Protozoa

Question 1

Protozoa that moves via pseudopods and causes bloody diarrhea

Answer 1

Entamoeba histolytica - fecal-oral transmission; cyst differentiates to trophozoite in ileum to cause amebic dysentery and/or liver abscesses; diagnosed via visualization of trophozoites with ingested RBCs or 4-nuclei cyst; treat with metronidazole (active state) or iodoquinol/diloxamide furoate (carrier stage)

Question 2

Protozoa that moves via 4 pairs of flagella and causes fatty diarrhea

Answer 2

**Giardia lamblia - **fecal-oral transmission; 4-nuclei cyst differentiates into 2-nuclei trophozoite in duodenum and attaches to duodenal wall via “suction” disk; damage to microvilli leads to malabsorption and fatty diarrhea; “string test” for duodenal pathogens; treat with metronidazole

Question 3

Non-motile protozoa that causes watery diarrhea in AIDS patients

Answer 3

Cryptosporidium parvum - fecal-oral transmission; acid-fast oocysts release sporozoites in small intestine which differentiate into trophozoites to produce watery diarrhea in immunocompromised;

Question 4

Protozoa that causes urogenital infection

Answer 4

Trichomonas vaginalis - green foul-smelling vaginal discharge; treat patient and patient’s sexual partner with metronidazole; no cyst form

Question 5

Protozoa that causes encephalitis and chorioretinitis in immunocompromised

Answer 5

Toxoplasma gondii - cysts ingested from undercooked meat or cat feces and release crescent-shaped trophozoites in small intestine where they are phagocytosed and disseminated by macrophages; congenital toxoplasmosis (MR, chorioretinitis); treat with sulfonamide + pyrimethamine

Question 6

Protozoa that is nonflagellated within macrophages and flagellated outside macrophages

Answer 6

Leishmania donovani - transmitted from dogs and rodents via sandfly; spreads via reticuloendothelial system; causes leishmaniasis (kala-azar) which presents with hepatosplenomegaly and hyperpigmented skin patches; treat with stiboglyconate

Question 7

Protozoa that is flagellated in blood and nonflagellated in cardiac muscle

Answer 7

Trypnasoma cruzi - transmitted by reduviid (kissing) bug; acute phase characterized by chagoma (inflammatory nodule at bite site), CHF, myocarditis; chronic phase characterized by arrhythmias, dilated cardiomyopathy, megacolon, megaesophagus; treat acute phase with nifurtimox, benzidazole

Question 8

Protozoa that is flagellated and causes recurrent fevers and somnolence

Answer 8

Trypnasoma brucei gambiense/rhodesiense - transmitted by the tsetse fly; hard red ulcer at bite site and enlarged lymph nodes; antigenic variation of surface coat impedes immune response; causes West African (gambiense) and East African (rhodesiense) Sleeping Sickness; treat blood-borne disease with suramin; treat CNS disease with melarsoprol

Question 9

Non-motile protozoa that causes cyclical anemia, fevers, and chills

Answer 9

Malaria - sporozoites transmitted by Anopheles mosquito and infect hepatocytes where they divide into infective merozoites which then invade RBCs and form trophozoites which divide into even more merozoites; some merozoites form gametocytes

• Plasmodium falciparum - small ring-shaped trophozoite, banana-shaped gametocyte; irregular cycle; forms knobs in infected RBCs which occlude vessels (cerebral malaria); treated with chloroquine or mefloquine (if chloroquine-resistance) or quinidine (if life-threatening)
• Plasmodium vivax/ovale - large irregular ring-shaped trophozoite, round gametocyte; 2-day cycle; primaquine required to kill hypnozoites in liver
• Plasmodium malariae - band/rectangular-shaped trophozoite, round gametocyte; 3 day cycle; infects old RBCs (vs. vivax/ovale which infect new RBCs)

Question 10

Protozoa transferred via Ixodes tick (often with Borrelia burgdorferi) and forms ring-form and “Maltese cross” in RBCs

Answer 10

Babesia - causes fever and hemolytic anemia, predominantly in the northeastern US; asplenia increases risk of disease; treat with atovaquone + azithromycin​