(cestodes) helminths quiz - microbio II (cls 542)

cestode general characteristics

• Least complex group of helminths

• One big gut with one big reproductive system

• Most are hermaphrodites--each segment has both male and female reproductive organs

• Flat and bilaterally symmetrical, like fettuccini (ok drew)

• Absorb nutrients from the host

intestinal cestode/tapeworm/flatworm illness

• Few clinical symptoms/psychosomatic

• Transmission by ingestion of cysticercus larvae in muscle of intermediate host

• Diagnose by finding eggs, gravid proglottids, or scolex in the feces

• Treatment:

  • enema, muscle relaxants (to release scolex), another enema

  • specific legal/illegal(?) drugs

  • niclosamide can be used as well

parts of a tapeworm

• Scolex: head

  • Suckers & Hooks

• Rostellum (not all have this)

• Proglottids: individual segments

• Strobila: string of proglottids

  • 1/3 are mature, 1/3 are immature, 1/3 are gravid

    • Gravid: sexually mature and producing infective eggs

dibrothriocephalus latus / diphyllobothrium latum

AKA fish or broad tapeworm

• Single worm infection

• Lives in cold, clear, freshwater lakes

• Incubation 5-6 weeks

• No symptoms, but can lead to:

  • Diarrhea, abdominal pain

  • B12 deficiency (competes with host for the vitamin)

  • Leads to bowel obstruction

life cycle of dibrothriocephalus latus

1. unembryonated egg passed in feces

2. embryonate in water

3. coracidia hatch & are ingested by crustaceans

4. develop into procercoid larvae

5. crustacean ingested by small freshwater fish—larva released and develops into pleocercoid larva

6. predator fish ingests small fish

7. human ingests undercooked predator fish

8. adults live in small intestine & proglottids release immature eggs

key info about d latus / latum life cycle

• Larvae live in the muscle of all intermediate hosts

• Eggs released from definitive host r unembryonated

• Definitive hosts: humans & other carnivores

• Matures in water & hatches a coracidium larvae

• Larvae eaten by 1st intermediate host--copepod

• 1st intermediate host eaten by second intermediate host--small fish

  • Second by the third & etc until a definitive host eats the last intermediate host

• Larvae rapidly mature in gut of definitive host

• Start laying eggs 2-6 weeks later

• Adult can reach 20 meters (65 ft) and can live for decades

d latus eggs

• Abopercular knob

• Indistinct, non-shouldered operculum

• Chicken shaped egg

  • 55-75 um in length

d latus proglottids

• Wider than they are long

• Rosette uterus

d latus scolex

• Length: 3-10 mm wide

• Two bothria sucking slits

taenia sp

aka cow and pig tapeworms

• Intermediate hosts: Cows/pigs/dogs

• Common

• Single worm infection

• Worldwide distribution

• 2-3 month incubation period

• No symptoms, but may see:

  • Abdominal discomfort, diarrhea, indigestion, occasional intestinal blockage

• Can find proglottids in stool

  • Actively migrate out the anus

life cycle of taenia sp

1. eggs/gravid proglottids in feces are passed & end up in environment

2. cows and pigs become infected by eating vegetation contaminated w proglottids

3. oncospheres hatch, penetrate intestinal wall & circulate to musculature

4. oncospheres develop into cysterci in muscle

5. humans acquire thru ingestion of raw/undercooked meat

6. scolex attaches to intestine

7. adults live in small intestine

taenia sp eggs

• 30 x 45 um

• Thick, smooth striated shell

• Oncosphere has 6 hooks

  • May not always be visible

  • Immature larvae

• Must find adults to speciate

how to differentiate between T solium & saginata

• T solium (pigs)

  • 7-13 uterine branches

  • “royal pig”—crown looking rostellum

• T saginata (cow)

  • 15-30 uterine branches

  • no rostellum—”common cow”

(taenia sp) acid fast staining

• Ziehl-Neelsen staining

• Not super reproducible study data backing

• The embryophore of T saginata is acid fast POS (?)

(taenia sp) cystercercosis

• Humans become an accidental intermediate host

• Human ingest eggs instead of larvae

• Larval form encysts in human muscle, eye, brain etc

hymenolepis nana

AKA dwarf OR bridge club tapeworm

• Most common tapeworm infection

• Multiple worms present

• Worldwide distribution—most common in SE region of US

• 2-3 weeks incubation

• Adults live 4-6 weeks

  • 15-40 mm long

• Severe toxicity if worm burden is high

  • Severe diarrhea, abdominal pain, convulsions, epilepsy, insomnia, behavioral issues

routes of transmission for h nana (3)

1. through insect intermediate host (beetles and fleas)

2. human ingested embryonated egg (no intermediate host)

3. autoinfection (entirely human)

life cycle of h nana

1. embryonated eggs passed in feces

2. egg can be ingested by intermediate host or by humans from contaminated food/water/hands

