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FM3_ EB > Parasitology 3 > Flashcards

Parasitology 3 Flashcards

1
Q

How is entamoeba histolytica transmitted?

A

Ingestive- fecal-oral

Direct- anal sex

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2
Q

The majority of chronic asymptomatic amoeba infections are likely due to

A

Entamoeba dispar

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3
Q

Describe endemic and epidemic causes of amebiasis in the US

A

Endemic: institutions, anal sex
Epidemic: faulty water purification

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4
Q

Describe the lifecycle of Entamoeba histolytica

A

Acid resistant cysts are ingested, excystation in distal small intestine
Trophozoites attach to colonic mucin and divide. can penetrate the mucosal layer leading to invasive disease
Resistant cysts form in the large intestine and divide

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5
Q

In amoeba infection, formed stools contain _____ and loose diarrheal stools contain

A

formed stools: cysts

diarrhea: trophozoites

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6
Q

Trophozoites of entamoeba histolytica can travel to the ______ and form an abscess

A

liver

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7
Q

Distinguish between asymptomatic, dysentery, and invasive disease with Entamoeba histolytica

A

carriers: chronic form for months or years, shed millions of cysts/day
dysentery: severe bloody diarrhea, invasion of colonic epithelium, submucosal ulcers
invasive: rare, not always associated with dysentery, formation of liver abscess

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8
Q

Describe any immunity to Entamoeba histolytica

A
  • humoral response in invasive disease

- possibly some acquired immunity in endemic areas

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9
Q

How is amebiasis diagnosed?

A

Cysts in stool
Trophozoites containing RBCs
Stool antigen, PRC, serology
Correlate to travel history

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10
Q

What is treatment for Entamoeba histolytica

A

metronidazole or tinidazole for invasive tissue phase

paromomycin for lumenal phase

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11
Q

True or false: like Entamoeba histolytica, Giardia can cause invasive disease

A

FALSE- luminal only, no invasive disease with Giardia

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12
Q

What is the reservoir for Giardia lamblia?

A

Wild and domestic animals

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13
Q

How is Giardia transmitted?

A

fecal-oral
sexual- oral/anal sex

endemic in developing countries, epidemics at day cares, resorts, camping

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14
Q

Describe the lifecycle of giardia

A

ID as low as 10-100 cysts

Cysts are eaten
Trophozoites excyst in upper small intestine, multiply by binary fission
Encystation in large intestine
Excretion of cysts and trophozoites in the feces but only cysts survive in the environment

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15
Q

Describe specific symptoms of giardia

A

explosive diarrhea with flatus, belching, cramps

malabsorption- don’t absorb fat, lactose, vitamin A, B12

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16
Q

Describe any immunity to giardia

A

re-infection is possible
humoral response seen
some resistance in endemic areas

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17
Q

How is giardia diagnosed?

A

stool examination, presence of cysts, ELISA antigen test on stool sample

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18
Q

What treatment is used for giardia?

A

metronidazole, tinidazole, nitazoxanide

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19
Q

List three genera within the family Apicomplexan

A

Cryptosporidium
Plasmodium
Toxoplasma

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20
Q

Apicomplexan parasites are____________ parasites, which allows them to remain hidden from immune response and thus the immune system is poorly able to control them

A

obligate intracellular

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21
Q

Felines are the definitive host of ________

A

toxoplasma gondii

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22
Q

Ticks are the definitive host of __________

A

babesia microti

23
Q

Mosquitoes are the definitive host of _______

A

Plasmodium species

24
Q

What is the definitive host of cryptosporidium hominis?

A

Humans

25
Q

Does Cryptosporidium cause invasive disease?

A

No. Luminal only

26
Q

How is cryptosporidium transmitted?

A

Fecal-oral route

27
Q

What is the reservoir of cryptosporidium?

