Micro - Parasitology (Protozoa)

Question 1

Which 3 protozoa cause GI infections? How is each transmitted?

Answer 1

(1) Giardia lamblia - Cysts in water (2) Entamoeba histolytica - Cysts in water (3) Cryptosporidium - Oocytes in water

Question 2

What disease does Giardia lamblia cause? How does it present, and in patients with what kind of exposures?

Answer 2

Giardiasis: bloating, flatulence, foul-smelling, fatty diarrhea (often seen in campers/hikers); Think: “FAT-rich GHIRARDELLI chocolates for FATTY stools of GIARDIA”

Question 3

How is Giardiasis diagnosed?

Answer 3

Trophozoites or cysts in stool

Question 4

What organism causes Giardiasis? What is its treatment?

Answer 4

Giardia lamblia; Metronidazole

Question 5

What disease does Entamoeba histolytica cause? How does it present?

Answer 5

Amebiasis: bloody diarrhea (dysentery), liver abscess (“anchovy paste” exudate), RUQ pain (histology shows flask-shaped ulcer if submucosal abscess of colon ruptures)

Question 6

How is Amebiasis diagnosed?

Answer 6

Serology and/or trophozoites (with RBCs in the cytoplasm) or cysts (with multiple nuclei) in stool

Question 7

What organism causes Amebiasis? What is its treatment?

Answer 7

Entamoeba histolytica; Metronidazole, Iodoquinol for asymptomatic cyst passers

Question 8

What condition/disease(s) does Cryptosporidium cause, and in what patient population(s)?

Answer 8

Severe diarrhea in AIDS; Mild disease (watery diarrhea) in nonimmunocompromised

Question 9

How is Cryptosporidium infection diagnosed?

Answer 9

Cysts on acid-fast stain

Question 10

How is Cryptosporidium prevented? How is Cryptosporidium treated, and in what patient population(s)?

Answer 10

Prevention (by filtering city water supplies); Nitazoxanide in immunocompetent hosts

Question 11

Which protozoa cause CNS infections?

Answer 11

(1) Toxoplasma gondii (2) Naegleria fowleri (3) Trypanosoma brucei, T. gambiense, T. rhodesiense

Question 12

What major sign/symptom does Toxoplasma gondii cause in HIV patients?

Answer 12

Brain abscess in HIV (seen as ring-enhancing brain lesions on CT/MRI)

Question 13

What are the signs/symptoms associated with congenital toxoplasmosis?

Answer 13

“Classic triad” of chorioretinitis, hydrocephalus, and intracranial calcifications

Question 14

How is Toxoplasma gondii transmitted? What is an important implication of T. gondii transmission?

Answer 14

Cysts in meat or oocytes in cat feces; Crosses placenta (pregnant women should avoid cats)

Question 15

How is Toxoplasma gondii diagnosed?

Answer 15

Serology, biopsy

Question 16

How is Toxoplasma gondii treated?

Answer 16

Sulfadiazine + Pyrimethamine

Question 17

What condition/disease does Naegleria fowleri cause?

Answer 17

Rapidly fatal meningoencephalitis

Question 18

How is Naegleria fowleri transmitted?

Answer 18

Swimming in freshwater lakes; Enters cribriform plate; Think: “NALGENE bottle filled with FRESHWATER containing NAEGLERIA”;

Question 19

How is Naegleria fowleri diagnosed?

Answer 19

Amoebas in spinal cord

Question 20

What is a possible treatment for Naegleria fowleri?

Answer 20

Amphotericin has been effective for a few survivors

Question 21

What disease does Trypanosoma brucei/T. gambiense/T. rhodesiense cause? What are its associated symptoms?

Answer 21

African sleeping sickness: enlarged lymph nodes, recurring fever (due to antigenic variation), somnolence, coma

Question 22

How is Trypanosoma brucei/T. gambiense/T. rhodesiense transmitted?

Answer 22

Tsetse fly, a painful bite

Question 23

What protozoa causes African sleeping sickness?

Answer 23

Trypanosoma brucei, T. gambiense, T. rhodesiense;

Question 24

How is Trypanosoma brucei, T. gambiense, and T. rhodesiense diagnosed?

Answer 24

Blood smear

Question 25

What is the treatment for Trypanosoma brucei, T. gambiense, and T. rhodesiense?

Answer 25

Suramin for blood-borne disease or Melarsoprol for CNS penetration; Think: "it SURe is nice to go to sleep, MELAtonin helps with sleep"

Question 26

What disease does Plasmodium cause? What are its general symptoms?

Answer 26

Malaria; Fever, headache, anemia, splenomegaly

Question 27

What are the different species of Plasmodium that can cause different kinds of malaria?

Answer 27

(1) P. vivax/ovale (2) P. falciparum (3) P. malariae

Question 28

What characterizes malaria due to P. vivax/ovale?

Answer 28

48-hr cycle (tertian; includes fever on first day and third day, thus fevers are actually 48 hr apart); Dormant form (hypnozoite) in liver

Question 29

What characterizes malaria due to P. falciparum?

