Flagellates(Parasitology 2nd yr 2nd Sem)

Notes for Parasitology

1. Flagellates belong to the phylum Protozoa and are members of the subphylum Mastigophora.
The flagellates can be categorized into two groups, intestinal and atrial.
Movement of the flagellates is accomplished by the presence of whiplike structures known as flagella in their trophozoite form.
It is this characteristic that distinguishes flagellates from the other groups of protozoans.

In those flagellate life cycles with no known cyst stage, the trophozoite is considered to be more resistant to destructive forces, surviving passage into the stomach
following ingestion. In addition, these trophozoites also appear to survive in the outside environment.

Unlike the amebas, however, flagellates reside mainly in the small intestine, cecum, colon and, in the case of Giardia intestinalis, the duodenum.

flagellate trophozoites are typically seen in loose, liquid, or soft stool specimens, whereas flagellate cysts are more common in formed stools.

Proper identification of structures specific to select flagellates, such as a finlike structure connected to the outer edge of some flagellates known as an undulating
membrane and axostyle (a rodlike support structure found in some flagellates),
is often even more crucial in determining proper parasite identification.

The use of saline and iodine wet preparations, as well as permanent stains, results in the same benefits in flagellate identification as those described for the
amebas.

It is important to note that there is only one intestinal flagellate, G. intestinalis, that is considered pathogenic. Infections with G. intestinalis may produce
characteristic symptoms
. Each of the atrial flagellates may cause symptoms in areas such as the mouth and genital tract.

the flagellates may be separated into two categories, intestinal and extraintestinal.


Giardia intestinalis was discovered in 1681 by Anton van Leeuwenhoek when he examined a sample of his own stool.



Giardia intestinalis
-​Initially known as Cercomonas intestinalis
-​examination of multiple samples is recommended prior to
reporting that a patient is free of Giardia.
-​Small intestine
-​one of the most common intestinal parasites, especially
among children.
-​resistant to the routine chlorination procedures
-​Filtration as well as chemical treatment of this water
Chilomastix mesnili
-​Large intestine
-​Humans (RH)
-​Cyst stage ( infective stage)
-​Stiff, rotary, directional
-​small central or eccentric karyosome
-​5-20, 5-10 (troph)
-​Pear-shaped-assymetrical-spiral groove
-​Single nucleus (troph)

2. -​
-​Humans (RH)
-​Mature quadrinucleated cyst (infective stage)
-​fecal -oral, person to person, sexual intercourse
-​10-20, 5-15 (troph)
-​8-12, 7-10 (cyst)
-​Two nuclei, large central karyosome
-​Tear-drop or pear-shaped
Ecto refractive - endo finely
-​8 flagella troph (4 pairs)
cyst
-​Mature cyst, four
-​Central karyosomes
-​Oval shaped
-​Shepherds crook (cytosome)
-​4 flagella
Cyst
-​5-10, 4-6
-​Single nucleus
-​One, with large central karyosome
-​Lemon-shaped-nipple like protuberance
The single nucleus, which is usually not visible in unstained
preparations, is located in the anterior end of the trophozoite.

Dientamoeba fragilis
-​mucosal crypts of the Appendix,cecum,colon
-​humans,macaques ,gorillas,swine (RH)
-​Trophozoite only
-​7-12
-​Ameboid-spoon-shaped
-​One to two rosette shaped nuclei
-​sluggish-non progressive
-​No flagella
-​transmitted via the eggs of helminth parasites such as
Enterobius vermicularis and Ascaris lumbricoides
-​
The typical D. fragilis trophozoite is irregular and roundish in shape
The trophozoite’s progressive motility, seen primarily in freshly passed
stool samples, is accomplished by broad hyaline pseudopodia that
possess characteristic serrated margins.
The stain of choice for distinguishing the individual chromatin granules
is iron hematoxylin. Although most trophozoites are
Trichomonas hominis
-​Cecal-large intestine
-​Trophozoite only
-​7-13,7-10
-​Pyriform shaped
-​single nucleus
-​raid , jerky motion
-​A cone-shaped cytostome cleft
-​5 ANTERIOR FLAGELLA
Contaminated milk is suspected of being one of the sources of
infection.

3. binucleated—hence, the name Dientamoeba—mononucleated forms
may also exist.
The treatment of choice for such infections is iodoquinol.

Enteromonas hominis
-​Cecum-large intestine
-​Humans,monkeys (RH)
-​4-10,3-6 (troph)
-​Pear shaped
-​Jerky
-​4 flagella
-​One with central karyosome
Cyst
-​Mimic E. nana
-​6-10,4-6
-​INFECTIVE STAGE
-​Oval shaped
-​2-4 nuclei located opposite ends

The single nucleus, visible only in stained preparations,



Retortamonas intestinalis
-​lumen-large intestine
-​humans,apes,monkeys(RH)
-​4-9,3-4
-​Elongated,pyriform
-​Two minute blepharoplast
-​Cleft like cytosome
-​Jerky forward
-​2 flagella
Cyst
-​Infective stage
-​Two fibrils cytoplasm
-​ovoid

Trichomonas tenax - Extraintestinal Species
-​Human mouth , tartar around the teeth
-​Trophozoite only
-​Small and slender, pyriform
-​Single nucleus
-​Jerky rapid
-​5 flagella
-​Mouth scraping specimen of choice

Trichomonas vaginalis - Extraintestinal Species
-​Pathogenic
-​Trophozoite only
-​Sexual intercourse
-​7-23,5-15
-​Pyriform or pear shaped
-​Rapid, jerky, twitching, corkscrew
-​5 flagella
prominent structure found in T. vaginalis trophozoites=Axostyle

4. On a rare occasion, T.tenax has been known to invade the respiratory
tract, but this appears to have mainly occurred in patients with
underlying thoracic or lung abscesses of pleural exudates.