Infectious Enterocolitis (Parasitic)

Question 1

What is the most common cause of dysentery in the world?

Answer 1

Entamoeba histolytica

Question 2

What enteric parasites travel to the lungs, are coughed up, and swallowed as part of their lifecycle?

Answer 2

• Ascaris lumbricoides (“giant” roundworm)
• Strongyloides stercoralis (roundworm)
• Ancylostoma spp. and Necator spp. (hookworms)

Question 3

What enteric parasites enter the body via the skin?

Answer 3

• Ancylostoma spp. and Necator spp. (hookworms)
• Schistosoma spp.

Question 4

What enteric parasites have something other than just eggs/ova passed in the stool?

Answer 4

• Strongyloides stercoralis -> rhabditiform larva (roundworm)
• Entamoeba histolytica -> trophozoites
• Giardia lambia -> trophozoites

Question 5

How does Entamoeba histolytica present?

Answer 5

• bloody diarrhea/dysentery (invasive)
• liver, lung, and brain abscesses (enter portal circulation)

Question 6

How is Entamoeba histolytica transmitted?

(route and infectious form)

Answer 6

• fecal-oral
• ingested cysts

Question 7

How is Entamoeba histolytica diagnosed/characterized?

Answer 7

• stool ova/trophozoites
• trophozoites with ingested erythrocytes
• “flask-shaped” ulcers on biopsy (lyses tissue -> histo lytica)

Question 8

How does Giardia lamblia present?

Answer 8

• recent hiking/camping
• foul smelling, fatty diarrhea/steatorrhea (damage to brush border -> malabsorption)
• no blood in stool (non-invasive)
• bloating/flatulence

Question 9

How is Giardia lamblia transmitted?

(route and infectious form)

Answer 9

• fecal-oral
• ingestion of cysts (contaminated water)

Question 10

How is Giardia lamblia diagnosed/characterized?

Answer 10

• stool trophozoites/cysts
• Ag detection

Description:

• “pear-shaped” trophozoite
• 4 flagella

Question 11

What factor is associated with increased risk of Giardia lamblia infection?

Answer 11

IgA deficiency (hints: transfussion reactions or multiple respiratory infections)

Question 12

How do Cryptosporidium spp. present?

Answer 12

-watery diarrhea (especially in HIV/AIDS)

Question 13

How are Cryptosporidium spp. transmitted?

(route and infectious form)

Answer 13

• fecal-oral
• oocyst ingestion (contaminated water; pools and drinking water)

Question 14

How are Cryptosporidium spp. diagnosed/characterized?

Answer 14

• stool oocysts that are acid-fast
• stool Ag

Description:

• acid-fast (only parasite)
• 4 motile sporozoites

Question 15

What factor is associated with increased risk of Cryptosporidium spp. infection?

Answer 15

immunosuppression -> HIV/AIDS (most common cause of diarrhea)

Question 16

How does Enterobius vermicularis present?

Answer 16

Pinworm:

-perianal itching (females migrate to perianal region at night to lay eggs)

Question 17

How is Enterobius vermicularis transmitted?

(route and infectious form)

Answer 17

• fecal-oral
• ingestion of eggs

Question 18

How is Enterobius vermicularis diagnosed/characterized?

Answer 18

-“scotch tape” test; picks up eggs on perianal folds that can be visualized on microscopy

Description:

• nematode
• pinworm

Question 19

How do Ancylostoma spp. and Necator spp. present?

Answer 19

Hookworms:

-iron defciency anemia (ingest blood from intestinal wall)

Question 20

How are Ancylostoma spp. and Necator spp. transmitted?

(route and infectious form)

Answer 20

• penetrate skin (sole of foot) -> blood stream -> lungs -> coughed up and swallowed (enters GI)
• **larva** from infected soil

Question 21

How are Ancylostoma spp. and Necator spp. diagnosed/characterized?

Answer 21

• eggs in stool
• eosinophilia (helminth)
• microcytic anemia

Question 22

How does Ascaris lumbricoides present?

Answer 22

Roundworm:

• intestinal obstruction (large number of worms)
• pneumonitis
• Löffler syndrome

Question 23

How is Ascaris lumbricoides transmitted?

