Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
128 Cards in this Set
- Front
- Back
|
How is enterobius vermicularis transmitted?
|
Fecal-oral
|
|
|
How long does it take for the larvae to mature?
|
6 weeks
|
|
|
What happens after the larvae mature in the cecum?
|
Males and females mate; females exit to lay eggs on skin
|
|
|
How long until the eggs are embryonated, and how long do they remain infectious?
|
3-6 hours until embryonated; infectious for 2 weeks
|
|
|
What are the sx of infection with enterobius vermicularis?
|
Most infections are asx; perianal itch is possible
|
|
|
What is the diagnostic stage of enterobius vermicularis?
|
Egg scotch-tape prep
|
|
|
What is the treatment?
|
bendazole (whole family.) Re-tx 3 weeks later. Reinfection nearly inevitable.
|
|
|
What are the four (five) types of intestinal roundworms?
|
Enterobius vermicularis (pinworms,) Ascaris lumbricoides, Ancyclostoma and Necator (hookworms,) and Strongyloides
|
|
|
How are all intestinal roundworms treated?
|
bendazoles
|
|
|
Which intestinal roundworm infections are acquired after ingestion of eggs?
|
Enterobius vermicularis and ascaris lumbricoides
|
|
|
Which intestinal roundworm infections are acquired after larvae penetrate skin?
|
Ancyclostoma and Necator, and Strongyloides
|
|
|
Which intestinal roundworms have stages where they partially mature in alveoli, ascend, and then are swallowed?
|
Ascaris, Ancyclostoma and Necator, and Strongyloides. (All except enterobius - no lung stage.)
|
|
|
Which parasite is diagnosed by scotch-tape prep?
|
Enterobius vermicularis
|
|
|
Which intestinal roundworm is diagnosed by the presence of worms in feces
|
Strongyloides
|
|
|
Which intestinal roundworms are diagnosed by finding eggs in feces?
|
Ascaris, Ancyclostoma, and Necator
|
|
|
What happens aftter Ascaris eggs are ingested?
|
Eggs hatch in the gut. Larvae travel through the portal vein to the lungs where they partially mature, ascend, and are swallowed. Larvae finish maturing in the small gut.
|
|
|
How long does it take for the larvae to mature?
|
2 months
|
|
|
What happens after the larvae mature in the gut?
|
The male and female mate. The female lays eggs, which are excreted in feces.
|
|
|
How long until the eggs are embryonated, and how long do they remain infectious?
|
3 weeks until embryonated; infectious for months (stable to freezing, but die if dried.)
|
|
|
What symptoms does Ascaris cause?
|
Malabsorption, gut/bile obstruction, hemorrhagic pneumonitis w/ fever
|
|
|
How is Ascaris diagnosed?
|
Eggs in feces
|
|
|
How is Ascaris treated?
|
bendazole
|
|
|
What are the two hookworms?
|
Ancyclostoma and Necator
|
|
|
How are hookworms acquired?
|
Larvae penetrate skin to blood and travel to alveoli where they partially mature, ascend, and are swallowed. They mature in the gut and mate. The female lays eggs which are released in feces. The eggs hatch to release free-living larvae which live in the soil.
|
|
|
What are the symptoms of hookworm infections?
|
Papule at entry site; pulmonary sx; anemia.
|
|
|
What is the diagnostic stage of hookworm infections?
|
Eggs in feces
|
|
|
What is the treatment?
|
bendazole
|
|
|
How is the lifecycle of Strongyloides different from that of hookworms?
|
Strongyloides has a free-living form like hookworms, but can also auto-infect via ingestion of eggs which hatch in the gut.
|
|
|
What are the symptoms of Strongyloides infection?
|
Most infections are asx; diarrhea, nausea, cutaneous and pulmonary sx are possible. Hyperinfection can cause fever, dyspnea, and septicemia.
|
|
|
What is the diagnostic stage of Strongyloides?
|
Worm in feces
|
|
|
What is the treatment?
