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IAHI Block 1 > 10 - Parasitology: 1 > Flashcards

10 - Parasitology: 1 Flashcards

1
Q

What is parasitism?

A

Beneficial for one, harmful for the other.

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2
Q

What is a parasite? What are the two main types?

A

Organism that feeds and grows in or on a host organism to the detriment of that host.

Ectoparasites: infestation on or tiwhtin the skin; usually arthropods

Endoparasites: infection inside the body; protozoans (unicellular) and helminths (multicellular worms).

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3
Q

What is a definitive host? What is an intermediate host? What are examples?

A

Harbors sexual stage of a parasite’s life cycle. We are the hosts for schistosoma.

Intermediate host: supports asexual reproduction or development of a parasite intermediate host for schistosoma is snails.

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4
Q

What is an incidental host? What is a reservoir host? What are examples?

A

Incidental: dead end host; not necessary to close the life cycle of the parasite. (humans for toxoplasma)

Reservoir: an animal species that maintains the parasite’s life cycle in the wild. (mice for toxoplasma.

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5
Q

What is a vector?

A

A host species that transmits infectious parasite to another host.

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6
Q

What is incidence? What is prevalence?

A

Incidence: The number of NEW cases of a disease in a given population that develop in a given period of time.

Prevalence: number or proportion of cases of a disease in a given population at a specific time

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7
Q

When do domestic physicians need to consider parasites as a cause of disease? What should they do when its suspected?

A
  1. Pts traveling abroad
  2. Pts born in endemic areas
  3. Pts with compromised immune systems due to steroid use, cancer therapy, transplant meds, AIDs, or advanced age.

Consult infectious disease specialist and obtain current information from the CDC hotline.

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8
Q

Worm infections typically involve ______ and elicit a ____ response. What do protozoan parasites elicit?

A

Worm: Eosinophilia and elicit a Th2 response.

Protozoan: Th1 response

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9
Q

What is a biological obstacle during development of parasites? How does development play into this?

A

They are eukaryotes and use many of the same basic molecular pathways as their human host.

Flat and round worms are in the same kingdom as humans; this makes them harder to target and treat.

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10
Q

What is an egg? What is a larva?

A

Egg: product of sexual reproduction that contains embryonated pre-larval form

Larva: immature post-ovum (pre-adult) form

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11
Q

what is a cyst? What is a cysticeri?

A

Cyst: dormant stage encapsulated in host tissues

Cyticerici: encysted cestode larvae in tissues of intermediate host (found in pork tapeworm in humans).

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12
Q

What is a hydatid cyst?

A

Specialized cysticercal form of Echinococcus granulosus in intermediate host.

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13
Q

What are the two classes of the phylum of flatforms - ie Platyhelmintes?

A

Class Cestoda

Class trematoda

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14
Q

What are the characteristics of the class cestoda of the platyhelminths?

A

Hermaphroditic tapeworms with flattened, segmented bodies.

No digestive system, absorbed through tegument

Anterior end (scolex) attaches to definitive host intestine wall. 
Segments (proglottids) mature anterior to posterior.

Transmission by ingestion of eggs or cysticerci.

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15
Q

What are the characteristics of the class trematoda? What is the main type we are concerned with?

A

Schistosoma - has both male and femal

Unsegmented

simple, blind digestive system

One or more intermediate host (snail)

invasive (penetrate skin)

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16
Q

What organisms are in the class cestoda?

A
  1. Teania saginata
  2. Taenia solium
  3. Diphyllobothrium latum
  4. Echinococcus granulosus
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17
Q

What organisms are in the class trematda?

A

schistosoma (blood flukes)

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18
Q

What is the life cycle of Taenia saginata and taenia solium?

A
  1. Eggs or proglottics in feces are passed into environemtn.
  2. Cattle (saginata) and pigs (solium) infected via ingestion
  3. Eggs hatch and penetrate intestinal wall and circulate to musculature
  4. Larva develop into cysticerci in muscle of cow or pig
  5. Humans eat raw or undercooked meat and scolex attached to intestine.
19
Q

How does the scolex and proglottid differ in taenia saginata and solium?

A

Taenia saginata: four suction cups on scolex; branching proglottid.

Solium: ring of spikes in center of scolex; less branching proglottid.

20
Q

How can the life cycle of taenia solium (pork tapeworm) differ from the one previously described? Ie why is it important to distinguish one from the other in treatment.

A

Its eggs can also infect humans and humans can be the intermediate host.

Larva will form cysticeri that can develop in any organ including the brain and eyes.

Much more dangerous.

21
Q

How is taenia solium transmitted? What are the two ways it can develop (ie what is the names of the illnesses)?

A

Through ingested of undercooked cork with cysticeri - grows into tape worm in intestine - called taeniasis

Cysticeri can form in muscle, brain, and eyes - called cysticercosis.

Both forms can occur in the same person.

22
Q

What are the symptoms of Taeniasis? What are the symptoms of Cysticercosis?

A

Taeniasis: usually asymptomatic, may cause abdominal pain,nausea, weight loss. Can still infect others.

Cysticercosis: cysts in muscle typically asymptomatic; may cause lumps. Cysts in brain can cause headaches, seizures, cunfusion, impaired balance, swelling, stroke, and death.

23
Q

How would you diagnosis Taeniasis? What about Cysticercosis? How would you treat them?

A

Taeniasis: see proglottids or eggs in stool.

Cysticercosis: X ray to see dead calcified larvae or cysticerci on CT/MRI.

Praziquantel, niclosamide, or albendazole (single dose for adult worm or prolonged treatment for cysticerci). Also need steroids to reduce inflammation.