A

wild animals, livestock

28
Q

Cryptosporidium parasites are unique in that they are located _____ but ______, which explains why drugs for other apicomplexan species are not effective against cryptosporidium

A

intracellular but extra-cytoplasmic

29
Q

_______ plays a major role in AIDS wasting syndrome

A

Cryptosporidium

30
Q

Shedding of cryptosporidium oocytes is highest in the _____ phase but continues after symptoms resolve

A

acute

31
Q

Describe any immunity to cryptosporidium

A

The fact that it is a self limiting illness suggests that there may be some immunity

32
Q

Cryptosporidium is usually a self limiting illness with 1-2 weeks of symptoms but people who are ________ may fail to resolve the infection

A

immunocompromised

33
Q

What is appropriate treatment for cryptosporidium?

A

oral rehydration, especially in immunocompromised
restore immune function with HAART for HIV infected
short course of nitazoxanide for immunocompetent/ longer course if immunocompromised, not clear how effective this is

34
Q

What organism is suspected if microscopy shows “cup in saucer” shaped cysts in the stool?

A

Cryptosporidium

35
Q

What is the location of infection with toxoplasma gondii?

A

tissue and blood

36
Q

What are intermediate hosts of toxoplasma gondii?

A

any warm blooded animal

37
Q

How is toxoplasma gondii transmitted?

A

ingestive: fecal-oral, undercooked meat
transplacental: congenital infection

38
Q

Congenital infection with toxoplasma gondii is most likely if maternal _______ infection during prengancy

A

primary- less risk if mother is previously seropositive, has strong IgG immunity

39
Q

Reactivation of a __________ is thought to play a role in toxoplasma infection in immune compromised individuals

A

latent reservoir

40
Q

Pregnant women should be advised to avoid the following activities to prevent congenital toxoplasmosis:

A

eat poorly cooked meat
change litter box
garden

41
Q

Initial infection with toxoplasma is often ________

A

asymptomatic

42
Q

Toxoplasma infection is rapidly controlled with ______ mediated immunity leading to a life long state of latent infection with sub-clinical reactivation

A

cell

43
Q

Toxoplasma _______ is a major cause of death in AIDS

A

encephalitis

44
Q

In utero infection with toxoplasma is most serious ______ in pregnancy

A

early- can cause miscarriage in first trimester

third trimester effects are often milder, can include retardation, birth defects

45
Q

Mild cases of congenital toxoplasmosis can develop ________ in later life

A

chorioretinitis

46
Q

Treatment for toxoplasmosis always involves ______ therapy

A

combination

47
Q

List some medication regiments for treatment of toxoplasma

A

pyrimethamine/sulfonamide
pyrimethamine/clindamycin if sulfa allergy

prophylactic trimethoprim (TMP)/sulfa if CD4 count <100
for sulfa allergy, prophylactic dapsone or atovaquone/ pyrimethamine

spiramycin if pregnant- pyrimethamine is a tetratogen

48
Q

How is toxoplasma diagnosed?

A

Serology, indirect immunofluorescence

49
Q

Interpret the following serology findings for toxoplasma: Seropositive for IgG and seropositive for IgM, High IgG avidity

A

Previously infected with toxoplasma, at least 12 weeks prior but less than 2 years prior

50
Q

Interpret the following serology findings for toxoplasma: Seropositive for IgG and seropositive for IgM, Low IgG avidity

A

Infected with toxoplasma, likely recent infection, sample again in three weeks

51
Q

Interpret the following serology findings for toxoplasma: Seronegative for IgG

A

Not previously infected

52
Q

Interpret the following serology findings for toxoplasma: Seropositive for IgG, seronegative for IgM

A

Infected for > 6 months, chronic infection

53
Q

Toxoplasma shows up on brain MRI as __________ lesions

A

ring enhancing

54
Q

If there is only one ring enhancing lesion on MRI, brain biopsy may be done to evaluate for ________

A

lymphoma

FM3_ EB (25 decks)

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