Parasitology Flashcards
Protozoa: Entamoeba histolytica
GI infection
Disease: amebiasis - bloody diarrhea (dysentery), liver abscess (“anchovy paste” exudate), RUQ pain, histology shows flask-shaped ulcer
Transmission: cysts in water
Diagnosis: serology and/or trophozoites (with engulfed RBCs in the cytoplasm) or cysts with up to 4 nuclei in stool
Treatment: metronidazole; iodoquinol for asymptomatic cyst passers
Protozoa: Cryptosporidium
GI infection
Disease: severe diarrhea in AIDS. Mild disease (water diarrhea) in immunocompromised hosts
Transmission: oocytes in water
Diagnosis: oocytes on acid-fast stain
Treatment: prevention (by filtering city water supplies); nitazoxanide in immunocompetent hosts
Protozoa: Toxoplasma gondii
CNS infection
Disease: congenital toxoplasmosis- classic triad of chorioetinitis, hydrocephalus and intracranial calcifications; reactivation in AIDS –> brain abscess seen as ring-enhancing lesions on MRI
Transmission: cysts in meat (most common); oocytes in cat feces; crosses placenta (pregnant women should avoid cats)
Diagnosis: Serology, biopsy (tachyzoite)
Treatment: sulfadiazine + pyrimethamine
Protozoa: Naegleria fowleri
CNS infections
Disease: rapidly fatal meningioencephalitis
Transmission: swimming in freshwater lakes (think Nalgene bottle filled with freshwater containing Naegleria); enters via cribiform plate
Diagnosis: amoebas in spinal fluid
Treatment: amphotericin B
Trypanosome brucei
CNS infections
Disease: African sleeping sickness - enlarged lymph nodes, recurring fever (due to antigenic variation), somnolence and coma
-two subspecies (trypanosoma brucei rhodesiense * trypanosoma brucei gambiense)
Transmission: tsetse fly, a painful bite
Diagnosis: trypomastigote in blood smear
Treatment: Suramin for blood-borne disease OR melarsprol for CNS penetration (SURe is nice to go to sleep; MELAtonin helps with sleep)
Protozoa: plasmodium
Hematologic infection
Disease: malaria - fever, HA, anemia, splenomegaly
-P.vivax/ovale: 48hr cycle (tertian: includes fever on first and third day, thus fevers are actually 48hrs apart); dormant form (hypnozoite) in liver
-P.falciparum: server; irregular fever patterns, parasitized RBCs occlude capillaries in brain (cerebral malaria), kidneys and lungs
-P.malariae: 72hr cycle (quartan)
Transmission: anopheles mosquito
Diagnosis: blood smear; trophozoite ring form within RBC, schizont containing merozoites; red granules (schuffner stippling) throughout RBC cytoplasm seen with P.vivax/ovale
Malaria Treatment
Chloroquinine (for sensitive species), which block plasmodium heme polymerase
If resistant: mefloquine or atovaquone/proguanil
If life-threatening: IV quinidine or artesian the (test for G6PD deficiency)
For P.vivax/ovale: add primaquine for hypnozoite (test for G6PD deficiency)
Protozoa: babesia
hematologic infection
Disease: Babesiosis-fever and hemolytic anemia; predominantly in NE USA; asplenia increases risk of severe disease
Transmission: Ixodes ticks (same with Lyme disease - may cause coinfection)
Diagnosis: blood smear; ring form “Maltese cross”; PCR
Treatment: atovaquone + Azithromycin
Protozoa: trypanosoma cruzi
Visceral infections
Disease: chaga’s disease - dilated cardiomyopathy with apical atrophy, megacolon, mega esophagus; predominantly in South America (unilateral periorbital swelling (Romana sign) characteristic of acute stage)
Transmission: reduviid but (“kissing bug”) feces, deposited in painless bite
Diagnosis: trypomastigote in blood smear
Treatment: Benznidazole or nifurtimox
(Cruzing in my Benz with a Fur coat on)
Protozoa: Leishmania donovani
Visceral infections
Disease: visceral leishmaniasis (kala-azar) - spiking fevers, hepatosplenomegaly, pancytopenia; cutaneous leishmaniasis - skin ulcers
Transmission: sandfly
Diagnosis: MPs containing amastigotes
Treatment: amphotericin B, sodium stibogluconate
Protozoa: Trichomonas vaginalis
Sexually transmitted infections
Disease: vaginitis - foul smelling, greenish discharge, itching and burning; (do not confuse with Gardnerella vaginalis - a gram variable bacterium associated with bacterial vaginosis)
Transmission: sexual (cannot exist outside human because it cannot form cysts)
Diagnosis: trophozoites (motile) on wet mount, “strawberry cervix”
Treatment: metronidazole for pt and partner (prophylaxis)
Nematode routes of infection
Ingested - Enterobius, ascaris, Toxocara, Trichinella
(you will get sick if you EATT these)
Cutaneous - Strongyloides, Ancylostoma, Necator
(these get into your feet from the SANd)
Bites - Loa loa, onchocerca volvulus, Wuchereria bancrofti
(lay LOW to avoid getting bitten)
Immune response to helminths
Eosinophils act by type I and type II hypersensitivity reaction in responding to helminths
Type I - neutralization of HA and LKT
Type II - eosinophils attach to surface of helminths via IgE and release cytotoxins (major basic protein) contained in granules
Nematodes (roundworms): Enterobius vermicularis (pinworm)
Disease: intestinal infection causing anal pruritus (diagnosed by seeing eggs via tape test)
Transmission: fecal-oral
Treatment: Bendazoles (because worms are bendy)
Nematodes (roundworms): Ascaris lumbricoides
Disease: Intestinal infection with possible obstruction of ileocecal valve
Transmission: fecal-oral; eggs visible in feces under microscope
Treatment: Bendazoles
