How do you tell Giardia from Cryptosporidium?

Both cause watery non-bloody diarrhea. Giardia gives fatty, foul-smelling malabsorptive stool after freshwater or daycare exposure, with pear-shaped two-nuclei (owl-face) trophozoites; treat with metronidazole. Cryptosporidium oocysts are acid-fast and cause severe chronic diarrhea in AIDS (CD4 under 100); the key intervention is immune reconstitution with antiretroviral therapy.

What parasite causes new-onset seizures with brain cysts?

Neurocysticercosis from Taenia solium. Ingesting the eggs (fecal-oral) seeds larval cysts in the brain that calcify and trigger seizures. It is a leading cause of adult-onset seizures worldwide. Treat with albendazole or praziquantel plus steroids to control inflammation from dying cysts.

Which parasite links to squamous cell bladder cancer?

Schistosoma haematobium. Freshwater snail-released cercariae penetrate skin; the worms lay terminal-spine eggs in the bladder wall, causing chronic granulomatous inflammation, hematuria, and squamous cell bladder cancer in the Middle East and Africa. Treat with praziquantel.

What is the treatment anchor for tapeworms and flukes?

Praziquantel treats the cestodes (tapeworms) and the trematodes (flukes). Albendazole covers most nematodes and tissue cysts. Ivermectin covers Strongyloides and Onchocerca. Metronidazole covers Giardia, Entamoeba, and Trichomonas. Pyrimethamine plus sulfadiazine treats Toxoplasma.

Microbiology · Parasitology

Fungi & Parasites

The board-heavy parasites and the high-yield fungi · each one by its exposure, its clue, and its one fix

Opening Challenge

A 26-year-old man is brought to the emergency department by his roommate after a seizure. He has no seizure history. He emigrated from a rural village in Central America two years ago, where the family raised free-roaming pigs. MRI of the brain shows multiple small cystic lesions, some with a tiny bright dot inside, and several calcified foci. There is no AIDS history and HIV testing is negative. Which of the following is the most likely cause of his seizures?

A) Reactivation toxoplasmosis

B) Neurocysticercosis from Taenia solium

C) Primary CNS lymphoma

D) Cerebral malaria

Neurocysticercosis from Taenia solium. Here is the move. Toxoplasma also makes ring lesions, but it lives in AIDS with CD4 under 100, and this man has a negative HIV test. The bright dot inside a cyst is the scolex (the worm's tiny head), and calcified foci are old, dead cysts. That combination, in someone from an endemic area with pig exposure, is cysticercosis: he swallowed Taenia solium eggs (fecal-oral), and the larvae seeded his brain. It is a leading cause of adult-onset seizures worldwide. Treat with albendazole or praziquantel plus steroids to blunt the inflammation when the cysts die. New-onset seizures plus brain cysts with a dot inside, in someone from an endemic area, equals neurocysticercosis. Eating the eggs seeds the brain. Eating the pork only gives you a gut worm.

01 · Exposure Tracing

The Travel Clinic

A patient walks in with one exposure. Trace it to the organism, then choose the one fix. Five patients.

How to play: read the exposure, tap the organism it points to on the map, then read the route, clue, and pearl card. The whole point: parasites are won at the exposure line. Snail water, raw fish, cat litter, undercooked pork, a tick. Each one has a fingerprint.

02 · Gut Protozoa

Bugs In The Lumen

Watery vs bloody is the first fork. Tap each card to open the full picture, then meet the decision tree.

The diarrhea fork: Giardia and Cryptosporidium are watery, no blood (they sit on the surface). Entamoeba is bloody dysentery (it invades and eats RBCs). That single split sorts the whole group before you name anything.

Decision Tree: Traveler With Diarrhea

Guess each fork before you tap. The reasoning is the lesson, not the answer.

03 · Blood & Tissue Protozoa

Vectors And Invaders

These come by a bite, a cat, or warm water. The vector is half the answer. Tap to open.

Vector cheat line: Anopheles mosquito = malaria. Ixodes tick = Babesia (Northeast, asplenic). Reduviid kissing bug = Chagas (Latin America). Tsetse fly = African sleeping sickness. Sandfly = Leishmania. Cat feces = Toxoplasma. Warm freshwater up the nose = Naegleria.

Memory Hooks: The One-Liners That Win Stems

04 · Roundworms

The Nematodes

Round worms, mostly soil and skin. Most get albendazole. The exceptions are the test. Tap to open.

Nematode drug line: most roundworms get albendazole (or pyrantel pamoate for pinworm). The two exceptions worth gold: Strongyloides and Onchocerca get ivermectin. Pinworm and Strongyloides both need the household or the immune status checked.

05 · Tapeworms & Flukes

Cestodes & Trematodes

Flat worms. Almost all answer to praziquantel. The exposure (fish, pork, snail water) names them. Tap to open.

Flatworm rule: praziquantel covers the tapeworms (cestodes) and the flukes (trematodes), with two asterisks: neurocysticercosis adds steroids, and Echinococcus hydatid cysts get albendazole plus careful surgery (do not rupture, or you get anaphylaxis).

