Lecture 6: Parasitology 1 Flashcards
(120 cards)
1
Q
What is a parasite?
A
a eukaryotic organism that is using another for a variety of purposes
2
Q
T/F
all parasites are worms
A
false
not all parasites are worms. some can be amoebas, protozoa, etc.
3
Q
T/F
Parasitic infections can manifest in many different ways.
A
true
4
Q
Why do the complex life cycles of parasites make diagnostics and treatment challenging?
A
- there are multiple stages for the parasite, which can target multiple locations within the body
- makes diagnostics, drug and vaccine development challenging
5
Q
T/F
Most parasitic infections are not clinical.
A
true
6
Q
infections are generally ____ –> most effective parasites are only ____ _____. that is to say, they will ____ but not ____
A
- chronic
- moderately virulent
- infect
- kill
7
Q
parasites have the biological imperative to ____, ____, and ___, so not killing the host is beneficial to their existence.
A
reproduce, find nutrients, and shelter
8
Q
If you are not the right host, how will a parasite respond?
A
it will try to get out of you by any means. Often kills the incidental host
9
Q
T/F
parasites have maintained their responses to the host body since their inception.
A
false
parasites have evolved to manipulate host immune responses and host
10
Q
routes of parasitic infection
A
- ingestion
- arthropod bite
- transplacental penetration
- direct penetration
- transmammary
11
Q
organisms that use ingestion to infect host
A
- Giardia
- E. histolytica
- Cryptosporidium spp.
- cestodes
- nematodes
12
Q
organisms that use arthropod vectors to infect host
A
- Malaria
- Babesia
- filaria
- Leishmania spp.
- Trypanosomes
13
Q
Organisms that use transplacental penetration to infect host
A
Toxoplasma gondii
14
Q
organisms that use direct penetration to infect host
A
- hookworm
- Strongyloides
- Schistosomes
15
Q
how can parasites harm their hosts?
A
toxic products
- proteases, phospolipase, lytic enzymes, collagenase, elastase
mechanical tissue damage
- intestinal and organ blockage, pressure atrophy, tissue migration
immunopathology
- hypersensitivity reactions, autoimmunity, metaplastic changes, chronic inflammatory changes
16
Q
Type 1 Reaction: ??
Mechanism: ??
Organism: ??
A
- anaphylactic
- Ag + IgE –> histamine
- helminths, trypanosomes
17
Q
Type 2 Reaction: ??
Mechanism: ??
Organism: ??
A
- cytotoxic
- Ab + Ag + C’ (ADCC)
- T. cruzi
18
Q
Type 3 Reaction: ??
Mechanism: ??
Organism: ??
A
- immune complex
- Ab + Ag complex
- Malaria, schistosomes, trypanosomes
19
Q
Type 4 Reaction: ??
Mechanism: ??
Organism: ??
A
- delayed
- T cells
- Leishmania, Schistosomes, trypanosomes
20
Q
What can a type 1 reaction result in?
A
anaphylactic shock, bronchospasms, local inflammation
21
Q
what can a type 2 reaction result in?
A
Ab + Ag on cell surface –> complement activation or ab-dependent cellular cytotoxicity. results in the lysis of cell-bearing microbial antigens
22
Q
What can a type 3 reaction result in?
A
inflammation and tissue damage; complex deposition in glomeruli, joints, skin vessels, brain; glomerulonephritis and vasculitis
23
Q
what can a type 4 reaction result in?
A
sensitized T-cell reaction with antigen, liberation of lymphokines, triggered cytotoxicity –> results in inflammation, mononuclear accumulation, macrophage activation, tissue damage
24
Q
What is released when a parasite is destroy and what can it cause?
A
proteases and phospholipases are released
can cause cell destruction, inflammatory response, and gross tissue pathology
25
differentiate between parasitic infection and parasitic disease.
parasitic infection is the presence of a parasite in the host; parasitic disease results when the parasitic infection damages the cells or body, thereby harming the host
26
T/F
| most parastic infections are acute
False
| most parasite infections are sub-acute or chronic
27
What determines the outcome of parasitic disease?
- route of exposure
- inoculum size and infective dose
- tissue tropism
- disruption, evasion, and inactivation of host immune system
- host age and immune status
- disease progression --> in for the long haul (unless immunocompromised)
28
How does Chagas disease demonstrate that parasitic complications can occur YEARS after initial infection?
- can initially see minor skin lesions at time of infection, but years later, the infected can develop complications from damage to cardiac muscle and nerve damage, leading to heart disease, GI issues, etc.
29
How do schistosome infections demonstrate that parasitic complications can occur YEARS after initial infection?
initial infections may have minor bleeding in the GI or urinary tract from beginning, but years of it develops into obstructions, cancer, etc.
30
How do eosinophils aid in parasite infections?
- these are the leukocytes that help neutralize infection with worms
31
what occurs in response to parasites' surface proteins?
