L38: Tapeworm and Fluke Infections of the GI Tract

Question 1

3 basic structures of adult tapeworms (cestodes)

Answer 1

1. Scolex (rounded head of worm with hooks/suckers)
2. Neck (area from which new body segments are generated)
3. Body (strobila) with segments (proglottids)

Question 2

Humans as hosts in cestodes

Answer 2

Can either be definitive host (adult tapeworms residing in small intestine like beef/pork/fish tapeworms) or intermediate host (larval stages present in various tissues (dog/pig tapeworm)

Question 3

Transmission of Taenia saginata (beef tapeworm)

Answer 3

Ingestion of undercooked beef containing encysted larvae (cysticerci) – humans generally infected with single giant worm

Question 4

Symptomology of Taenia saginata (beef tapeworm)

Answer 4

Generally asymptomatic except for mild abdominal pain and feeling of fullness

Question 5

Diagnosis of Taenia saginata (beef tapeworm)

Answer 5

Identification of proglottids or eggs passed by infected individual

Question 6

Control and prevention of Taenia saginata (beef tapeworm)

Answer 6

Prevent cattle from becoming infected by eliminating their contact with human feces and cook meat thoroughly

Question 7

Transmission of Taenia solium (pork tapeworm)

Answer 7

Ingestion of undercooked pork containing cysts leads to intestinal disease and ingestion of embryonated eggs results in extraintestinal disease – less common than beef tapeworm

Question 8

Intestinal disease of Taenia solium (pork tapeworm)

Answer 8

Similar to beef tapeworm disease

Question 9

Extraintestinal infection of Taenia solium (pork tapeworm)

Answer 9

Ingested eggs hatch in intestine and release infectious larvae which enter cirulation and travel to various body sites where they encyst, creating a lesion that induces inflammation (pathology determined by location/size)

Question 10

Neurocysteicercosis of Taenia solium (pork tapeworm)

Answer 10

Severe complication that leads to seizure and neurological defects – VERY big problem because it can infect brain (or eye)

Question 11

Diagnosis of Taenia solium (pork tapeworm)

Answer 11

Proglottids or eggs in stool for intestinal infection, CT scan/MRI or serology for extraintestinal infection

Question 12

Prevention and control of Taenia solium (pork tapeworm)

Answer 12

Keep pigs away from human feces and cook pork thoroughly

Question 13

Life cycle of Diphyllobothrium latum (fish tapeworm)

Answer 13

When eggs get into the water, they release a coracidium that gets ingested by a crustacean –> fish ingests crustacean and gets infected

Question 14

Transmission of Diphyllobothrium latum (fish tapeworm)

Answer 14

Ingestion of raw or undercooked fish with infectious larvae – infected fish can be found in freshwater lakes in MN, MI, FL, and CA

Question 15

Symptomology of Diphyllobothrium latum (fish tapeworm)

Answer 15

Transient nausea, abdominal pain, diarrhea, etc. – infection with multiple worms can cause intestinal obstruction – 2% of patients develop macrocytic anemia

Question 16

Diagnosis of Diphyllobothrium latum (fish tapeworm)

Answer 16

Eggs in stool

Question 17

Control and prevention of Diphyllobothrium latum (fish tapeworm)

Answer 17

Cook fish adequately and limit exposure of fish to human feces

Question 18

Transmission of Echinococcus granulosus (dog tapeworm)

Answer 18

Humans are accidental/intermittent host between dogs and sheeps/goats when they come into contact with infected dog feces (ingestion of eggs) – happens where livestock are raised in association with dogs

Question 19

Life cycle of Echinococcus granulosus (dog tapeworm)

Answer 19

Ingested eggs hatch in the intestine, releasing larvae which travel via bloodstream to multiple body sites where they secrete a hyaline membrane and a cyst forms

Question 20

Symptomology of Echinococcus granulosus (dog tapeworm)

Answer 20

Depends on location of the cysts, but ruptured cysts release large amounts of antigen and can induce anaphylactic response (hyatid cyst disease – large bag of cysts)

Question 21

Trematode (fluke) basics

Answer 21

Humans are definitive host, freshwater snails are intermediate hosts – larval forms released from snails encyst on fish, shellfish, or vegetation and are acquired by ingestion

Question 22

Fasciolopsis buski basics

Answer 22

Intestinal fluke with leaf-shaped appearance that comes from water chestnuts

Question 23

Transmission of Fasciolopsis buski

Answer 23

Ingestion of freshwater aquatic plants with encysted cercariae attached – pigs, dogs, and rabbits can be reservoirs

Question 24

Life cycle of Fasciolopsis buski

Answer 24

Cercariae excyst in the small intestine, attach to columnar epithelium and mature to egg-laying adults

Question 25

2 types of infection by Fasciolopsis buski

Answer 25

1. Light infection (single worm) – focal inflammation, intermittent diarrhea
2. Heavy infection (multiple worms) – continuous diarrhea, intestinal hemorrhage, ulceration, abscess formation

Question 26

Diagnosis of Fasciolopsis buski

Answer 26

Presence of eggs in stool

Question 27

Prevention of Fasciolopsis buski

Answer 27

Control snail populations, improve sanitation, restrict harvesting of aquatic plants from contaminated areas

Question 28

2 types of liver flukes

Answer 28

Fasciola hepatica and Clonorchis sinesis

Question 29

Life cycle of Fasciola hepatica

Answer 29

Lives in bile duct –> gets out through feces into water –> gets into snails –> comes out of snails (comes from aquatic plants originally)

Question 30

Life cycle of Clonorchis sinesis

Answer 30

Larval forms exist in fish and are ingested

Question 31

Fasciola hepatica (transmission and disease)

Answer 31

Found in SE US, acquired through ingestion of aquatic plants, migrates through liver and causes liver tenderness, hepatomegaly, fever, and eosinophilia – sometimes causes biliary obstruction (jaundice)

Question 32

Fasciola hepatica (diagnosis and control)

Answer 32

Diagnosed by eggs in feces, controlled by controlling snail populations, improving sanitation, restricting harvesting of aquatic plants from contaminated areas

Question 33

Clonorchis sinesis (Opisthorchis sinesis)

Answer 33

Endemic in Asia (25% of Chinese immigrants), acquired by ingestion of under-prepared freshwater fish with encysted cercariae, can be asymptomatic (light) or cause biliary obstruction, jaundice, hepatitis, hepatomegaly, and gallstones (heavy) – 10-15x more likely to develop bile duct cancer if heavy infection