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2nd year - Microbiology > Semester 2 - Parasitic Infections > Flashcards

Semester 2 - Parasitic Infections Flashcards

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0
Q

What is the biological definition of parasites?

A

Parasites are eukaryotic organsisms which live on or in a host organism, and which utilize its resources for their own survival and propagation

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1
Q

What is the broad definition of a parasite?

A

Requires a host organism to survive/propagate

This includes viruses, bacteria, symbiotic organisms

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2
Q

What are the classifications of parasites?

A

Protozoa - unicellular

Metazoa - multicellular, include helminths (internal) and ectoparasites (external)

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3
Q

How do parasites replicate?

A

Extracellularly, some have intracellular stages

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4
Q

Where do parasites generally infect and how is it transmitted?

A

Largely infect the GI tract and blood
GI - fecal:oral route
Blood - animal vector
A number of parasitic infections are not communicable

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5
Q

Outline the life cycle of a parasite that uses two species.

A

Definitive host - sexual stage of reproduction is completed (primary host)
Intermediate host - non-sexual stages of reproduction are completed. May not reproduce at all, or may undergo differentiation

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6
Q

What are the characteristics of amoebas?

A

They obtain nutrients via phagocytosis and move with pseudopodia formation. These push cytoplasm to produce false feet and covert ectoplasm to endoplasm (and vice versa) to allow movement.

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7
Q

What are the characteristics of Entamoeba histolytica?

A

Endemic to tropical areas
Cyst stage is infective (4 nuclei)
Trophozoite stage is replicative (pathogenic, diagnostic)
Trophozoite stage ingests host cells to acquire nutrients
Phagocytosis of tissue = ulcer/abscess
Phagocytosis of erythrocytes indicates invasion

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8
Q

What are characteristics of an Entamoeva histolytica infection?

A

Intestinal amoebiasis, amoebic dysentery, extra-intestinal amoebiasis
Invasion of peripheral tissues: liver, lung, brain, skin
70-80% asymptomatic
Infective dose = 1 cyst

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9
Q

How is Entamoeba histolytica transmitted?

A

Fecal:oral - contaminated water and food
Cysts may survive for months in most conditions
Decontaminate food/water

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10
Q

What are the symptoms of intestinal ameobiasis?

A

Mild
Infection of the large intestine
Abdominal discomfort, colitis, diarrhea

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11
Q

What are the symptoms of amoebic dysentery?

A

Non-febrile
Frequent bloody and mucoid stool, severe fluid/electrolyte loss
Proteolytic enzymes causes intestinal abcess
Complications: amoeboma (amoebic granuloma), perianal fistula

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12
Q

What are the symptoms of extra-intestinal amoebiasis?

A 
Invasive
Systemic symptoms - fever, sepsis
Liver most common - liver abscess, hepatitis
Lung - abscess, pneumonia
Brain - abscess, encephalitis
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13
Q

How is an entamoeba histolytica infection diagnosed?

A

Cyst detection in stool samples
Trophozoite detection in tissue
Serology (PCR)

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14
Q

What are the characteristics of flagellates?

A

They have a long flagella that whip to facilitate movement
Organisms may vear one or multiple flagella
Variety of cellular structures between flagellated protozoan parasites

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15
Q

What are the flagellate human pathogens?

A

Giardia lamblia (giardiasis)
Trichomonas vaginalis
Trypanosoma cruzi

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16
Q

What are some characteristics of giardia lamblia?

A

Beaver fever
Worldwide prevalence: acquired from contaminated still water
Highly contagious
Cyst is hearty and resistant to chlorination. Cyst is infective (4 nuclei, aflagellate) and the trophozoite is replicative (2 nuclei, flagellate)

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17
Q

What are the signs and symptoms of a Giardia lamblia infection?

A

Diarrhea, abdominal pain
Fluid/electrolyte loss, malabsorption of lipid and nutrients
Greasy, floating stool (no blood or mucus)
No extra-intestinal phase, no tissue invasion
Afebrile

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18
Q

How is Giardia lamblia transmitted?

A

Fecal:oral

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19
Q

How is a Giardia lamblia infection diagnosed?

