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Flashcards in Parasitology Deck (39):

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


Nematodes (roundworms): Stronglyoides stercoralis (threadworm)

Disease: Intestinal infection causing vomiting, diarrhea, epigastric pain (may mimic peptic ulcer)
Transmission: larvae in soil penetrate the skin
Treatment: Ivermectin or Bendazoles


Nematodes (roundworms): Ancylostoma duodenale, Necator americanus (hookworms)

Disease: intestinal infection causing anemia by sucking blood from intestinal wall
-cutaneous larva migrans: pruritic serpiginous rash from walking barefoot on contaminated beach
Transmission: larvae penetrate skin
Treatment: Bendazoles or pyrantel pamoate


Nematodes (roundworms): Trichinella spiralis

Disease: intestinal infection; larvae enter bloodstream and encyst in striated muscle cells (inflammation of muscle)
-Trichinosis: fever, vomiting, nausea, periorbital edema, myalgia
Transmission: fecal-oral, undercooked meat (esp pork)
Treatment: Bendazoles


Nematodes (roundworms): Toxocara canis

Disease: visceral larva migrans - nematodes migrate to blood through intestinal wall causing inflammation and damage. Organs frequently affected include heart (myocarditis), liver and CNS (seizures, coma)
Transmission: Fecal-oral
Treatment: Bendazoles


Nematodes (roundworms): Onchocerca volvulus

Disease: skin changes, loss of elastic fibers and river blindness (*black flies, black skin nodules, black sight*); allergic reaction tomicrofilaria possible
Transmission: female black fly
Treatment: Ivermectin (*IVERmectin for rIVER blindness*)


Nematodes (roundworms): Loa loa

Disease: swelling in skin, worm conjunctiva
Transmission: deer fly, horse fly, mango fly
Treatment: Diethylcarbamazine


Nematodes (roundworms): Wuchereria bancrofti

Disease: elephantiasis - worm invades lymph nodes and causes inflammation which can block lymphatic vessels (takes 9mo-1yr after bite to become symptomatic)
Transmission: female mosquito
Treatment: Diethylcarbamazine


Cestodes (tapeworms): Taenia solium

Disease: intestinal tapeworm
Transmission: ingestion of larvae encyst end in undercooked pork
Treatment: praziquantel
Disease: cysticercosis, neurocysticercosis
Transmission: ingestion of eggs contaminated with human feces
Treatment; praziquantel; albendazole for neuro type


Cestodes (tapeworms): Diphyllobothrium

Disease: vitamin B12 deficiency (tapeworm competes for B12 in intestine) --> megaloblastic anemia
Transmission: ingestion of larvae from raw freshwater fish
Treatment: praziquantel


Cestodes (tapeworms): Echinococcus granulosus

Disease: hydatid cysts in liver causing anaphylaxis if Ag released (hydatid cyst injected with EtOH or hypertonic saline to kill daughter cysts before removal)
Transmission: ingestion of eggs from dog feces, sheep are an intermediate host
Treatment: albendazole


Trematodes (flukes): Schistosoma

Disease: liver and spleen enlargement (S.mansoni, egg with lateral spine), fibrosis, and inflammation
-chronic infection with S.haematobium (egg with terminal spine) can lead to squamous cell carcinoma of the bladder (painless hematuria) and pulmonary HTN
Transmission: snails are host, cercariae penetrate skin of humans
Treatment: praziquantel


Trematodes (flukes): Clonorchis sinensis

Disease: biliary tract inflammation --> pigmented gallstones (associated with cholangiocarcinoma)
Transmission: undercooked fish
Treatment: praziquantel


Biliary tract disease, cholangiocarcinoma

Clonorchis sinensis


Brain cysts, seizures

Taenia solium (neurocysticercosis)


Hematuria, squamous cell bladder cancer

Schistosoma haematobium


Liver (hydatid) cysts

Echinococcus granulosus


Microcytic anemia

Ancylostoma, Necator


Myalgia, periorbital edema

Trichinella spiralis


Perinatal pruritus



Portal HTN

Schistosoma mansoni, Schistosoma japonicum


Vitamin B12 deficiency

Diphyllobothrium latum


Ectoparasite: Scabies (sarcoptes scabiei)

Mites that burrow into the stratum cornermen and cause pruritus
Causes serpiginous burrows (lines) in we spaces of hands and feet
Common in children; crowded populations (jails, nursing homes); transmission through of mites
Treatment: permethrin cream, washing/drying all clothing/bedding, treat close contacts


Ectoparasite: Lice (pediculus humanus/phthirus pubis)

Blood sucking insects that preference to live on clothing
Cause intense pruritus, pink macula sand papules commonly in intertriginous regions
Can transmit Rickettsia prowazekii (typhus), Borrelia recurrentis (relapsing fever), Bartonella quintana (trench fever)
Treatment includes: pyrethroids, malathion or ivermectin lotion and nit combing
Children with head lice can be treated at home without interrupting school


Protozoa: Giardia lamblia

GI infection
Disease: Giardiasis - bloating, flatulence, foul-smelling, fatty diarrhea (often seen in campers/hikers)
Transmission: cysts in water
Diagnosis: multi cleated trophozoites or cysts in stool
Treatment: metronidazole