Clinical Parasitology 2 - Protozoa Flashcards
0
Q
What kind of disease does Entamoeba histolytica cause?
A
Bloody diarrhea
1
Q
What kind of organisms are protozoa?
A
Single-celled eukaryotic organisms
2
Q
How does E. histolytica get into the human host?
A
Ingestion of mature cysts in fecally contaminated food, hands, water
3
Q
What is the transmission route of E. histolytica?
A
fecal-oral
4
Q
In the small intestine, the cysts mature into what in the E. histolytica life cycle?
A
Cysts release Trophozoites, which migrate to the large intestine
5
Q
How do trophozoites cause bloody diarrhea in E. histolytica?
A
Invade the intestinal mucosa causing erosions–> results in abdominal pain, loose stools and flecks of blood
6
Q
What is the characteristic lesion formed in the intestine by E. hustolytica?
A
Flask-shaped ulcers in large intestine
7
Q
What other two places can E. histolytica travel in the body? How does it get to each?
A
- Liver–> penetrates portal circulation and forma abscesses in liver
- Lung–>after portal invasion, spreads above diaphragm and forms pulmonary abscesses
*may also disseminate to brain and abscess there
8
Q
What is the characteristic appearance of the contents of E. histolytica liver abscesses?
A
“Anchovy paste” aspirate
9
Q
How is Dx of E. histolytica made?
*How can active vs. asymptomatic carriage be determined?
A
ID of cysts or trophozoites in the stool
- Trophozoites with RBCs in their cytoplasm suggest active dz; those without likely reflect carriage state only
- PCR test for amoeba antigen exists also
10
Q
What is DOC for symptomatic E. histolytica infection?
A
Metronidazole
*Paromomycin for eradication of luminal carriage
11
Q
What form of E. histolytica is excreted in the feces?
A
Cysts–> trophozoites can convert to a precyst form with two nuclei, that matures into a tetranucleated cyst by the time it leaves the colon. Precysts contain chromotid bodies (aggregates of ribosomes), when these disappear, it is a mature cyst
12
Q
What kind of organism is Naegleria fowleri?
A
Free-living amoeba that lives in fresh water
13
Q
How are N. fowleri infections obtained?
A
Swimming in fresh water–> penetrates the nasal mucosa, passes through the cribiform plate and into brain and spinal fluid
14
Q
What symptoms are seen with N. fowleri infection?
A
Fever, headache N/V, stiff neck–> looks just like a bacterial meningitis
15
Q
What might CSF analysis show in N. fowleri infection?
A
Increased neutrophils, low glucose, and increased protein
- is exactly like bacterial meningitis, but gram stain will be negative
16
Q
Treatent for N. fowleri?
A
Kiss your ass goodbye; 95%+ are dead w/in a week
*intrathecal Amphotericin B has saved a select few people
17
Q
What kind of organism is Trichimonas vaginalis?
A
Flagellated protozoan (like Giardia lamblia)
18
Q
How is T. vaginalis transmitted?
A
STD–> men are asymptomatic carriers who pass it on to women
19
Q
What symptoms are seen in T. vaginalis infection?
A
- Vaginal itching
- Dysuria
- Copious, frothy discharge (usually malodorous)
- “strawberry” cervix on speculum exam
20
Q
How is dx of Trichomonas confirmed?
A
PCR detection of trophozoites in discharge
21
Q
Tx for trichimoniasis?
A
Metronidazole
*need to treat male partner or woman will be continously reinfected from carrier state
22
Q
Where does T. vaginalis live in the human host?
A
Female–> lower genital tract
Male–> urethra
23
Q
How does T. vaginalis replicate? Where in host?
A
Replicates via binary fission; usually in female genital tract
*no cyst stage; and cannot survive outside the host. No known other reservoir hosts
24
What type of organism is Giardia lamblia? What two forms can it take?
Flagellated protozoan--> has both a trophozoite stage and a cyst stage
*compare to T. vaginalis, also a flagellated protozoan, but doesnt have a cyst stage
25
What kind of dz in general does G. lamblia cause?
Intestinal disease--> most common protozoan intestinal disease in the US
26
What is the classical case scenaria for getting G. lamblia infection?
Campers/ other people in the woods who drink water from clear streams
27
What is the source of water infection of G. lamblia?
Rodents and beaver shit all in the water and you drink it
28
Other than the Great Outdoors, what environment is G. lamblia common in?
Day-care centers
29
What form in the life cycle of G. lamblia is ingested in contaminated water?
Cysts--> also the infectious form via the fecal-oral route like in day care centers
30
After ingestion, what happens to the G. lamblia cysta?
Turn into trophozoites, which multiply via binary fission in the small intestines
*Encystation occurs as parasites move towards colon
31
What do G. lamblia trophozoites do in the small intestines to contribute to Giardiasis symptoms?
Attach to the intestinal wall and interfere with absorption
32
What are some symtoms due to Giardia lamblia infection?
1. Foul-smelling, bulky diarrhea
2. Flatulence
3. Abdominal distention
* due to Giardia coating the intestines and interfering with fat absorption--> NO BLODD IN STOOL
33
What histopath changes may be seen due to Giardia infection on intestines?
