Platyhelminths Flatworms unit 2

Helminths

“BIG PARASITIC WORMS”

= eukaryotic + multicellular parasites (BIG worms)
Think:
🧠 “Not tiny like bacteria — these are full-on worms living in you”

🧩 THE 2 MAIN GROUPS- helminths

1. 🪱 Platyhelminthes, 2. 🪱 Nemathelminthes

1. 🪱 Platyhelminthes- helminths

type 1

FLATworms

👉 “Platy = flat like a plate”

• Tapeworms

• Flukes

🧠 Catchy phrase:
👉 “Platy = Plate = Flat”

2. 🪱 Nemathelminthes-helminths

ROUNDworms (Nematodes)

👉 long, round, spaghetti-like worms

🧠 Catchy phrase:
👉 “Nema = Noodle”

⚠ HOW YOU GET INFECTED- helminths

🚨 Main themes:

• 💩 Fecal-contaminated food/water

• 🍖 Undercooked meat

• 🔁 Multiple hosts (animals + humans)

🧠 Catchy phrase:
👉 “Dirty food, raw meat, many hosts = worms”

🩸 IMMUNE RESPONSE- helminths

👉 Helminths increase eosinophils

• Type of white blood cell

• Specialized for fighting worms

🧠 Catchy phrase:
👉 “Eosinophils = worm killers”

🧬 phylum PLATYHELMINTHES (FLATWORMS) DETAILS

🔻 Simple body systems:

• Reduced nervous system

• Reduced excretory system

• Reduced digestive system

👉 Some have:

• 1 opening (mouth = anus 😬)

👉 Others:

• ❌ NO digestive system at all

• absorb nutrients through body wall

🧠 Catchy phrase:
👉 “Flatworms = simple, lazy eaters”

🪱 CLASS CESTODA

TAPEWORMS

🧱 BODY PARTS (SUPER IMPORTANT)

1. 🧲 Scolex = head

• Attaches to intestine

• Has hooks + suckers

🧠 Phrase:
👉 “Scolex = sticky head”

2. 🧩 Proglottids = segments

• Each segment = full of eggs

• Break off and spread infection

🧠 Phrase:
👉 “Proglottids = egg packets”

❤ PLAYBACK (WEIRD BUT IMPORTANT)- class cestoda

long words

👉 Most tapeworms are hermaphrodites/ hermaphroditic

• Have male and female organs

2 options:

• 🧍 One worm → self-fertilize

• 🧍‍♂🧍‍♂ Two worms → exchange sperm

🧠 Phrase:
👉 “Tapeworms don't need a partner… but can have one”

🔄 LIFE CYCLE- class cestoda/ hermaphroditic

🏠 Adult stage:

• Lives in intestines of 1st host

• Can grow up to 20 feet 😳

• 🧠 Larval stage:

  • Lives in 2nd host tissues

  • Can go to:

    • muscle

    • brain

    • eyes

    • liver

    • heart

  🚨 MOST DANGEROUS STAGE

  🧠 Phrase:
  👉 “Larvae invade, adults chill”

⚖ DAMAGE TO HOST- class cestoda/ hermaphroditic

😈 Larval stage:

• Invades tissues

• Causes serious damage

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😐 Adult stage:

• Stays in intestines

• Usually less harmful

🧠 Golden phrase (VERY TESTABLE):
👉 “Larvae = dangerous travelers, Adults = lazy residents”

🔥 SUPER SIMPLE SUMMARY- HELMINTHS

big parasitic worms

👉 Two types:

• Flat (Platy = plate)

• Round (Nema = noodle)

👉 Infection:

• Dirty food 💩

• Raw meat 🍖

• Multiple hosts 🔁

👉 Immune response:

• Eosinophils ↑

👉 Tapeworm:

• Scolex = attach

• Proglottids = eggs

• Hermaphrodite

👉 Life cycle:

• Adult = intestine (less harmful)

• Larva = tissues (VERY harmful)

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🪱 1. Taenia saginata

BEEF TAPEWORM

👉 You eat undercooked beef 🍖
→ meat has cysticercus (cyst)
→ called “measly meat” (mucousy look)

👉 In your body:

• cyst survives stomach

• becomes adult tapeworm in small intestine

• attaches with scolex (hooks/suckers)

👉 Then:

• makes proglottids (egg segments)

• Each one has ~50,000 eggs 🤯

• segments leave in feces 💩

👉 Cow eats contaminated grass 🌱
→ eggs hatch in cow
→ larvae move into body
→ form cysts in muscle (and tongue)

🔁 cycle repeats

🚫 IMPORTANT- Taenia saginata

👉 If humans eat eggs of beef tapeworm:

