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Flashcards in Parasites Deck (70):


a prodrug that's converted to dihydroartemisinin (DHA), which generates reactive oxygen species (ex: Plasmodium)


Babesia microti treatment and prevention

Treatment: Atovaquone (inhibits mitochondrial function) and Azithromycin (disrupts protein synthesis); Clindamycin (inhibits protein synthesis) and Quinine (disrupts food vacuole)

Prevention: Avoid tick bites 


Leishmania diseases and pathogenesis 

Variety of Leishmaniasis:

  1. Cutaneous (least severe) - skin ulcers, black spots
  2. Mucocutaneous
  3. Visceral (most severe) - spiking fevers, hepatosplenomegaly, pancytopenia 

Leishmania has a protease that destroys complement components 

It is an intracellular parasite that destorys phagocytes 


Leishmania treatment, resistance, and prevention

Treatment: Amphotericin B, Miltefosine (interferes with lipids and disrupts mitochondria)

Resistance: Amphotericin B resistance due to altered membranes and drug efflux pumps.

Prevention: Avoid sandlfy bites


Cryptosporidium hominis treatment and prevention

Treatment: Nitazoxanide

Prevention: Clean food/water, filter water, boil water, avoid swimming in contaminated water sources


Plasmodium vivax/ovale infection and diagnosis 

Infection: Sporozoites injected into bloodstream from bite of Anopheles mosquito

Diagnosis: Trophozoite rings within RBC's on peripheral blood smear, Schizont containing merozoites - red granules throughout RBC cytoplasm 


Albendazole, Mebendazole

Binds to beta-tubulin of microtubules; broad spectrum against helminths (ex: Ascaris, hookworms)


Entamoeba histolytica treatment, resistance, and prevention

Treatment: Metronidazole, Diloxanide

Resistance: Decreased drug uptake or increased extrusion

Prevention: Filter or boil water; can survive harsh water treatments 


Plasmodium malariae disease/pathogenesis

Follow quartan fever cycle (72 hr - 1st and 4th day)


Parasites that form metabolically inactive cysts

Giardia, Cryptosporidium, Cyclospora, Toxoplasma, Naegleria



generates free radicles that damage parasite DNA and proteins (ex: Trypanosoma cruzi)


Amphotericin B

damages egosterol-rich parasite membranes (ex: Naegleria, Leishmania)


Schistosoma pathogenesis and disease

Schistosoma mansoni larvae coat themselves in ABO blood group antigens and MHC molecules to avoid immune detection 

In early stage, Schistosoma penetrates skin and migrates to liver

S. mansoni leads to portal hypertension, liver cirrhosis, and granulomas 

S. haematobium can lead to carcinoma of the bladder 


Plasmodium vivax/ovale disease and pathogenesis 

Remain dormant in liver as hypnozoites 

Follow tertian fever cycle (48 hr - fever on 1st and 3rd day)


Plasmodium falciparum infection and diagnosis  

Infection: Sporozites injected by bite of Anopheles mosquito

Diagnosis: Banana-shaped gametocytes seen on peripheral blood smear with trophozoite rings forming within RBC's


Naegleria fowleri pathogenesis and symptoms

Enters CNS through cribiform plate where proteases rapidly degrade brain cells for nutrients to replicate; rapidly fatal meningoencephalitis 


Trypanosoma brucei treatment, resistance, and prevention 

Treatment: Melarsoprol for CNS infection (binds parasite pyruvate kinase and inhibits energy production), Suramin for bloodborne disease

Resistance: Altered transporters leaving it unable to take up drug

Prevention: avoid insect bites 


Trypansoma cruzi infection and diagnosis 

Infection: Kissing bug has painless bite and poops on your face. The poop contains trypomastigote and you scratch that into the bite. Common in Central and South America 

Diagnosis: Trypomastigote on peripheral blood smear 


Ascaris lumbricoides pathogenesis 

After ingestion, eggs hatch and larvae penetrate intestinal mucosa, enter bloodstream, and pass through liver, heart, then lungs

Can rupture into alveolar spaces where they are coughed up and swallowed 

Adults mature in small intestine 

Can cause ileoceccal obstruction or biliary obstruction 


Entamoeba histolytica disease and pathogenesis 

Bloody diarrhea, "anchovy paste" liver abscesses, RUQ pain, flask-shaped mucosal ulceration 


Naegleria fowleri infection and diagnosis

Infection: Trophozoite gets into brain through cribiform plate; Affects people who swim in freshwater rivers/lakes in Southern states

Diagnosis: Amoebas in spinal fluid 


Giardia intestinalis disease and pathogenesis

Causes smelly yellow diarrhea

Colonizes upper part of small intestine and causes intestinal malabsorption due to damage to microvilli 


