Worms

Question 1

What are nematodes that I need to know

Answer 1

whipworm, pinworm, ascaris, hookworm, stongyloides

Question 2

Whipworm: cycle and clinical signs. Dx.

Answer 2

eggs ingested and mature in intestine. often asymptomatic but may involve iron deficient anemia and rectal prolapse. Dx with fecal smear to look for eggs.

Question 3

Pinworm: cycle, symptoms, Dx

Answer 3

pinworm: eat eggs, eggs mature in intestine, female worm comes out anus and plants more eggs in that area at night. Causes nocturnal itching due to inflammed anal area (eggs are irritating). Dx is the scotch tape test

Question 4

Ascaris: cycle

Answer 4

egg ingestion, larvae hatch in sm intestine, penetrate the venous blood system, get into pulmonary capillaries, break into alveoli, crawl up airway, get swallowed. some people have eosinophilic lung response with CXR infiltrates during the lung phase. larvae mature in the intestine, make eggs, and the person poops them out.

Question 5

Clinical manifestation of ascaris

Answer 5

many are asymptomatic and self-limited (no automatic autoinfection cycle, though fecal oral contamination is possible). many cause eosinophilic lung response with CXR infiltrates during the lung phase. may cause intestinal blockage and acute choecystitis. worms are quite large and may be seen in the stool

Question 6

Hookworm: cycle

Answer 6

larval penetration of skin to bloodstream to lungs then swallowed then attach to upper small intestine. they suck blood.

Question 7

Hookworm: clinical manifestation and dx.

Answer 7

maybe itching. Anemia. may be asymptomatic. Dx: look for eggs in the stool

Question 8

Stongyloides: cycle.

Answer 8

larval penetration of skin, goes to bloodstream, goes to lungs, goes to GI, maturation and egg laying in the intestine, eggs hatch, larvae released, larvae either go to poop or penetrate the bowel wall and go to the bloodstream to start the cycle again.

Question 9

strongyloides clinical manifestation

Answer 9

itching and rash at penetration site, eosinophilic rxn in the lungs during the lung phase, hyperinfection among the immunocompromised. hyperinfection involves pulmonary infiltrates, severe abdominal pain, rash, gram negative spsis, and gram negative meningitis. If you see gram neg meningitis, suspect stongyloides. Dx with ELISA

Question 10

benzimidazoles: MOA, sides

Answer 10

benzimidazoles: bind beta tubulin and inhibit tubulin polymerization and microtubule dependent glucose uptake. NOT for pregnant women.

Question 11

nematode treatments

Answer 11

benzimidazoles and ivermectin

Question 12

What is abendazole used for? What about membendazole?

Answer 12

abendazole: for neurocystocercosis, echinococcosis (dog tapeworm), ascariasis, hookworm, whipworm. take with fat. not for pregnant women.
mebendazole is better tolerated in kids than abendazole

Question 13

Ivermectin: MOA and indications

Answer 13

opens glutamate sensitive Cl channels in helminths. good for strongyloides and ectoparasites like scabies. not good for hookworm. not for preg women and kids.

Question 14

Cestodes

Answer 14

fish, beef, pork tapeworm; dog tape worm* echinococcosis)

Question 15

fish and beef tapeworm

Answer 15

humans are definite host. we harbor adults and make eggs. eggs in stool that is eaten by a fish or cow. the eggs mature to larvae, which migrates to the flesh of fish or cow and encysts. we eat that and get infected. often asymptomatic.

Question 16

pork tapeworm:

Answer 16

definitive host is the pig. pigs eat poop with eggs in it. eggs hatch. larvae go to muscle and encyst. humans eat it. larvae make more eggs, humans poop out eggs. OR, we can be accidental intermediate hosts: humans eat eggs, eggs hatch, larvae look for pig flesh and end up in brain, spinal cord, ventricles, skin, and muscle.

Question 17

Neurocysticercosis

Answer 17

humans ate eggs and are intermediate hosts of pork tapeworm. larvae in brains. diagnose with CT and MRI combined with serology.

Question 18

Echinococcus

Answer 18

dog tape worm.
dogs expel eggs in poop. humans eat contaminated food, eggs hatch, larvae go to liver, lung, and brain. cysts can be large and make new daughter cysts. may survive asymptomatically for decades, though may be a problem if cyst gets too big and starts to compress things or erode bronchi. Cyst rupture may lead to such a strong immune response that the pt dies of anaphylaxis.

Question 19

Praziquantel: MOA and uses

Answer 19

treats cestodes. it induces ultrastructural changes in cestode tegumentum (skin) that causes an immune response and worm expulsion. only works for adult worms, and you have to make sure the head comes out because otherwise the worm will regrow.

Question 20

Niclosamide

Answer 20

not available in US but uncouples oxidative phsphorylation in tapeworms. only kills adult worms.

Question 21

treatment of neurocysticercosis

Answer 21

1. stop seizures: anti-epileptics
2. maybe antiparasitics: helps resolve the infection and decrease seizures and hydrocephalus, but increases inflammation as the worms die, which can lead to severe disability or death. so combine antiparasitic therapy (albendazole) with STEROIDS.

Question 22

treatment of ecchinococcus

Answer 22

cyst evacuation and anti-parasitic drugs. PAIR procedure: percutaneous drainage, aspiration, installation of a scolicidal agent, reaspiration.
or surgical/laproscopic removal. use albendazole before any procedure. be careful of anaphylaxis. if you can’t ressect, albendazole or mebendazole are good options.