Unit 2: Protozoa
14
Lecture 6 – Subphylum Mastigophora
Characterized by having flagellae in its trophozoite stage,
connected to an axonemes and kinetoplast (like brain in
human). The microorganism flagellum, an axonemes and
kinetoplast performing the neuromotor apparatus. The last
one kinetoplast is energizing & the first one is motor part.
The kinetoplast formed from the blepharoplast &
parabasal body, The blepharoplast either connected
together or scattered.
Some of flagellate is free living, and other are parasitizing
arthropods, plants, animal & man.
The flagellates which parasites human are:
1) Flagellate of digestive tract & urogenital system.
2) Flagellate of blood (haemoflagellate) & tissues.
The flagellate of digestive tract & urogenital systems:-
Live in the lumen.
Not tissues invader, but the (Giardia lamblia) &
(Trichomonas vaginalis) may evoke symptoms.
The flagellate of digestive tract &
urogenital systems:-
1)
Giardia lamblia
It also called Giardia intestinalis, a parasite of small
intestine, cosmopolitan, common in warm & temperate
climates.
Morphology
Both trophozoite & cyst stages are considered as a
diagnostic stages, while the infection stage is only the
cyst stage, because the trophozoite stage when ingested it
will killed by the gastric acid.
The trophozoite stage
The shape of trophozoite is pear shape, broad rounded
anteriorly, tapered to point posteriorly. Anteriorly
there is a sucking disk & side bilaterally, so the
trophozoite is described by bilaterally symmetrical. In
middle of sucking disk situated 2 nuclei in stage of
trophozoite. In middle of trophozoite from anterior to
posterior is complex system of an axoneme.
There is transverse curve broad, called the parabasal
body. The trophozoite length (9-
-15
-
The profile also called side view, show outside
curvature, anterior concavity and posterior curvature,
flagellae are distributed on many sites.
Giardia lamblia trophozoite stage: (1), ventral view; (2),
lateral view
The cyst stage
Thick hyaline membrane around avoidal shape cyst stage.
When parasite facing un suitable or unconventional
condition, it convert to cyst stage by retracting the
flagellae back on axoneme to form the parallel curved
fibrils, and each of 2 nuclei divided into 2 to form 4 nuclei
in cyst stage.
The cyst length (8-
-
The Life cycle
Usually infection arise from ingestion of contaminated
food or water, and after passing the stomach the
Exystation occur in small intestine and immediately 2
trophozoites arises from the cyst. Then the trophozoite
starting the multiplication and forming the colonies in
small intestine. When trophozoite goes down the
Encystation occur. So the summary of life cycle is:
1) Exystation
2) Multiplication
3) Encystation
Unit 2: Protozoa
15
Pathogenesis & Symptoms
Infection with Giardia called Giardiasis. The majority of
Giardiasis is asymptomatic, but some of them presented
with symptoms like fatty diarrhea, weight loss (due to
malabsorption), epigastric pain, abdominal cramps.
Giardia lamblia is not tissue invader, but by (E.M) had
shown that the trophozoite attached tightly to mucosa, so
covering and damaging to mucosa, so causing functional
derangement & reducing brush border enzymes. Diarrhea
& malabsorption may be caused by this mechanism.
Course of giardia infection in humans
Clinical manifestations in Giardiasis
Acute
Chronic
Diarrhea ( foul smelling
)
Greasy stools
Weight loss
Anorexia , vomiting
Headache
Low grade fever
Chills
Mucous in stools
Abdominal cramps
Recurrent diarrhea
Periodic constipation
Abdominal distension
Nausea
Substernal burning
Urticaria
Erythema nodosum
Malabsorption
syndrome
Fatigue
Diagnosis:
Recovering of cyst stage & trophozoite stage by:
General stool examination, or by
Concentration method
Treatment:
By Metronidazole, 250 mg/ 5-10 days.
Epidemiology
Infection occurs by viable cyst from human sources-
human faeces.
Giardiasis most common in warm moist climates. Type of
living is effecting its transmission, large families, and
children asylum.
Heavily infected groups, the infection start with infants &
goes to juveniles stage, and then go down to adult stage.
This occurs mainly in travelers or resort population.
Control
1) Treatment of patient.
