Parasites

Question 1

Strongyloides

Answer 1

INTESTINAL NEMATODE

Key:

• intact skin penetration (larvae)
• intense puritis (itching) and rash at invasion site
• diarrhea and cough
• immunocompromised pseudo Gram (-) pneumonia & sepsis
• eosinophilia, *stool larvae
• temperate climate

Extra:

• larvae penetrate skin -> venous migration to lungs -> migrate up to trachea -> swallowed -> adults develop in small intestine -> deposita ova in mucosa -> hatch and larvae pass through stools
• micro larvae in stool

Question 2

Hookworm (Ancylostoma d. or Necator a.)

Answer 2

INTESTINAL NEMATODE

Key:

• larvae skin penetration
• buccal capsules (small intestine attachment)
• tropical & subtropical, southeast U.S.
• Anemia, eosinophilia, *ova in stool
• ground itch-cutaneous larva migrans

Extra:

• larva skin penetration -> lung migration -> alveoli break out -> trachea migration and swallowing -> buccal capsule small intestine attachment -> ova release in stool
• infection site rash

Question 3

Ascariasis (round worm)

Answer 3

INTESTINAL NEMATODE

Key:

• ova are ingested/stool
• tropical, subtropical (most common worldwide)
• intestinal/billiary tract obstruction, cough
• eosinophilia
• large worm

Extra:

• ova ingested -> embryos migrate to lungs and break out in alveoli -> migrate to trachea and are swallowed -> adults develop in intestines -> release ova in intestine -> stool ova

Question 4

Enterobiasis (pin worm)

Answer 4

INTESTINAL NEMATODE

Key:

• ova ingested, *NO lung migration
• perianal worms (white threads)
• Scotch tape test (cellophane tape)
• temperate zones, most common U.S. helminth infection

Extra:

• ova ingested -> adult develop in intestine -> inhabit cecum -> females migrate at night to perianal and perineal regions to deposit ova

Question 5

Trichinosis

Answer 5

TISSUE NEMATODE

Key:

• raw meat (pork) - larvae encysted muscle
• *mainly asymtpomatic, diarrhea from adults in intestine
• periorbital edema from migration
• biopsy of swollen muscle (rare), serum antibodies

Extra:

• larvae ingested -> digestion release -> small intestine attachement and adult development -> larva released and penetrate intestinal wall -> larvae migration to skeletal muscle
• humans are dead-end host

Question 6

Filariasis

Answer 6

TISSUE NEMATODE

Key:

• mosquito transmission
• night time blood microfilaria, often asymptomatic
• tropics, subtropics
• acute lymphangitis & lymphadenitis
• chronic lymph elephantiasis -> increase pathogenic susceptibility
• *NO eosinophilia

Extra:

• mosquite bite -> larvae pass into lymphatics -> adult development (yrs) -> adult discharge microfilaria into lymph and blood -> mosquitos ingest microfilaria -> larvae develop in mosquito
  *

Question 7

Onchocerciasis (River Blindness)

Answer 7

TISSUE NEMATODE

Key:

• black -> blindness -> black fly -> rapid running water -> river
• Africa, fast-flowing streams/rivers
• blindness from microfilaria corneal migration
• cutaneous lymphadema/nodules
• skin snips in saline show microfilaria migration, slit lampe exam (cornea)
• NO eosinophilia

Extra:

• blackfly bite larvae -> larva migrate to superficial CT, adult development -> microfilaria production -> microfilaria skin & CT migration -> black fly bite, ingest microfilaria -> black fly larvae development
  *

Question 8

Schistosomiasis

Answer 8

TREMATODES (FLUKES)

Key:

• fresh water, skin penetration, snails
• developing world, Great Lakes swimmer’s itch
• acute: swimmer’s itch (papular itchy rash from penetration). Katayama fever -hepatosplenomegaly, lymphadenopathy
• chronic: *liver fibrosis (massive hepatosplenomegaly) -> abdominal edema, abdominal pain and diarrhea, urinary obstruction and hematouria
• diagnose by stool eggs, urine eggs, eosiniphilia in acute

Extra:

• water cercariae penetration -> schistosomulae migration to lungs and liver -> adult maturation & mating -> venous descent to portal vessels -> egg production (liver inflammation) -> eggs passed in stool in fresh water -> hatch releasig miracidia -> penetrates snail (intermediate host) -> miracidia multiply producing cercariea releasing into water

Question 9

Liver Flukes

Answer 9

TREMATODES (FLUKES)

Key:

• *raw freshwater fish, freshwater snail presence
• Southeast asia
• billiary (bile duct) inflammation, scarring, obstruction
• eggs in stools, NO eosinophilia

Extra:

• raw fish ingested -> metacercariae in duodenum -> bile duct maturation adult -> eggs passed in stool -> ingested by snails (eggs hatch) -> cercaria penetrate freshwater fish skin

Question 10

Taenia (tapeworm), Cysticercosis

Answer 10

CESTODES (TAPEWORMS)

Key:

• raw meat (pork and beef) [human definitive host–only humans], feces eggs consumption [human intermediate host]
• Teania - mild abdominal cramps & weight loss. stoll examination
• Cysticercosis - CNS mass lesion, radiograph, serum antibodies
• Pork - T. solium. Beef- T. saginata

Question 11

Echinococcus (Hyatid Disease)

Answer 11

CESTODES (TAPEWORMS)

Key:

• grazing animals meat + dog feces for cycle (shepherds-Greece)
• symmetrical liver cysts + smooth rim of calcification
• serum antibody to hyaid antigens, careful not to rupture cysts upon invasive procedure

Extra:

• humans are intermediate hosts, natural cycle betwn dogs and grazing animals. dog eats animal tissue -> dog poop eggs -> animals eat eggs
• humans ingest dog feces