|
bendazole
|
|
|
What are the important tissue roundworms?
|
Visceral larva migrans (basically ascaris acquired from dog or cat,) Trichinella, and the filariases (Wuchereria and Onchocerca)
|
|
|
How is visceral larva migrans acquired?
|
Eggs are ingested from dog or cat feces, which hatch. Larvae spread to liver, lungs, retina.
|
|
|
What are the sx of visceral larva migrans?
|
Most infections are asx; fever, hepatomegaly, and RB-like lesions are possible
|
|
|
How is visceral larva migrans diagnosed?
|
Hx, aby to worm, larvae in liver bx
|
|
|
How is it treated?
|
bendazole
|
|
|
How is Trichinella acquired?
|
Encysted larvae are ingested via undercooked pork. These are released, invade the gut mucosa, and mature after 2 days to mate.
|
|
|
When do live larvae appear in the gut?
|
Beginning 1 week after ingestion, and continuing for up to a month.
|
|
|
What do the larvae do?
|
Invade striated muscle, where they die and encyst.
|
|
|
What are the sx of Trichinella infection?
|
Most infections are asx; periorbital edema, HA, fever, and pain due to muscle invasion are possible. Heart or CNS invasion is fatal.
|
|
|
How is Trichinella diagnosed?
|
Larvae in bx, or migrating larvae.
|
|
|
How is Trichinella treated?
|
Steroids and 'bendazole
|
|
|
What are filariases?
|
A subset of tissue roundworms where infection occurs after insects inject larvae into the human host
|
|
|
What are the two important filariases?
|
Wuchereria and Onchocerca
|
|
|
Where is Wuchereria found?
|
In tropical areas
|
|
|
Where is Onchocerca found?
|
Africa, and Central and South America.
|
|
|
Which insect carries Wuchereria?
|
a mosquito
|
|
|
Are the microfilariae of Wuchereria harmful?
|
No. Pathology is due to lymphatic obstruction from adult worms.
|
|
|
How is Wuchereria diagnosed?
|
Microfilariae in blood
|
|
|
What is the treatment?
|
Ivermectin
|
|
|
What insect carries Onchocerca?
|
the black fly (Simulium)
|
|
|
What are the sx of Onchocerca infection?
|
Adults are contained in subcutaneous nodules at the bite site. Microfilariae cause itchy dermatitis, keratitis, corneal fibrosis, iris atrophy, and chorioretinitis (river blindness.)
|
|
|
How is Onchocerca diagnosed?
|
Microfilariae in skin or adults in nodules
|
|
|
How is it treated?
|
Ivermectin (kills only larvae)
|
|
|
Do worms multiply in humans?
|
No. Disease severity is a funciton of the number of worms or larvae that enter.
|
|
|
MC parasitic disease in developed countries
|
enterobius
|
|
|
What is the prevalence worldwide of enterobius?
|
30% of children and 15% of adults are infected
|
|
|
How long do hookworms survive in the small intestine?
|
5 years. They secrete an anticoagulant and suck blood, so heavy infections may cause anemia.
|
|
|
How long do free-living hookrowms survive?
|
6 weeks
|
|
|
What parasite can cause recurrent gram-negative bacteremia?
|
Strongyloides - pts w/ autoinfection can have recurrent gram-negative bacteremia from E coli carried by larvae penetrating the intestinal mucosa.
|
|
|
What does the Strongyloides larva look like?
|
Short buccal cavity, hourglass-shaped esophagus, genital primordium, anus.
|
|
|
Is an intestinal phase seen for visceral larva migrans?
|
No. Humans are accidental hosts.
|
|
|
How long can visceral larva migrans cause sx?
|
Sx remit in a year as larvae become encased in granulomas.
|
|
|
Which worm is viviparous? What does that mean?
|
Trichinella is viviparous - the female releases live larvae
|
|
|
How long until Trichinella encapsulations calcify?
|
Up to 2 years.
|
|
|
What are the symptoms of a heavy infection with Trichinella?