• ❌ NO infection

• ❌ NO larvae

• ❌ NO cysts

🧠 Catchy phrase:
👉 “Beef eggs = harmless to humans”

😐 SYMPTOMS (usually mild)-Humans if they eat cow tapeworm eggs

• vague abdominal pain

• nausea

• anemia

💡 WHY anemia?
👉 tapeworm steals Vitamin B12

🧠 Phrase:
👉 “Tapeworm eats your B12 before you do”

🐷 2. Taenia solium

PIG TAPEWORM (MORE DANGEROUS)

WHY IT'S WORSE

👉 Key difference from beef tapeworm:

❗ Humans CAN get infected from eggs

• eggs → larvae in humans

• larvae → cysts in:

  • muscle

  • brain 🧠

  • other organs

👉 This is called cysticercosis (VERY serious)

🧠 EASY COMPARISON beef vs pig tapeworm

• 🐮 Beef tapeworm → stays in intestine

• 🐷 Pig tapeworm → invades your body

🧠 Catchy phrase:
👉 “Pig worms DIG (invade), beef worms chill”

🐶 3. Echinococcus infection

DOG TAPEWORM

🧠 THE STORY

👉 Adult worms live in:

• dogs 🐶

• coyotes

• wolves

👉 Eggs released in dog feces 💩

🐑 NORMAL CYCLE - echinococcus

👉 Grazing animals (sheep, deer, etc.) eat eggs
→ larvae hatch in intestine
→ move into body
→ form hydatid cysts in muscle

👉 Dog eats infected animal
→ cycle continues 🔁

😬 HOW HUMANS GET INFECTED - echinococcus

👉 Accidentally:

• contaminated food 🍎/ eggs in food

• dirty hands ✋ from dog feces

• dog saliva (“dog kisses”) 😬

⚠ WHAT HAPPENS IN HUMANS - echinococcus

👉 Eggs → larvae → hydatid cysts in body

• can grow in organs (like liver/lungs)

• can be dangerous

🧠 Catchy phrase:
👉 “Dog worms = cysts from kisses”

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Cysticercus

larval cyst in meat

Scolex

attachment head

Proglottids

• egg segments

• 50,000 eggs per segment 😳

• Eosinophils ↑ in worm infections

WORM TYPES DIFFERENCES- 3

Worm	How you get it	What happens
🐮 Beef (Taenia saginata)	Undercooked beef	Stays in intestine
🐷 Pig (Taenia solium)	Undercooked pork OR eggs	Invades tissues (dangerous)
🐶 Dog (Echinococcus)	Dog feces/contact	Hydatid cysts in organs

🐟 1. Diphyllobothrium latum

FISH TAPEWORM

fresh water and salt water

👉 You eat raw or undercooked fish 🍣🐟
→ fish has cysts (larvae)
→ becomes adult tapeworm in your intestine

🌎 IMPORTANT FACTS

Dyphilobothrium latum

• 🌍 Found in:

  • Great Lakes

  • Alaska

  • Canada

• 🇺🇸 Brought to US by Scandinavian immigrants

• 🏆 Largest tapeworm in humans
  👉 can grow up to 30 feet 😳

• 🐻 Infects fish-eating animals too (like bears)

⚠ VERY IMPORTANT DETAIL

Dyphilobothrium latum

👉 Eggs/larvae in sushi = NOT infectious to humans directly
(you need the cysts in fish tissue)

🧠 Catchy phrase:
👉 “Fish cysts infect, eggs don't”

😬 SYMPTOMS - dyphilobothrium latum

Causes anemia

💡Why?
→ steals nutrients (like B12)

🧠 Phrase:
👉 “Fish worm = food thief → anemia”

❄ PREVENTION

👉 Freezing kills cysts:

• -20°C / -4°F

🧠 Phrase:
👉 “Freeze the fish, kill the worm”

🐜 2. Hymenolepis infection= 2

DWARF / RAT TAPEWORM

👉 You get it by swallowing eggs :

• contaminated food/water 💩🍎

• dirty hands ✋

• insects in food 🐜 (beetles, fleas in cereal 😬)

• 🏆 IMPORTANT FACTS

• ⭐ Most common tapeworm in humans

• 📏 Smallest tapeworm
  → called dwarf tapeworm

🔁 UNIQUE THING- Hymenolepis

👉 Can spread:

• Human → Human 👥

• No animal needed!

