UNIT 3A- PHYLUM PLATYHELMINTHES

Parasitic Flukes & Tapeworms

CLASS TREMATODA1. Common name- flukes

2. Endoparasitic- live inside host

3. Wide, flat with oval or elongate bodies

4. Have 2-3 hosts1. Intermediate hosts- where asexual

part of life cycle occurs

2. Definitive host- final host where sexual part of life cycle occurs

5. Almost all adult flukes are parasites of vertebrates (fish, frogs, turtles, livestock, and humans)

6. Internal anatomy is similar to Turbellarians (planarians).

CLASS TREMATODAEX: Liver Flukes

1. Types:a. Chinese liver fluke- common

parasite of humans that live in Asia.

b. Sheep liver fluke- common in sheep or people who raise sheep

2. Lives in the liver where it eats tissue & blood.

3. Contracted by a. Eating uncooked contaminated

food (sushi)

b. Eating water plants (water cress) infected with larvae

CLASS TREMATODAEX: Liver Fluke

4. Signs & Symptoms:• Enlarged liver• Feeling of fullness• Abdominal discomfort• Jaundice• Fatigue• Weakness• Nausea• Weight loss

5. Detection: look for eggs in stool or larvae in blood

6. Treatment: triclabendazole

Liver Fluke Life Cycle1. Eggs passed out w/feces2. Eggs ingested by a snail- the first

intermediate host.a. Inside the snail, the eggs undergo

asexual reproduction & metamorphosis

1. Miracidia- cilia for swimming2. Sporocysts- asexual reprod.3. Rediae- worm like stage4. Cercariae- has tail for swimming

3. Free swimming cercariae burrow out of skin of snail and search out fish or plant- the second intermediate host.

4. Cercariae encyst in fish/plant and are called metacercariae which is then ingested by a human or other vertebrate.

5. Metacercariae excyst in the intestine and migrate to the liver where they live, feed & reproduce sexually.

CLASS TREMATODAEX: Blood Flukes

1. Common in Africa, Asia, S. America

2. Cause disease known as Schistosomiasis (A.K.A. bilharzia)

3. Symptoms:– Fever & chills

– lymph node enlargement

– liver and spleen enlargement

– frequent urination, blood in urine and in stool

– Invasion in skin may cause rash (swimmer’s itch)

Swimmer’s Itch Signs from Lake Michigan Area

CLASS CESTODA

1. Common name: tapeworms

2. Endoparasitic: live inside host

3. Long, flat ribbon-like bodies

4. White w/shades of yellow or gray

5. Size: 1mm to 15 m in length (up to 60 ft!)

CLASS CESTODA

6. Body Structurea. Scolex- head-like structure;

hooks & suckers for attachment (not feeding)

b. Neck- contains immature proglottids- series of repeating units of reproductive organs.

c. Strobila- rest of body; contains proglottids that are mature and gravid- full of eggs.

CLASS CESTODA

7. Digestiona. No mouth or digestive tract.b. Absorb nutrients directly across their body wall.

CLASS CESTODA8. Signs/Symptoms:

– Nausea & Weakness– Loss of appetite– Weight loss & diarrhea– Inadequate absorption of nutrients in

food– Can lead to Cysticercosis disease in

humans where larvae encyst in your muscle.• These cysts can end up in brain and cause

death.

9. Detection: MRI or Xrays can detect cysts in muscle.

10. Treatment: Depends on infection & location of cysts. Albendazole and anti-inflammatory drugs help but surgical removal may be necessary.

California had the highest percentage of fatal cysticercosis from 1990-2002!

Life Cycle of a Tapeworm1. Eggs or gravid proglottids are passed

with feces into environment.2. Cows, pigs, fish ingest eggs/gravid

proglottids from vegetation in environment.

3. Oncospheres (larva) hatch in intestine, burrow thru intestinal wall, and enter circulatory system where they end up in muscle where they become a bladderworm inside a cyst.

4. Humans are infected by ingesting uncooked infected meat.

5. Bladderworm will hatch in stomach and migrate to intestine where they attach to intestinal wall with hooks and suckers and begin absorbing nutrients.

6. Adults sexually reproduce in final vertebrate host (human)

Life Cycle of Tapeworm in Dog

• Tapeworm inside fleas• Dog chews when flea

bites and ingests fleas• Dog may also eat feces

infected with tapeworm eggs/proglottids

• Tapeworm Lifecycle Movie - YouTube

Environmental/Economic Significance of Parasitic Flatworms

1. Cause disease in vertebrates in many countries

2. Must study the worms to figure out how to treat infected people.

• Journals if needed

Unit 3A Journal #5 9/16

• How does a person contract a fluke infestation?

• What are 3 ways a person could reduce the chance for a fluke infection?

Unit 3A Journal #6 9/17

• Use the following SAT words to write 5 sentences that pertain to this unit on flatworms. Your sentences must use the SAT word and have something to do with flatworms!– Latent: dormant– Mediocre: ordinary– Maritime: near or on the sea– Noisome: very offensive; especially with smell– Obligatory: mandatory; required