ParasitologyTest2Flagellates

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ParasitologyTest2Flagellates
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2014-10-10 00:07:24
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  1. What is the phylum and subphylum that encompasses the flagellates?  What are the characteristics of a flagellate?
    • Phylum: Sarcomastigophora
    • Subphylum: mastigophora
    • Flagella present in trophozoites
    • Replication by binary fission
  2. What are the important classes and orders associated with subphylum Sarcomastigophora?  Give a brief description and an example organism
    • CLASS Zoomastigophora: lack chloroplasts (unlike class Phytomastigophorans)
    • ORDER Retortamonadida: 2-4 flagella (1 turned posteriorly and associated with ventrally located cytosomal area)
    • Cysts present
    • EX- Chilomastix mesnili
    • ORDER Diplomonadida: 2 equal nuclei side by side
    • 1-4 pairs of flagella
    • EX- Giardia lamblia
    • ORDER Trichomonadida: anterior tuft of flagella
    • axostyle (stout median rod)
    • undulating membrane along recurrent (posteriorly bending) flagellum
    • Cysts absent
    • Frequently commensals
    • EX- Dientamobea fragilis, Trichomonas tenax, T. vaginalis, and T. hominis
  3. Chilomastix mesnili- location, host, life cycle, transmission, and disease state of
    • Live in large intestine of humans, primates, other vertebrates, and invertebrates
    • Cyst stage present (required to survive gastric juices during infection)
    • Transmitted through ingestion of cysts (usually fecal contamination of water)
    • Nonpathogenic, may cause diarrhea
  4. Chilomastix mesnili- physical description of all stages
    • Trophozoite: pear shaped
    • ~12um long
    • anterior (rounded) end and posterior (pointed) end
    • large nucleus located anteriorly
    • 3 free flagella extend anteriorly
    • 1 shorter flagella recurves into cytostomal groove (undulates)
    • Cyst: uni-nucleated
    • thick walled
    • ~8um
    • lemon shaped
  5. Giardia lamblia- AKA, discovery, location, most basic ID, intensity of average infection? what happens during severe infection?
    • AKA Giardia intestinalis
    • Discovered 1681 by Leeuwenhoek in his own stool
    • Lives in duodenum and upper intestine of humans
    • resembled a face staring back at you
    • 1 diarrhetic stool can contain 14 billion parasites
    • 1 moderately infected stool can contain 300 million cysts
    • In severe infections the free surface of nearly every epithelial cell is covered by the adhesive disc of Giardia
  6. Giardia lamblia- physical description of all stages
    • Trophozoite: rounded at anterior end, tapered posteriorly, flattened dorso-ventrally
    • ~12-15um in length
    • concave, rigid bi-lobed adhesive disc (supported by microtubules)
    • 1 nuclei in center of each lobe (2 total)
    • 4 pair of flagella arise from basal bodies (between the 2 nuclei)
    • - 1 pair extends straight down the cell's midline posteriorly
    • - 2 pair emerge from the posterior side of the discs, extending on either side of the 1st pair
    • - 1 pair extends anteriorly and extends outward from either side of the disc
    • **NOTE- see images if unsure
    • 1 pair of large, curved, dark-staining median bodies (unknown function) is found posterior to the disc
    • Cyst: ~10-12um length
    • Thick hyaline cyst wall
    • flagella shorten (no longer extend out)
    • older cysts have 4 nuclei, and sucking disc/locomotor apparatus are double shortly after
    • Excystation will therefor result in 2 trophozoites
  7. Giardia lamblia- life cycle
    • Trophozoites divide in stepwise binary fission (1st nuclei, 2nd locomotory apparatus/disc, 3rd cytoplasm) allowing rapid replication
    • Trophozoites are exclusively found in small intestine (and watery stool)
    • Cysts are formed as feces enters colon and dehydrates
    • Flagella shorten, cytoplasm condenses, and cyst wall is formed
    • When cysts are swallowed by host they pass safely through the stomach (cell wall) and excyst in the duodenum (2 trophozoites)
    • Flagella grows out and parasites are trophozoites
  8. Giardia lamblia- epidemiology (distribution, frequency in humans, transmission, vulnerable hosts, transmission factors, reservoirs, preventative measures)
    • Distributed universally, but more frequent in warm climates (frequent in US)
    • Most common flagellate of human digestive tract
    • Highly contagious (giardiasis), entire families usually quickly infected
    • Transmission requires ingestion of cyst
    • Children and homosexual men especially susceptable
    • Contaminated water supply (crossed with sewage line?) leads to easy infection
    • Other animals (dogs/cats) can serve as reservoir
    • Boil/filter water, avoid raw fruits/veggies, check water pipes regularly
  9. Giardia lamblia- disease facts (name, symptoms, damage, additional symptoms)
    • Giardiasis
    • causes severe intestinal disorders, intense diarrhea, etc
    • Cause damage to mucosa and degeneration (shriveling) of villi
    • Interference with food absorption (especially fats) may lead to diarrhoeic feces
    • Giardia may also swim up bile duct to gall bladder, leading to nausea, vomiting, severe abdominal pain, weight loss, and jaundice
  10. Giardia lamblia- diagnosis
    • Confirmed by identifying cysts during microscopic exam of feces
    • Cysts are typically numerous and easily identified morphologically
  11. Giardia lamblia- Treatment
    • Metronidazole may kill intestinal Giardia after 1 week of treatment
    • *NOTE- if gall bladder/bile duct is infected then relapse can occur for years
    • *NOTE- all members of a family should be treated simultaneously due to its high contagiousness
  12. Dientamoeba fragilis- taxonomy, geographical location, life cycle, location, disease, transmission,
    • Initially classified as sarcodine (amoeba), but now considered an abnormal flagellate - 2 nuclei but no flagella or median bodies.  No cysts.
