Protozoal Infections Flashcards
Giemsa Stain
Trypanosomes
Plasmodium
Entamoeba histolytica - Pathogenesis
Ingestion of cysts from containated food / water
Cysts become trophozoites in the GI tract and attach to the colonic mucosa, causing “flask-shaped” ulceration
Entamoeba histolytica - Presentation
Amebiasis: bloody diarrhea (dysentery) + RUQ pain due to liver abscess
Entamoeba histolytica - Diagnosis and treatment
Cysts / trophozoites in stool or tissue (liver abscess)
Stool assay - GalNAc antigen
Serology - Ab assay
Treatment: Luminal disease treated with Paromomycin; liver abscess treated with Metronidazole
Giardia lamblia - Pathogenesis
Ingestion of cysts from contaminated food / water
Cysts become trophozoites in the small intestine causing variable crypt hypertrophy / villous flattening
Giardiasis - Presentation
Bloating, flatulence, foul-smelling fatty diarrhea
Giardia - Diagnosis and Treatment
Cysts / trophozoites in stool
Treated with Metronidazole
Cryptosporidium - Pathogenesis
Ingestion of oocytes from contaminated water; may occur in outbreaks from pools, water parks; also sexually transmitted
Cryptosporidium - Presentation and Treatment
Mild watery diarrhea in non-immunocompromised; important cause of intractable, severe diarrhea in AIDS patients
Treated with Nitazoxanide (immunocompetent) or Pentamadine (immunocompromised)
Trichomonas vaginalis - Pathogenesis and Presentation
Sexual transmission of trophozoite by vaginal / prostatic fluid; causes damage to genital mucosa (microulceration)
Often asymptomatic in men; causes yellow/green discharge and burning/itching vaginitis in women + “strawberry cervix”
Trichomonas vaginalis - Diagnosis and Treatment
Diagnosed by demonstration of pear-shaped trophozoite on wet mount
Treated with Metronidazole for patient and partner (prophylaxis)
Plasmodium - Pathogenesis
Mosquitos inject sporozites into the blood; sporozoites infect the liver and undergo primary replication to produce merozoites
Merozoites released into blood infect RBCs and undergo asexual reproduction to produce gametes
Gametes in blood are picked up by mosquitos and fuse to form zygotes; zygotes mature to infectious sporozoites in the salivary gland
RBC age preferences of Plasmodium sp.
P. vivax and P. ovale - young RBCs
P. malariae - old RBCs
P. falciparum - RBCs of any age
Which Plasmodium sp. establish latent infection?
P. vivax and P. ovale can establish latent infection of the liver via the hypnozoite stage
Temporal patterns of different Plasmodium sp.
Tertian (fever on days 1 and 3 - 48 hours apart) = P. vivax and P. ovale (“benign”) and P. falciparum (“malignang”)
Quartan (fever on days 1 and 4 - 72 hours apart) = P. malariae
General signs and sx of malaria
Fever - cyclical Hemolytic anemia Splenomegaly Jaundice Hemoglobinuria Tachycardia Hypotension / shock
Malaria - Diagnosis
Blood smear shows trophozoite ring forms within RBCs
mAb detection of PfHRP2 is specific for P. falciparum
Trypanosoma brucei - Pathogenesis
sub-species Rhodensiense (E. Africa) and Gambiense (W. Africa)
Infectious trypomastigote is injected into blood by Tsetse fly; initially causes a local chancre followed by parasitemia
Stage I: IgM immune complex deposition causes vasculitis (fever, rash, headache, lymphadenopathy)
Stage II: CNS involvement causes convulsions , somnolence, coma, and death
Trypanosoma brucei - Treatment
Stage I: Suramin
Stage II: Eflornithine, Melasporol
Trypanosoma cruzii - Pathogenesis & Presentation
Infective trapanomastigote passed by bite of Reduviid (“kissing”) bug causing an indurated lesion (chagoma)
Trypanomastigotes spread to lymphatics and blood, causing acute phase of fever, lymphadenopathy, and hepatosplenomegaly followed by late dilated cardiomyopathy, thromboembolism
Trypanosoma cruzii - Diagnosis / specific signs
Giemsa stain
Romana’s sign - periorbital edema
Leishmaniasis - Pathogenesis & Diagnosis
Transmitted of promastigote by sandfly bite; promastigotes activate complement and become phagocytosed; multiplication within phagocytes allows spread and invasion
Diagnosed by macrophages containing amastigotes
Leishmaniasis - Clinical Presentation and Treatment
Cutaneous - ulceration
Mucocutaneous - erosion of nasal septum / palate
Visceral - disseminated disease; presents with fever, diarrhea, hepatosplenomegaly, ascites, hyperpigmentation of skin, death
Treatment: Sodium stibogluconate, Amphotericin B
Toxoplasmosis - Pathogenesis and Presentation
Ingestion of bradyzoites in cysts via contaminated / under-cooked meat, cat feces; vertical transmission also occurs
Presents with acute, mononucleosis-like illness + brain abscess