|
Mucosal invasion by adult worms can cause diarrhea and gastroenteritis.
|
|
|
How does Trichinella cause death?
|
Invasion into CNS or heart.
|
|
|
What causes elephantiasis?
|
Wuchereria bancrofti
|
|
|
What causes river blindness?
|
Onchocerca volvulus
|
|
|
What is tropical pulmonary eosinophilia?
|
A rare, potentially fatal form of Wuchereria infection characterized by pulmonary infiltrates
|
|
|
What is the treatment for Wuchereria?
|
ivermectin
|
|
|
Do Wuchereria microfilariae cause sx?
|
No.
|
|
|
Do Onchocerca microfilariae cause sx?
|
Yes. Microfilariae in tissues cause dermatitis and blindness.
|
|
|
Where are adult worms found in Onchocerca infections?
|
In subcutaneous nodules at the site of the infecting black fly bite.
|
|
|
How is Onchocerca diagnosed?
|
Microfilariae in a skin snip, or adult worms in a nodule bx.
|
|
|
How is it treated?
|
Ivermectin. This does not kill adult worms, but a single annual tx will kill microfilariae before they can cause harm.
|
|
|
How do flatworms reproduce?
|
Sexually in humans; asexually in snails
|
|
|
How is schistosomiasis acquired?
|
Cercariae (from snails) penetrate skin
|
|
|
What happens then?
|
The larvae migrate to the lung and the portal system. Mated pairs penetrate mesenteric veins (mansoni or japonicum) or bladder (hematobium) and lay eggs
|
|
|
How are eggs excreted?
|
In urine or stool. They hatch into a ciliated form in the water to infect snails, where they become cercerariae.
|
|
|
How do Schistosomas cause sx?
|
Eggs cause pipestem fibrosis in the liver, and portal HTN (which leads to esophageal varices.) Eggs in the lung and CNS also cause disease. S hematobium eggs calcify within the bladder causing UT disease and hematuria, and increased tumor risk.
|
|
|
What is schistosome dermatitis?
|
Cercariae of bird or other animal penetrate skin and die, causing itch.
|
|
|
How is schistosomiasis diagnosed?
|
Excreted eggs in urine or feces
|
|
|
How is shistosome dermatitis diagnosed?
|
Clinical dx
|
|
|
How are schistosome infections treated?
|
praziquantel
|
|
|
What is the beef tapeworm?
|
Taenia saginata
|
|
|
How is T saginata acquired?
|
Ingestion of encysted larvae in beef
|
|
|
What happens then?
|
Larvae mature over months in the wall of the GIT into hermaphroditic tapeworms up to 30 feet long. Proglottids excreted in feces, which are eaten by cow.
|
|
|
What are the sx of T saginata infection?
|
No sx except possible discomfort
|
|
|
How is it diagnosed?
|
Proglottids in feces w/ 15-20 uterine branches
|
|
|
How is it treated?
|
praziquantel
|
|
|
What is the pork tapeworm?
|
Taenia solium
|
|
|
How is the lifecycle of T solium different from T saginata?
|
Same lifecycle for ingestion of cysticeri. If eggs are ingested, cysticeri can form in tissues, including the CNS.
|
|
|
How is T solium diagnosed?
|
Proglottids in feces w/ 8-13 branches
|
|
|
How is it treated?
|
Praziquantel or albendazole
|
|
|
What is the lifecycle of Diphyllobothrium?
|
Fish release proglottids, which mature into a free-living ciliated stage in larva. These are eaten by copopods and mature into larvae, which are eaten by fish.
|
|
|
How is Diphyllobothrium infection acquired?
|
Humans eat fish containing larvae.
|
|
|
What are the sx of Diphyllobothrium infection?
|
Anemia is possible
|
|
|
How is Diphyllobothrium diagnosed?
|
Eggs in feces w/ trap-door
|
|
|
How is it treated?
|
praziquantel
|
|
|
What causes hydatid disease?
