Micro Id #1 - Parasitology

Front 1

What is "zoonosis"?

Back 1

Any infectious disease that is naturally transferable between animals and humans.

Front 2

What are two varieties of African or Old World Trypanosomiasis and what are their differences?

Back 2

East African = T. Rhodesiense = fulminating infection, acute

West African = T. Gambiense = slowly progressing, chronic

Front 3

Why do individuals infected by Trypanosomiasis get fluctuating bouts of infection and fever?

Back 3

The protozoa has variant antigenic types and can form different glycoproteins (VSG or variant surface glycoproteins) on it's surface (thus, escapes from killing).

New antigens = new infections. Thus there is a fluctuating parasitemia.

Front 4

What is "xenodiagnosis"?

Back 4

It is an outdated diagnostic technique where a bit of blood was taken from an infected human and injected into rats or mice to see if they developed the same symptomatology.

Front 5

What is "dysentery"?

Back 5

Blood + mucous + stool (happens in some parasitic infections)

Front 6

What is the life cycle of a trophozoite such as entammoeba histolytica?

Back 6

trophozoite (feeds,motile, and replicates) > It the encysts (protective coating) > it is excysted (amoeba is released and becomes trophozoite again)

It cycles in this way

Front 7

If someone comes to you with bloody diarrhea, what is this a sign of?

Back 7

Invasion! It might not be severe and systemic, just a little bit of necrosis, but it means invasion (not the same as traveler's diarrhea or watery stool)

Front 8

What is the infective form of the amoeba- the cyst form or the trophozoite?

Back 8

The cyst form (what the humans will consume). Whenever the amoeba is traveling it protects itself in a capsule coat.

Front 9

What distinguishes the pathogenic vs. non pathogenic form of entamoeba?

Back 9

Hemophagocytic = eats RBCS = E. Histolytica

Front 10

What is not unusal that we don't find blood in the stool of patient's infected with Giardia?

Back 10

Because it is not invasive (does not invade intestinal wall!). Thus you get a greasy, frothy, foul-smelling stool but no blood or mucous (no dysentery).

Front 11

The following are part of what group?:

- Cryptosporidium parvum
- Cyclospora cayetanensis
- Isospora belli

what is the treatment for them?

Back 11

Intestinal coccidians

Treated by modified Acid Fast Bascilli stain

Front 12

What is dangerous about free-living amoeba?

How is Naegleria fowleri acquired and what does it do?

Back 12

Cause lethal meningoencephalitis

The Naegleria fowleri can be acquired from ponds or lakes and enters brain via cribriform plate.

Front 13

T or F

Parasites that are less dependent on Oxygen and do not consequently migrate to lung or intestinal invasion are less adapted to parasitism.

Back 13

False

They are actually more adapted to parasitism! Just think about it in the sense that they are more advanced organisms and can be less commensal and more parasitic.

Front 14

For the Enterobius vermicularis do we see:
soil phase
lung migration phase
GI invasion phase

Back 14

Pinworm

no soil phase, no lung phase, no GI migration phase

* this means it is the most advanced (also most common human helminth in the US!)

Front 15

How is enterobius vermicularis obtained?

Back 15

Adults lay eggs on butt (around perinium) at night > child scratches butt (itchy butt) > child sucks thumb and ingests eggs > the larvae hatch in small intestine and mature in colon > migrate to anus and cycle continues

Front 16

What is the pathognomonic feature of the Enterobius vermicularis egg?

Back 16

Flat on one side

Front 17

How is Enterobius vermicularis diagnosed?

Back 17

Stick tape test- at night stick tape to the external anus and place tape on slide. Use microscopic examination to analyze.

Front 18

How is Enterobius vermicularis treated?

What is the single most important thing to keep in mind regarding it's prevention?

Back 18

Albendazole (1 dose)
Mebendazole (2-3 days)

*both worm microtubule inhibitors. prevent movement and starve worm.

Hang hygiene!