3. if ingested by beetles, egg develops into cysticercoid

4. rodents/humans consume insect

5. autoinfection when eggs remain in intestine

   • release hexacanth embryo—penetrates intestinal vilus

   • adults live in ileal portion of small intestine

   • eggs released by gravid proglottids; proglottids can also disintegrate & release eggs that way

h nana eggs

• Polar filaments present

• More oval than round

• Hooked oncosphere with 6 hooks

• Size 47 x 57 um

hymenolepis diminuta

AKA rat tapeworm

• Rare infection

• Multiple tapeworms

• Worldwide distribution

• No symptoms

• Does not cause hyper infections

• Adult size: 20-60 cm

life cycle of h diminuta

1. embryonated eggs pass in feces

2. eggs ingested by an arthropod intermediate host

3. oncospheres hatch and penetrate intestinal wall

4. cysticerci in body cavity of insect ingested by rodent/human

5. scolex attaches to small intestine

6. adults live in small intestine

h diminuta eggs

• 58 x 85 um

• More round than oval

• No polar filaments

• Shell looks thicker, may appear striated

• Hooklets visible

dipylidium caninum

• Rare infection ; common in kids

• Multiple worms ; adults are 10-70 cm

• Worldwide distribution

• Acquired by ingested of infected fleas

• Known by many names:

  • Flea tapeworm

  • Double-pored tapeworm

  • Cucumber tapeworm

life cycle of d caninum

1. gravid proglottids are passed intact in the feces or emerge from perianal region of either animal/human hosts

2. larvae of flea (int host) ingests egg packets

3. oncospheres hatch and develop into cystercoids

4. definitive host infected by contaminated fleas

5. adults live in small intestine

key info for d caninum life cycle

• Scolex has suckers and hooks to cling onto the intestinal wall

• Proglottids mature, fill with eggs and separate from the tapeworm

• Pass out host with feces

• Looks like grains of rice

d caninum eggs (packet)

• Eggs are 35-40 um

• Found in packets usually containing 5-15 eggs

  • Must see packets to diagnose by eggs alone because they look like Taenia eggs

• 6 hooked oncosphere

• Where the cucumber name comes from

answer the following about d latus:

• What form is shed/acquired from the human?

• If, an egg, is it embryonated or not?

• If it is a larvae, what kind of larvae?

• What hatches from the egg?

• unembryonated eggs are shed in feces ; no larvae shed

• coracidia/coracidium larvae hatch from egg (d latus)

answer the following about d latus:

• intermediate host? reservoir host?

• What is the infective stage that gets back into the human?

• How does the infective stage get back into the human?

• General info about what happens once it gets back into the human.

• Where do adults live?

• intermediate host: crustaceans/small fish; reservoir: predator fish/fish eating mammals

• infective stage: pleocercoid larvae

• humans ingest raw/undercooked infected fish

• attaches to small intestine and release proglottids

• adults: small intestine

answer the following about taenia sp:

• What form is shed/acquired from the human?

• If, an egg, is it embryonated or not?

• If it is a larvae, what kind of larvae?

• What hatches from the egg?

• embryonated eggs/gravid proglottids are shed in feces ; no larvae shed

• egg hatches into oncosphere/hexacanth larvae and then develops into cysticerci in muscle of intermediate host

answer the following about taenia sp:

• intermediate host? reservoir host?

• What is the infective stage that gets back into the human?

• How does the infective stage get back into the human?

• General info about what happens once it gets back into the human.

• Where do adults live?

• intermediate & reservoir: pigs/cows

  • humans can become both hosts when cystercosis develops

• infective stage: cystererci

• humans ingest raw/undercooked pork/beef

• scolex attaches to intestine

• adults: small intestine

answer the following abt h nana:

• What form is shed/acquired from the human?

• If, an egg, is it embryonated or not?

• If it is a larvae, what kind of larvae?

• What hatches from the egg?

• embryonated egg in feces shed from humans ; no larvae shed

• if in intermediate host, egg develops into cysticercoid ; if not, oncosphere hatches (autoinfection)

answer the following about h nana:

• intermediate host? reservoir host?

• What is the infective stage that gets back into the human?

• How does the infective stage get back into the human?

• General info about what happens once it gets back into the human.

• Where do adults live?

• intermediate: insects/grain beetles; reservoir: rodents/mice

• infective stage: cysticercoid

• humans consume cysticercoid infected arthropods or eat embryonated eggs or autoinfection occurs

• scolex attaches to intestine & release eggs thru proglottids

• adults: ileal portion of small intestine

answer the following about h diminuta:

• What form is shed/acquired from the human?

• If, an egg, is it embryonated or not?

• If it is a larvae, what kind of larvae?

• What hatches from the egg?

• embryonated eggs passed in feces; no larvae shed

• egg hatches into oncosphere & develops into cysticerci in insect ingested by rodent/human

answer the following about h diminuta:

• intermediate host? reservoir host?

• What is the infective stage that gets back into the human?

• How does the infective stage get back into the human?

• General info about what happens once it gets back into the human.

• Where do adults live?

• intermediate: arthopods ; reservoir: rodents

• infective stage: cysticerci in insects

• humans ingest insect

• scolex attaches to small intestines & adults live there

  • gravid proglottids release eggs

answer the following about d caninum:

• What form is shed/acquired from the human?

• If, an egg, is it embryonated or not?

• If it is a larvae, what kind of larvae?

• What hatches from the egg?

• gravid proglottids are shed from human/dogs ; no larvae shed

• eggs hatch into oncospheres and develop into cysticercoids in fleas

answer the following about d caninum:

• intermediate host? reservoir host?

• What is the infective stage that gets back into the human?

• How does the infective stage get back into the human?

• General info about what happens once it gets back into the human.

• Where do adults live?

• intermediate: fleas/flea larvae ; reservoir: dogs/cats

• infective stage: cysticercoids in fleas

• humans ingest infected fleas

• scolex attaches to small intestine & lives there & releases proglottids