Amebiasis, Giardiasis Cryptosporidium, Trichomonmiasis

Question 1

In the lifecycle of protozoa, __ are the forms that eat, replicate and move, and the __ forms don’t do any of these things (except that they’re the infectious form)

Answer 1

In the lifecycle of protozoa, trophic forms are the ones that eat, replicate and move, and the cystic forms don’t do any of these things (except that they’re the infectious form)

**trophic forms responsible for pathology in host**

Question 2

Pathogenic intestinal protozoa

Answer 2

E. histolytica: invasive; inhabits colon

Giardia intestinalis, Coccidia (Cryptosporidium, Cyclospora, Isospora): cause watery diarrhea, dysentery; inhabit small bowel

Question 3

Non pathogenic intestinal protozoa

Answer 3

Other Entamoeba (besides histolytica)

Question 4

3 parasites most common for causing diarrheal disease

Answer 4

Cryptosporidium parvum

Entamoeba histolytica

Giardia lamblia

Question 5

Lifecycle of E histolytica inside host

Answer 5

ingested cyst >> trophic form in colon >> replication and escape into other organs >> excreted trophic forms (repeat of cycle)

Question 6

Transmission of E histolytica is __

Answer 6

Tx: fecal-oral >> person to person, contaminated food/water

Question 7

Trophozoites feed by __, colonize the colon and replicate by binary fission

Cysts have a __ that allow them to resist gastric acidity and are infective even in small doses

Answer 7

Trophozoites feed by phagocytosis and eat RBCs, colonize the colon and replicate by binary fission

Cysts have a strong cyst wall that allow them to resist gastric acidity and are infective even in small doses

Question 8

Mechanisms of contact-mediated cytolysis for Entamoeba histolytica (3)

Answer 8

Adherence to epithelial cells via Gal/GalNac lectin

Cysteine proteases >> act on ECM

Amebapores >> pores in target cells

Question 9

Which organism contributes to flask-shaped lesions pathology in the colon?

Answer 9

E histolytica

Question 10

Presentation of amebiasis

Answer 10

Presentation: bloody diarrhea/dysentery, gradual onset (1+ week symptoms), ameboma

Question 11

Dx of amebiasis

Answer 11

Microscopy of stool + fecal Ag testing +/- serology

Imaging and needle aspiration of liver abscess

Question 12

Rx for amebiasis (asymptomatic carrier vs invasive disease)

Answer 12

Asymptomatic carrier: paromomycin/iodoquinol

Invasive disease: metronidazole/tinidazole

Question 13

Which bug is this?

Answer 13

Giardia intestinalis (lamblia, duodenalis)

Question 14

In Giardia, the __ stage colonizes the upper small intestine, attaches via “sucking disk” but doesn’t invade + replicates by binary fission

The __ stage is the infective stage passed in infected people’s feces

Answer 14

In Giardia, the trophozoite stage colonizes the upper small intestine, attaches via “sucking disk” but doesn’t invade + replicates by binary fission

The cyst stage is the infective stage passed in infected people’s feces

Question 15

Giardiasis presentation

Answer 15

Main presentation: watery and foul smelling diarrhea (no blood) and abdominal cramps

(also note malabsorption due to damage to villi >> weight loss)

Question 16

Giardiasis Dx and Rx

Answer 16

Dx: Microscopy and antigen testing

Rx: Metronidazole/Tinidazole/NITAzoxadine

Question 17

Cryptosporidium life cycle

Answer 17

Lifecycle:; oocyst ingestion >> sporozoite formation in gut >> invasion of enterocytes >> sexual cycle >> thick/thin walled cyst formation

Thin walled cyst mediates auto re-infection (starts the cycle back), thick walled cyst is excreted and becomes the infectious form

Question 18

Main method of Cryptosporidium transmission

Answer 18

Main method of transmission: contact with treated recreational water

Question 19

Which group of people is especially susceptible to Cryptosporidium infection?

Answer 19

Immune compromised folks

Question 20

Presentation of cryptosporidium

Answer 20

Very heavy and watery diarrhea

Marked weight loss

Question 21

Dx of Cryptosporidiosis

Answer 21

Dx: modified acid fast stain

Question 22

Rx for Cryptosporidiosis (immunocompetent vs immunocompromised host)

Answer 22

Rx for Cryptosporidiosis: immunocompetent pt >> nitazoxanide; immunocompromised pt >> HAART (basically remove the immunosuppression)

Question 23

Cyclospora transmission

Answer 23

Fecal oral; mainly contaminated food/water/produce (US)

Question 24

Cyclospora lifecycle

Answer 24

Lifecycle similar to other parasites (ingestion of sporulated oocyst >> infection in host >> excretion of unsporulated oocysts)

Note that the unsporulated oocysts need to sit in the environment for a while before they are infectious (considered the diagnostic stage)

**each oocyst contains 2 sporozoites. sporozoites infect the epithelial cells of the upper small intestine**

Question 25

Presentation of cyclospora

Answer 25

Sudden onset

Fever, abdominal cramping

Frequent watery diarrhea

Question 26

Dx for Cyclospora

Rx for Cyclospora

Answer 26

Microscopy of stool + PCR

Rx: TMP/SMX

Question 27

Trichomonas vaginalis transmission

Answer 27

Sexual transmission

**bug only exists as trophozoite**

Question 28

Presentation of Trichomonas vaginalis

Answer 28

Vaginal discharge, vulvovaginal soreness

Question 29

In women, trichomonas vaginalis infection increases risk of __ infection

Answer 29

HIV-1

**

weakens the integrity of the epithelial barrier

decreases innate immunity and normal epithelial defenses

disrupts the lactobacilli dominated vaginal microbiome

Question 30

Trichomonas vaginalis presentation in men

Answer 30

asymptomatic or have mild urethra discharge

(higher risk for HIV + unusual complications e.g. prostatitis)

Question 31

Trichomoniasis Dx and Rx

Answer 31

Dx: wet mount microscopy; pap smears; cultures; NAATs

Rx: Metronidazole/Tinidazole