A 
Cyst detection in multiple stool samples
Fecal immunoassays (ELISA etc.)
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20
Q

What are some characteristics of Trichomonas vaginalis?

A

Trophozoite is infective, replicative
No cyst stage
Anaerobic organisms

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21
Q

What are the signs and symptoms of a Trichomonas vaginalis infection?

A

50% women symptomatic, generally men asymptomatic in men
Persistent infection associated with long term complications; infection restricted to urogenital tract (infertility, cervical erosion, cervical cancer)
Vaginitis, vulvitis, urethritis, PID
Purulent foul smelling discharge, itching, burning
Colpitis macularis (strawberry cervix)
In men: urethritis, prostatitis, epydidymitis

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22
Q

How is Trichomonas vaginalis transmitted?

A

Mucosal (sexual)

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23
Q

How is Trichomonas vaginlais diagnosed?

A 
Vaginal/urethral swab
Microscopic examination (must be performed immediately after swab - why?)
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24
What are some characteristics of Trypanosoma cruzi?
American trypanosomiasis, Chaga's disease Endemic to South and Central America, emerging in North America Transmitted by Triatoma insects Trypomastigote stage is infective Replication occurs in insect vector
25
What are signs and symptoms of a Trypanosoma cruzi infection?
Acute inflammation near the point of infection Fever, lymphadenopathy Severe/chronic cases have cardiac manifestations - cardiomyopathy, arrhythmia, tachycardia
26
How is Trypanosoma cruzi transmitted?
Vector - also blood transfusion, placental
27
How is Trypanosoma cruzi diagnosed?
Blood smear
28
What are characteristics of ciliates?
Cilia provide motility, aid in feeding (phagocytosis) | Variety of feeding strategies, cellular structures
29
What are the human pathogens of ciliates?
Balantidum coli - the only human pathogen
30
What are some characteristics of Balantidum coli?
Endemic to tropical areas, common where pigs are raised (animal resevoir)
31
How is Balantidum coli transmitted?
Fecal:oral by contaminated food/water
32
What are the signs and symptoms associated with Balantidum coli?
GI infection: Diarrhea, abdominal pain, nausea, vomiting
33
How is Balantidum coli diagnosed?
Stool examination (microscopy)
34
What are some characteristics of sporozoa (Apicomplexa)?
``` Complex subcellular structure Apicoplast organelle - potential functions include fatty acid synthesis and heme synthesis Sporogony yields oocysts and sporozoites Merogony yields shizonts and merozoites Gametogony yields gamets and zygotes ```
35
What are human sporozoa (Apicomplexa) pathogens?
Cryptosporidium sp. Toxoplasma gondii Falciparum sp. Babesia sp.
36
What are some characteristics of Cryptosporidium sp.?
Cryptosporidiosis, crypto Widespread prevalence Sporozoite is hearty - resistant to heat, desiccation, chlorination All stages of reproduction occur in one host - can be communicated between individuals
37
What are the signs and symptoms of a Cryptosporidium sp. infection?
Generally asymptomatic, self-limiting, non-invasive Watery, non-bloody diarrhea (1-2 weeks), afebrile In immunocompromised individuals: severe chronic diarrhea and fluid loss, chronic infection, risk of dissemination
38
How is Cryptosporidium sp. transmitted?
Fecal-oral
39
How is a Cryptosporidium sp. infection diagnosed?
Stool sample analysis (multiple samples) | Immunoassay, PCR detection
40
What are some characteristics of Toxoplasma gondii?
Toxoplasmosis, associated with cat litter
41
What are the signs and symptoms of a Toxoplasma gondii infection?
Mild flu like illness in immunocompetent individuals Risk of teratogenesis if acquired during pregnancy In severe/immunocompromised individuals: Encephalitis (cognitive symptoms), Toxoplasma chorioretinitis (retinal inflammation/lesion, unilateral decreased visual acuity) Tissue cysts lead to severe complications of infections: Myocardial, skeletal muscle, eye, brain
42
How is Toxoplasma gondii transmitted?
