Clinical Parasitology 1 - Roundworms and Flatworms Flashcards
What is the life cycle of ascaris lumbricoides, starting with an egg?
- Egg is consumed, usually in contaminated food.
- Larvae emerge when eggs reach the small intestine.
- Larvae penetrate through the intestinal wall and traveling in the bloodstream to the lungs.
- Grow in alveoli and are coughed up and swallowed; larvae again reach the small intestine and mature into adults.
- Adults release eggs, which are excreted with the feces
- in severe invasion, may invade bile ducts, gall bladder, appendix, and liver
Which three intestinal nematodes (roundworms) are inquired by the ingestion of eggs?
- Ascaris lumbricoides
- Trichuris triciura (whipworm)
- Enterobius vermicularis (pinworm)
What are three signs seen with ascariasis?
- Pneumonitis (cough, pulmonary infiltrate on CXR)
- Abdominal cramping
- Intestinal obstruction (occasional perforation)
What three drugs can be used to treat Ascaris lumbricoides?
- Mebendazole*
- Pyrantel pamoate*
- Albendazole
- ones given in the clinical lecture; piperazine is an alternative
What makes the Dx of ascariasis (ascaris lumbricoides) definitive?
Eggs in stool–> make dx definitive
What finding in the blood test makes a parasite infection likely?
High eosinophil count (in ascariasis can be high in the sputum as well)
What is the life cycle of Trichuris trichuiria (whipworm) starting with the egg?
- Egg is ingested (via contaminated food) and hatch in intestine
- Mature in the cecum and ascending large intestine
- Mature adult produces eggs there
- no filariform larvae stage, no tissue invasion, and no lung involvement
What two symptoms may be seen in trichuris trichiura (whipworm) infection?
- Abdominal pain
- Diarrhea
- may appear like chronic blood loss or IBD
What makes the diagnosis of trichuris trichiura?
Visualization of eggs in the feces–> look like footballs with bumps on each end
What blood finding is seen in trichuris trichiura?
None–> eosinophilia is not present, since it doesn’t invade tissues
What is unique about the the egg excreted in the feces of a person infected by trichuris trichuria (whipworm)?
Must grow in moist soil for 3-6 weeks before infective, so cannot infect self
What are the two drugs of choice to tx trichuris trichiura (whipworm)?
- Albendazole
- Mebendazole
- pyrantel pamoate is an alternative
What is the life cycle of Enterobius vermicularis (pinworm), beginning with an egg?
- Eggs are ingested,
- Pinworms mature in the cecum and ascending large intestine,
- Female migrates to perianal area (usually at night) to lay eggs, which become infectious 4-6 hours later
- infected individual will scratch! then reinfect self via hand-to-mouth
What are the symptoms of Enterobius vermicularis (pinworm) infection? What is the definitive test?
- Usually just an itchy ass (g.i. problems are rare)
* Sticky-tape test–> finds adults or eggs in perianal region
What is seen on the blood test in Enterobius vermicularis (pinworm) infection?
NO eosinophilia–> worms don’t penetrate the tissues
- Enterobius vermicularis is the most common helminth (worms) infection in the U.S.
What is treatment for Enterobius vermicularis (pinworm) infection? (2 choices)
- Mebendazole
- Pyrantel pamoate (2 doses, 2 weeks apart)
- Albendazole is an alternative
What is the life cycle of Necator americanus (hookworm), beginning with it getting into the host?
- Larval form lives in the soil and transforms into filariform larva after 1 week
- Filariform larva can penetrate the skin
- Travel to lung/alveoli, where they are coughed up and swallowed
- Adult worms develop as they arrive at the small intestine, where they attach and suck blood; here they reproduce and release fertilized eggs
What 4 places is Necator americanus (hookworm) found?
- New world Americas
- Africa
- Southern Asia
- Australia
What is the distribution of Ancylostoma duodenale (hookworm)? (2 places)
Mediterranean and northern Asia
Which two intestinal nematodes (flatworms) are acquired when their larvae penetrate through the skin?
- Necator americanus (hookworm)
- Strongyliodes stercoralis (threadworms)
- also Ancylostoma duodenale (it is same as hookworm, but has a different worldwide distribution)
Where do Necator americanus (hookworm) travel after the filarifirm larvae penetrate the skin?
Directly to the alveoli, where they grow and are coughed up and swallowed.
When are Necator americanus fully mature (where in body)?
Are fully mature by the time they reach the small intestines after getting coughed up and swallowed.