Flattened intestinal epithelium
34
What confirms the Dx of Giardiasis?
ID of cysts and trophozoites in stool
35
Tx for Giardiasis?
Metronidazole
36
What are the two blood-borne flagellates?
1. Leishmania
| 2. Trypanosoma
37
What organism causes African sleeping sickness?
Trypsanosoma brucei
| rhodesience and gambiense species exist, both are T. brucei though
38
What organism transmits T. brucei to the human host? Which form of T. brucei is the infectious form transmitted by the bite?
Tsetse fly--> trypomastigote is the form transmitted
39
Where does the trypomastigote go once in the person's bloodstream?
To the CNS and lymph nodes
40
What is the first manifestation of T. brucei infection?
Chancre (hard, red, painful ulcer) on the skin at the site of the Tsetse fly bite
41
What four symptoms are see with systemic spread of T. brucei?
1. Fever
2. Headache
3. dizziness
4. Lymphadenopathy
42
What is unique about the fevers due to T. brucei infection?
They are undulating--> fevers will come and go in a pattern for a few months, likely due to antigenic variation (variant surface glycoproteins)
43
What CNS symptoms eventually develop later on in T. brucei infection, after the waxing/waning fevers?
1. Drowsiness in the daytime
2. Behavioral changes
3. Difficulty walking
4. Slurred speech
5. Eventually, coma and death
44
What is a main difference between t. brucei gambiense and T. brucei rhoesciense?
Gambiense--> "West African sleeping sickness"; slowly progressive fevers, wasting and LATE neuro symptoms
Rhodesiense--> "East African sleeping sickness"; rapid progression from fevers to EARLY neuro disease; death usually within weeks to months
45
What two methods are used to confirm T. brucei infection?
1. Microscopic visualization of trypomastigotes in peripheral blood or lymph nodes
2. Card agglutination test (assay for anti-T. brucei Abs in serum)
46
What is tx for T. brucei infection if CNS is not involved?
Suramin or pentamidine
47
What is tx for T. brucei if there are CNS manifestations? (different 1st line drugs depending on if infection is rhodesiense or gambiense)
1. Melarsoprol (rhodesiense, 1st line; 2nd line for gambiense)
2. Eflornithine + Nifurtimox (1st line for CNS gambiense)
48
What organism is responsible for American tryanosomiasis?
T. cruzi
49
Where is T. cruzi endemic (2 places)?
Central and South America
*also found in Mexico and SW U.S.
50
What organism transmits T. cruzi?
Reduviid bug (aka "kissing bug"<--- WTF?)
*populations of rodents, opossums, and armadillos serve as the reservoir for T. cruzi; is where the reduviid bug gets infected
51
How do reduviid bugs infect humans?
Feed on us while we sleep and shits while eating; T. cruzi trypomastigotes are excreted in reduviid feces and they burrow into our skin
52
Once inside human cells, what happens in the life cycle of T. cruzi?
1. Inside cells, trypomastigotes transform into amastigotes
| 2. Amastigotes replicate via binary fusion inside infected tissue
53
How do amastigotes, once replicated, spread inside the host?
Spread via the blood and lymph nodes to distant organs
*are also able to infect macrophages
54
What is the 1st sign of T. cruzi infection?
Chagoma--> hardened red area
*is often on the face; called Romaña's sign
55
What are three symptoms of systemic disease from T. cruzi?
Fever, myalgia, lymphadenopathy (also rash)
56
What 2 blood findings are seen in Acute Chagas' (ameriacn typanisomiasis) disease?
1. parasitemia
| 2. lymphocytosis
57
What two organs may be involved in acute Chagas'?
1. heart--> tachycardia, EKG changes
| 2. CNS--> severe meningoencephalitis (usually in young pts)
58
What is the intermediate phase of Chagas'?
Acute symptoms (fever, malaise, heart and CNS abnormalities) usually resolve in about a month, although there are usually persistently low levels of parasite in the blood
*most people remain in this Intermediate phase for life and have no further issues
59
What are the three main organs affected by chronic Chagas' disease, which develops for unknown reasons in people years to decades after intitial, acute disease?
1. Heart
2. Colon
3. Esophagus
(heart and some hollow organs)
60
What heart complications may develop in chronic Chagas' disease? (2 main ones)
1. Arrhythmias (heart block and ventricular tachycardia)
2. Dilated cardiomyopathy (increased heart size + heart failure)
*#2 is prob the one they'd ax on STEP
61
What complication may occur due to chronic Chagas' disease in the esophagus and/or colon?
1. Dilated esophagus (lead to dysphagia and odynophagia)
2. Megacolon(constipation and abdominal pain)
* destruction of autonomic ganglia
62
How can T. cruzi dx be confirmed?