24
Q

What is the life cycle of Diphyllobothrium latum (fish tapeworm)?

A
  1. Unembryonated eggs passed in feces and eggs embryonate in water
  2. Coracidia hatch from eggs and injested by crustaceans and larva grow in body of it
  3. Small fish eats crustacean; Big fish eats small fish; we eat big fish
  4. humans ingest raw or undercooked infected fish; grow to adults in small intestine where proglottids release immature eggs
25
Q

What is the epidemiology of diphyllobothrium latum? What is the pathology of it?

A

Global in temperate sones with cool lakes; diet rich in pickled fish (usually freshwater)

Pathology similar to taeniasis; vitamin B12 deficiency because adult worms absorb ~80% of dietary B12

26
Q

How would you diagnose diphyllobothrium latum? How would you differentiate between this and Taenia?

A

Diagnosis same as taenia: single dose of praziquantel or niclosamide. Vt B12 supplements if necessary.

Fish tapeworm eggs are ovoid (oval), operculated, and non-embryonated eggs.

27
Q

What is the life cycle of Echinococcus granulosus?

A

Canines are definitive hosts. Can transport to int. host of sheep or farm animals.

Humans can ingest embryonated eggs from fecal contamination of dogs or sheeps. (why its important to de worm dogs).

28
Q

What is the morphology of echinococcus granulosus?

A

Adult is 3-6 mm. Very small, hard to see.

Hydatid cyst can be up to 20cm

29
Q

How is echinococcus granulosus transmitted? What is the epidemiology?

A

Ingestion of eggs from dogs living in close contact with humans.

Global, but rare in north america. Pastoral cycle between grazing livestock and dogs.

30
Q

What is the pathology of echinococcus granulosus?

A

Cystic echinoccosis (hydatid disease).

Cysts mainly in liver and lungs but also spleen, kidney, bone, and CNS.

Can be latent up to 20 years and onset will be when cysts cause pain or rupture. Anaphylaxis after rupture can be fatal.

31
Q

How would you diagonise and treat echinococcus granulosus?

A

CT/MRI, ultrasound; often presents as slow growing tumor. Serology for confirmation.

Surgery avoiding cyst rupture, lap surgery, PAIR percutaneous aspiration, injection of chemicals and reaspiration. Chemo.

32
Q

What is the life cycle of Echinococcus multilocularis? Where does this occur? What are the definitive hosts and intermediate hosts?

A

Safe as E. granulosus; size of adult worn is 15-3.5 mm.

Globally including northern US and canada.

Definitive hosts: fox, coyote, wolf, dog, cat

Intermediate host: rodents. humans

33
Q

How is E. multilocularis transmitted?

A

Ingestion of eggs from wold canines via contaminated fur or food items.

Dogs can be infected by scent rolling in wild animal feces.

34
Q

What does E. multilocularis cause? How would you diagnose it? Treatment?

A

Alveolar echinococcosis: Larvae produce small cysts in liver that mimic carcinoma; often spread to over others.
If they mature fatality reaches 75% (more dangerous than granulosus)

Diagnose with imaging and serology.

Treat: radical surgery and/or long-term chemo (mebendazole/albendazole).

35
Q

What is the life cycle of schitosoma ssp (blood flukes)?

A

Haematobium in urine and Mansoni and japonicum in feces. Eggs hatch in water.

Miracidia penetrate snail tissue and sporocysts grow in snails.

Cercariae released by snail into water and these penetrate human skin.

This lose tails during penetration and enter circulation to get to the portal blood and liver to mature.

36
Q

What are the three different types of schistosoma eggs? Where is each found?

A

S. haematobium: in urine, have a terminal spine

S. japonicum: circular and in stool

S. mansoni: in stool, lateral spine.

37
Q

What are the shapes and sizes of schistosoma mansoni miracidium and cercaria?

A

Miracidium: length ~150 microM. Oval.

Cercaria: IUD shaped. ~325 microM.

38
Q

What arethe sizes of male and female adult schistosoma mansoni?

A

Male: 6-11 microM

Female: 10-14 microM.

39
Q

What three organisms can cause Schistosomiasis (Bilharziasis, snail fever)? Where is the location of the adult work and the location of the eggs

A

S. haematobium: venous plexus of bladder, bladder (eggs)

S. mansoni: inferior mesenteric veins, lg intestine (eggs)

S. japonicium: superior mesenteric veins, sm. intestine (eggs).

40
Q

How is schistosomiasis transmitted? What is the epidemiology?

A

Invasive; aquatic, free-living cercaria penetrate skin,.

most common in places with poor sanitation with presence of snail int. host. Peak infection rate in school-age children playing in water.

41
Q

What is the pathology of schistosomiasis? What are the immediate and delayed symptoms?

A

Early symptoms: (days of infection) - rash from invading cercaria.

Delayed: (weeks) immune response to eggs, katayama syndrome: fever, cough, chills,. headache, abd. pain. Diarrhea.

Chronic: (years) strong inflamm response with granuloma formation. Severe liver disease, portal hypertension, hepatomegaly. Bleeding eso. varices. Fibrosis of bladder, loss of bladder funciton.

42
Q

What is the immunity of schistosomiasis?

A

Adults masked by host serum proteins; some form of protective immunity occurs in people living in endemic areas after years of exposure.

Intense effect for vaccine development.

43
Q

How would you treat or prevent schistosomiasis?

A

Treat: praziquantel single or multiple doses.

Prevent: treat infected pts, proper public hygiene, control intermediate hosts. Avoid contact with infested water.

IAHI Block 1 (19 decks)

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