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Flashcards in Parasitology 3 Deck (54):
1

How is entamoeba histolytica transmitted?

Ingestive- fecal-oral
Direct- anal sex

2

The majority of chronic asymptomatic amoeba infections are likely due to

Entamoeba dispar

3

Describe endemic and epidemic causes of amebiasis in the US

Endemic: institutions, anal sex
Epidemic: faulty water purification

4

Describe the lifecycle of Entamoeba histolytica

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

5

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

formed stools: cysts
diarrhea: trophozoites

6

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

liver

7

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

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

8

Describe any immunity to Entamoeba histolytica

- humoral response in invasive disease
- possibly some acquired immunity in endemic areas

9

How is amebiasis diagnosed?

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

10

What is treatment for Entamoeba histolytica

metronidazole or tinidazole for invasive tissue phase
paromomycin for lumenal phase

11

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

FALSE- luminal only, no invasive disease with Giardia

12

What is the reservoir for Giardia lamblia?

Wild and domestic animals

13

How is Giardia transmitted?

fecal-oral
sexual- oral/anal sex

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

14

Describe the lifecycle of giardia

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

15

Describe specific symptoms of giardia

explosive diarrhea with flatus, belching, cramps
malabsorption- don't absorb fat, lactose, vitamin A, B12

16

Describe any immunity to giardia

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

17

How is giardia diagnosed?

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

18

What treatment is used for giardia?

metronidazole, tinidazole, nitazoxanide

19

List three genera within the family Apicomplexan

Cryptosporidium
Plasmodium
Toxoplasma

20

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

obligate intracellular

21

Felines are the definitive host of ________

toxoplasma gondii

22

Ticks are the definitive host of __________

babesia microti

23

Mosquitoes are the definitive host of _______

Plasmodium species

24

What is the definitive host of cryptosporidium hominis?

Humans

25

Does Cryptosporidium cause invasive disease?

No. Luminal only

26

How is cryptosporidium transmitted?

Fecal-oral route

27

What is the reservoir of cryptosporidium?

wild animals, livestock

28

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

intracellular but extra-cytoplasmic

29

_______ plays a major role in AIDS wasting syndrome

Cryptosporidium

30

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

acute

31

Describe any immunity to cryptosporidium

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

32

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

immunocompromised

33

What is appropriate treatment for cryptosporidium?

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

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

Cryptosporidium

35

What is the location of infection with toxoplasma gondii?

tissue and blood

36

What are intermediate hosts of toxoplasma gondii?

any warm blooded animal

37

How is toxoplasma gondii transmitted?

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

38

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

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

39

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

latent reservoir

40

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

eat poorly cooked meat
change litter box
garden

41

Initial infection with toxoplasma is often ________

asymptomatic

42

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

cell

43

Toxoplasma _______ is a major cause of death in AIDS

encephalitis

44

In utero infection with toxoplasma is most serious ______ in pregnancy

early- can cause miscarriage in first trimester
third trimester effects are often milder, can include retardation, birth defects

45

Mild cases of congenital toxoplasmosis can develop ________ in later life

chorioretinitis

46

Treatment for toxoplasmosis always involves ______ therapy

combination

47

List some medication regiments for treatment of toxoplasma

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

How is toxoplasma diagnosed?

Serology, indirect immunofluorescence

49

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

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

50

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

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

51

Interpret the following serology findings for toxoplasma: Seronegative for IgG

Not previously infected

52

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

Infected for > 6 months, chronic infection

53

Toxoplasma shows up on brain MRI as __________ lesions

ring enhancing

54

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

lymphoma