I. Lumen or Atrial Flagellates –
usually found or inhabit the visceral organ; non–tissue invaders
A. Buccal
cavity – Trichomonas tenax
B. Genito–urinary
tract – Trichomonas vaginalis
C. GIT
– Giardia lamblia, Trichomonas hominis, Chilomastix mesnili
II. Blood or Tissue Flagellates –
under 2 groups:
A. Leishmania
Group
L. tropica
L.
braziliensis
L. donovani
B. Trypanosome
Group
T. gambiense
T. rhodesiense
T. cruzi
****** THE LUMEN OR ATRIAL FLAGELLATES ******
****** GIARDIA LAMBLIA ******
– the only pathogenic intestinal
flagellate
Disease: Giardiasis, flagellate diarrhea
Morphology:
1.
Trophozoite
a. Symmetrically
pear–shaped, rounded anteriorly and pointed posteriorly, convex dorsally and
flat ventrally and is provided with a sucking disc which is used for
attachment; a pair of nuclei, one on each side of the midline about ¼ of the
body length from the anterior end, are ovoidal and contain central karyosome
consisting of a single dense chromatin mass or a large number and relatively
discrete granules, no chromatin lines on the delicate membrane; 4 pairs of
flagella arise from the superficial organelles on the central side of the body
(lateral pair of crossed flagella, central pair of flagella and lateral pair of
uncrossed flagella); a sausage–shaped parabasal body.
b. In
fresh specimen, it has a jerky, falling leaf motility.
c. Divides
by longitudinal binary fission.
d. Characteristic
location is in crypts at the duodenal level of the small intestine.
2.
Cysts
a. Ovoidal
objects with finely granular cytoplasm clearly separated from the thin cyst
wall; there are 2–4 nuclei pushed to one side of the cyst; remains of the axonemes
are seen as parallel bodies; cytoplasm often retracts from a portion of cell
wall.
Life cycle
****** CHILOMASTIX MESNILI ******
– a normal habitat of the cecal region
of the large intestine, where the trophozoite
live on mesenteric bacteria in the
lumen of the glands and multiply by binary fission.
– a harmless commensal and is not
responsible for symptoms, therefore no treatment indicated. Better sanitation
and personal hygiene will reduce the incidence of the infection.
Morphology:
1. Trophozoite
a. 6–20u
x 3–10u
b. Assymetrically
pear–shaped as a result of a spiral groove extending through the middle half of
the body.
c. Spherical
nucleus is situated medially bear the anterior pole; it has a small distinct;
central karyosome, a few achromatic fibrils extending to the nuclear membrane
and chromatin plaques lining the membrane; a well – defined cytostome, seen on
one side of the nucleus. Is rounded posteriorly and anteriorly and has a median
constriction; just anterior to the nucleus, there is a complex of 5 minute
blepharoblast which give rise to three free anterior flagella, a delicate
flagellum lying within the cytostome and two axonemic fibrils; cytoplasm is
delicately granular and contains numerous food vacuoles.
2. Cysts
a. Characteristically
pear or lemon–shaped rather than broadly rounded at one end, somewhat bluntly
conical at the other end. They are colorless with a densely granular cytoplasm
and a thick tough wall.
b. It
contains a single large vesicular nucleus and a cytostome which is almost as
long as the encysted organism.
****** THE TRICHOMONAS GROUP ******
General characteristics
1. It
only has a trophozoite, no cystic stage.
2. Pyriform
or filiform in shape.
3. With
one nucleus on the anterior portion.
4. Anterior
to the nucleus is a single blepharoblast from which arises 4 anterior flagella
and a 5th one runs along the undulating membrane.
5. An
axostyle for anchorage.
6. Highly
vacuolated cytoplasm
7. Fast
jerky tumbling movement
8. Multiply
by longitudinal binary fission
·
Species is determined by source
of specimen
****** TRICHOMONAS TENAX ******
Morphology:
1. Size:
5–12u
2. Shape:
Four free
flagella of equal length; a single blepharoblast; a parabasal apparatus; a
thick axostyle; an inconspicuous cytostome; undulating membrane is 2/3 of body length.
Mode of transmission
Kissing, common use of contaminated
dishes and drinking glasses
Habitat
Buccal cavity, tartar around the teeth
Clinical manifestations
Trichomonas tenax is a harmless
commensal of the human mouth, living in the tartar around the teeth, in
cavities of carious teeth, in necrotic mucosal cells in gingival margins of the
gums or associated with oral spirochetes in Vincent’s angina and in pus pocket
in tonsillar follicles. They are quite resistant to changes in temperature and
will survive for several hours in drinking water but do not survive through
intestinal tract and cannot permanently establish in the vagina.
******
TRICHOMONAS HOMINIS ******
Morphology:
1. Size: 5
– 12u
2. Shape:
A single
nucleus, longest undulating membrane with free trailing posterior end, has 5th
flagellum, semi–rigid axostyle, a highly conspicuous cytostome, no parabasal
body.
Habitat
Cecal area of the large intestine
****** TRICHOMONAS VAGINALIS ******
– largest and only pathogenic
trichomonas thus considered as a STD.
Morphology:
1. Size:
7 – 23u
2. Shape:
Has a shorter
undulating membrane, axostyle is split into several fibrils, nuclear chromatin
unformally distributed and cytoplasm contains a remarkably large amount of
siderophil granules which are numerous around the delicate costa and the
axostyle, cytostome is very inconspicuous.
Habitat
Human vagina and prostate gland
Mode of transmission
During sexual intercourse, ping pong
infection, direct contact with infected fomite, toilet seats, can also be transmitted
congenitally but rare.