2) Ordinary or chlorination water be found not enough to kill
cyst stage in endemic or hyperendemic, there for boiling
of water is important to kill the cyst stage.
3) Improving the habits of the person & community.
2) Chilomastix mesnili
Cosmopolitan, more prevalent in warm climates.
Morphology
It has 2 stages in its life cycle, trophozoite & cyst stage.
The trophozoite stage
Pear in shape, anteriorly broad and rounded, has one
nucleus, beside the nucleus is a groove called cytostome,
which represent the mouth of it. Regarding the flagella,
most of them directed forward & one directed backward
toward the cytostome , It has spiral groove which pass in
spiral path & its function is the movement. The
multiplication is by longitudinal binary division. The
movement is a jerky movement with spiraled path.
The cyst stage
Smaller than trophozoite, lemon shaped, (7-
length & (4.5-
Unit 2: Protozoa
16
hyaline wall, there is anterior projection like a lemon. There
is a groove in cyst stage which represents the cytostome.
Regarding the flagella, it retracted backward into the
organism and appears as a fibril inside the organism as well
as inside the cytoplasm. Also it has one nucleus.
3) Trichomonas
Pear shaped, have a single nucleus, infront the nucleus
situated the blepharoplast.
Most of flagella directed forward & one of them directed
backward, and this backward directed flagella forming
undulating membrane, which is a fold of membrane of
organism.
It characterized by presence of axostyle, which is semi
rigid translucent supported structure.
There are 3 species adapted to the human host, and only
these species contain axostyle.
There is a cytostome on the lateral side.
Line drawing of the three Trichomonads that parasitized
human beings. (1) Trichomonas vaginalis; (2)
Trichomonas tenax; (3) Trichomonas hominis.
Trichomonas hominis
shaped, marginal flagellum which forms undulating
membrane, the undulating membrane extend short
distance behind the posterior end. The axostyle is also
protruding behind the posterior extremity. It is non-
pathogen, although it feeds on bacteria, mucous & RBCs
if present. It live in large intestine.
Trichomonas buccalis
It also called Trichomonas tenax, smaller than T.
hominis, has small undulating membrane. It is non-
pathogenic, but it is found in diseased gum, tartar around
the teeth and carious teeth, so it is opportunistic parasite.
It is existence indicates poor oral hygiene.
Trichomonas vaginalis
It present in male & female, the diseased caused is called
Trichomoniasis or Trichomonas vaginitis.
Cosmopolitan parasite of man, size frequently larger than
other Tricomonas, it reach up to 27 mm in size. Maginal
flagellum does not extend byyond the undulating
membrane.
It inhibits vagina in female, and urethra + prostate in
male. It transmitted by sexual intercourse, although may
transmitted by other way (fomits). This parsite can
survive for few hours on dry fomites & longer if moist.
In male, is often asymptomatic, although it may cause
urethritis, also called non-specific urethritis.
In female, again may be asymptomatic or may produce
vaginitis complicated by bacteria, fungus & spirochete.
The chief complaints are dysuria, leukorrhea (white
discharge), urticaria, and acute vulvitis. The symptoms
vary from mild to sever, but the disease is annoying rather
than disabling.
Phagocytosis & killing of Gono cocci by Trichomonas
vaginalis have been reported.
Diagnosis: Made in male by recovery of the organism in
urine, prostatic or urethral discharges, by add normal
saline to dry smear, we show T. vaginalis. In female, by
recovery urine, vaginal discharge or vaginal swabs by also
adding normal saline to wet smear.
Treatment: Metronidazol 250 mg TID (three times per
day) for 7 days. In resistant cases, vaginal suppositories of
Metronidazol are useful.
Diantamoeba fragilis
Causes disease called Diantamoebiasis. It was considered
as an amoeba until 1974, when Honigberg put it in Order
– Trichomonadida & Species-Trichmonas
Only trophozoite stage is known, (5-
In stained preparation, 2 nuclei are evident, but with no
chromatin granules at nuclear membrane. The karyosome
being large central & appear to consist from 4 granules.
The Diantamoeba frgilis colonizes ceacum & upper colon
& does not invade the mucosa. It may cause anorexia,
abdominal discomfort & diarrhea and can be treated with
Tetracycline or Metronidazole.
Diantamoeba frgilis
trophozoite