Derm | ID | OSCE

Ectoparasites (Scabies & Lice) + Parasite Clue-Chains

Bodyland story: Tiny thieves living on the skin cause itch; tiny squatters living in the gut or blood leave clue-prints in labs and symptoms. Let’s learn to spot both—fast.

Why am I learning this (off-hand answers)?

• Common + contagious: You’ll meet scabies and head lice in real life, wards, schools, shelters, and care homes.
• High-yield patterns: Certain parasites scream specific complications (e.g., biliary cancer ⇢ Clonorchis). These show up in exams and in clinic.
• Public health impact: Treating the person + close contacts + clothing/bedding stops outbreaks.

Street-Simple Analogy

Scabies = tunnel diggers. Imagine tiny miners with itchy jackhammers digging under the upper road of the skin (the stratum corneum). They leave wiggly pencil lines (serpiginous burrows) especially between fingers and toes. Itch flares at night when the miners are busy.

Lice = bus stop vampires. Little blood-sippers cling to hair at popular “bus stops”: scalp (kids), armpit/waist (body lice), and pubic hair. They glue eggs (nits) to hair shafts like superglue beads.

What to do (essentials you can say in one breath)

• Scabies: Permethrin 5% cream neck-down overnight; repeat in 1 week. Wash/dry hot all clothes/bedding; treat close contacts, too.
• Lice: Permethrin/pyrethroids, or malathion, or ivermectin lotion + meticulous nit combing. Kids with head lice can usually stay in school once treatment starts.
• Itch control: antihistamines at night; explain post-scabetic itch can last weeks even after cure.
• Body lice can transmit bad actors (e.g., Rickettsia prowazekii, Bartonella quintana): think crowding, homelessness, war—treat the person and the environment.

Jargon Demystified (tiny dictionary)

burrow

little tunnel in top skin layer.

serpiginous

wavy/zig-zag like a snake’s track.

fomite

object that carries infection (towel, bedsheet).

permethrin/pyrethroid

bug-nerve blockers—paralyze and kill mites/lice.

malathion

another insect killer (cholinesterase inhibitor) used topically.

ivermectin

anti-parasite drug; lotion/oral in some cases.

nits

lice eggs glued to hair shafts.

excoriations

scratch marks from intense itch.

pruritus

medical word for itch.

Parasite “Domino Chains” — see one clue, think one culprit

• Biliary tract disease / cholangiocarcinoma → think Clonorchis sinensis (Chinese liver fluke from raw fish).
• Brain cysts, seizures → think Taenia solium (neurocysticercosis from pork tapeworm eggs).
• Hematuria; squamous bladder cancer → think Schistosoma haematobium (freshwater snails; eggs lodge in bladder wall).
• Liver hydatid cysts → think Echinococcus granulosus (dog tapeworm; risk of anaphylaxis if cyst ruptures).
• Microcytic anemia → think Ancylostoma/Necator (hookworms sipping iron).
• Myalgias + periorbital edema → think Trichinella spiralis (larvae in muscle from undercooked pork/wild game).
• Perianal pruritus (night) → think Enterobius (pinworm; tape test).
• Portal hypertension → think Schistosoma mansoni/japonicum (eggs fibrose portal tracts).
• Vitamin B₁₂ deficiency → think Diphyllobothrium latum (fish tapeworm steals B₁₂).

Case Scenario (OSCE-style)

Stem: 7-year-old returns from a sleepover with intense night-time itch between fingers. Exam: thin serpiginous lines on wrists, burrows in web spaces, scattered excoriations. Siblings also itching.

Think: Scabies.

Say/Do quickly: “We’ll use permethrin 5% cream neck-down overnight, repeat in 7 days, treat everyone at home the same night, and wash/dry all clothes/bedding hot. Itch may linger for weeks—this doesn’t mean failure.”

Red flags: crusted scabies (thick scaly plaques, immunocompromised) → consider oral ivermectin + infection control.

Memory Hooks (quick mnemonics)

• ScaBies loves Between digits—B for Burrows Between.
• Lice = Line of nits on hair—look for shiny beads glued to shafts.
• “CLAW at the canal”: CLo-norchis ⇢ bile canal scars/cancer.
• “H for Haematuria”: S. Haematobium → bladder blood & cancer.
• “Fish steals B-12”: Diphyllobothrium takes your “both-amine” (B-12).

Spiritual Lesson

Little hidden things—like mites in tunnels—can steal peace if ignored. In Bodyland and in life, light + cleansing + community care bring healing. “In Him all things hold together.” (Colossians 1:17) — we honor Jesus, the Eternal Scientist of Bodyland, by caring for the smallest and the least.

Practice Links & Drills (click & do)

🧪 Self-Check: Scabies 3-liner

🧪 Spot the Nits

🧪 Domino Recital

🧪 Tape Test Steps

Domino Web — Connect to Other Scrolls

• Itch science: Histamine, C-fibers, why night itch worsens (heat, less distraction).
• Outbreak control: Fomites, laundry temps, contact tracing.
• Helminth iron loss: Hookworms → microcytic anemia → iron studies (ferritin, TIBC).
• Cancer links: Chronic inflammation → cholangiocarcinoma (Clonorchis); squamous bladder cancer (S. haematobium).
• Neurology tie-in: Seizures from neurocysticercosis (Taenia solium) → imaging and antihelminth therapy considerations.

One-Minute Recap

Scabies = tunneling mite → nocturnal itch; treat with permethrin 5% neck-down, repeat, treat contacts, hot-wash.
Lice = hair-clinging vampires → treat with permethrin/pyrethroid or malathion/ivermectin + nit comb.
Parasite clue chains you must know: biliary cancer ⇢ Clonorchis; brain cysts ⇢ Taenia solium; hematuria/bladder CA ⇢ S. haematobium; liver hydatid ⇢ Echinococcus; microcytic anemia ⇢ hookworms; myalgia + periorbital edema ⇢ Trichinella; perianal itch ⇢ Enterobius; portal HTN ⇢ Schisto mansoni/japonicum; B12 loss ⇢ Diphyllobothrium.

✝️ “In Him all things hold together.” – Colossians 1:17
This scroll honors the One who formed every skin cell with love — Jesus Christ, the Eternal Scientist of Bodyland.