Front 19

Which of the following exist in the Trichuris trichiura?
- soil phase
- GI invasion phase
- Lung phase

Back 19

Has a soil phase AND local GI invasion

NO lung phase

*3rd most common helminth globally!

Front 20

Why is the trichuris trichiura called the "whip worm"?

What do it's eggs look like?

Back 20

Because the worm itself has a slender, whip-like tail.

Eggs look like "Tea-trays" (remember T...T..trichuris trichiura)

Front 21

What is the most serious encountered symptom associated with Trichuris trichiura?

Back 21

Rectal prolapse

Front 22

What is the life cycle for trichuris trichiura (i.e. how is it passed to humans)?

Back 22

Eggs in soil are ingested by humans > larvae hatch in small intestine > they migrate to the colon where they mature > eggs pass out in feces which is used as night soil for instance

Front 23

How do you diagnose Trichuris trichiura and what is the treatment for it?

Back 23

Diagnosis via stool O&P (ova and parasites)

Albendazole (3 days)
Mebendazole (3 days)

Front 24

What is the most common human helminth globally?

Do they possess or lack a soil phase, GI invasion, and lung migratory phase?

Back 24

Ascaris lumbricoides

They have all 3: soil, transient GI invasion, and lung phase

Front 25

What is the natural cycle of ascaris lumbricoides (i.e. how does it get into human)?

Back 25

Humans ingest eggs (laid in soil) > larvae hatch in small intestine and migrate to lungs > larvae enter alveolar space > adults mature in intestine and lay eggs that are passed out into feces (ex: used as night soil)

Front 26

What clinical symptoms are associated with infection with Ascaris lumbricoides?

Back 26

They can be asymptomatic.
However they can also lead to malnutrition, bowel obstruction, perforation, and migration up liver can cause liver abscess. Loeffler's Syndrome in lung.

Front 27

How do the eggs of the Ascaris lumbricoides look under microscopic examination?

Back 27

Pigmented brown because of stool and lobulated appearance.

Front 28

What is used to treat Ascaris lumbricoides?

Back 28

Albendazole (1 dose)
Mebendazole (3 doses)

Front 29

Does the hookworm have a soil phase, GI invasion phase, and lung migratory phase?

Back 29

Yes, it has all three.

It has a major GI invasion phase. 2nd most common human helminth globally after Ascaris!

Front 30

What is the natural cycle of the hookworm (i.e. how does it get into humans)?

Back 30

Worm enters through bare feet > larvae enter bloodstream and migrate > adults mature in small intestine > eggs pass out in feces and develop in soil

Front 31

What is the single most effective way of controlling hookworm?

Back 31

The Pit latrine (a latrine built with a pit underneath it that was a particular depth such that worms would not be able to crawl up it.

Front 32

What clinical symptoms can a person infected with a hookworm present with?

Back 32

1. IRON-DEFICIENCY ANEMIA
2. Failure to thrive

Front 33

There is a specific form of hookworm called ancylostoma caninum. Where is it transmitted from and what symptom can it cause?

Back 33

Comes from dogs (caninum) and can cause "ground itch" it can't penetrate dermis so humans are incompatible or "dead end" hosts.

In the skin, it forms a "Serpiginous" lesion.

Front 34

What is the treatment for Ancylostoma caninum?

Back 34

albendazole (3 days)
ivermectin (1-2 days)- effective for small round worms, microfillari (binds to Cl- channels in muscle and causes paralysis, also GABA agonist causing inhibition of synapses)

Front 35

What does the hookworm egg look like?

Back 35

It has a transparent shell and thus we can see lobulated larvae within.

Front 36

Does the Strongyloides stercoralis possess a soil phase, GI invasion phase, and lung phase?

Back 36

Yes (has soil, GI invasion, and lung phase) AND a Free-Living Cycle

* thus, very difficult to irradicate

Front 37

What is the natural cycle of the Strongyloides stercoralis (how does it get into humans)?

