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GI Week 5 > GI Parasites > Flashcards

GI Parasites Flashcards

1
Q

True or false: GI parasite infecions typically cause chronic disease.

A

true - or at least have the potnetial to cause chronic disease

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2
Q

True or false: people with GI parasite infections are almost always symptomatic.

A

false - often asymptomatic

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3
Q

What transmission route is an essential part of parasite infections regardless of if they’re water-borne, zoonotic or live in soil?

A

fecal transmission

so inadequate disposal/treatment of human waste, inadequate treatment of drinking water, lack of handwashing, lack of food washing

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4
Q

What makes protozoa differ from helminths?

A

protozoa are unicellular eukoaryotes while helminths are multicellular eukaryotes

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5
Q

What are the three main protozoan GI parasites? At least in the US….

A

Giardia - GIardiasis
Crytoposidium - Crypto
Entameoba - Amebiasis

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6
Q

In general, what stage of the protoxoa is ingested for disease to occur?

A

cysts or oocysts

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7
Q

True or flase: protozoan infections are typically very serious and require drugs

A

false - usually not serious for healthy indviduals

most don’t need treatment with drugs and some are asymptomatic

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8
Q

What are the common symptoms of the protozoan infections?

A

stomach cramps, gas, nausea, fluid loss with diarrhea lasting over a week

often noted upon return from travel

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9
Q

Is the onset for a protoxoan infection sudden or gradual?

A

gradual - the indubation period can be weeks

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10
Q

What is the most common protozoal infection in the US?

A

giardia lamblia

although it’s 10-fold more common in developing countries

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11
Q

How long do you have symptoms with giardia?

A

1-2 weeks or more - but it may seem to resolve and then come back so it can be longer

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12
Q

What is the mechanism of symptoms for giardia? Is it invasive?

A

just the presence of the parasite causes a loss of epithelial absorptive surface area

other factors may play a role but we really don’t understand it well

doesn’t invade

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13
Q

Describe the life stages of giardia?

A
  1. The trophozoites (swimming protozoa) in the gut will attach to the mucosal lining (but don’t penetrate)
  2. generate cysts in the gut
  3. cysts release in fecal matter (as are trophozoites, but they die)
  4. cysts survive in the water until ingested by a new host
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14
Q

So what will you see in the stool to confirm a diagnosis of giardia?

A

cysts

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15
Q

What are the useful symptoms for diagnosis of giardia?

A

the diarrhea is foul smelling, greasy and tend to float because it causes malabsorption of fat

issue with fat soluble vitamins

flatulence

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16
Q

How can you prevent getting giardia?

A

filter the water in areas wehre the cysts are likely - boil basically

doesn’t have to be contaminated by human sewage because wildlife like beavers can deposit the cysts

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17
Q

Where s cryptosporidium parvum a problem?

A

in populated areas wehre a sanitation system fails - like a pool or waterpark when the chlorination fails or a city after a big storm compromises its water supply

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18
Q

True or false: crypto can be considered an opportunistic infection.

A

true - HIV and immunocompomised individuals are at higher risk and can develop a chronic diarrhea which is potentially fatal

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19
Q

Describe the symptoms of cryptosporidium parvum.

A

it’s watery, non-bloody stool lasting for 1-2 weeks or up to a month

fever sometimes

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20
Q

Is cryptosporidium parvum invasive?

A

slightly - it disrupts the epithelial microvilli and slides into the surface of the host. but doesn’t go very far, which is why the diarrhea is non-bloody

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21
Q

Describe the life cycle of cryptosporidium parvum.

A
  1. Sporozoite invade the epithelial surface
  2. generates oocysts
  3. oocysts released in feces
  4. picked up by another human in water
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22
Q

So what will give you a positive idagnosis of crypto?

A

the oocysts found in feces

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23
Q

What subclass is cryptosporidium a part of ?

A

the coccidia subclass of apicomplexan protist

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24
Q

What are two other coccidia that cause human GI infections?

A

cystoisospora belli

Cyclospora cayetanensis

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25
Q

Where is Entamoeba histolytica most prevalent?

A

not very common in the US - more prevalent int ropical and subtropical climates

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26
Q

What disease is caused by entamoeba histolytica?

A

Amebiasis, AKA amebic dysentery, amebic liver abscesses

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27
Q

What percentage of individuals infected with entamoeba will become ill?

A

only 10-20%

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28
Q

Of the US population, which group is most vulnerable for entamoeba?

A

male homosexuals

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29
Q

What are the symptoms of amebiasis? What can it do to the liver?

