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MAD Exam 3 > Parasites > Flashcards

Parasites Flashcards

1
Q

definitive host

A

the host in which the parasite reaches SEXUAL MATURITY (usually where gametocytes fuse and form a complete zygote)

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2
Q

intermediate host

A

a host that is required for parasite development but in which the parasite does NOT reach sexual maturity

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3
Q

malaria - definitive and intermediate hosts

A

definitive = mosquito
intermediate = humans

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4
Q

schistosoma - definitive and intermediate hosts

A

definitive = human
intermediate = snail

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5
Q

“dead end” or accidental host

A

when a helminth that usually infects another animal attempts to invade or infect a human but cannot complete the necessary stage of its lifecycle (not the correct host)

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6
Q

when is eosinophilia seen with parasitic infections

A

ONLY in TISSUE INVASIVE or migratory portions of the parasite’s life cycle

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7
Q

do you see eosinophilia with protozoal infections

A

NO

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8
Q

do you see eosinophilia with adult worms in the intestinal lumen

A

NO

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9
Q

are parasites prokaryotes or eukaryotes

A

EUKARYOTES
*can be one-celled or multi-cellular

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10
Q

protozoa

A

simple, unicellular parasites
*can be in blood, tissue, gut, and/or genital system

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11
Q

helminths

A

multicellular, complex organisms
(worms)
*covered by a cuticle or tegument that protects them from digestion and environmental stresses

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12
Q

do you have eosinophilia with malaria

A

NO

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13
Q

entamoeba - 2 species

A

1) entamoeba histolytica (pathogenic)
2) entamoeba dispar (non-pathogenic)

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14
Q

entamoeba histolytica - transmission

A

fecal-oral (through contaminated food and water)
person-to-person spread may occur

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15
Q

entamoeba histolytica - 2 forms

A
  1. trophozoite
  2. cyst
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16
Q

entamoeba histolytica - life cycle

A
  1. ingest cysts
  2. cysts transform to trophozoite upon exposure to stomach acid
  3. trophozoites colonize and subsequently invade intestinal mucosa
  4. invasion causes COLITIS
  5. some of the trophozoites transform into infective cysts and are released in stool, allowing for spread
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17
Q

entamoeba histolytica - disease

A

DYSENTERY (bloody, mucous-y diarrhea)
complications = liver abscesses and intestinal perforation

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18
Q

entamoeba histolytica - virulence factors

A
  1. galactosamine adherence lectin
  2. proteinases
  3. lysis of WBCs
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19
Q

entamoeba histolytica - 3 stages for infection

A
  1. attachment to host mucosal colonic epithelium through receptors
  2. contact-dependent killing
  3. ingestion of the killed host cell
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20
Q

entamoeba histolytica - host defense

A

cell-mediated immunity (T cells)

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21
Q

giardia lamblia - transmission

A

WATER, predominantly

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22
Q

giardia lamblia - epidemiology/risks

A

WATER
examples:
1) backpackers drinking from a stream
2) go to water park and swallow a lot of water
3) daycare

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23
Q

giardia lamblia - life cycle

A
  1. ingest cysts
  2. cysts transform to trophozoite upon exposure to stomach acid
  3. trophozoites colonize and subsequently ATTACH TO SMALL INTESTINAL VILLI
  4. some of the trophozoites transform into infective cysts and are released in stool, allowing for spread
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24
Q

compare and contrast - giardia vs. amoeba

A

*amoeba goes to COLON and invades; causes dysentery
*giardia goes to small intestine and attaches to villi; causes watery diarrhea

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25
Q

giardia lamblia - host defense

A

IgA immunoglobulin
(so IgA deficiency people are at high risk)

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26
Q

giardia lamblia - disease

A

WATERY diarrhea

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27
Q

cryptosporidium - characteristics

A

INTRACELLULAR pathogen

28
Q

cryptosporidium - transmission

A

water > fecal-oral > person-to-person

29
Q

cryptosporidium - problem with oocysts

A

resistant to disinfection, including chloride

30
Q

cryptosporidium - epidemiology

A

day care
swimming pools/water parks
food-borne (especially CALVES)

31
Q

cryptosporidium - staining

A

ACID FAST STAINING ORGANISM

32
Q

high risk populations for malaria

A

*children less than 5 yo
*pregnant women
*non-immune travelers

33
Q

4 malaria-causing species

A
  1. Plasmodium falciparum (most dangerous)
  2. / 3. P. vivax & ovale (can RELAPSE because of “hidden liver” stage that can persist)
  3. P. malariae (rare)
34
Q

what species of mosquito transmits malaria

A

Anopheline mosquito (females only; night biters)

35
Q

malaria life cycle

A
  1. anopholene mosquito inoculates SPOROZOITES into human
  2. sporozoites infect LIVER CELLS
  3. sporozoites MATURE INTO SCHIZONTS
  4. schizonts rupture and release MEROZOITES
  5. merozoites infect RED BLOOD CELLS
  6. merozoites mature into TROPHOZOITES
  7. trophozoites mature into schizonts
  8. schizonts rupture and release merozoites
  9. cycle continues
36
Q

important difference in P. vivax and P. ovale life cycle (compared to falciparum)

