Deck

• Protozoans


  One-celled eukaryotes bounded only with a cell membrane
• Protozoan characteristics

  • Heterotrophic
  • Autotrophic
  • Mixotrophic
• Asexual reproduction


  Binary fission
• Sexual reproduction


  Varies in life cycle
• Protozoan life cycle


  • Simple asexual cell division of the active feeding cell (trophozoite)
  • Formation of a cyst
  • Complex life cycle with asexual and sexual phases
• Trophozoite


  Large, motile cell with pseudopods
• Cyst


  Smaller, non-motile form
• Entamoeba histolytica and Amebiasis

  • Alternates between trophozoite and cyst
  • Trophozoite has a large nucleus and lacks most other organelles
  • Humans are the primary hosts
  • Ingested and carried by 10% of world population
• Amebiasis infection


  1. Cysts are swallowed and arrive at small intestine

  2. Alkaline pH and digestive juices stimulate cysts to release trophozoites

  3. Trophozoites attach, multiply, actively move about and feed
• Asymptomatic amebiasis


  In 90% of patients
• Trophozoites may secrete enzymes


  Dissolve tissues and penetrate deeper layers of the mucosa
• Severe manifestations of amebiasis

  • Hemorrhage
  • Perforation
  • Appendicitis
  • Tumorlike growths (amebomas)
• Amebic liver and lung invasion


  May occur
• Amebiasis fatality rate


  10% for severe forms of disease
• Effective amebiasis drugs


  • Iodoquinol
  • Metronidazole
  • Chloroquine
• Naegleria fowleri and Acanthamoeba spp.


  • Free-living, ubiquitous protozoans
  • N. fowleri is thermophilic
  • Ordinarily inhabit standing water
  • Cause primary acute meningoencephalitis through nasal contact or traumatic eye damage
• Trichomonads


  Small, pear-shaped flagellates with 4 anterior flagella and an undulating membrane
• Trichomonas species


  Exist only in trophozoite form
• Trichomonas species that infect humans

  • Trichomonas vaginalis
  • Trichomonas tenax
  • Trichomonas hominis
• Trichomoniasis


  An STD caused by Trichomonas vaginalis
• Trichomonas vaginalis


  • Reservoir is human urogenital tract
  • 50% of infected are asymptomatic
  • Strict parasite, cannot survive long outside of host
• Trichomoniasis symptoms


  • Foul-smelling, green-to-yellow discharge (females)
  • Vulvitis (females)
  • Cervicitis (females)
  • Urinary frequency and pain (females)
  • Urethritis (males)
  • Thin, milky discharge (males)
  • Occasional prostate infection (males)
• Giardia lamblia and Giardiasis


  • Pathogenic flagellate
  • Unique symmetrical heart shape with concave ventral surface that acts like a suction cup
  • Cysts are small, compact, and multinucleate
  • Reservoirs include beavers, cattle, coyotes, cats, and humans
  • Cysts can survive for 2 months in environment
  • Usually ingested with water and food
• Giardiasis


  Diarrhea, abdominal pain
• Giardiasis diagnosis


  Difficult because organism is shed in feces intermittently
• Giardiasis treatment


  • Quinacrine
  • Metronidazole
• Giardia lamblia cysts


  ID 10 to 100 cysts
• Giardia lamblia cysts


  Killed by boiling, ozone, and iodine
• Hemoflagellates


  Vector-borne blood parasites that are obligate parasites of human hosts
• Hemoflagellates


  • Cause life-threatening and debilitating zoonoses
  • Spread in specific tropical regions by blood-sucking insects that serve as intermediate hosts
  • Have complicated life cycles and undergo morphological changes
• Trypomastigote


  Elongate, spindle-shaped cell with tapered ends and eel-like motility
• Types of trypanosomiasis


  • Trypanosoma brucei - African sleeping sickness
  • Trypanosoma cruzi - Chagas disease
• Trypanosoma brucei and African sleeping sickness

  • Spread by tsetse flies
  • Harbored by reservoir mammals
  • Two variants caused by subspecies T. b. gambiense and T. b. rhodesiense
• African sleeping sickness infection

  1. Biting of fly inoculates skin with trypomastigotes

  2. Trypomastigotes multiply in blood and damage spleen, lymph nodes and brain
• African sleeping sickness chronic symptoms


  Sleep disturbances, tremors, paralysis and coma
• African sleeping sickness treatments

  • Melarsoprol
  • Eflornithine
• Trypanosoma cruzi and Chagas disease

  • Reduviid bug (kissing bug) is the vector
  • Infection occurs when bug feces is inoculated into a cutaneous portal
  • Local lesion, fever, and swelling of lymph nodes, spleen, and liver
  • Heart muscle and large intestine harbor masses of amastigotes
  • Chronic inflammation occurs in the organs (especially heart and brain)
• Chagas disease treatments


  • Nifurtimox
  • Benzonidazole
• Leishmaniasis


  Zoonosis transmitted among mammalian hosts by female sand flies that require a blood meal to produce eggs
• Leishmaniasis endemic regions


  Equatorial regions