What three symptoms does hookworm (Necator) infection cause?
- diarrhea
- abdominal pain
- weight loss
What do the hookworms do once in the intestine and what sign may this cause?
Attach to the intestinal wall and suck blood–> may lead to an iron-deficiency anemia
What three signs/ symptoms might lung infection due to hookworm cause?
- cough
- infiltrate on CXR
- eosinophilia
* pnemonitis
What may seen as a result of hookworm invasion through skin?
itching and rash at the site of penetration (usually between the toes)
What confirms Necator americanus (hookworm) infection?
Eggs in stool
What is DOC for Necator (hookworm) infection?
Mebendazole
*Pyrantel pamoate or albendazole may be used as well
What is the common name for Strongyloides stercoralis infection?
Threadworm
How does Strongylides stercoralis infect the host? Which stage in life cycle infects?
Via penetration of the skin by filariform larvae
What organism is Strongyloides stercoralis’ life cycle extremely similar to?
Necator americanus–> the filariform larvae penetrate the skin, travel to the lung then are coughed up and swallowed; mature into adults by the time they reach the small intestines where they lay eggs
What happens in the cycle of autoinfection in Strongyloides stercoralis?
Filariform larvae penetrate the intestine directly without leaving and go to the lung to continue the cycle.
What happens in the direct cycle of Strongyloides stercoralis life cycle?
Filariform larvae pass out in the feces, survive in the soil, penetrate the next passerby, and migrate to the lungs–> almost exactly same as N. americanus
What is the indirect life cycle of Strongyloides stercoralis?
Filariform larvae are passed out in the stool, mature in the soil, lay eggs which mature into infective filariform larvae.
What 5 symptoms are seen in Strongyloides stercoralis infection?
- vomiting
- abdominal bloating
- diarrhea
- iron-deficiency anemia
- weight loss
What skin symptom may be seen with Strongyloides stercoralis?
Purpuric papule
What is Loeffler’s syndrome? (is a part of Strongyloides stercoralis infection)
Eosinophilia in the lung
- eosinophilia may also be seen in the blood, these are invasion
How is the definitive diagnosis made of Strongyloides stercoralis (threadworm)?
Filariform larvae in the stool–> these DO NOT release eggs into the stool (enterotest, in which a string is swallowed and larvae come out on it)
*thereis also an ELISA test for antibodies
What is DOC for Strongyloides stercoralis (threadworm) infection?
Ivermectin
*albendozole is an alternative
What infection can occur after ingestion of pork (other than tapeworm)?
Trichinella spiralis
What is ingested to actually cause trichinosis?
encysted larvae of Trichinella spiralis
After ingestion of encysted larvae, what is the lifecycle of Trichinella spiralis?
- Cysts travel to small intestines
- Larvae leave the cysts and mature into mating adults.
- Mature females penetrate into the intestinal mucosa and produce larvae; adult males passed in the stool.
- Larvae enter bloodstream and spread to organs and skeletal muscle
* Larvae become encysted in skeletal muscle and may persist for years
What three initial complaints may be seen in pts with the intestinal phase infection of Trichinella spiralis? (~1 week after initial infection)
- abdominal pain
- diarrhea
- fever
About 1week after initial abdominal infection, what two complaints may be seen?
- Fever
- Muscle aches (inflammation and tenderness)
*in severe infection, may get into brain or heart tissue
What 3 lab findings may be seen with trichinosis?
- elevated WBC
- eosinophilia (by day 12)
- elevated CPK (due to muscle invasion)
What is DOC for Trichnella spiralis?
Mebendazole (eliminates adults, but not larvae)
What organism is responsible for lymphatic filariasis (elephantiasis)?
Wucheria bancrofti
*endemic in Pacific Islands and much of Africa
How is Wucheria bancrofti transmitted?
Via mosquito bite
What stage of life cycle is transmitted by the mosquito in Wucheria bancrofti?
Microfilariae (is the offspring of the adults)
After mosquito bite, what happens to the transmitted Wucheria bancrofti?
Microfiliariae mature into adults in the lymphatic vessels and lymph nodes of the lower extremities and genitals of the host. They mature and new offspring enter the blood vessels.
What are the main two symptoms seen in Wucheria bancrofti infection?
- Headaches
2. Swollen inguinal nodes
How does elephantiasis develop with Wucheria infection?
With chronic infection, fibrosis develops around dead filariae that remain in lymphatic channels and this plugs them up leading to edema
How is Dx of Wucheria made?