    • Occurs worldwide
    • No cysts.  Trophozoites rapidly disintegrate outside of host.
    • reside in large intestne
    • Considered a commensal, but many intestinal problems (diarrhea, pain, etc) in those infected
    • Mode of transmission unknown (no cysts = can't survive stomach), but eggs of intestinal nematodes may serve as carriers
  13. Dientamoeba fragilis- physical description of all stages
    • Trophozoite: 6-12um
    • single lobopod
    • food vacuoles contain bacteria, starch granules, cell debris
    • 60% have 2 nuclei connected by a filament, 40% have a single nucleus
  14. Dientamoeba fragilis- diagnosis/identification, treatment
    • Identification of trophozoite in feces
    • Trophozoite swells in the presence of water and its cytoplasmic granules exhibit brownian movement (unique)
    • Treatment parallels Giardia (metronidazole)
  15. Trichomonas spp- general morphology, life cycle, hosts, keys to differentiation
    • Anterior tuft of flagella
    • Axostyle (stout median rod)
    • Hydrogenosomes are associated with axostyle and perform respiration (mito are not present)
    • Undulating membrane along recurrent (posterior) flagellum
    • All flagella originates from anterior basal bodies (# varies with spp)
    • No cyst stage
    • Common in vertibrates and invertebrates (termites)
  16. Trichomonas tenax- discovered, distribution, location, life cycle, transmission, disease, treatment/prevention
    • Discovered by Muller (1773) when he examined culture of tartar from teeth
    • Worldwide distribution
    • Found exclusively in mouth area (can't survive in GI)
    • Common between teeth and gums, cavities
    • Has been found in lungs/trachea
    • No cyst stage, trophozoite replicates by binary fission
    • Transmission is direct (kissing, contaminated utensils, etc)
    • *NOTE- resistant to temp change and can survive for hours in water
    • Harmless commensals (feed on bacteria and other mouth debris)
    • Common in those with poor oral hygiene (but not the cause)
    • Controlled with proper oral hygiene
  17. T. tenax- physical description of all stages
    • Trophozoite: 10um x 6um
    • 5 flagella
    • - 4 from basal body
    • - 1 fused to form undulating membrane
    • Undulating membrane extends ~2/3 the length of the cell
  18. Trichomonas hominis- AKA, disease state, life cycle, transmission, reservoirs
    • AKA T. Pentatrichonomas
    • Harmless commensal of the colon
    • *NOTE- heavy infection may cause upset stomach
    • Trophozoite divides by binary fission
    • Present in diarrhoetic stool (not the cause)
    • Transmission via trophozoites in contaminated food/water (no cysts)
    • Trophozoites are hardy (can survive acidic stomach)
    • Dogs, cats, mice, and other rodents serve as reservoirs
  19. Trichonomas hominis- Physical description of all stages
    • Trophozoite: ~10um x 8um
    • 5 anterior flagella are present and arranged as 4+1 (the 5th originates and beats independently)
    • The 6th recurrent flagellum is fused to the undulating membrane which extends the full length of the cell and protrudes beyond the posterior end as a trailing flagellum
  20. Trichomonas vaginalis- Discovery, location, life cycle, disease name, transmission
    • Discovered by Donne (1836) in vagina/penile secretions
    • Found in vagina of females and urethra/prostate in males
    • Reproduces by binary fission
    • Optimal pH for reproduction is 5-6 (normal vagina pH is 4-4.5)
    • When vaginal pH is disturbed replication occurs rapidly and contributes to the pH shift
    • Causes vaginitis (AKA trichomoniasis)
    • Transmission by direct contact (sex)
    • Damp cloths (underwear, bedsheets) can have viable trophozoites for 24 hours+
    • Fetus can acquire organism while passing through the birth canal
  21. Trichomonas vaginalis- physical description of all stages
    • Trophozoite: 7-32um long, 5-12um wide (large)
    • 4 free anterior flagella
    • 1 flagellum fused to short undulating membrane (1/3 length of cell)
    • Occasionally produces pseudopodia
    • Mass of hydrogenosomes extend along axostyle
  22. Trichomonas vaginalis- disease/infection, symptoms
    • Rarely pathogenic in men (may cause mild urethritis/prostatitis)
    • In most women (10-25%)  it is nonpathogenicHeavy infections (shifted pH >5) occur in ~15% of women
    • Causes deterioration of vaginal mucosa cells (vaginitis AKA trichomoniasis)
    • Symptoms include genital inflammation, intense vaginal itching/burning, bad odor, leukorrhea (profuse white/yellow/greenish discharge filled with parasites)
    • *NOTE- has been linked to cervical cancer
  23. Trichonomas vaginalis- prevalence data (% infected, risk groups, reservoir, persistance in host, cases each year)
    • Found in 3-5% of female population
    • Increased in STD clinics (50%) and prostitutes (50-75%)
    • Only in humans, no animal reservoir
    • Can persist for 2 years in host
    • 200 million diagnosed each year (2-3mil in US alone)
  24. Trichomonas vaginalis- diagnosis, treatment, and prevention
    • Diagnosed with microscopic ID of motile trophozoites from vaginal/urethra/prostate/discharge smears)
    • Treated with metronidazole (clears <1 week)
    • Restoration of vaginal pH through vinegar douches can control AND prevent infection
    • Sexual partners should be treated simultaneously
    • Sexual abstinence/use of condoms will prevent infection
    • Promiscuity increases risk of infection

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