FLAGELLATES

• Flagellates

  Belong to the phylum Protozoa and are members of the subphylum Mastigophora
• Flagellates

  • Intestinal flagellates
  • Atrial flagellates
• Flagellates

  • Movement is accomplished by whiplike structures called flagella in their trophozoite form
  • All flagellate life cycles consist of the trophozoite form
  • Cysts are not known to exist in several of the flagellate life cycles
• Trophozoite


  More resistant to destructive forces, surviving passage into the stomach following ingestion<|>Appear to survive in the outside environment
• Flagellate cysts

  Equipped with thick, protective cell walls<|>May survive in the outside environment
• Typical intestinal flagellate life cycle

  Similar in process to that of the typical amebas
• Atrial flagellate life cycles

  Differ from those of the intestinal flagellates
• Flagellate trophozoites


  Typically seen in loose, liquid, or soft stool specimens
• Flagellate cysts

  More common in formed stools
• Flagellate identification

  • Nuclear characteristics such as number of nuclei present and the presence and positioning of the nuclear structures are helpful
  • Proper identification of structures specific to select flagellates, such as an undulating membrane and axostyle, is often crucial
• Flagellate trophozoites technically possess flagella, but these structures are not always visible</b>
• Permanent smear procedure may shrink flagellate parasites, resulting in smaller than typical measurements
• Nonpathogenic flagellates


  Suggest the ingestion of contaminated food or drink
• Only one intestinal flagellate, Giardia intestinalis, is considered pathogenic
• Atrial flagellates may cause symptoms in areas such as the mouth and genital tract
• Giardia intestinalis


  Also known as Cercomonas intestinalis and Giardia lamblia
• Giardia intestinalis trophozoite


  • Pear or teardrop shaped
  • Bilaterally symmetrical
  • Two ovoid nuclei with large karyosomes
  • No peripheral chromatin
  • Four pairs of flagella
  • Sucking disk covering 50-75% of ventral surface
• Giardia intestinalis cyst

  • Ovoid shape
  • 8-17 μm long, 6-10 μm wide
  • Colorless and smooth cyst wall
  • Cytoplasm often retracted from cyst wall
  • Immature cyst contains two nuclei and two median bodies
  • Mature cyst contains four nuclei
• Giardia intestinalis trophozoite

  • Two pairs of flagella located laterally, extending from the axonemes in the center of the body
  • Equipped with a sucking disc covering 50% to 75% of the ventral surface, serving as the nourishment point of entry by attaching to the intestinal villi of an infected human
• Giardia intestinalis cyst


  Typical ovoid shape, ranging in size from 8 to 17 μm long by 6 to 10 μm wide, with an average length of 10 to 12 μm<|>Colorless and smooth cyst wall is prominent and distinct from the interior of the organism<|>Cytoplasm is often retracted away from the cyst wall, creating a clearing zone<|>Immature cyst contains two nuclei and two median bodies<|>Mature cyst contains four nuclei and four median bodies<|>Mature cysts contain twice as many interior flagellar structures as immature cysts
• Laboratory diagnosis of Giardia intestinalis

  1. Stool specimen is the traditional recovery technique

  2. Duodenal contents obtained by aspiration or upper small intestine biopsies can also be used

  3. Fecal antigen detection by EIA and ELISA

  4. Direct Fluorescence detection

  5. Giardia Western immunoblotting

  6. Real-time PCR
• Giardia intestinalis life cycle

  Infective cysts enter the stomach, excyst in the duodenum<|>Trophozoites multiply via binary fission, attach to the duodenal mucosa<|>Trophozoites may also infect the common bile duct and gallbladder<|>Encystation occurs as trophozoites migrate to the large bowel<|>Cysts are excreted in feces and can remain viable for up to 3 months in water<|>Trophozoites entering the outside environment quickly disintegrate
• Groups at high risk of contracting Giardia intestinalis


  • Children in day care centers
  • People living in poor sanitary conditions
  • Travellers to endemic areas drinking contaminated water
  • Those who practice unprotected sex, particularly homosexual males
• Animal reservoir hosts for Giardia intestinalis

  • Beavers
  • Muskrats
  • Water voles
  • Domestic sheep
  • Cattle
  • Dogs
• Asymptomatic carrier state

  Infections with Giardia intestinalis are often completely asymptomatic
• Giardiasis (Traveler's Diarrhea)


  Symptomatic infections can cause a wide range of clinical symptoms including mild diarrhea, abdominal cramps, anorexia, flatulence, tenderness of the epigastric region, steatorrhea, and malabsorption syndrome<|>Typical incubation period is 10 to 36 days, after which patients suddenly develop watery, foul-smelling diarrhea, steatorrhea, flatulence, and abdominal cramping<|>Giardia is generally a self-limiting condition that resolves in 10-14 days, but chronic cases with multiple relapses can occur
• Treatment for Giardia intestinalis

  Primary choices are metronidazole, tinidazole, and nitazoxanide<|>Metronidazole and tinidazole are potentially carcinogenic, while nitazoxanide is approved by the FDA for treatment of Giardia-related diarrhea
• Prevention and control of Giardia intestinalis

  1. Proper water treatment with chemical therapy and filtration

  2. Guarding water supplies from contamination by reservoir hosts

  3. Practicing good personal hygiene

  4. Proper cleaning and cooking of food

  5. Avoiding unprotected oral-anal sex

  6. Campers/hikers using bottled water or treating potentially contaminated water with iodine or portable purification systems
• Giardia intestinalis was discovered in 1681 by Anton van Leeuwenhoek
• The first recorded water outbreak of Giardia intestinalis occurred in St. Petersburg, Russia
• Giardia intestinalis is known to be a carrier of double-stranded RNA viruses, along with Trichomonas vaginalis
• Giardia intestinalis trophozoites have often been referred to as resembling an old man with whiskers, a cartoon character, and/or a monkey's face
• Studies have suggested that several zymodemes (genetic variants) of Giardia intestinalis exist
• Giardia intestinalis and Entamoeba histolytica cysts were isolated from the Hudson River and East River in New York City in the early 1980s
• Chilomastix mesnili trophozoite


  Pear-shaped, ranging from 5-25 μm long by 5-10 μm wide, with an average length of 8-15 μm<|>Exhibits stiff, rotary, directional motility<|>Has a single nucleus located in the anterior end
• Chilomastix mesnili cyst

  Size range of 5-10 μm long, average size of 7-10 μm by 3-7 μm
• Chilomastix mesnili trophozoite


  • No peripheral chromatin
  • Three extending from anterior end
  • One extending posteriorly from cytostome region
  • Prominent cytostome extending 1/3 to 1/2 body length
  • Spiral groove
• Trophozoites


  The pear-shaped Chilomastix mesnili trophozoite ranges from 5 to 25 μm long by 5 to 10 μm wide, with an average length of 8 to 15 μm
• Motility

  Stiff rotary motility in a directional pattern
• Nucleus

  • Usually not visible in unstained preparations
  • Typical small karyosome may be found located centrally or eccentrically in the form of chromatin granules that form plaques against the nuclear membrane
  • Peripheral chromatin is absent