Isolation of microfiliae in the blood AT NIGHT (have a nocturnal periodicity)
*or serology (IgG4)
What is tx for Wucheria bancrofti infection?
Diethylcarbazamine (kills adults); steroids can reduce inflammation
What is Taenia saginata?
beef tapeworm
What is Taenia solium?
pork tapeworm
What is the head portion of a tapeworm called?
Scolex
What are the other portions of tapeworms called that are the reproductive portions?
Proglottids
*segments with branched uteri designed to produce thousands of eggs; those closest to the scolex are immature; terminal ones are gravid and brak off, releasing numerous eggs
What kind of worm is a tapeworm?
Flatworm, or platyhelminthes; also more specifically known as a Cestode
How do humans acquire T. solium?
Ingestion of undercooked pork infected with larvae
*pigs get the larvae by eating eggs that have been dropped in the feces of infected organisms
What is a cysticercus?
a round, fluid filled bladder with T. solium larvae inside; develops once inside pork muscle and lives when pork is undercooked
What are symptoms of tapeworm disease?
Usually none, unless intestinal load is very heavy
How is dx of tapeworms (cestodes) made?
Recovery of eggs or proglottids from stool
Which organism is responsible for Cysticercosis? How?
T. solium only; occurs when eggs, rather than larvae, are ingested by humans
What happens when T. solium eggs are ingested?
Eggs hatch in the intestines and larvae spread systemically
What two places does Cysticercosis usually infect?
- Skeletal muscle
2. Brain (called neurocysticercosis)
What are the symptoms of Neurocysticercosis?
Seizures, focal neurological deficits, obstructive hydrocephalus
DOC for tapeworm infection?
Praziquantel
What dz does Echinococcus cause?
Hyatid cyst disease
How does one become infected with Echinococcus granulosus?
By eating eggs excreted in dog and sheep feces
What disease does hydatid cyst dz resemble?
Cysticercosis–> eggs hatch in small intestine and spread hematogenously after penetrating intestinal wall
Echinococcus granulosus is the smallest of all tapeworms
After hematogenous spread, how do hydatid cysts grow?
Inner part of cyst differentiates into a germinal layer and produces protoscolexes (hydatid cyst); fully mature cyst contains many thousand protoscolexes
What kind of symptoms are seen with Hydatid cyst dz?
Mass effects depending on organ affected–> obstructive jaundce if liver cyst; increased ICP if brain cyst. Can also infect kidneys
What is the main danger/ complication of hydatid cyst dz?
Rupture of E. granulosus cysts–> severe anaphylactic reaction that can be fatal
What can make a dx of hydatid cyst dz?
Space occupying lesion on CT scan, along with eosinophilia and clinical picture
TX for hydatid cyst dz?
- Surgical removal of cysts
2. Mebendazole in high doses
What are Schistosomas also known as?
Blood flukes
Which Schistosoma is indigenous to Africa and the Americas?
S. mansoni
Which schistosoma is indigenous to Africa only?
S. haematobium
Which schistosoma is indigenous to Eastern Asia?
S. japonicum
After their eggs hatch in freshwater, what is the intermediate host Schistosomas mature into larvae in?
Freshwater snails; larvae are infectious to humans
After penetrating the skin, where to Schistosomas go in the body?
To the intrahepatic portion of the portal venous system (where schistosmas mature and mate)
Where do Schsitosomes migrate in the body to lay eggs after mating?
To veins surrounding either the intestines or bladder (excreted via feces or urine)
4-8 weeks after initial infection (which causes dermatititis as Schistoma entry site), what develops (dz)?
Katayama fever (part of Schistosomiasis)
What symptoms are seen with Katayama fever?
Fever, hives, HA, weight loss and cough; usually accompanied by lymph node, liver and spleen enlargement, with eosninophilia–> all an allergic reaction to eggs in the blood stream
What major complications of schistosomiasis may be seen with S. haemotobium?
Bladder granulomas, hematuria
*associated with bladder CA
What complication may be seen due to S. mansoni or S. japonicum infection?
Periportal fibrosis, portal HTN w/ hepatosplenomegaly
*eosinophilia common; hypersensitivity to eggs is common
How is dx of Schistosomas made?
ID of egg in stool or in urine
DOC for Schistosomiasis?
Praziquantel
- may be transient exacerbation of symptoms with treatment
- Schistomsomas are trematodes which are flatworms