- eosinophilia
| - -> accompanied by increased levels of IgE and is triggered by increased IL-5
32
eosinophilia helps to identify parasitic infection with ___, but doesn't help much with ____
- helminths
| - protozoa
33
T/F parasites are only a type 2 response.
false
| parasites can be either type 1 or type 2
34
```
Th Group: Th1
Cell products: ??
Cell receptor: ??
Cell target: ??
Infectious agent(s): ??
```
- interferon-gamma, IL-2
- IL-12R
- macrophages, DCs
- intracellular bacteria, fungi, viruses, INTRACELLULAR PARASITES
35
```
Th Group: Th17
Cell products: ??
Cell receptor: ??
Cell target: ??
Infectious agent(s): ??
```
- IL-17A, IL-17F, IL-21, IL-22
- IL-23R
- Neutrophils
- Extracellular bacteria, fungi, EXTRACELLULAR PARASITES (?)
36
```
Th Group: Th2
Cell products: ??
Cell receptor: ??
Cell target: ??
Infectious agent(s): ??
```
- IL-4, IL-13, IL-5
- IL4R
- Eosinophils, basophils
- parasites
37
Types of interference/avoidance
- antigenic variation
- molecular mimicry
- concealment of antigenic site (masking)
- intracellular location
- immunosuppression
38
mechanism of antigenic variation
variation of surface antigens within the host
39
mechanism of molecular mimicry
microbial antigens mimicking host antigens leads to poor Ab response
40
mechanism of masking (concealment of antigenic site)
acquisition of coating host molecules
41
mechanism of intracellular location
- failure to display microbial antigen on host cell curface
- inhibition of phagolysosomal fusion
- escape from phagosome into cytoplasm with subsequent replication
42
mechanism of immunosuppression
- suppression of parasite-specific B- and T-cell responses
| - degradation of immunoglobulins
43
trophozoite
motile, feeding stage, causes pathogenesis
- these are the ones interfering with cell lining in the gut, blocking absorption
- "out and about," so the immune response can recognize them
44
cyst
infectious (immediately), non-motile, passed in feces (or in tissue and consumed to cause infection)
- often very resistant to immune system or to chemicals
- stage isn't really doing anything
45
oocyst
protozoan version of egg; passed in feces; often takes 1-2 days to sporulate and be infectious
46
sporulate
when oocysts develop from undifferentiated cellular material to sporozoites
47
merozoite
stage that undergoes asexual reproduction; feeding stage (seen with malaria and coccidia)
48
schizont
whole cell full of multiplying merozoites; schzogeny is the process by which asexual reproduction may occur
49
what are the 3 main geohelminths?
- hookworms
- roundworms
- whipworms
50
T/F
| eggs are immediately infectious
false
51
At which stage is a parasite infectious
L3 stage
52
Are eggs environmentally resistant or labile
resistant
53
examples of nematodes
ascarids, strongylids, filarids
54
ascarids, strongylids, and filarids are examples of what?
nematodes
55
examples of cestodes
tapeworms
56
tapeworms are examples of what
cestodes
57
flukes are examples of what
trematodes
58
examples of trematodes
flukes
59
What is one of the leading causes of death in children under 5 years of age
diarrheal illness
60
what percent of childhood mortality is attributed to diarrhea?
10%
61
what are the 3 main protozoa that cause diarrhea?
- Giardia
- Cryptosporidium
- Entamoeba histolytica
62
T/F
| illness in early childhood has no longterm physical and cognitive development effects
false
it does
63
what is the most common intestinal parasite in humans/
Giardia lamblia
64
what is the route of contamination for giardiasis?
fecal-oral contamination (cysts in feces)
65
what is the distribution of giardia?
what is it generally associated with?
- world-wide distribution
| - water contamination
66
what is the prevalence of giardia in developed countries?
- 2% in adults, 6-8% of children
67
what is the prevelance of giardia in developing countries?
33% prevalence
68
T/F
| Giardiasis is rarely zoonotic
true
69
what could be a reason for the difference in prevalence between developed and developing countries
water purifying systems
70
What is more likely to affect whether one has Giardiasis: immune status or infectivity?
immune status
71
which stage of giardia is responsible for transmission of giardiasis?
cysts
72
how can you diagnose giardiasis?
fecal examination and detecting cysts or trophozoites
73
what do giardia trophozoites prevent when the affect the intestinal lining?
absorption of fat, leading to diarrhea of a fatty nature
74
how long can giardia cysts persist in the environment?
several months in cold water
75
how may trophozoites are released from a cyst?
2
76
where does giardia typically infect in the body?
small intestine
77
how do trophozoites multiply?
longitduinal binary fission
78
when does encystation occur?
as the parasites transit toward the colon
79
why is person-to-person transmission of giardia possible?
cysts are infectious when passed in the stool or shortly afterward
80
when trophozoites attach to the intestinal wall with their sucking disks, what do they cause?