A
  1. BLOODY MUCUS-FILLED diarrhea
  2. relatively mild symptoms
  3. can invade the liver and form an abscess
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30
Q

What do you have to differentiate amebiasis from?

A

bacillary dysentery

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31
Q

What will give you a positive diagnosis of entamoeba?

A

cysts in the stool samples

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32
Q

Describe the life cycle of entamoeba?

A

the cyst is ingested in water

  1. cysts hatch to trophozoites in the gut
  2. trophozoites migrate form small intestine to alrge itnestine
  3. Invade from there - can go to liver
  4. patient will excrete cysts in the feces
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33
Q

What lobe of the liver is usually affected by an absces sin amebic hepatitis?

A

right -usually just a single abscess

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34
Q

On histology, what would you expect the appearance of entamoeba to be?

A

you’ll eitehr be able to see the round disc of th enuclus or you’ll see phagocytosed red blood cells inside

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35
Q

What 7 drugs do we use as anti-protoxoals?

A 
metronidazole
tinidazole
Iodoquino;
Nitazoxanide
Paromomycin
Trimethroprim:Sulfamethoxazole
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36
Q

Metronidazole and TInidazole are both from what class of drugs?

A

nitroimidazoles

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37
Q

What is the spectrum for metronidazole and tinidazole?

A

giardiasis, amebic dysenteri, also anaerobic GI bacteria

NOT crypto

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38
Q

Are metronidazole and tinidazole tissue or luminal antiparasitics?

A

tissue antiparasitis - the oral dose is almost completely absorbed with high bioavailability so it has low concentrations in the intestinal lumen

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39
Q

What is the mechanism of action for metronidazole?

A

Toxic metabolites will generate free radicals to induce DNA strand breakage

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40
Q

What are the side effects of metronidazole?

A

disulfiram reaction with alcohol
nausea, diarrhea, metallic taste

will disturb normal GI flora (but used to treat c diff)

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41
Q

What is the spectrum for nitazoxanide?

A

Giradiasis and ctyprosporidosis

but healthy hosts are typically not treated and it’s not all that effective in immunocompromised

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42
Q

Is nitazoxanide a luminal or tissue antiparasitic?

A

luminal - it’s only moderately absorbed (33%)

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43
Q

What is the mechanism of action for iodoquinol?

A

unknown

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44
Q

What’s the toxicity for iodoquinol?

A

loss of visual acuity

also use with caution in patients with thyroid diasease

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45
Q

Is iodoquinol a luminal or tissue antiparasitis?

A

luminal - only 10% of the drug is absorbed so it works locally on the protozoa including the cysts within the GI lumen

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46
Q

What is the spectrum for iodoquinol? I.e. what parasite do we use it for most?

A

amebic dysentery

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47
Q

What is the mechanism of action for Paromomycin?

A

it’s an aminoglycoside, so it targets the 30S ribosomal subunit to inhibit protein synthesis

48
Q

What are the side effects of paromomycin?

A

diarrhea, issues with intestinal flora

49
Q

Is paromomycin luminal or tissue?

A

luminal

50
Q

What is the spectrum for paromomycin?

A

most intestinal protozoa, but it’s only partially effective against cryptosporidium

51
Q

Why is the luminal vs. tissue consideration ipmortant for entamoeba?

A

it invades and destroys tissue, so you need both a luminal amebicide and a tissue amebicide to treat effectively

52
Q

What broad spectrum antimicrobial can be used for the other special ones like cystoisospora and cyclospora?

A

TMP-SMX

53
Q

What are the toxic effects of TMP-SMX?

A

it’s well tolerated in general

crosses BBB so can have neurological side effects. High potential to interfere with normal GI flora, can’t give in pregnancy

54
Q

What are the three groups of worms?

A

nematodes (roundworms)
cestodes (tapeworms)
Trematodes (flukes)

55
Q

What are the 5 nematodes we need to know?

A 
Enterobius (pinworms)
Ascaris (giant roundworms)
Strongyloides
Ancylostoma/Necator (hookworm(
Tirchuris (whip worm)
56
Q

What is Enterobius vermicularis also known as?

A

pinworm

57
Q

Enterobius wins the prize for what?

A

most common helminth infectin in the US

58
Q

What is the prevalence of enterobisu infection?

A

u to 50% in children, caregivers of infected children and institutionalized idnividausl

59
Q

What are the symptoms of enterobius infection?

