Trematodes and Cestodes

Question 1

What is the general term to refer to both trematodes and cestodes?

Answer 1

Flat worms

Question 2

What is a simple distinction between trematodes and cestodes?

Answer 2

Tremtodes - non-segmented

Cestodes - segmented

Question 3

What are commonalities of all trematodes?

Answer 3

Non-segmented flat worms
Molluscan intermediate host and vertebrate adult host
Digenetic (asexual and sexual phase)
Hermaphrodites (except shistosoma)

Question 4

What is the method of transmission of Schistosomiasis?

Answer 4

Water-borne

Commonly seen in snails with lily pads

Question 5

What is the life cycle of Schistosomiasis?

Answer 5

Miricidia: photosensors swim upward toward light to snails (intermediate host)
Cercaria: released by snails into fresh water and can penetrate skin
After penetration of skin, cercariae shed glycocalyx and become schistosomulum and migrate in blood vessels
Mature into adults and male and female worms mate for life and produce eggs
Eggs cause immune response

Question 6

What is an almost immediate sign of Schistosomiasis?

Answer 6

Hypersensitivity rash at site of cercarial penetration

Penetrate epidermis within 5 minutes, dermis within 20

Question 7

What is the presentation of acute schistosomiasis?

Answer 7

Katayama fever

Fever, headache, cough, abdominal pain, eosinophilia, prostration, death

Question 8

What is the presentation of chronic schistosomiasis?

Answer 8

Eggs become trapped in tissue, granulomas develop and fibrosis
Commonly affects liver or bladder, can go to lungs or CNS
- Liver: bloody diarrhea, intestinal polyps, periportal fibrosis
- Urinary: hematuria, polyps, bladder calcifications and strictures, bladder cancer
- CNS: neuro-schistosomiasis, transverse myelitis or brain lesions

Question 9

Which species cause liver schistosomiasis?

Answer 9

S. mansoni

S. japonicum

Question 10

Which species cause urinary schistosomiasis?

Answer 10

S. haematobium

Question 11

How is schistosomiasis diagnosed?

Answer 11

Microscopically

Serologic tests

Question 12

How does Schistosoma mansoni appear microscopically?

Answer 12

Lateral spine

Question 13

How does Schistosoma haematobium appear microscopically?

Answer 13

Terminal spine

Question 14

How does Schistosoma japonicum appear microscopically?

Answer 14

Small lateral spine with round egg

Question 15

What is the treatment for schistosomiasis?

Answer 15

Praziquantel

Question 16

What are species are in the category of liver fluke (also trematodes)?

Answer 16

Clonorchis sinensis

Opisthorchis

Question 17

What is the mode of transmission of liver flukes?

Answer 17

Undercooked fish (cercariae are in flesh of fish)

Question 18

What is the presentation of infection with liver fluke?

Answer 18

Inflammation of biliary tree since adults reside there
Cause massive RUQ abdominal pain
Cholangiocarcinoma

Question 19

What are commonalities of all cestodes?

Answer 19

Flatworms but without GI tract (trematodes have GI tract)
Segmented
Segments contain male and female organs - hermaphrodites
Humans can harbor tapeworm itself or larval hydatid cyst

Question 20

What are the major species of cestodes?

Answer 20

Diphyllobothrium latum - fish tapeworm
Taenia solium - pork tapeworm
(Taenia saginata - beef tapeworm)
Echinococcus granulosum

Question 21

What is the mode of transmission of diphyllobothrium latum?

Answer 21

Undercooked fish

Question 22

What makes the eggs of diphyllobothrium latum unique?

Answer 22

Has operculum that pops open when egg encysts

Question 23

What are symptoms of diphyllobothrium latum infection?

Answer 23

Non-specific abdominal discomfort

Can develop megaloblastic anemia (tapeworm competes for B12 in intestine)

Question 24

How is diphyllobothrium latum infection diagnosed?

Answer 24

Proglottids (tapeworm segments) or eggs in stool

Question 25

What is the treatment for diphyllobothrium infection?

Answer 25

Praziquantel

Question 26

How can you differentiate between different raw fish infections?

Answer 26

Liver flukes will have lots of symptoms

Diphyllobothrium will be relatively asymptomatic

Question 27

What is the mode of transmission of Taenia solium and saginata?

Answer 27

Ingestion of raw pork or beef (can ingest either the worms or the cysticerci [egg form])

Question 28

What are symptoms of Taenia infection when the worm is ingested?

Answer 28

Mild, non-specific

Intestinal infection

Question 29

What are symptoms of Taenia infection when the cysticerci are ingested?

Answer 29

Cysticercosis

Predilection to infect nervous system, causing seizures, hydrocephalus, brain damage, adult epilepsy

Question 30

What is the treatment for Taenia infection?

Answer 30

Praziquantel

Albendazole and surgery too for neurocysticercosis

Question 31

What is the mode of transmission of Echinococcus granulosum?

Answer 31

Ingestion of eggs from dog feces

Question 32

What are symptoms of Echinococcus granulosum infection?

Answer 32

Larvae develop into large hydatid cysts, usually in the liver
Rupture can be serious and cause anaphylaxis or biliary obstruction

Question 33

How is the diagnosis of Echinococcus granulosum infection made?

Answer 33

CT scan, ultrasound, aspirate

Question 34

What is the treatment for Echinococcus granulosum infection?

Answer 34

Inactivate cysts with hypertonic saline or ethanol and surgically remove
Albendazole/mebendazole