****** BLOOD
AND TISSUE FLAGELLATES ******
Characteristics in general
1. Have
a single flagellum, a nucleus and a kinetoplast from which the flagellum
arises.
2. The
blepharoblast and parabasal body are connected by one or more possibly more
delicate fibrils.
3. The
inner portion of the flagellum extending from the blepharoblast to the surface
of the body is the axial filament or the axoneme.
4. They
are divided into six genera
Leptomonas
Crithidia
Herpetomonas
Leishmania
Phytomonas
Trypanosoma
Four stages of morphological
development
1. Leishmania
(Amastigote) – oval in shape with nucleus, a kinetoplast which consists of a
blepharoblast giving rise to a rhizoplast or axoneme and a parabasal body.
2. Leptomonas
(Promastigote) – broadly spindle–shaped with an oval nucleus, a kinetoplast
which gives rise to an axoneme with a long flagellum.
3. Crithidia
(Epimastigote) – spindle in shape and more slender, with a kinetoplast directly
anterior to the nucleus and is provided with a short undulating membrane
4. Trypanosome
(Trypomastigote) – more slender and spindle–shaped with the kinetoplast
situated way below the nucleus from which arises a very long undulating
membrane, the cytoplasm contains volutin granules.
****** GENUS LEISHMANIA ******
There are only two stages
present:
1. Leishmania
stage – pathogenic stage to man; infective stage to invertebrate host.
2. Leptomonad
stage – infective stage to man.
****** LEISHMANIA DONOVANI ******
Disease: Visceral leismaniasis or Kala–azar
Death
Fever
Dum–dum
fever
Tropical
splenomegaly ponos
Morphological stages:
1. Leishmania
– intracellular in macrophages; predominantly in liver, spleen, bone marrow
& lymph nodes.
2. Leptomonas
– in mid–gut and later in proboscis of sandfly (Phlebotomus); transfer stage to
man.
Habitat
Intracellular; reticuloendothelial
cells
Mode of transmission
Skin bite by anthropod vector called
sandfly or Phlebotomus papatasi
Ingestion of food or drink
contaminated with L. dononvani
Diagnosis
1. Demonstration
of Donovan bodies in peripheral blood smear, lymph node aspirate, splenic
aspirate, sternal bone marrow puncture.
2. Non–specific
test like:
a. Aldehyde
test of Napier
b. Precipitin
test of Sia
c. Antimony
test of Chopra
d. Montenegro
Test (Leishmanin Test)
3. NNN
(Nicole, Novy, McNeal) culture
Life cycle
****** LEISHMANIA TROPICA ******
Disease: Cutaneous leishmaniasis
Oriental
sore
Delhi
boil
Aleppo
button
Jericho
boil
Habitat
In man, L. tropica is a parasite of
the skin being found in the endothelial cells of the capillaries of the
injected areas, in nearby lymph nodes and within large monocytes and PMN, not
found in the peripheral blood and do not invade the viscera.
Two types of lesions are
produced
1. Dry
type – urban type; has a chronic course with late ulceration due to prolonged
incubation period. Low virulence to mice. Numerous leishmaniasis in lesions.
2. Moist
type – rural type; has an acute course with early ulceration and a short incubation
period. High virulence to mice. Few organisms in lesions.
****** LEISMANIA BRAZILIENSIS ******
Disease: American leishmaniasis
Bubas
brazilianas
Naso–pharyngeal
leishmaniasis
Insect vector: Phlebotomus intermedius
Habitat
L. braziliensis lives in tissue cells,
endothelial cells and large mononuclears in the involved portion of the skin
and mucous membranes of the nose, mouth and pharynx. Not seen in circulation
and in the viscera.
****** GENUS TRYPANOSOME ******
****** TRYPANOSOMA GAMBIENSE ******
Disease: Gambian trypanosomiasis
West
African sleeping sickness
Developmental stages:
1. Crithidia
– in salivary glands of tsetse fly
2. Metacyclic
trypanosome – developed from the crithidial form in 2–5 days after the slender
form reach the salivary glands, where upon the fly becomes infective to man
(infective stage)
3. Trypanosome
– in man, after bite of insect, they are seen in bloodstream, then in lymph
nodes, later the CNS (pathogenic stage)
Insect vector: Glossina (tsetse fly), male and female
G.
palpis, G. tachinoides, G. morsitans
Mode of transmission:
Anterior station – the parasite is in
the saliva of the insect host and is inoculated into the host during feeding.
****** TRYPANOSOMA RHODESIENSE ******
Disease: Rhodesian trypanosomiasis
East–African
sleeping sickness
Insect vector: Male and female glossina
(tsetse fly)
G.
morsitans, G. swynnertoni, G.pallidipes, G. palpalis
****** TRYPANOSOMA CRUZI *******
Disease: Chaga’s disease
South
American trypanosomiasis
Development stages:
1. Leishmania
– intracellular in macrophage especially in the skin, lymph nodes, liver and
spleen; also in myocardium, brain & endocrine glands.
2. Leptomonas
– transitional stage only
3. Crithidia
– midgut of triatomid bug (kissing bug)
4. Trypanosome
– in feces of triatomid bug, transfer stage to man; present in blood stream
only during acute attacks.
Insect vector: Triatomid bug –
Panstongylus egistus
Triatoma
infestans & Rhodnius prolixus
Mode of transmission:
Posterior station – infective stage
is transmitted when the vector bites and defecates on the wound
Diagnosis:
Complement Fixation Test (Machado–Guerreiro
Test)
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