7 - PARASITOLOGY (PROTOZOA)

Host that harbors the asexual or larval stage of a parasite

Intermediate Host

Host where the parasite attains sexual maturity

Definitive Host

Gold standard in diagnosing intestinal protozoans

Direct Fecal Smear

Most common location of amebic liver abscess

Anterior-superior aspect of the liver

Microscopic hallmark of E. histolytica trophozoite

Ingested RBC

Drug of choice for asymptomatic intestinal E. histolytica infection

Luminal agents(Iodoquinol or Paromomycin)

Characteristic ulcer in amebic colitis

Flask-shaped ulcers

Secondary amebic meningoencephalitis causative agent

Entamoeba histolytica

Commensal amoeba morphologically identical to E. histolytica but nonpathogenic:

Entamoeba dispar

Microscopic finding diagnostic of Iodamoeba butschlii

Large glycogen body

Causative agent of primary amebic meningoencephalitis (PAM)

Naegleria fowleri

Causative agent of Granulomatous amebic encephalitis

Acanthamoeba

A hiker develops foul-smelling, greasy stools and bloating. Motile trophozoites show "old man with glasses" appearance and falling leaf motility

Giardia lamblia

Ciliated protozoan acquired from pigs; causes dysentery-like symptoms

Balantidium coli

Characteristic ulcer in Balantidium coli infection

Wide neck ulcers

Acid-fast protozoan causing severe diarrhea in immunocompromised patients (AIDS)

Cryptosporidium parvum

Drug of choice for C. parvum in immunocompetent patients

Nitazoxanide

Primary treatment for C. parvum in HIV-positive patients

HAART

A woman presents with frothy greenish vaginal discharge. Wet mount shows motile, pear-shaped trophozoites. Treatment

Metronidazole or Tinidazole (2g single dose)

CT scan shows multiple ring-enhancing brain lesions in an HIV patient.

Toxoplasma gondii (bradyzoite stage)

Prophylaxis for Toxoplasma gondii

Pyrimethamine + Sulfadiazine + Folinic acid

Definitive host of Toxoplasma gondii

Domestic Cats

Test used to detect antibodies to Toxoplasma

Sabin-Feldman methylene blue dye test

Vector for Leishmaniasis

Sandfly

(Phlebotomus/Lutzomyia)

Drug of choice for free-living amoebas

Miltefisone

Infective stage of Leishmania

Promastigote

Diagnostic stage of Leishmania

Amastigote

Skin test to assess exposure to Leishmania spp.

Montenegro skin test

Patient from South America with history of reduviid bug bite and unilateral periorbital swelling (romana sign), presents with fever, cardiomyopathy, megaesophagus, hepatosplenomegaly.

T. cruzi (Chagas disease)

Infective stage of T. cruzi

Metacyclic Trypomastigote

Diagnostic stage of T. cruzi

Trypomastigote (in blood)

Common features seen in Chronic Chagas Disease

Arrhythmias

Megaesophagus

Megacolon

Causative agent of acute, rapidly fatal East African sleeping sickness

Trypanosoma brucei rhodiense

Vector of African trypanosomiasis

Tsetse fly

(Glossina)

CSF histopathologic feature in African trypanosomiasis

Morula cells of Mott

Pathognomonic feature of Babesia microti on smear

Maltese cross formation

Intermediate host of Plasmodium species

Humans

Stage of Plasmodium that infects RBCs

Schizonts

Gold standard for detection of malaria

Thin and thick blood smear

Populations with RBC defects like G6PD deficiency or sickle cell disease are

Relatively immune to malaria

Coarse granulation seen in Plasmodium falciparum

Maurer Dots

Punctate granules in P. vivax

Schuffner Dots

Fine granules in P. malariae

Ziemann stippling/dots

Band form trophozoites are characteristic of:

Plasmodium malariae

Recurrence of malaria after months of latency:

Relapse

Cause of relapse in P. vivax and P. ovale

Reactivation of hypnozoites

Drug to prevent relapse in P. vivax / P. ovale:

Primaquine

Sausage/banana-shaped gametocytes seen in:

Plasmodium falciparum