Answer 29

Severe; Irregular fever patterns; Parasitized RBCs occlude capillaries in brain (cerebral malaria), kidneys, lungs

Question 30

What characterizes malaria due to P. malariae?

Answer 30

72-hr cycle (quartan)

Question 31

What protozoa causes Malaria? How is it transmitted?

Answer 31

Plasmodium (P. vivax/ovale, P. facliparum, P. malariae); Mosquito (Anopheles)

Question 32

How is Malaria diagnosed?

Answer 32

Blood smear, trophozoite ring form, RBC schizont with merozoites

Question 33

How is Malaria treated, and why? More specifically, explain treatment protocols in the following contexts: (1) First line therapy (2) If resistant to first line therapy (3) If life threatening (3) Vivax/Ovale.

Answer 33

Begin with chloroquine, which blocks Plasmodium heme polymerase; If resistance, use mefloquine or Atovaquone/Proguanil; If life-threatening, use intravenous quinidine (test for G6PD deficiency); Vivax/ovale - Add primaquine for hypnozoite (test for G6PD deficiency)

Question 34

Which protozoa cause hematologic infections?

Answer 34

(1) Plasmodium (P. vivax/ovale, P. falciparum, P. malariae) (2) Babesia

Question 35

What disease does Babesia cause? What are its symptoms?

Answer 35

Babesiosis: Fever and hemolytic anemia

Question 36

Where is Babesiosis predominately found? What increases risk of severe disease?

Answer 36

Predominately in northeastern United States; Asplenia increases risk of severe disease

Question 37

How is Babesia transmitted? What other pathogen has this same mode of transmission, and what disease does it cause? What is an important implication behind this commonality?

Answer 37

Ixodes tick; Same as Borrelia burgdorferi of Lyme disease, may often coinfect humans

Question 38

How is Babesiosis diagnosed?

Answer 38

Blood smear, ring form, "Maltese cross"; PCR

Question 39

What is the treatment for Babesiosis?

Answer 39

Atovaquone + Azithromycin

Question 40

Which protozoa cause visceral infections that are NOT considered GI, CNS, or hematologic infections?

Answer 40

(1) Trypanosoma cruzi (2) Leishmania donovani

Question 41

Which protozoa causes STDs?

Answer 41

Trichomonas vaginalis

Question 42

What disease/condition does Trypanosoma cruzi cause? What are its associated symptoms?

Answer 42

Chagas' disease: Dilated cardiomyopathy, megacolon, megaesophagus

Question 43

What pathogen causes Chagas' disease? Where is it predominately found? How is it transmitted?

Answer 43

Trypanosoma cruzi; Predominately in South America; Reduviid bug ("kissing bug"), a painless bite (much like a kiss)

Question 44

Again, what pathogen causes Chagas' disease? How is it diagnosed?

Answer 44

Blood smear

Question 45

Again, what disease/condition does Trypanosoma cruzi cause? What is its treatment?

Answer 45

Chagas' disease; Benznidazole or Nifurtimox

Question 46

What condition/disease does Leishmania donovani cause? What are its associated symptoms?

Answer 46

Visceral leishmaniasis (kala-azar): Spiking fevers, hepatosplenomegaly, pancytopenia

Question 47

What pathogen causes visceral leishmaniasis (kala-azar)? How is it transmitted?

Answer 47

Leishmania donovani; Sandfly

Question 48

Again, what condition/disease does Leishmania donovani cause? How is it diagnosed?

Answer 48

Macrophages containing amastigotes

Question 49

What is another name for visceral leishmaniasis? What pathogen causes it? How is it treated?

Answer 49

Kala-azar; Leishmania donovani; Amphotericin B, Sodium stibogluconate

Question 50

What condition/disease does Trichomonas vaginalis cause? What are its associated symptoms?

Answer 50

Vaginitis: Foul-smelling, greenish discharge; Itching and burning

Question 51

What other pathogen should you be careful not to confuse with Trichomonas vaginalis? How is this other pathogen characterized, and what disease/condition does it cause?

Answer 51

Gardnerella vaginalis, a gram-variable bacterium that associated with bacterial vaginosis

Question 52

How is Trichomonas vaginalis transmitted? What is important to remember about its transmission?

Answer 52

Sexual (cannot exist outside human because it cannot form cysts)

Question 53

Again, what condition/disease does Trichomonas vaginalis cause? How is it diagnosed?

Answer 53

Vaginitis; Trophozoites (motile) on wet mount; "Strawberry cervix"

Question 54

What protozoa causes vaginitis? What is the treatment protocol for this condition?

Answer 54

Trichomonas vaginalis; Metronidazole for patient and partner (prophylaxis)

Question 55

What are the 2 subspecies of Trypanosoma brucei?

Answer 55

Two subspecies: (1) Trypanosoma brucei rhodesiense (2) Trypanosoma brucei gambiense