A

perianal pruritis is a dead giveaway

can also present with insomnia, abdominal pain, anorexia, irritability

rarely peritoneal granulomas and volvovaginitis

60
Q

What stage of the enterobius is ingested to start an infection?

A

the pinworm egg

which can remain viable on surfaces for 2-3 weeks

61
Q

Describe the lifecycle of the pinworm.

A
  1. eggs ingested
  2. laveae hatch in the small itnestine
  3. adult worms mature in the gut and head to the anus to lay their eggs on the surface at night

maturation takes several months

62
Q

How can you diagnose pin worm?

A

appearance of worms 2-3 hours after the patient is asleep - can do the scotch tape method to pick up eggs

sample from under fingernails

note that eggs will likely not be found in the stool sample

63
Q

What are the two soil-transmitted roundworms that enter via skin penetration?

A

necator

strongyloides

64
Q

What two soil-transmitted roundworms get intot he body via egg ingestion?

A

ascaris

trichuris

65
Q

For Necator hookworm, what will be present in the stool?

A

egg

66
Q

For strongolides, what will be in the stool?

A

larvae

67
Q

Describe the life cycle of necator and strongolides? they’re basically the same….

A
  1. larvae in soil
  2. penetrate through the skin of bare feet
  3. enter the circulatory system and enter lungs
  4. cough them up to the throac and then swallow them
  5. get down into the gut where it establishes infection and matures into adult worm
68
Q

What will be the first presenting sign of a necator infection?

A

a pruritic papular, erythematous rash

69
Q

Why do hookworms cause iron-deficiency anemia as the main symptom?

A

they suck blood! about 1/4 a ml of blood per day per worm

70
Q

What are the symptoms of strongolides?

A

stomach and GI complaints
dry cough and throat irriation
itchy red rash on feet - recurrent along the thighs and buttocks

71
Q

what makes strongolides different from necator ,expecially with immunosuppressed individuals?

A

autoinfection is possible with strongolides

72
Q

What’s another name for Trichuris trichiura?

A

whipworm or trichuriasis

73
Q

How can you make a positive diagnosis for trichuris trichiura?

A

eggs in feces will have a characteristic barrel-shaped appearance

74
Q

What happens to the hands of people with trichuris trichiura?

A

finger clubbing - the best indicator of severity of infection

75
Q

How does trichuris cause iron deficiency anemia?

A

different from necator….it just causes chronic bloody diarrhea

76
Q

What is the technical name for the giant roundworms?

A

ascaris lumbricoides - disease is ascariasis

77
Q

What proportion of tropical populations is infected with ascaris?

A

about half!

78
Q

Typically ascaris infections as asymptomatic - maybe just abdominal discomfort. What’s the complication in severe cases?

A

intestinal blockages that require surgery

79
Q

What will be seen on histology due to eosinophil breakdown in an ascaris infection?

A

charcot-;eyden crystals

80
Q

How can you diagnose ascaris? besides imaging in the blockage cases….

A

eggs with thick shells in the stool

81
Q

What is the general mechanism of drugs that affect roundwrms?

A

they target the worm’s motor activity or reactions that generate metabolic energy for motion

if you inhibit their ability to get around, they’ll be more likely to be pooped out

82
Q

What are the two broad spectrum benzimidazole drugs used for roundworms and tapeworks?

A

albendazole and mebendazole

83
Q

Albendazole and mebendazole have limited oral absorption - which is better if you’re targeting tissue-migrating larvae?

A

albendazole - it’s slightly better absorbed than mebendazole

84
Q

What is the mechanism of action for albendazole and mebendazole?

A

bind to parasite beta tubulin and inhibit the formtaion of microtubules such that the helminths can’t move and die after several days

85
Q

What are the toxic effects of albendazole and mebendazole?

A

systemic toxic affects on the liver and bone marrow (rare)

abdominal pain, nausea, dizziness, headache

teratogenis in pregnanc rates

safe for use in children!

86
Q

What are the two chlinergic antihelminthics?

A

pyrantel pamoate and levamisole

87
Q

How does levamisole work?

A

it selectively opens a trstricted subgroup of nematode acetlcholine receptor ion chnannels in their nerve and muscle

this causes depolarization with an entry of calcium to trigger spastic muscle contractions, thus making the worm unable to maintain its location and gets swept away

88
Q

What are the side effects of pyrantel pamoate and levamizole?

A

nausea, vomiting diarrhea

89
Q

What is the spectrum for pyrantel pamoate and levamisole?

A

only roundworms

90
Q

What is the mechanism of action for ivermectin?