Fecal:oral | Ingestion of undercooked infected animals, handeling of infected feces/cat litter (cat reservoir)
43
How is a Toxoplasma gondii infection diagnosed?
Serology, immunoassays
44
Where is Malaria endemic and what is the name of the parasite?
Plasmodium sp. Endemic in tropical/developing nations (Africa, South America, SE Asia, Central America) Largest worldwide parasite epidemic
45
What are the signs and symptoms of a Plasmodium sp. infection?
Cyclical fever, fatigue, chills, nausea, myalgia, Liver stage and blood stages of infection: Hepatomegaly, splenomegaly, jaundice, anemia, respiratory distress Cerebral malaria in severe cases: cognitive impairment, confusion, lethargy, seizure
46
What are some characteristics of Plasmodium sp.?
Intracellular pathogen (hepatocytes and erythrocytes) Asexual stages of reproduction occur in humans Sexual stages occur in mosquitoes
47
How is Plasmodium sp. transmitted?
``` Vecotr borne (Anopheles mosquito) Malaria is NOT typically communicated between individuals ```
48
How is a Plasmodium sp. infection diagnosed?
Blood smear/film Thick film: drop of blood on glass slide determines % of infected erythrocytes Thin film: Drop of blood smeared across slide determines species of pathogen based on morphology
49
What are some characteristics of Babesia sp.?
Infects erythrocytes NOT hepatocytes Life cycle similar to Plasmodium sp. and requires two hosts: asexual reproduction in humans and sexual in ticks. Babesia microti most common
50
How is Babesia sp. transmitted?
Tick-borne parasite
51
What are the signs and symptoms of a Babesia sp. infection?
Mild malaria like illness: fever, chills, myalgia, nausea, fatigue. No liver stage, not cyclical.
52
What are the complications of a Babesia sp. infection in immunocompromised individuals?
Hemolytic anemia, jaundice, DIC
53
How is Babesia sp. diagnosed?
Blood smear, molecular tests to distinguish from malarial parasites
54
What are characteristics of trematodes?
Flukes, flatworms Dioecious or hermaphroditic Require at least 1 intermediate host (mollusk) Sexual stages in definitive host, asexual in intermediate hosts Complex structure
55
What are the human pathogens of trematodes?
Schistosoma sp. Paragonimus westermani Fasciola hepatica
56
What are the characteristics of Schistosoma sp.?
Schistosomiasis aka bilharzia, snail fever Endemic to Asia, Africa, South America, areas containing high levels of freshwater snails Dioecius (female embedded in male adult) Circarium infectious to humans, eggs secreted in urine or stool
57
What are the signs and symptoms of a Schistosoma sp. infection?
Swimmers itch - itch and rash Acute infection: fever, chills, liver/spleen enlargement, lymphadenopathy, eosinophilia Organ specific effects vary with species (Intestine, Urinary, kidney) CNS invasion rare: transverse myelitis, flaccid paraplegia
58
What are the symptoms of a chronic Schistosoma infection?
Chronic infection: egg deposition, granuloma formation, fibrosis in affected tissue leading to long term complications - portal hypertension - bladder cancer - hepatomegaly - splenomegaly - kidney failure
59
How is Schistosoma sp. transmitted?
Contaminated water, fecal/urine | Cercaria stage burrow into skin and migrate to liver to mature into adult stage
60
What are the signs and symptoms of the incubation period of Schistosoma sp.?
Many subclinical Rash may appear days after exposure Febrile illness may appear 1 - 2 months following infection
61
How is Schistosoma sp. diagnosed?
Serology (antibodies) Urinalysis, stool sample analysis (eggs) Tissue biopsy
62
What are some characteristics of cestodes?
Tapeworms Segmented, hermaphroditic (each segment), macroscopic Adult tapeworms lead to intestinal infections Larval infections leads to extra-intestinal cyst depostion
63
What are the human cestodes pathogens?
``` Taenia solium (pork) Taenia saginata (beef) Diphyllobothrium latum (fish) Echinococcus sp. (dogs) ```
64
What is the scolex of a cestode?
The head. Responsible for attachment to the intestine, distinct structural anatomy
65
What is the proglottid of a cestode?
