Parasites IV

Question 1

What physical features characterizes the cestodes?

Answer 1

anterior attachment organ called the scolex.
can involve suckers, sometimes adorned with chitinous hooks.
soclex followed by segmented chain of proglottids that contain male and female reproductive organs

Question 2

Describe tapeworm sex

Answer 2

Tapeworms have a chain of proglottids called a strobilla. each proglottid has male and female reproductive bits. the mature segments toward the middle have mature reproductive organs. the segments at the end of the worm become filled with eggs- “gravid.” Egg release is due to the breakup of the gravid proglottid in the colon or in the environment after being excreted from the body.

Question 3

On what is cestode diagnosis based?

Answer 3

morphological characteristics of eggs, scolex, and proglottids passed in the stool.

Question 4

Where do cestodes live in the body? How do they get nutrients?

Answer 4

live in the small intestine and attach to intestinal mucosa via the scolex. they do not have an oral opening for food digestion- also no vascular, respiratory or digestive system. nutrients are absorbed across the tegument (outer layer) covering each proglottid.

Question 5

How do you treat cestode infection?

Answer 5

praziquantel (primary)

niclosamide (alternative) –> ATPase inhibitor

Question 6

How are cestode infections transmitted?

Answer 6

oral route

Question 7

What happens if mature cestode larvae are ingested? How are they ingested?

Answer 7

mature cestodes ingested through infected undercooked/underfrozen meat (fish, beef, pork)
they mature into adults and live their life in the intestine and produce eggs.
symptoms vary depending on many factors (parasitic burden, worm byproducts, pt’s rxn to byproducts, metobolite absorption by the worm, esp. of B12)
In this case, humans are the definitive hosts

Question 8

What happens if eggs or immature larvae are ingested? (cestode infection) How are they ingested?

Answer 8

Fecally contaminated food or water
no maturation of larvae to adults and the organism remains as a larvae. Humans are the intermediate hosts. Larva finds the intestine inhospitable and migrate into the tissues. they become trapped in other sites, including the brain- devastating, painful, and hard to treat.

Question 9

Describe the taenia solium lifecycle

Answer 9

cysticerci ingested in raw pork
cysticerci released from muscle in the stomach
worms mature in the small intestine
adults live in small intestine
adults grow and release proglottids into the feces
eggs eaten by pig, larvae mature in pig tissue, cysticerci are formed

Question 10

How do you acquire taenia solium? Who is the definitive host, and who is the intermediate host in most cases?

Answer 10

pig tapeworm- ingest undercooked pork

humans are definitive host and pigs are the intermediate hosts

Question 11

Cysticercosis: causative agent? how?

Answer 11

this is a disease that is caused by taenia solium when humans eat human fecal matter containing T. solium eggs. In this case, HUMANS are the intermediate hosts.
If a person has a T. solium infection, educate them on good hygiene so that they can avoid auto-infection with eggs and the development of cysticercosis.

Question 12

What are some signs and symptoms of cysticercosis?

Answer 12

subcutaneous nodules

headaches, seizures, lesions in the brain.

Question 13

How is cysticercosis treated?

Answer 13

treat with albendazole or (binds to tubulin) or praziquantel
this can increase symptoms as worms die. treat with steroids to reduce swelling
if in brain, may also treat with anti-epileptic drugs to control seizures

Question 14

What are some characteristics of nematodes?

Answer 14

roundworms
non-segmented
complete digestive tube with oral and anal openings (trematodes have closed digestive tract and cestodes have no digestive tract)
also have a durable cuticle

Question 15

What is the causative agent of pinworms?

Answer 15

enterobius vermicularis

Question 16

What is the life cycle of enterobius vermicularis? How is enterobius vermicularis spread?

Answer 16

male and female worms mate in the colon
gravid female migrates down the colon and out through the anal canal
deposits eggs in the perianal area, which make their way to the bedclothes and linen (perianal itching). Eggs transferred to fingers –> can be ingested again for re-infection. Or person to person transfer or inhaled. cycle takes 2 wks.