Exposure	Organism	Signature Clue	Fix
Raw freshwater fish	Diphyllobothrium latum	B12 deficiency, megaloblastic anemia	Praziquantel
Undercooked pork (eggs)	Taenia solium	Neurocysticercosis, seizures, brain cysts	Albendazole/praziquantel + steroids
Beef	Taenia saginata	Intestinal only, no brain disease	Praziquantel
Dog/sheep (eggs)	Echinococcus granulosus	Hydatid liver cyst, eggshell calcification	Albendazole + careful surgery
Freshwater snail (skin)	S. haematobium	Hematuria, squamous cell bladder cancer	Praziquantel
Freshwater snail (skin)	S. mansoni / japonicum	Portal hypertension, hepatosplenic disease	Praziquantel
Raw fish	Clonorchis sinensis	Biliary disease, cholangiocarcinoma	Praziquantel
Undercooked crab	Paragonimus	Lung disease, hemoptysis	Praziquantel

06 · Fungi

The Fungi: Geography & Villains

Geography names the dimorphics. The opportunists name the host. Tap the map, then flip the villains.

Dimorphic Rule

❄

25°C (cold lab)

MOLD form

Branching hyphae

↔

🩹

37°C (body temp)

YEAST form

Round budding cells

Memory: Mold in the Cold, Yeast in the Beast. Exception: Coccidioides makes spherules with endospores at 37°C (not true yeast).

Fungi

The Board Killers

Tap to flip. Geography, clue, host, drug, next move on the back.

🦠

Histoplasma

Dimorphic Fungus

Tap to reveal

Geography

Ohio + Mississippi River Valleys · bat/bird droppings, spelunking

Key Clue

Macrophages packed with intracellular oval yeast on Wright/Giemsa stain

Host

HIV CD4 <150 = disseminated · healthy spelunker = self-limited pneumonia

Drug

Itraconazole (mild) · AmB (severe)

Ohio + bat cave + cough = Histo first

🏞

Coccidioides

Dimorphic Fungus

Tap to reveal

Geography

SW United States (Arizona, San Joaquin Valley, desert soil)

Key Clue

Spherules with endospores · NOT true yeast · exception to dimorphic rule

Host

Filipino and African American ancestry disseminate · HIV also at risk

Drug

Fluconazole (mild) · AmB (severe/meningitis)

Arizona + dust storm = Cocci

🌿

Blastomyces

Dimorphic Fungus

Tap to reveal

Geography

Great Lakes + SE United States · soil, decaying organic matter

Key Clue

Broad-based budding yeast with double-contoured wall · figure-8 on KOH

Host

Hunters, trappers, campers in Great Lakes · can affect healthy hosts

Drug

Itraconazole (mild) · AmB (severe)

Great Lakes + skin/lung lesion = Blasto

🨐

Cryptococcus

Encapsulated Yeast

Tap to reveal

Geography

Worldwide · pigeon droppings, eucalyptus trees

Key Clue

India ink: clear capsule halo in CSF · narrow-based budding · latex agglutination detects antigen

Host

HIV CD4 <100 gets meningitis · soap bubble basal ganglia lesion

Drug

AmB + Flucytosine (induction) → Fluconazole (maintenance)

HIV + meningitis + clear CSF = India ink STAT

🌼

Aspergillus

Mold (Septate)

Tap to reveal

Microscopy

Septate hyphae, 45-degree branching · halo sign on CT chest

Forms

Invasive: neutropenic + CT halo
Aspergilloma: fungus ball in old TB cavity
ABPA: asthma + eosinophilia

Drug

Voriconazole (invasive) · Itraconazole (ABPA)

Neutropenic + CT halo = Aspergillus until proven otherwise

💀

Mucor / Rhizopus

Mold (Non-Septate)

Tap to reveal

Microscopy

Non-septate hyphae, 90-degree branching · ribbon-like

Key Clue

Black necrotic palate/sinus · angioinvasion = eschar

Host

DKA (most classic) · deferoxamine feeds Mucor (provides iron) · neutropenic

Drug

Amphotericin B + surgical debridement

DKA + black sinus = Mucormycosis STAT

The branching rule: Septate + 45-degree = Aspergillus (voriconazole). Non-septate + 90-degree = Mucor (amphotericin B). Wrong drug = wrong answer.

Public references: standard medical microbiology and board review texts (Murray, Levinson) and clinical practice guidelines for endemic and opportunistic mycoses and parasitic infections.

07 · Elimination Game

Narrow It Down

Use clues to eliminate wrong answers. One organism survives.

Scenario 1 of 4

08 · Clinical Walkthrough

Board-Style Vignettes

26 original third-order vignettes, parasite-weighted. One at a time, shuffled, never repeats until the bank is done.

Exam tools: right-click or long-press an option to cross it out · double-click or double-tap to highlight. Tools pause after you answer.