(route and infectious form)

Answer 23

• fecal-oral
• ingestion of eggs from contaminated soil
• once in GI tract, larvae travel to lungs via cirucalation -> cough up and swallowed (auto-infection)

Question 24

How is Ascaris lumbricoides diagnosed/characterized?

Answer 24

• eggs in stool
• eosinophilia (helminth)

Description:

• helminth
• giant round worm

Question 25

How does *Strongyloides stercoralis* present?

Answer 25

_Roundworm_: - **larva currens** (itchy, cutaneous condition from migration through dermis) - **Löffler's syndrome** (esoinophil accumulation in lungs -\> coughing and dyspnea) - abdominal pain - diarrhea

Question 26

How is *Strongyloides stercoralis* transmitted? (route and infectious form)

Answer 26

- **penetrate skin** (sole of _foot_) -\> **blood stream** -\> **lungs** -\> **coughed up and swallowed** (enters GI) - \*\***larva\*\*** from _infected soil_ - once in GI tract, larvae **lay eggs in intestinal wall** -\> hatched _larvae_ enter blood and _travel to lungs_ -\> _cough up and swallowed_ (**auto-infection**)

Question 27

How is *Strongyloides stercoralis* diagnosed/characterized?

Answer 27

- \*\***_rhabditiform_ larvae\*\*** in stool (**lay eggs in intestinal wall** that hatch there -\> eggs not passed in stool) - **eosinophilia** (helminth) Description: -**threadworm**

Question 28

How does *Dihyllobothrium latum* present?

Answer 28

_Fish tapeworm_: - **typically asymptomatic** - **pernicious anemia** - neurologic symptoms

Question 29

How is *Diphyllobothrium latum* transmitted? (route and infectious form)

Answer 29

-ingestion of contaminated **fish** (intermediate host)

Question 30

How is *Diphyllobothrium latum* diagnosed/characterized?

Answer 30

- **eggs** in feces - **eosinophilia** - **megaloblastic anemia/vitamin B₁₂ deficiancy** Description: - **cestode** - flatworm/**tapeworm**

Question 31

What are the *Taenia spp.*?

Answer 31

- *Taenia _saginata_* (**beef** tapeworm) - *Taneia _solium_* (**pork** tapeworm)

Question 32

How do *Taenia spp.* present?

Answer 32

_Beef/pork tapeworms_: - both typically asymptomatic * T. solium* **cyst accumulation** in _non-GI tissues_ -\> **cysticercosis** (rare) - **seizures** w/ increased intracranial pressure (_neuro_ cysticercosis) - **myalgia** (_muscle_ cysticercosis) - **eye pain/vision loss** (_ocular_ cysticercosis)

Question 33

How are *Taenia spp.* transmitted? | (route and infectious form)

Answer 33

* T. _saginata_*: - ingestion of contaminated **beef** ( (intermediate host) * T. _solium_*: - ingestion of contaminated **pork** (intermediate host)

Question 34

How are *Taenia spp.* diagnosed/characterized?

Answer 34

-**eggs or \*\*proglottids\*\*** in stool Description: - **cestodes** - flatworm/**tapeworm** (up to _meters in length_) - **scolex** at "head" for attachment

Question 35

What are the *Schistosoma spp.*?

Answer 35

_Bladder_: -*S. haematobium* _Intestinal/liver_: * -S. masoni* - *S. japonicum* - *S. mekongi*

Question 36

How do *Schistosoma spp.* present?

Answer 36

Intestinal: -**bloody diarrhea** Liver: -**liver cysts** -\> **cirrhosis/portal hypertension** (_second leading cause of cirrhosis_ after EtOH) Bladder (*S. haematobium*): - **hematuria** - **dysuria** - **bladder cancer** (SCC)

Question 37

How are *Schistosoma spp*. transmitted? | (route and infectious form)

Answer 37

- **swimming** in **water** with infected **snails** (intermediate host) - **cercariae** penetrate **skin** -\> **circulation** (portal) -\> liver/intestine

Question 38

How are *Schistosoma spp*. diagnosed/characterized?

Answer 38

- **eggs** in **feces/urine** - **eosinophilia** Description: -**trematode/fluke**