Parasites Flashcards
Artemisinin
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:
- Cutaneous (least severe) - skin ulcers, black spots
- Mucocutaneous
- 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
Benznidazole
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
Chloroquine
disrupts parasite waste disposal and causes accumulation of free heme (ex: Plasmodium)
Merozoites
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
Praziquantel
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
Ivermectin
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
Metronidazole
inhibits nucleic acid synthesis in anaerobic cells (ex: Trichomomas, Entamoeba, Giardia)