🧠 Catchy phrase:
👉 “Tiny worm, easy spread”

Hymenolepis insects

🐜 INSECT CONNECTION

👉 You can get infected by eating:

• beetles 🪲

• fleas

(in contaminated food like cereal)

🧠 Phrase:
👉 “Bug in your food = worm in your gut”

🔥 SIDE-BY-SIDE COMPARISON fish vs dwarf

Worm	Source	Special Feature
🐟 Fish (Diphyllobothrium latum)	Raw fish	Largest (30 ft), anemia
🐜 Dwarf (Hymenolepis)	Eggs/insects	Smallest, human-to-human

🪱 TAPEWORMS MASTER

👉 All tapeworms:

• live in intestines (adult stage)

• have scolex (head) + proglottids (egg segments)

• Infection usually from food

• Many involve animals

🧠 Core phrase:
👉 “Head hooks, body eggs, food spreads worms”

🐮 Taenia saginata (BEEF)

🚀 Key Points

• Source: undercooked beef 🍖

• Infective stage: cyst (cysticercus)

• Adult lives in intestine

• releases proglottids (50,000 eggs each) 💩

🚫 IMPORTANT

• Eggs DO NOT infect humans

😐 Symptoms

• mild

• anemia (↓ B12)

🧠 Memory:
👉 “Beef = safe-ish, stays in gut”

🐷 Taenia solium (PIG)

🚀 Key Points

• Source:

  • undercooked pork 🍖

  • OR eggs 💩

⚠ DANGEROUS PART

• Eggs → larvae → cysts in body

  • brain 🧠

  • muscle

  • organs

👉 causes cysticercosis

🧠 Memory:
👉 “Pig worms DIG into your body”

🐶Echinococcus infection (DOG)

🚀 Key Points

• Source:

  • dog feces 💩

  • contaminated food/hands

  • dog saliva 😬

⚠ In humans:

• forms hydatid cysts

• can grow in organs (liver/lungs)

🧠 Memory:
👉 “Dog kisses → dangerous cysts”

🐟Diphyllobothrium latum (FISH)

🚀 Key Points

• Source: raw/undercooked fish 🍣

• 🏆 Largest tapeworm (30 ft)

• found in:

  • Great Lakes

  • Alaska

  • Canada

⚠ Important

• eggs/larvae alone don't infect → need cysts

😬 Symptoms

• anemia

❄ Prevention

• freezing kills it

🧠 Memory:
👉 “Fish = HUGE worm, steals nutrients”

🐜 Hymenolepis infection (DWARF)

🚀 Key Points

• Source:

  • eggs in environment 💩

  • insects (beetles, fleas in food) 🐜

🏆 Special

• most common tapeworm

• smallest tapeworm

🔁 Unique

• human → human transmission

🧠 Memory:
👉 “Tiny worm, spreads easily”

all worm types differences

Worm	Source	Danger Level	Key Feature
🐮 Beef	Undercooked beef	😐 Low	Stays in intestine
🐷 Pig	Pork OR eggs	⚠ High	Invades tissues
🐶 Dog	Dog feces	⚠ High	Hydatid cysts
🐟 Fish	Raw fish	😬 Medium	Largest (30 ft), anemia
🐜 Dwarf	Eggs/insects	😬 Medium	Smallest + spreads easily

“Beef chills, Pig drills, Dog cysts, Fish huge, Dwarf spreads”

⚡ RAPID REVIEW

• Scolex = attach

• Proglottids = eggs

• Beef → safe-ish

• Pig → brain cysts

• Dog → hydatid cysts

• Fish → anemia + biggest

• Dwarf → smallest + human spread

🪱 Class Trematoda

FLUKES (Flat Parasites)

👉 Flukes = flat, leaf-like worms (NOT segmented)

🔑 Body Features

• flat body

• ❌ no segments

• 🧲 2 suckers :

  • oral sucker (mouth)

  • ventral sucker (attachment)

🧠 Catchy phrase:
👉 “Flukes = flat + double suck”

Class Trematoda—🍽 DIGESTIVE SYSTEM

• only 1 opening

  • mouth = anus 😬

🧠 Phrase:
👉 “One hole does it all”

Class Trematoda-❤ REPRODUCTION

• can be:

  • hermaphroditic (both sexes)

  • OR separate male/female

🧠 Phrase:
👉 “Flukes are flexible with reproduction”

⚠ TRANSMISSION- Class Trematoda- flukes

👉 You get infected from:

• 💩 fecal-contaminated water

• 🍣 undercooked/raw food

👉 Life cycle often needs:

• 2–3 hosts

🧠 Master phrase:
👉 “Dirty water + multiple hosts = flukes”

🐟 Clonorchis sinensis infection

LIVER FLUKE

Asia, Africa, South America

Clonorchis- 🧠 THE LIFE CYCLE 1-3

1⃣ 💩 EGGS LEAVE HUMAN

• Adults live in liver

• Eggs released in feces → water

2⃣ 🏊 MIRACIDIUM (1st larva)

• eggs hatch → miracidium (swimming larva)

