Life cycles in Helminths

Question 1

Trematode life cycle

Answer 1

DH
1. Adult
Environment
2. Egg
3. Miracidia (infects 1st IH)
Snail (1st IH)
4. Sporocyst
5. Redia
Environment
6. Cercariae
7. Metacercariae

Question 2

Schistosomiasis life cycle

Answer 2

DH
1. Adult
Environment
2. Egg
3. Miracidia
Snail
4. Sporocyst
Environment
5. Cercariae

Question 3

Taenia saginata life cycle

Answer 3

1. Eggs or gravid proglottids in feces and passed into environment
2. Cattle (T. saginata) and pigs (T. solium) become infected by ingesting vegetation contaminated by eggs or gravid proglottids
3. Oncospheres hatch, penetrate intestinal wall, and circulate to musculature
   -Oncospheres develop into cysticerci in muscle
4. Humans infected by ingesting raw or undercooked infected meat
5. Scolex attaches to intestine
6. Adults in small intestine