Order Pseudophyllidea

What is the common name for Diphyllobothrium latum?

broad fish tapeworm

draw the life cycle for Diphyllobothriid tapeworms

What are the steps in the life cycle of a Diphyllobothriid tapeworm?

1. adults in small intestine

2. eggs exit in feces

3. eggs embryonate in water

4. coracidium hatches from egg

5. coracidium is ingested by a crustacean

6. coracidium becomes a procercoid

7. crustacean with procercoid is ingested by a small fish (then small fish is eated by bigger fish)

8. procercoid becomes a plerocercoid

9. fish with the plerocercoid is ingested by human/piscivores

How are pseudophyllidean eggs released?

anapolysis

Coracidia can ___ rapidly.

swim

What eats the coracidium?

copepod (microcrustacean)

What is the 1st IH in the life cycle of a pseudophyllidean?

copepod (microcrustacean)

What happens when the coracidium is eaten by the copepod?

• sheds its outer ciliated layer

• oncosphere hooks penetrate into hemocoel

What does the procercoid do to the copepod?

impairs the copepod’s motility → more vulnerable to predation (PITT)

What is the 2nd IH in the pseudophyllidean life cycle?

small fish

What happens when the copepod (microcrustacean) is eaten by the small fish?

the procercoid penetrates the gut and moves into the muscle

What is the metacestode in the pseudophyllidean life cycle?

plerocercoid

What is the transmission stage in the pseudophyllidean life cycle?

plerocercoid

What are the two possible fates of the plerocercoid in the 2nd IH (bigger fish)?

1. eaten by a mammal (DH)

2. eaten by another fish (paratenic host)

What is a paratenic host?

transport host;

• plerocercoid penetrates gut and enters skeletal muscle

• no further development

What is the adult morphology of diphyllobothriid tapeworms?

• up to 10 m (33 ft)

• 2 bothria

• proglottids

What are the proglottids of diphyllobothriid tapeworms like?

• wider than long

• scattered vitelline glands

• genital pore opens midventrally

What is the morphology of diphyllobothriid tapeworms uterus?

• opens to midventral uterine pore

• many loops “rosette” in gravid proglottids

What is the pathology of diphyllobothriid tapeworms?

• vague symptoms

• pernicious (megaloblastic) anemia

What are the vague symptoms of diphyllobothriid tapeworms pathology?

reaction to waste products and intestinal irritation;

diarrhea, nausea, weakness, abdominal discomfort

What is the normal state of parietal cells in the stomach?

• parietal cells in stomach produce intrinsic factor (IF) (glyocoprotein)

• IF binds to vitamin B12

• enables vitamin B12 absorption across the gut wall

• Hgb synthesis

• normal RBCs

What happens in pernicious anemia?

• worms secrete substances that cause dissociation of vitamin B12

• less vitamin B12 absorbed

• formation of megaloblasts in bone marrow

• large, abnormal RBCs

• destroyed

How much vitamin B12 do the worms absorb?

80 - 100%

anemia

blood lacks enough healthy RBCs or Hgb;

insufficient oxygen to cells;

fatigue, pallor, light-headedness, etc

How do you diagnose Diphyllobothrium latum?

detect eggs in feces

How do you treat Diphyllobothrium latum?

• Praziquantel

• Niclosamide

• vitamin B12 to anemic patients

How do you control Diphyllobothrium latum?

• control preparation of fish

• control sewage drainage into lakes & rivers

What is human sparganosis?

a food-borne zoonosis where a human is an accidental IH

What is the plerocercoid larvae in human sparganosis?

spargana

What is the genus in human sparganosis?

Spirometra

draw the life cycle of Spirometra

What are the steps in the life cycle of Spirometra?

1. adults in small intestine

2. eggs passed in feces

3. eggs embryonate in water

4. coricidium hatches from eggs

5. crustacean ingests coricidium

6. coricidium becomes procercoid

7. crustacean with procercoid is ingested by 2nd IH (fish/reptile/amphibian)

8. procercoid becomes plerocercoid

9. predator eats 2nd IH

What are the 3 possible routes of infection in human sparganosis?

1. drink water containing infected copepods → procercoids penetrate intestinal wall and plerocercoids enter tissues

2. ingest uncooked infected animals → plerocercoid penetrates intestinal wall and enter tissues

3. physical contact with flesh of infected IH → plerocercoid in tissue

What are the 3 types of human sparganosis?

1. subcutaneous sparganosis

2. ocular sparganosis

3. cerebrospinal sparganosis

What is the pathology of human sparganosis?

plerocercoid migrates into tissues & forms a nodular mass

subcutaneous sparganosis

• rubbery, irregular lump

• itchy, painful

ocular sparganosis

• invade conjunction & orbit of eye

• glaucoma, blindness

cerebrospinal sparganosis

• in spinal cord or cerebral hemispheres

• headache, seizures, hemiparesis

How do you diagnose human sparganosis?

detect plerocercoid in host tissue

What is the treatment for human sparganosis?

surgical removal