Parasitic Infections

Protozoa: Gut & Blood - Microbe Mayhem

• Gut Protozoa

  • Giardia lamblia (Giardiasis):
    • Greasy, foul stools; steatorrhea.
    • Dx: Stool (cysts/trophozoites).
    • Rx: Metronidazole.
    • 📌 "Giardia gives Gas & Greasy stools."
  • Entamoeba histolytica (Amoebiasis):
    • Dysentery; liver abscess (anchovy sauce).
    • Flask-shaped ulcers.
    • Dx: Stool (trophozoites + RBCs).
    • Rx: Metronidazole + Diloxanide.

    ⭐ Amoebic liver abscess: most common extra-intestinal manifestation.

• Blood Protozoa

  • Plasmodium spp. (Malaria):
    • Cyclical fever, anemia, splenomegaly.
    • P. falciparum: Severe, cerebral malaria. Rx: ACTs.
    • P. vivax/ovale: Hypnozoites (Primaquine).
    • Dx: Smear (ring forms).
  • Leishmania donovani (Kala-azar/Visceral Leishmaniasis):
    • Fever, HSM, pancytopenia, weight loss.
    • Dx: LD bodies (BM/spleen aspirate).
    • Rx: Amphotericin B.

Protozoa: Systemic & Congenital - Silent System Invaders

• Toxoplasmosis (Toxoplasma gondii)
  • Transmission: Oocysts (cat feces), tissue cysts (undercooked meat); transplacental.
  • Congenital (📌 Sabin's Triad): Chorioretinitis (most common), hydrocephalus, intracranial calcifications.
  • Diagnosis: Maternal serology (IgM/IgG avidity); PCR (amniotic fluid); Neonatal IgM.
  • Treatment: Pyrimethamine + Sulfadiazine + Folinic acid for 1 year (congenital).

  ⭐ Reactivation in AIDS (CD4 < 100) causes multiple ring-enhancing brain lesions.

• Malaria (Plasmodium spp.)
  • Congenital: Rare; fever, anemia, jaundice, hepatosplenomegaly. Risk ↑ with maternal malaria near term.
  • Systemic (Peds): High fever, chills, sweats, splenomegaly. Severe: cerebral malaria, profound anemia.
  • Diagnosis: Peripheral blood smears (Giemsa); RDTs.
  • Treatment: Artemisinin-based Combination Therapies (ACTs).

Helminths: Intestinal Roundworms - Roundworm Rumble

• Ascaris lumbricoides (Giant Roundworm):
  • Most common. Larval migration → Loeffler's.
  • Intestinal obstruction, malnutrition.
  • Dx: Bile-stained, mammillated eggs (stool).
  • Tx: Albendazole/Mebendazole.
• Trichuris trichiura (Whipworm):
  • Rectal prolapse, dysentery, anemia.
  • Dx: Barrel-shaped eggs, bipolar plugs (stool).
  • Tx: Albendazole/Mebendazole.
• Ancylostoma duodenale & Necator americanus (Hookworms):
  • Ground itch; IDA (blood loss).
  • Dx: Non-bile stained, thin-shelled eggs (stool).
  • Tx: Albendazole/Mebendazole; Iron.
• Enterobius vermicularis (Pinworm):
  • Nocturnal perianal itching.
  • Dx: Scotch tape test (eggs).
  • Tx: Albendazole/Mebendazole; treat family.
• Strongyloides stercoralis:
  • Autoinfection; hyperinfection (immunocompromised).
  • Dx: Larvae in stool.
  • Tx: Ivermectin (DOC), Albendazole. 📌 Mnemonic: "Roundworms Are Nasty Trouble" (RANT: Roundworm, Ancylostoma, Necator, Trichuris).

⭐ Loeffler's syndrome (eosinophilic pneumonitis): Ascaris larval lung migration.

Helminths: Tissue & Tapeworms - Tapeworm Terrors & Tissue Trials

Tapeworms (Cestodes):

• Taenia solium (Pork):
  • Causes cysticercosis; Neurocysticercosis (NCC) is a major cause of seizures.
  • Dx: CT/MRI (ring-enhancing lesions, scolex), EITB. Rx: Albendazole + steroids for viable cysts.
• Taenia saginata (Beef): Taeniasis only. Rx: Praziquantel.
• Echinococcus granulosus (Dog):
  • Hydatid disease: Forms cysts (liver, lung). "Eggshell calcification" characteristic.
  • Rx: PAIR, Albendazole, surgery. ⚠️ Anaphylaxis risk on cyst rupture.
• Hymenolepis nana (Dwarf): Most common human tapeworm. Autoinfection cycle. Rx: Praziquantel.

Tissue Nematodes:

• Trichinella spiralis: From undercooked pork. Classic triad: myalgia, periorbital edema, eosinophilia. Rx: Albendazole, steroids.
• Dracunculus medinensis (Guinea worm): Painful skin ulcer with visible emerging worm. Rx: Slow extraction.
• Larva Migrans:
  • Cutaneous (CLM): Hookworm larvae. Itchy, serpiginous skin eruptions. Rx: Albendazole.
  • Visceral (VLM): Toxocara spp. Fever, hepatomegaly, marked eosinophilia. Rx: Albendazole.

⭐ > Neurocysticercosis is the most common preventable cause of epilepsy in the developing world.

High‑Yield Points - ⚡ Biggest Takeaways

• Malaria: P. falciparum causes cerebral malaria; peripheral smear for diagnosis.
• Giardiasis: Presents with chronic, foul-smelling, fatty diarrhea; treat with Metronidazole.
• Amebiasis: Can cause bloody dysentery and liver abscess; Metronidazole is key.
• Ascariasis: Commonest helminth; may cause intestinal obstruction or Loeffler's syndrome.
• Hookworm: Leads to iron deficiency anemia due to chronic blood loss.
• Visceral Leishmaniasis (Kala-azar): Features fever, massive splenomegaly, pancytopenia; LD bodies confirm.
• Neurocysticercosis: Common cause of acquired seizures in endemic areas.