appearance of Taenia saginata proglottid
15-20 lateral branches on each side; count branches that come off central stem (count one side only)
Signs and symptoms of Taenia saginata
No convincing evidence that the worm causes any marked symptoms
Presentation of Taenia saginata
Patient reports proglottid in feces, or patient reports feeling worm exit anal sphincter
This giant tapeworm is highly prevalent in Africa, where cattle and extensive human fecal contamination co-exist
Taenia saginata
Transmission of Taenia saginata
Human feces -> Cow ingests egg-containing human feces -> Beef -> Human ingests larvae-containing beef
Definitive host of Taenia solium
Intermediate host of Taenia solium
Human, pig
Transmission of Taenia solium
Ingestion of raw or undercooked pork containing cysticerci (pig eats human feces containing proglottid or free eggs -> human eats pig)
How does somebody get Cysticercosis
Direct ingestion of Taenia solium eggs (vs. ingesting contaminated, undercooked pork)
Pathogenesis of cysticercosis
Cysticerci form in the tissues rather than the gut lumen--occurs when humans ingest the eggs of Taenia solium, rather than the larvae
Cysticercosis can affect these tissues
Lung, heart, brain, eye, connective tissue (serious, life-threatening disease)
Diagnostic stage of Taenia solium
Mature proglottid in human feces, free eggs may also be seen
Appearance of Taenia solium proglottid
8 to 13 (<15) lateral branches on each side; count branches that come off central stem (count one side only)
How do you differentiate between T. solium and T. saginata infection?
The eggs look the same, but the proglottids differ -- T. solium proglottid has <15 branches one each side, whereas T. saginata has >15
Signs and symptoms of T. solium
No convincing evidence that the worm causes any marked symptoms; but if eggs rather than larvae are ingested, cysticercosis can result
This worm can cause epilepsy
Taenia solium (cysticercosis can affect the brain)
Presentation of Taenia solium
Patient reports proglottid in feces
T/F: Taenia solium is widespread in the US
False. It is not endemic in the USA. It is more common in Central and South America so it is seen in US hospitals.
Why is treatment of infection with adult T. solium mandatory?
Cysticercosis can be caused by ingestion of eggs present in the proglottids and in fecal contamination
Diagnosis of neurocysticercosis
Radiological imaging showing calcified cysts (easy) or live cysts (may be more difficult to see)
Treatment of neurocysticercosis
Praziquantel or albendazole
Prevention of T. solium and T. saginata infection
For T. saginata, cook beef and protect cows from human fecal contamination. For T. solium, cook pork and protect pigs and humans both from human fecal contamination. Ingestion of eggs by humans is not a risk in T. saginata because humans are not an intermediate host, but ingestion of eggs by humans *is* a risk in T. solium because the eggs can hatch and larvae can get into tissues.
T/F: "Intermediate host" implies that eggs of a species can hatch in that host
True. "Definitive host" implies that the already-hatched larvae can sexually reproduce in the host
The life cycle of this human pathogenic giant tapeworm is the most complex
Diphyllobothrium latum
Diagnostic stage of Diphyllobothrium latum
Unembryonated egg in feces
Infective stage of Diphyllobothrium latum
Cysticercus (encysted larva, NOT egg) in fish meat
Life cycle of Diphyllobothrium latum
Egg hatches in fresh WATER --> free-living ciliated stage --> COPEPOD eats ciliated stage --> worm matures into later stage larva --> FISH eats copepod --> larva encysts in fish muscle --> HUMAN eats infected fish
Appearance of Diphyllobothrium latum egg
"Trap door", underdeveloped ciliated stage
This worm can cause B-12 deficiency
Diphyllobothrium latum
This worm has great affinity for B-12
Diphyllobothrium latum
Signs and symptoms of Diphyllobothrium latum
B-12 deficiency, diarrhea
Geographic distribution of Diphyllobothrium latum
Great Lakes region, Alaska; highly prevalent in Finland
This tapeworm is sensitive to freezing
Diphyllobothrium latum (fish worm)
Human disease caused by this worm requires transmission to three different hosts
Diphyllobothrium latum requires a copepod host, fish host, and human host
This is a tapeworm of dogs that can cause human disease
Echinococcus granulosus, which causes Hydatid disease
It is this form (egg, larva, adult) of Echinococcus granulosus that causes serious cystic disease in humans
Larval form (though the human ingests the egg, which matures - the human is an intermediate host)
Humans are the accidental intermediate host of this tapeworm
Echinococcus granulosus
Life cycle of Echinococcus granulosus
Sheep/swine/cattle ingest egg-containing dog feces --> early stage larvae hatch and enter sheep's portal circulation --> eggs mature in liver over the course of years --> sheep viscera are fed to dogs --> larva mature in dog gut
Transmission of Echinococcus granulosus
Humans are infected (like the sheep) by ingesting eggs from dog feces
Site of maturation of Echinococcus granulosus
Maturation of Echinococcus granulosus
Occurs over the course of years. Eggs become trapped in liver and develop into cysts with an inner germinal layer which grows, vesiculates and differentiates into larval scolices (rudimentary heads). Diameter may be >20 cm.
This worm undergoes asexual multiplication by a larval stage worm in the intermediate host
Echinococcus granulosus
Definitive host of Echinococcus granulosus
Intermediate host of Echinococcus granulosus
Sheep, swine, cattle
Length of mature Echinococcus granulosus
6 mm
How many eggs does Echinococcus granulosus lay?
500 eggs per gravid segment (proglottid)
This worm causes hydatid disease
Echinococcus granulosus
Hydatid cysts
Slow-growing cysts that undergo asexual multiplication to contain many larval scolices
Hydatid sand
Refers to the larval scolicies within hydatid cysts
Location of hydatid cysts in hydatic disease in humans
Liver (65%), lung (25%), other organs (10%) [similar distribution as CRC mets]
Signs and symptoms of hydatid disease
Usually asymptomatic. Symptoms are caused by gradual expansion. Hepatic cysts cause pain and hepatomegaly. Pulmonary cysts cause cough and dyspnea. Cysts in other organs cause sx of space-filling lesions in that organ
Complications of hydatid disease
Ruptured cyst causing anaphylactic shock
This worm infection can present with anaphylactic shock
Hydatid disease caused by Echinococcus granulosus; anaphylactic shock is caused by rupture of cyst
Diagnosis of hydatid disease
Calcified cysts on x-ray, specific serological tests for Ig to E. granulosus
Geographic distribution of Echinococcus granulosus (hydatid disease)
Sheep and cattle livestock areas of South America, USSR, South Africa, Mediterranean basin; in Alaska, dogs are infected by eating wild animals (deer, etc.)
This disease is notable because infection could have occurred decades before symptoms begin
Hydatid disease (cysts are slow growing). Therefore geographic history should not be just recent, but also past (eg, a trip to South America 10 years ago)
Treatment of hydatid disease
Surgical excision of cyst -- sterilize cyst with disinfectant (eg, ethanol) before removal to prevent initiation of new cysts by scolices that happen to be released
Prevention of hydatid disease
Avoid dog feces in endemic areas, protect dogs vs. infection, treat infected dogs
Intermediate host of Echinococcus multilocularis
Treatment of Echinococcus multilocularis
Surgical excision of cyst -- more difficult than in hydatid disease because metastatic growth at distant sites can occur (lung, brain)
Life cycle of Echinococcus multilocularis
Same as E. granulosus
Definitive host of Echinococcus multilocularis
Dog, fox
Geographic distribution of Echinococcus multilocularis
Far northern climates (Alaska, but also seen in Minnesota and adjacent northern states)