Trypanosoma cruzi disease and pathogenesis 

Parasites replicate and form cysts in heart, esophagus, and GI tract

Chagas Disease - dilated cardiomyopathy with apical atrophy, megacolon, megaesophagus

Unilateral periorbital swelling (Romana sign) characteristic of acute stage 



disrupts parasite waste disposal and causes accumulation of free heme (ex: Plasmodium)



Released into bloodstream upon lysis of Plasmodium-infected RBC's 


Trypanosoma cruzi treatment, resistance, and prevention

Treatment: Nifurtimox, Benznidazole "Cruzing in by Benz with a fur coat"

Resistance: Loss of function mutations in enzymes that activate prodrugs

Prevention: Vector control 


Taenia solium treatment and prevention 

Treatment: Praziquantel, Albendazole

Prevention: Good hygeine, treat tapeworm carriers  


Babesia microti disease and pathogenesis 

Causes fever and hemolytic anemia; asplenia increases risk of severe disease 

Parasite replication destroys RBC's


Ascaris lumbricoides treatment and prevention

Treatment: Mebendazole or Albendazole

Prevention: don't use poop as fertilizer 


Cryptosporidium hominis infection and diagnosis

Infection: Ingestion of oocysts from contaminated water

Diagnosis: Oocysts seen in feces


Definitive Host

host in which parasite reaches adulthood and where sexual reproduction occurs


Diagnostic indicator of parasitic infection

Eosinophilia and high IgE count


Trypanosoma brucei infection and diagnosis 

Infection: Bite of Tsetse fly injects metacyclic trypomastigote into bloodstream

Diagnosis: Trypomastigote in blood smear 


Trypanosoma brucei pathogenesis and disease 

Causes African Sleeping Sickness - enlarged lymph nodes, recurring fever (due to antigenic variation), somnolence, coma, death

Parasite replicates in bloodstream, lymph, and spinal fluid where it enters CNS


Trichomonas vaginalis disease and pathogenesis 

Causes persistent inflammation in vagina because it produces mechanical stress on host cells until their death

Vaginitis - foul-smelling, greenish discharge; itching and burning; do NOT confuse with Gardnerella (gram-variable bacterium)


Trichomonas vaginalis treatment, resistance, and prevention 

Treatment: Metronidazole, Tinidazole

Reistance: loss of ability to activate prodrug

Prevention: Condoms 


Trichomonas vaginalis infection and diagnosis 

Infection: Trophozoite transmitted sexually; cannot exist outside humans because it cannot form cysts 

Diagnosis: Motile trophozoites on wet mount; "strawberry cervix" 


Treatments and resistance for Pasmodium species 

Treatment: 1st line - Chloroquine (blocks heme polymerase), 2nd line - Mefloquine or Atovaquone/progranil. For serious infections use Artemisinin

Resistance: Plasmodium is has high resistance to all agents. Chloroquine resistance due to pumps. Artemisinin resistance due to decreased degradation of parasite kinase that activates protective cellular pathways. 


Entamoeba histolytica infection and diagnosis 

Infection: Cysts are ingested from contaminated water 

Diagnosis: Trophozoites with engulfed RBC's are seen in stool 

"Entamoeba eats Erythrocytes"


Giardia intestinalis infection and diagnosis

Infection: Cysts transmitted via fecal/oral route; associated with camping or water sports Diagnosis: Cysts or live characteristic trophozoite seen in stool


Ascaris lumbricoides infection and diagnosis 

Infection: Ingestion of eggs via fecal/oral route; especially those who use human feces as fertilizer 

Diagnosis: oval eggs with rough coat seen in feces 


Enterobius vermicularis infection and pathogenesis 

Infection: Adult female migrates down colon at night and deposits eggs on anus. These eggs infect via fecal/oral route.

Diagnosis: Scotch tape test shows eggs 


Naegleria fowleri treatment adn prevention

Treatment: Amphotericin B, Miltefosine (disrupts mitochondrial function)

Prevention: Don't get water up your nose if swimming in freshwater 



increases permeability of parasite cell membranes, causing rapid calcium influx and paralysis in worms (ex: Schistosoma, Taenia)


Schistosoma infection and diagnosis

Infection: Snails are intermediate host; infectious stage is free-swimming and penetrates skin of humans swimming in water 

Diagnosis: Eggs with spines seen in feces 


Cyclospora prevention

avoid contaminated water, wash fruits and veggies, boil water


Cyclospora (general)

similar overall features to Cryptosporidium


Strongyloides stercoralis infection and diagnosis 

Infection: Contains free-living stage that does not require host. Larvae in the soil penetrate skin in people who walk barefoot. Larvae migrate to the lungs where they are coughed up and swallowed. They can also migrate directly to intestines via connective tissues. 