1. On clinical grounds in endemic regions
2. Examination of blood smear for motile trypomastigotes
* also via tissue histological examination
* in chronic Chagas' dz, there should be serologic evidence of past T. cruzi infection, either parasitemia or anti-T. cruzi Abs
63
What is treatment for acute Chagas' disease? (2 drugs)
Nifurtimox + benznidazole
* treating chronic Chagas' is harder, doesnt respond as well to meds; so best plan is dont get disease (insect repellent and bednets when in endemic areas)
64
What places in the world is Leishmania sp. endemic?
Asia, India, Mediterranean, North and Central Africa, Central and South America--> basically everywhere but the U.S.
*8 different species in notes, dont know if they want us to know all that. If you have free time look over it Wally
65
What organism transmits Leishmania spp. to humans?
Sandfly
*rodents, dogs, and foxes are the natural reservoirs
66
What form of Leishmania is transmitted by a bite?
Promastigote
67
What happens to promastigote of Leishmania once in the body?
Taken up by macrophages and differentiates into a nonmotile amastigote
amastigote replicates within phagocytic cells in lymph nodes, spleen, liver and bone marrow (the reticuloendothelial system; makes sense since they replicate in macrophages)
68
What three varieties of Leishmaniasis exist?
1. Cutaneous
2. Mucocutaneous
3. Visceral
*depends on the invasiveness of the actual contracted species of Leishmania and the host immune response
69
What are symptoms of cutaneous leishmaniasis?
Skin ulcer develops at site of sandfly bite (called "oriental sore)
* heals in ~ 1 year, leaving a depigmented scar
* this variety sometimes seen in Texas
70
Dx of cutaneous leishmaniasis?
Scrapings of ulcer base reveal Leishmania
71
What are symptoms of mucocutaneous leishmaniasis?
Initially the same as cutaneous (ulcer); however, months to years later, ulcers arise in the mucous membranes of mouth and nose
*if untreated, may erode nasal septum, soft palate, and lips; death may result due to secondary bacterial infection
72
What are symptoms of visceral leishmaniasis (Kala-azar)?
Months after infection--> fever, anorexia, weight loss, abdominal pain and distention (distension due to massive hepatosplenomegaly, remember these organisms multiply in the RES)
*often seen in children; over 90% fatality rate if untreated
73
What two blood abnormalities may occur in visceral leishmanasis?
1. Anemia
| 2. Low WBC
74
How is dx of visceral leishmaniasis made?
1. Liver and spleen biopsy demonstrating protozoa
| 2. High titers of anti-leishmanial IgG levels
75
What is tx for all forms of leishmaniasis?
Sodium stibogluconate (an antimonial)
76
What two parasites are often found in AIDS patients, other than Cryptosporidium?
1. Toxoplasma gondii
| 2. Pneumocystis carinii
77
What two ways can humans be infected with Toxoplasma gondii?
1. Ingestion of cysts in raw/undercooked meat
| 2. Contact with cat feces (up to 80% of cats in U.S. are infected)
78
What is Toxoplasmosis gondii the most common cause of in AIDS patients?
CNS infection--> causes an encephalitis
*often due to reactivation of latent organism in immunocompromised people; infection doesnt usually cause any symptoms in those w/ intact immune systems
79
What symptoms can be seen in a person with CNS infection due to T. gondii?
Headache and focal neuro signs (seizures, gait instability, weakness, sensory loss)--> acts very similar to a CNS mass
* outside CNS may cause fever, lymphadenopathy, hepatosplenomagaly, or pneumonia; frequently infects the retina (chorioretinitis) producing white, fluffy cotton like patches surrounding a red retina
80
Other than immunocompromised, what other pt. population is at risk of infection with T. gondii?
Newborns--> of mothers with infection, 5-10% have miscarriage, 10% of newborns will have brain damage; 10% will have vision loss. But 70% of births will be normal
*pregnant women SHOULDNT PLAY WITH CAT SHIT
81
How can dx of toxoplasmosis be made?
1. CT scan of brain showing constrast-enhancing mass
2. Retinal examination revealing retinal inflammation
**in all susceptible pts, Toxoplasma gondii is toxic to BRAIN and EYES
82
Tx for T. gondii? (2 dug regimen)
Sulfadiazine + pyrimethamine
83
What kind of issues can Cyrptosporidium infection cause?
Usually severe diarrheal disease, esp. in AIDS/immunocompromised and in young children (daycare centers)
*also can be transmitted infected water; not killed by chlorine
84
What form of Cryptosporidium is ingested? Where in body does life cycle occur?
Round oocyst--> life cycle occurs within intestinal epithelial cells
85
After oocysts infect intestinal epithelial cells, what do they differentiate into? (specifically what does each of the four sporozoites each oocyte contains differentiate into)
Merozoites (these grow via asexual reproduction)--> some differentiate into male gametes, others into females; gametes fuse to form oocyst
86
What are the symptoms of Cryptosporidiosis?
Severe diarrhea and abdominal pain
* severity depends on inoculum; pts can lose b/n 3-17 L of stool/day
* in I.C. patient, may disseminate to gallbladder, biliary tract, or lung
87
How is Cryptosporidium infection dx'd?
Via antigen testing or stool microscopy
88
Tx for Cryptosporidiosis?
Nitazoxamide
*also want to tx that fluid loss via the anus. supportive care