A

It binds to glutamate-gated chloride channels in invertebrat nerve and muscle cells , causing deactivation of the channel

this means they can’t move and the worm dies of starvation

91
Q

What are the toxic effects of ivermectin?

A

it’s generally well tolerated
itching, swollen lymph nodes and rarely dizziness

can get an inflammatory reaction due to the dead worms

92
Q

What is the spectrum of action for ivermectin?

A

the type of channel affected is only in nematodes like ascaris, strongyloides and onchocerca

93
Q

Tapeworms are segmentted. What is one section called?

A

a proglottid

94
Q

What’s the latin name for the typicla human tapeworm, beef tapeworm or pork tapeworm?

A

Taenia

95
Q

What’s the latin name for the fish tapeworm - the one that can reach 30 feet long?

A

Diphyllobothrium

96
Q

What tape worm can cause disease of the liver, lungs, brain and other organs with hidadid cysts?

A

echinococcus

97
Q

How do you get taenia or diphyllobothrium?

A

improprtly cooked meat or fish

for fish tapeworm - you ingest larvae in the musculature of fish

98
Q

What is the main symptoms of diphyllobothrium/fish tapeworm?

A

you get the standard intestinal problems and then megaloblastic anemia due to comeptition for B12 in the ileum

99
Q

What will the stool contain in a diphyllobothrium infection?

A

proglottins and/or eggs

100
Q

An infection of taenia can sometimes have the cysterci migrating to muscle, brain or other tissue. What’s this called?

A

Cysticercosis (can cause seizures if in the brain)

101
Q

Describe the lifecycle of Echinococcosis.

A
  1. Dog is the definitive host
  2. Dog will have eggs in feces
  3. We ingest the eggs4. the Oncosphere hatches and penetrates the intestinal lining
  4. Enters the circulation and travels to other organs
  5. Grow into cysts within those organs
102
Q

What will the symptoms of echinococcosis be?

A

depending on where hte cysts form - upper abdominal pain or chest pain

103
Q

Again, what drugs can we use against tapeworms that would also work against round worms?

A

benzimidazoles like albendazole and mebendazole

104
Q

What other drug besides the benzimidazoles will work against tape worms?

A

praziquantel

105
Q

What is the mechanism of praziquantel?

A

increases permeability of the parasite to divalent cations, leading to C2+ entry and contraction of worm musculature

106
Q

What are the side effects of praziquantel?

A

well tolerated

dizziness and nausea

107
Q

What other class of helminths will praziquantel work on?

A

trematodes or flukes

It’s the only one FOR TREMATODES!!!

108
Q

What is the main trematode affecting humans?

A

schistosoma (mansoni or japonicum)

disease is schistosomiasis

109
Q

What are the two main forms of schixtosomiasis?

A

intestinal and urogenital

110
Q

True or false - we are not a definitive host for schistosoma.

A

false - we are definitive

111
Q

What is the intemediate host for schisotoma mansoni?

A

snails - especially biomphalaria glabrata

112
Q

What causes the general symptoms of schistosomiasis?

A

our immune response to the egg stage of the schistosoma in our bodies

they can be lodged in the intestine or bladder causing inflammation an dscarring

113
Q

Why is this such a big public health issue among children?

A

kids can get repeated infections which causes organ damage, anemia, malnutrition and learning difficulties

114
Q

What are the symptoms of schistosomiasis?

A

Rash or itchy skin within days of infection

fever, chills, cough and muscle aches in 1-2 months

chronic form with abdominal pain, hepatomegaly, bloody stool, hematuria or problems passing urine

increases risk fo bladder cancer

115
Q

Describe the life cycle of schistosoma.

A
  1. eggs passed in urine or stool
  2. enters the water supply
  3. snails pick up the eggs
  4. eggs turn to sporocysts
  5. sporocysts released into water
  6. humans pick up the sporocysts while they swim
  7. sporocyst enters circulatory system
  8. travels to lungs, then heart, then liver and matures to adult worm

adult worm can live for many years

116
Q

Why might you need to give a second dose of praziquantel after an initial treatment 2-3 months prior?

A

praziquantel has low efficacy against immature worms, so sometimes you have to wait for the last ones to grow up

note this is also why they usually wait 3 months after an acute infection to treat - if they do it before, it won’t work

117
Q

What class of drugs can be used to relieve the symptoms of acute schistosomiasis?

A

corticosteroids - help control the allergic reaction to the eggs

GI Week 5 (6 decks)

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