Back 37

penetrates unbroken skin > reach blood stream > adult worms live in Small Intestine > larvae can be infectious (L3) and pass out in feces

Front 38

Why is it particularly bad for an HIV patient to be infected by Strongyloides stercoralis?

Back 38

It can cause hyperinfection syndrome in immunocompromised syndrome, leading to massive invasion and secondary bacterial infection.

Front 39

Would you treat a person who has eosinophilia and in whom you suspect a strongyloides infection but have not yet received stool culture results?

Back 39

YES! or else they will die (and also, not many things cause eosinophilia)

treatment with ivermectin and albendazole.

Front 40

What is a Definitive host vs. an Intermediate host?

Back 40

Definitive= host where adults of parasite are (and where they reproduce). Typically human.

Intermediate host= host in which larvae are laid (typically mosquito or some other creature).

Front 41

What is unique about the feeding pattern of mosquitos that are responsible for Lymphatic filariasis?

Back 41

They feed at night (the nematode has evolved to lay larvae at night so that mosquito can take them up).

crrrraaaazy!

Front 42

What clinical symptoms might you see ina patient infected with Lymphatic filariasis (think of the anatomic site)?

Back 42

painful lymph nodes, lymphangitis, ulcerations and abscesses.

Elephantitis= thick, hardened skin with edema. Hydrocele in groin.

Front 43

What tests are used to diagnose lymphatic filariasis?

Back 43

1. Blood test (done at night!)
2. Antibody & antigen capture assay
3. Demonstration of worms by ultrasound (Filarial Dance sign)

Front 44

T or F

Malaria is the most important single agent killer of children on the planet.

Back 44

True

8% of all childhood deaths on the planet are from Malaria (1 child dies every 15 seconds)

Front 45

Sickel Cell anemia is a uniformly fatal disease in the developing world. Most people homozygous for the mutated gene will die before reproductive age. Why, then is the gene/disease still maintained?

Back 45

Heterozygote advantage

People who are heterozygous for Sickel Cell disease are protected against malaria (why the allele propagates).

Front 46

What species of malaria is the one that kills?

Back 46

P. Falciparum

Front 47

How is malaria transmitted?

What types of areas does the vector like to live in?

Back 47

Through the bite of the female anopheline mosquito.

Water breeding sites.

Front 48

What is the life cycle of the Falciparum malaria?

Back 48

1. female anopheles injects sporozoites while taking blood meal.
2. sporozoites infect hepatocytes (1 spor/hepatocyte) and multiply asexually.
3. after 6 days, up to 40,000 merozoites rupture from infected hepatocyte
4. Each merozoite infects a single RBC.
5. Merozoites asexually reproduce and can differentiate into male and female gametocyte, taken up by mosquito
6. In mosquito they fuse in the gut and develop sporozoite that migrate to mosquito's salivary gland to complete the cycle.

Front 49

What parts of the world are primarily affected by malaria?

Back 49

Tropics and subtropics

*ALWAYS take a TRAVEL HISTORY from someone who has recently visited these areas and comes down with a FEVER!

Front 50

T or F

If a person does not have periodic fevers, they can't get malaria.

Back 50

False!

RBCs do not all rupture at the same time. (Fevers, btw, are caused by activation of immune system by parasites pyrogenic antigens. Also ruptured RBCs express phosphatidyl serine that activates macrophages)

Front 51

How do you diagnose malaria?

Back 51

- Travel history!!
- Microscopy (blood smears)
- PCR

Front 52

If someone with malaria turns up, what should you do to obtain treatment?

Back 52

Call the CDC Malaria Hotline (treatment depends on parasite species, severity, etc.)

Front 53

Who's is most susceptible to Maternal Malaria (i.e. placenta is infected)? :

Primigravid, Secundigravid, or Multigravid women?

Back 53

Primigravid

Multigravids make antibodies against the parasite receptor to CSA (chondroitin sulfate) on syncytiotrophoblasts (placental cells). So multigravids are protected. Primagravids are not. (this is why you have to vaccinate them, so they can immunologically mimic multi-gravid state).