• finds and infects snail 🐌

🧠 Phrase:
👉 “Miracidium = must find snail”

3⃣ 🐌 INSIDE SNAIL

• develops into cercaria (2nd larva)

Clonorchis- 🧠 THE LIFE CYCLE 4-6

4⃣ 🏊 CERCARIA (2nd swimmer)

• leaves snail

• swims and infects fish 🐟

🧠 Phrase:
👉 “Cercaria = leaves snail, chases fish”

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5⃣ 🐟 METACERCARIA (CYST IN FISH)

• forms cyst (metacercaria) in fish

👉 THIS is the infective stage for humans

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6⃣ 🍣 HUMAN INFECTION

👉 You eat raw/undercooked fish

• cyst enters body

• becomes larva in intestine

• travels to liver

• becomes adult fluke

Clonorchis flow

👉 Egg → Miracidium → Snail → Cercaria → Fish → Human liver

🧠 Even easier phrase:
👉 “Swim → snail → swim → fish → human liver”

Clonorchis infection

where?

🌍 LOCATION

• Asia

• Africa

• South America

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⚠ WHAT IT INFECTS

👉 Adults live in:

• liver (bile ducts)

🪱 Schistosomiasis

BLOOD FLUKE

👉 This fluke is DIFFERENT from all others

❗ Key differences:

• 🩸 lives in blood (veins)

• 🐌 only needs snail + human (2 hosts)

• ❌ NO cyst stage

• 🚶‍♂ enters through skin or hair follicles (not food!)

🧠 Master phrase:
👉 “Schisto swims in, not eaten”

🔁 LIFE CYCLE1-3 Schistosoma

1⃣ 💩/🚽 EGGS LEAVE HUMAN

eggs released in:

• feces 💩

• OR urine 🚽

• 2⃣ 🏊 MIRACIDIUM → SNAIL 🐌

• eggs hatch in water

• larva infects snail

3⃣ 🏊 CERCARIAE (INFECTIVE STAGE)

• leave snail

• swim in water

Schistosoma life cycle 4-5

4⃣ 🚶‍♂ ENTER HUMAN SKIN

👉 penetrate:

• skin

• hair follicles

🧠 Phrase:
👉 “Cercaria = skin burrower”

5⃣ 🩸 ADULTS IN BLOOD

• mature in:

  • intestinal veins (hepatic portal)

  • OR genitourinary veins

❤ UNIQUE MALE + FEMALE

Schistosoma

• small female lives inside body groove of a larger male

👉 “Schisto = worm couple (female rides male)”

Schistosoma egg cycle

6⃣ 🥚 EGGS PRODUCED

• 1000s per day 😳

👉 eggs:

• have spines + enzymes

• cut through tissues

• penetrate through blood vessels walls and tract wall

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7⃣ 🚪 EGGS EXIT BODY

• move into:

  • intestines → feces

  • urinary tract → urine

⚠ BIG PROBLEM - Schistosoma

👉 Many eggs get stuck in tissues

do not enter tract

→ form granulomas (inflammation lumps)

🧠 Phrase:
👉 “Eggs stuck = damage”

🛡 IMMUNE EVASION- Schistosoma

👉 Worms:

• mimic human antigens/ adults produce antigens

• coat themselves with human proteins

• avoid immune response

👉 immune system can't detect them easily

🧠 Phrase:
👉 “Schisto hides in disguise”

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⏳ HOW LONG THEY LIVE

👉 can live up to 40 years 😳

💊 TREATMENT - Schistosoma

👉 Praziquantel

• removes worm's protective coating

• exposes worm to immune system

🧠 Phrase:
👉 “Praziquantel = removes disguise”

🌊 SWIMMER'S ITCH- Schistosoma

🧴 What it is:

👉 Schistosoma dermatitis

• caused by bird Schistosoma

• happens in lakes (northern US)

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⚠ What happens:

• cercariae enter skin

• ❌ cannot go deeper

• cause itchy rash

🧠 Phrase:
👉 “Wrong host = itchy skin only”

Schistosoma- 🌍 GLOBAL IMPACT

• 🌎 250 million infected

• 🌍 74 countries

• ☠ 200,000 deaths/year (Africa)

Schistosoma review

Feature	Schistosoma
Entry	Skin
Hosts	Snail + human
Cyst stage	❌ None
Adults live	Blood veins
Eggs exit	Feces or urine
Damage	Granulomas
Special	Male + female pair

👉 “Schisto swims through skin, hides in blood, eggs cause damage”

Schistosoma does what?

• enters through skin (NOT food)

• snail host required

• no cyst stage

• lives in blood

• eggs cause damage

• hides from immune system

• praziquantel treats it