Diagnosis: Larvae seen in feces


Taenia solium disease and pathogenesis 

Cysticerosis - Occurs by ingesting food contaminated with tapeworm eggs. The eggs hatch and get into tissues, including your brain. May lead to "swiss cheese brain" with seizures and hydrocephalus.

Taeniasis - Occurs when you ingest the larval form; larvae get into your intestines, mature, and lay eggs. May lead to Autoinfection and Cysteicerosis 


Taenia solium infection and diagnosis 

Infection: Ingestion of larvae from undercooked pork, or ingestion of eggs in food contaminated with human feces.

Diagnosis: Eggs or gravid proglottids in feces 


Antifolates, Pyrimethamine

inhibit folic acid biogenesis (ex: Toxoplasma gondii)


Strongyloides stercoralis pathogenesis 

Cause vomiting, diarrhea, epigastric pain (mimic peptic ulcer)

Hyperinfection can lead to heavy worm burden

Disseminated disease with septic shock due to bacteremia from translocation of gut lumen bacteria due to larval invasion across gut wall


Toxoplasma gondii treatment and prevention 

Treatment: Sulfonamides and Pyrimethamine 

Prophylaxis: Sulfonamides for HIV patients when T Cell count is below 100

Prevention: Wash hands after handling raw meat, avoid unpasteurized milk, avoid cleaning liter box if pregnant


Enterobius vermicularis treatment, resistance, and prevention

Treatment: Mebendazole or Albendazole, Pyrantel pamoate

Resistance: mutations in beta-tubulin

Prevention: Don't bite nails, wash hands thoroughly, change bed sheets 


Plasmodium falciparum disease and pathogenesis 

Most severe form of malaria; irregular fevers; parasitized RBC's can occlude capillaries in brain, kidneys, and lungs. This is the cause of cerebral malaria


Schistosoma treatment and prevention 

Treatment: Praziquantel (calcium influx causing paralysis)

Prevention: Avoid fecal contamination of water sources


Giardia intestinalis treatment and resistance mechanisms 

Treatment: Metronidazole, Tinidazole, Quinacrine hydrochloride

Resistance: loss of ability to convert prodrugs to active form 


Toxocara canis pathogenesis and disease

Visceral larva migrans - nematodes migrate to blood through intestinal wall causing inflammation and damage. Often affects the heart, liver, eyes (visual impairment and blindness), and CNS (seizures, coma)


Toxocara canis infection and diagnosis

Infection: Over 200k eggs/day released in feces; Eggs mature in soil and are ingested by canines and humans

Diagnosis: Larvae seen in tissue 



disrupts helminth nerves and muscles by binding to chloride channels causing hyperpolarization and paralysis/death of worm (ex: Strongyloides, Onchocera)


Leishmania donovani infection and diagnosis 

Infection: Sandfly bite injecte promastigote into the skin, which are phagocytized by macrophages 

Diagnosis: Macrophages containing amastigotes 


Cryptosporidium hominis disease and pathogenesis

Severe diarrhea in AIDS patients (CD 4 < 100)

Sporozoites invade epithelial cells and damage microvilli in a 7-10 day cycle, so classic symptom is diarrhea once every 7-10 days


Toxoplasma gondii infection and diagnosis 

Infection: Cysts in meat, oocytes in cat feces, or crossing placenta

Diagnosis: Trophozoites on serology or cysts in tissues 


Toxoplasma gondii disease and pathogenesis 

Toxoplasma gondii resides in immunoprivileged sites like brain and eye

Congenital toxoplasmosis is the classic triad of Chorioretinitis, Encephalitis, and Intracranial Calcifications. Can also cause hearing loss

Reactivation in AIDS leads to multiple ring-enhancing brain lesions


Toxocara canis treatment and prevention

Treatment: Albendazole or Mebendazole

Prevention: De-worm household pets, wash hands 


Cyclospora treatment

Antifolates: TMP-SMX


Strongyloides stercoralis treatment, resistance, and prevention 

Treatment: Ivermectin (inhibits nerves and muscles by binding chloride channels)

Resistance: increased membrane transporter activity to remove drug

Prevention: Avoid contaminated soil, medical professionals should wear gloves and gowns 


Accidental host

host cannot support any stage of parasite's development


Babesia microti infection and diagnosis 

Infection: Ixodes tick bite transfers sporozoite into bloodstream; typically infects people who have been hiking in Northeast. Often co-infection with Lyme Disease

Diagnosis: Peripheral blood smear shows ring form and "Maltese Cross" within RBC's



inhibits nucleic acid synthesis in anaerobic cells (ex: Trichomomas, Entamoeba, Giardia)