A

have a dormant stage (hypnozoites) in liver and can persist for years, causing RELAPSES when they invade the bloodstream

37
Q

primary vaccine approach for malaria

A

form immunity to the SPOROZOITE (because that is what infects us)

38
Q

pathogenesis of P falciparum malaria disease

A

*causes MICROVASCULAR DISEASE
*adherence to endothelial receptors
*infect RBCs clogging up capillaries, leading to cytokine release and reduced blood flow, and hypoglycemia in tissues

39
Q

host factors against malaria

A

*normal spleen function is important (removes parasitized RBCs from circulation)
*G6PD deficiency and sickle cell anemia may be protective against malaria transmission

40
Q

malaria clinical presentation

A

fever, headache, myalgias

41
Q

malaria prevention

A

vector control
bednetting
mosquito avoidance
antimalarial prophylaxis

42
Q

malaria diagnosis

A

blood smear (Giemsa or wright staining)
antigen detection
PCR

43
Q

babesiosis - 2 species

A
  1. B. microti (most common in USA, esp Connecticut and New England)
  2. B divergens
44
Q

babesiosis tick vector

A

Ixodes tick (same as Lyme disease and ehrlichiosis)

45
Q

babesiosis life cycle

A

requires tick, mouse, AND deer
*humans are a dead-end host

46
Q

trypanosomiasis brucei

A

*found in Africa
*causes sleeping sickness (encephalitis brain infection)
*vector = tsetse fly, through its bite

47
Q

trypanosomiasis cruzi

A

*found in South America
*causes Chagas disease (infection of GI tract and heart)
*vector = reduvid bug, through its defecation

48
Q

trypanosomiasis - life cycle

A

1) promastigote (insect stage in GI tract)
2) amastigote (tissue infective stage)
*promastigote enters human blood stream where it is distributed to tropic tissues

49
Q

trypanosomiasis - host immunity

A

*main immunity is HUMERAL (immunoglobulin)

50
Q

trypanosomiasis - how do parasites avoid immunity

A

*periodically change its glycoprotein coat through antigenic variation
*occurs through movement of genetic “cassettes” that code glycoprotein into portion of active genome that is being expressed

51
Q

toxoplasma - definitive and intermediate hosts

A

definitive = cats
intermediate = humans

52
Q

toxoplasma transmission

A

*ingestion of a small amount of cat feces (cats get infection from eating a mouse)
OR
*ingestion of under-cooked meat

53
Q

toxoplasma - disease

A

*reactivation of LATENT INFECTION in AIDS PATIENTS, causing toxoplasma ENCEPHALITIS

54
Q

toxoplasma - congenital infection

A

*in first trimester of pregnancy, can cause chorioretinitis, cerebral calcifications, disseminated disease in fetus

55
Q

hookworms - 2 species

A
  1. ancylostoma duodenale (middle east)
  2. NECANTOR AMERICANUS = USA, etc
56
Q

risk for hookworm infection

A

SKIN EXPOSURES TO FECALLY CONTAMINATED SOIL in endemic areas
*especially seen in people walking BAREFOOT
*also seen in troops

57
Q

hookworm life cycle

A
  1. infective larva penetrate SKIN that contacts soil
  2. migrates through systemic venous circulation to LUNG
  3. matures in lung, migrates up trachea, and SWALLOWED
  4. matures further in small intestine; attaches to mucosa
  5. causes IRON DEFICIENCY ANEMIA due to slow, chronic blood loss
  6. eggs passed into stool and hatch in soil
  7. cycle repeats
58
Q

hookworm - disease presentations

A

*eosinophilic pneumonia
*iron deficiency anemia

59
Q

cutaneous larva migrans (creeping eruption)

A

*HOOKWORM example of humans as a dead-end host
*worm crawling around under skin, causing a rash

60
Q

schistosomiasis - exposure

A

FRESH WATER

61
Q

schistosomiasis - 3 species

A
  1. schistosoma mansoni
  2. schistosoma japonicum
  3. schistosoma hematobium
62
Q

schistosoma mansoni and japonicum

A

*reside in the venous plexuses of the GI TRACT
*cause portal hypertension and cirrhosis in liver (after 20 years)

63
Q

schistosoma hematobium

A

*resides in venous plexuses of the URINARY TRACT
*high risk of bladder cancer

64
Q

schistosomiasis - evasion of immune response

A

*absorb host proteins onto their own tegument surfaces, thus masquerading as the host by displaying the host’s antigens

65
Q

schistosomiasis - life cycle

A

*eggs get into SNAIL and mature, forming a CERCARIAE
*CERCARIAE penetrates skin and enters circulation
*goes to its tissue (GI or bladder)

66
Q

3 tapeworms

A
  1. saginata (beef tapeworm)
  2. solium (pork tapeworm)
  3. diphyllobothriasis (FISH; causes vitamin B12 deficiency)
67
Q

cysticercosis - disease of tapeworms

A

*occurs when humans are the INTERMEDIATE host of a cestode (tapeworm)
*humans infected when eggs make it into the stomach, then the intestine
*eggs hatch in the intestine and then enter the blood
*most serious infections include the brain and eyes
*you DO see eosinophilia when humans are the intermediate host

MAD Exam 3 (28 decks)

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