Question 17

How do you diagnose enterobius vermicularis infection? What are possible complications?

Answer 17

diagnosis: cellophane tape blot of the perianal area and microscopic exam looking for eggs
you need a minimum of 4-6 consecutive negative days to rule out infection
complications- bacterial infection secondary to scratching

Question 18

How do you treat enterobius vermicularis?

Answer 18

pinworm
treat with albendazole
pyrantel pamoate as an alternative choice
treat all co-habitants

Question 19

What are characteristics of hookworms? Who are the hosts?

Answer 19

characteristics: bent neck (hook); cutting plates/teeth in the oral opening
humans are the definitive host

Question 20

Describe the hookworm life cycle?

Answer 20

filariform larvae penetrate the skin
they migrate to the heart, lungs, alveoli, trachea.  they get swallowed
adults mature in the small intestine
eggs pass out in the feces
larvae hatch in the soil
filariform larvae develop in the soil
filariform larvae penetrate the skin

Question 21

What is one of the most serious considerations with hookworm infection?

Answer 21

blood loss- some species can draw as much as 150 microliters of blood a day per worm

Question 22

What helps reduce the burden of hookworm?

Answer 22

outhouses; toilets; sanitation

Question 23

What are two primary species of hookworm?

Answer 23

necator americanus and ancylostoma duodenale

Question 24

How do you treat hookworm?

Answer 24

mebendazole, albendazole, pyrantel pamoate

Question 25

What is a a paratenic host?

Answer 25

no larval maturation in this host, though paratenic hosts can transmit the parasites.

Question 26

Dog hookworm: what disease? what kind of host?

Answer 26

cutaneous larva migrans
larvae enter the skin but can’t mature. they induce an inflammatory rxn; itching can cause secondary bacterial infections
we are paratenic hosts

Question 27

Toxocara: what disease? what kind of host?

Answer 27

disease: visceral larva migrans
caused by ingestion of infective eggs. migrate to organs, like liver and spleen, and induce inflammatory response.
spread by dogs and cats
humans are paratenic hosts

Question 28

how do you treat cutaneous larva migrans or visceral larva migrans?

Answer 28

albendazole or mebendazole

Question 29

Anisakis: what kind of host? How acquired? what disease/symptoms

Answer 29

humans are paratenic hosts
infects marine fish
worms mature in fish but stays as larvae in humans
can cause nausea, vomiting, burrowing into stomach, stomach eosinophilic granulomas; occult blood
if anisakis penetrates the stomach, surgical intervention is sometimes indicated

Question 30

What is the causative agent of trichinosis?

Answer 30

trichinella spiralis

Question 31

What is the trichinella spiralis life cycle?

Answer 31

infected raw or undercooked meat is ingested

2. larvae are freed in the stomach
3. they migrate to the small intestine
4. they mature there
5. they shed live newborns to the lymph
6. newborns migrate (Problems happen)
7. newborn larvae penetrate muscle cells and mature in muscle.
8. calcified larvae form in muscle

Question 32

What is the primary pathologic effect of trichinosis? Other symptoms? Classic sign?

Answer 32

muscle destruction
other symptoms: fever, eosinophilia, CNS involvement (very rare)
classic sign is circumorbital edema due to invasion of surround musculature

Question 33

How do you diagnose trichinosis?

Answer 33

serologic diagnosis. NOT muscle biopsy

Question 34

How do you treat trichinosis?

Answer 34

mebendazole; albendazole is an alternative

coritocsteroids may help alleviate symptoms by dulling immune response

Question 35

What are the most important differences between ascaris lumbricoides and trichuris trichura (whipworm)? What about them is similar?

Answer 35

ascaris eggs are infectious immediately upon release
trichuris need to mature in the enviroment
BOTH are transmitted when unprocessed human feces is used as a fertilizer