The body of the worm, each segment Each segment is hermaphroditic. Proglottid secments can tear away and be shed in feces without consequence to the parasite.
66
What are the symptoms of an intestinal infection of a cestode?
Often asymptomatic Abdominal pain, upset stomach, weight loss E. granulosus - absorbs 80% of B12 ingested from food leading to anemia
67
What are the symptoms of an extra-intestinal infection of a cestode?
Taenia solis - Cysticercosis: deposition of cysts in muscle (generally asymptomatic) or brain (neurocystircercosis, seizure, confusion, difficulty with balance, hydrocephalus) Echinococcus sp. Hydatid disease: humans are incidental dead end hosts. Occurs fecal/oral from dogs. Deposition of cysts in lung, alveoli, etc. Symptoms based on area of deposition. Cystic rupture leads to anaphylaxis
68
How is a cestode infection diagnosed?
Multiple stool sample Tapeworm segments may be visible in stool CT/MRI for suspected cystic echinococcosis followed by serology
69
What are nematodes?
Roundworms Dioecious Intestinal and extra intestinal pathogens
70
What are the human pathogens of nematodes?
``` Enterobias vermicularis (pinworm) Necator americanus (hookworm) Trichura trichiuris (whipworm) Ascaris lumbricoides (giant roundworm) ```
71
What are the signs and symptoms of a E. vermicularis infection (pinworm)?
Itchy anal region - larvae mature at perianal region Vaginal itching - infection of vaginal canal Restlessness, difficulty sleeping
72
How is E. vermicularis transmitted?
fecal-oral Contact with contaminated surfaces, linens May survive for weeks on inanimate surfaces
73
How is E. vermicularis diagnosed?
Tape test - clear adhesive tape in perianal region for 3 consecutive mornings Stool, fingernail analysis for eggs
74
What are the signs and symptoms of an N. americanus (hookworm) infection?
mild/absent, children more commonly get symptoms Intestinal inflammation, vomiting, abdominal pain, diarrhea Anemia and protein deficiency (suck blood through intestine) Ground-itch - local invasion of larvae in skin leads to lesions and itching
75
What are complications of an N. americanus (hookworm) infection?
Chronic anemia/protein deficiency in children may lead to growth retardation and delayed development
76
How is N. americanus transmitted?
soil transmitted helminth | Infects through the skin (walking barefoot on contaminated soil)
77
How is N. americanus diagnosed?
Stool analysis
78
What are signs and symptoms of a T. trichuris (whipworm) infection?
May be mild/absent severe infections: painful passage of stool containing blood/mucus, rectal prolapse rare complication Anemia, growth retardation and developmental delay in children
79
How is T. trichuris (whipworm) transmitted?
Fecal:oral | Contaminated soil, human fertilizer, contaminated fruits/vegetables
80
How is T. trichuris (whipworm) diagnosed?
Stool analysis
81
What are the signs and symptoms of an A. lumbrocoides (ascariasis) infection?
Most experience no symptoms Intestinal primary infection: abdominal pain, vomiting, bloody stool Lungs (invasive disease): migration of larvae lead to pneumonitis, similar to asthma attack. Wheezing, coughing, shortness of breath
82
How is A. lumbrocoides (ascariasis) transmitted?
Fecal-oral | Contaminated soil, human fertilizer, contaminated fruits/vegetables
83
How is a A. lubrocoides infection diagnosed?
Stool analysis
84
What are general characteristics of protozoa?
Unicellular eukaryotes causing a variety of parasitic infections in humans Cyst stage generally infective to humans and is the result of the sexual reproductive phase of the parasite Classified based on method of motility
85
What are general characteristics of helminths?
Multicellular eukaryotes causing a variety of parasitic infections in humans Classified based on morphological features Many dioecious or hermaphroditic
86
How can parasitic infections of the blood and GI tract distinguished?
``` Clinical features: Type of diarrhea Fever Extra-intestinal symptoms Paroxysmal features Dissemination of infection ```

2nd year - Microbiology (21 decks)

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