- malabsorption
- inflammation
- hyperplasia
81
50% of infected indivduals are ____
asymptomatic
82
symptoms of giardiasis
- fatty diarrhea
- gas
- abdominal cramps
- nausea
- vomiting
dehydration
83
in children with giardiasis, malnutrtion may result in what?
delayed physical and mental growth
84
what age group is most likely to be infected with giardia?
ages 1-4
85
what are the two crypto species most common in humans? Which is zoonotic
- C. hominis
| - C. parvum (zoonotic)
86
distribution of Crytposporidium
world wide
87
T/F
| cryptosporidium has a transplacental route of contamination
false
| fecal oral contamination, possibly even respiratory secretions
88
is the cryptosporidium oocyst environmentally labile or resistant?
resistant
89
what are large risk factors for c. hominis?
daycare and swimming
90
how can one acquire C parvum zoonotically?
from neonatal calves
91
how does cryptosporidiosis occur?
- the protozoa colonizes microvilli on the apical surface of the epithelial cells, predominantly in the small intestine
92
symptoms of cryptosporidiosis
- watery diarrhea
- dehydration
- cramps
- weight loss
- nausea
- - occasionally may see resp. symptoms
93
when might one consider cryptosporidiosis zoonotic?
in immunocompromised individuals, like those with AIDS
94
T/F in healthy individuals, crypto is generally self-limiting and symptoms resolve after ~10 days
true
95
how has water been treated to prevent crypto infection?
with UV treatments
96
where are most people getting infected with cryptosporidium
recreational water parks
97
what is the pathogenesis of both giardia and cryptosporidium
1. interaction between Crypto/Giardia and the apical surface of the epithelial cells of the GI wall results in a localized activation of signalling cascades, culminating in barrier disruption and polymerization of actin filaments in the region with host-parasite interaction
2. several molecules result in cellular damage, enhancing fluid secretion from the crypts and supporting diarrhea due to active secretion and malabsorption, which can lead to cell death
3. essentially, they come in, and penetrate or bloc the cell, which gets your immune system involved. The activation of the immune system can disrupt the barrier through cell death, and other forms of disruption
98
which parasite is responsible for human coccidosis?
cyclospora spp.
99
cyclospora distribution
worldwide, but most tropical and subtropical
100
prevalence of cyclospora in
- endemic areas.
- developed countries
- 2-18% in endemic areas
| - 0.1-0.5% in developed countries
101
T/F
| cyclospora oocysts are not initially infective, thus fecal-oral transmission cannot occur.
true
102
when does Cyclospora sporulation occur?
- after days or weeks at 22C-32C
103
what can serve as the vehicle for cyclospora sporulated oocyst transmission
fresh produce and water
104
Where do Cyclospora oocysts excyst in the host?
GI tracted, thus freeing sporozoites which invade the epithelial cells of the Small Intestine.
105
what symptoms are seen with human coccidiosis?
- watery diarrhea
- dehydration
- cramps
- weight loss
- nausea
- - occasionally may see resp. symptoms
106
Cyclospora is ____ in healthy individuals and ____ in immune-compromised individuals
- self-limiting
| - chronic
107
What is the route of infection for Entamoeba histolytica?
fecal-oral contamination
108
infective stage of Entamoeba histolytica
the cyst
109
motile feeding stage of entamoeba histolytica
trophozoite
110
distribution of Entamoeba histolytica
worldwide, but mostly tropical and subtropical areas
111
what can lead to increased risk of E. histolytica infections
poor sanitation / contaminated water
112
prevalence of E. histolytica
- globally
- US
- 10-15%
| - 1-2%
113
Is one more likely to get E. histolytica in a crowded or low-density area?
crowded
114
which stage of E. histolytica are you more likely to find in feces?
cysts
115
Where does E. histolytica generally stay in the host?
where can it migrate to if it leaves that location?
- the gut
| - can go to the bloodstream --> liver --> lungs or brain
116
T/F
| an individual may be an asymptomatic carrier of Entamoeba histolytica
true
117
Entamoeba histolytica
| intestinal amebiasis symptoms
- related to tissue destruction in LI
- -> abdominal pain
- -> cramping
- -> colitis
- -> bloody diarrhea
- -> necrosis in intestine (flask-shaped lesions)
118
entamoeba histolytica
| extraintestinal amebiasis symptoms
- invasion into deeper mucosa & peritoneal cavity (liver, heart, & brain may be affected)
- systemic fever
- rigors
- abcess formation and enlargement of liver from filtering trophozoites, hepatomegaly
119
Intestinal Protozoa
- Giardia
- Cryptosporidium
- Cyclospora
- Entamoeba histolytica
120
blood and tissue protozoa
- plasmodium (4 spp.)
- Trypanosoma cruzi
- Trypanosoma brucei spp.
- Leishmania spp.
- Toxoplasma
- Babesia spp.