|
Echinococcus granulous (dog tapeworm) or multilocularis (dog/fox)
|
|
|
How do humans get hydatid disease?
|
Humans are accidental hosts. Eggs are ingested from dog feces, and the embryos form syts (hydatids) w/ larval scolices (hydatid sand.) They reproduce asexually in the liver (65%) and lung (25%).
|
|
|
How does hydatid disease cause sx?
|
Sx are due to space-filling cysts or cyst rupture (which may cause anaphylaxis.)
|
|
|
How is it diagnosed?
|
X-rays showing calcified cysts, or serologic tests for aby
|
|
|
How is it treated?
|
With difficulty. Surgery is necessary.
|
|
|
What are the important flatworms?
|
Tapeworms - T saginata, T solium, and D latum (all treated w/ praziquantel,) and echinococcus (needs surgery.) Flukes - schistosomes (S mansoni, S japonicum, S haematomium, and generic schistosomes that cause dermatitis.) Tx: praziquantel.
|
|
|
How are flatworm infections treated?
|
Praziquantel for all (+ surgery for echinococcus.)
|
|
|
What is the intermediate host for flukes (schistosomes?)
|
All flukes have a snail intermediate host, in which they multiply asexually.
|
|
|
What are the sx of acute schistosomiasis?
|
3-6 weeks after exposure, the pt may have fever, flu-like sx, hepatosplenomegaly, lymphadenopathy, and eosinophilia.
|
|
|
What causes pathology due to schistosoma infection?
|
Chronic immune response to eggs.
|
|
|
Suspect schistosomiasis in pts w/ what?
|
Eosinophilia, hepatosplenomegaly, and bloody vomit or hematuria.
|
|
|
Where is S mansoni found?
|
North Africa, Arabia, South America, and Caribbean islands (S mansoni travels AAA to the Caribbeans)
|
|
|
Where is S haematobium found?
|
Africa and the Middle East (classically Egypt)
|
|
|
Where is S japonicum found?
|
China, Japan, and SE Asia
|
|
|
Where in the world does schistosome dermatitis occur?
|
Worldwide. Can be acquired from either fresh or salt water.
|
|
|
Are schistosomes hermaphroditic?
|
No. There is a mated male and female.
|
|
|
Are tapeworms hermaphroditic?
|
Yes. They produce proglottids.
|
|
|
Do tapeworms have an intestinal system?
|
No. The adult worm absorbs food from the host's intestinal contents.
|
|
|
Where is T saginata found?
|
Wherever cattle and human fecal contamination co-exist. Highly prevalent in Africa.
|
|
|
Where is T solium found?
|
Wherever pigs have contact w/ human fecal contamination, but not endemic in US.
|
|
|
Where is Diphyllobothrium found?
|
In the Great Lakes region and Alaska in the US. It is also seen worldwide, particularly in Finland.
|
|
|
How does echinococcus granulosus reproduce?
|
Larvae entrapped in hydatid cysts vesiculate (asexual multiplication,) forming larval scolices (rudimentary heads called hydatid sand.)
|
|
|
How large are the hydatid cysts?
|
Up to 20 cm.
|
|
|
How is hydatid disease diagnosed?
|
It is usually found incidentally on X-ray. Calcified cysts occur in the liver (65%) and lung (25%.)
|
|
|
Where does hydatid disease occur?
|
South America, USSR, South Africa, and the Mediterranean basin. Remember that infection may occur decades before presentation.
|
|
|
How is echinococcus infection treated?
|
Cysts must be removed surgicaly. Asx pts may not require tx.
|
|
|
How is echinococcus multilocularis different from E granulosis?
|
It is endemic in far northern climates (e.g. Alaska.) The lifecycle is the same, but the intermediate host is a rodent. The cysts are usually in the liver, and can give rise to metastatic growth at distant sites, so surgery is more difficult.
|
|
|
Which worms do not cause eosinophilia?
|
Enterobius and Wuchereria (no worm migration through tissue.)
|
