Transcript INTESTINAL AND LUMINAL PROTOZOA - Al al

BLOOD AND TISSUE
PROTOZOA
MASTIGOPHORA
Blood Flagellates
TRYPANOSOMA
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Classification
• Trypanosomes are a group of
kinetoplastid protozoa distinguished by
having only a single flagellum.
• All members are exclusively parasitic,
found primarily in insects.
• A few genera have life-cycles involving a
secondary host, which may be a
vertebrate or a plant.
• These include several species that cause
major diseases in humans.
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History
The condition has been present in Africa
since at least the 14th century, and
probably for thousands of years before
that. The causative agent and vector were
not identified until 1902–1903 by Sir David
Bruce ,and the differentiation between
protozoa was not made until 1910. The
first effective treatment ,Atoxyl ,an arsenic
based drug developed by Paul Ehrlich and
Kiyoshi Shiga was introduced in 1910 but
blindness was a serious side effect.
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Trypanosoma brucei is a
parasitic protist species that
causes African trypanosomiasis
(or sleeping sickness) in humans
and nagana in animals in Africa.
There are 3 sub-species of T.
brucei; T. b. brucei, T. b.
gambiense and T. b. rhodesiense.
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These obligate parasites have two hosts - an
insect vector and mammalian host.
Because of the large difference between
these hosts the trypanosome undergoes
complex changes during its life cycle to
facilitate its survival in the insect gut and
the mammalian bloodstream. It also
features a unique and notable variable
surface glycoprotein (VSG) coat in order to
avoid the host's immune system
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The insect vector for T. brucei is the tsetse
fly (Glossina spp ). The parasite lives in
the midgut of the fly (procyclic form),
until it migrates to the salivary glands for
injection to the mammalian host on
binding. The parasite lives within the
bloodstream (bloodstream form) where it
can reinfect the fly vector after biting.
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Later during a T. brucei infection
the parasite may migrate to
other areas of the host. A T.
brucei infection may be
transferred human to human
via bodily fluid exchange,
primarily blood transfer.
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There are three different sub-species of T.
brucei, which cause different variants of
trypanosomiasis.
T. brucei gambiense - Causes slow onset chronic
trypanosomiasis in humans. Most common in
central and western Africa, where humans are
thought to be the primary reservoir
T. brucei rhodesiense - Causes fast onset acute
trypanosomiasis in humans. Most common in
southern and eastern Africa, where game
animals and livestock are thought to be the
primary reservoir
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T. brucei brucei - Causes animal African
trypanosomiasis, along with several other
species of trypanosoma. T. b. brucei is not
human infective due to its susceptibility to
lysis by human apolipoprotein L1
However, as it shares many features with T.
b. gambiense and T. b. rhodesiense (such
as antigenic variation) it is used as a
model for human infections in laboratory
and animal studies.
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Geographic distribution and
epidemiology
The disease is found in two forms, depending on the
parasite, either Trypanosoma brucei gambiense or
Trypanosoma brucei rhodesiense. T. b. gambiense is
found in central and western Africa; it causes a
chronic condition that can extend in a passive phase
for months or years before symptoms emerge.
T. b. rhodesiense, is the acute form of the disease but
has a much more limited range. It is found in
southern and eastern Africa; its infection emerges in a
few weeks and is more virulent and faster developing.
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The disease has been recorded as occurring in 36
countries, all in sub-Saharan Africa. It is
endemic in southeast Uganda and western
Kenya and kills more than 40,000 Africans a
year.
Humans are the main reservoir for Trypanosoma
brucei gambiense, but this species can also be
found in pigs and other animals. Wild game
animals and cattle are the main reservoir of T.
b. rhodesiense.
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African Trypanosomes.
African trypanosome – protozoan - causes
fatal neurologic disease – trypanosomiasis.
Trypanosoma brucei rhodesiense &
Trypanosoma brucei gambiense – Human
sleeping sickness.
Trypanosoma brucei nagana (N’gana) in
cattle.
Geographic distribution limited to subSaharan Africa by tsetse fly vector.
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Life cycle
The tsetse fly is large, brown and stealthy. While taking blood
from a mammalian host, an infected tsetse fly (genus
Glossina) injects metacyclic trypomastigotes into skin tissue.
The parasites enter the lymphatic system and pass into the
bloodstream (1). Inside the host, they transform into
bloodstream trypomastigotes (2), are carried to other sites
throughout the body, reach other blood fluids (e.g., lymph,
spinal fluid), and continue the replication by binary fission (3).
The entire life cycle of African Trypanosomes is represented
by extracellular stages. A tsetse fly becomes infected with
bloodstream trypomastigotes when taking a blood meal on an
infected mammalian host (4,5). In the fly's midgut, the
parasites transform into procyclic trypomastigotes, multiply by
binary fission (6), leave the midgut, and transform into
epimastigotes (7). The epimastigotes reach the fly's salivary
glands and continue multiplication by binary fission (8). The
cycle in the fly takes approximately 3 weeks to progress.
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Trypanosoma b. gambiense &T. b. rhodesiense
Life cycle
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Trypanosoma b.gambiense
&T.b.rhodesiense
Thin blood film containing
Trypomastigote stage:
• “S” shape
• Have small Kinetoplast near
blunted, posterior end .
• Conspicuous undulating membrane
with flagellum.
• One nucleus
• This is Dividing stage in definitive
host.
-----------------------------------------------• Infective stage: Trypomastigote
Disease: African trypanosomiasis or
sleeping sickness.
Vector: Glossina spp. ( Tsetse fly)
Drug of choice: Melarsoprol,
Suramin, Pentamidine,
Eflornithin.
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Trypanosoma cruzi
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Trypanosoma cruzi
Thin blood film containing Trypomastigote
stage:
Size range: 12-35 um long by 2-4 um wide.
• Shape: “C” or ”U” in stained blood films.
• Appearance: Long and slender
• Nucleus: One, located anterior to the
kinetoplast.
• Large Kinetoplast near the pointed posterior
end.
• Inconspicuous undulating membrane.
----------------------------------------------• Infective stage: Trypomastigote
• Vector: Triatoma spp. (Triatomid bug).
• Disease: American Trypanosomiasis
( chagas’ disease).
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• Trypanosoma cruzi is found in many countries in
the Americas, and is carried by insects to
animals and human in much the same way as its
African counterpart, although rather than the
tsetse fly, the vecters are bedbugs or "assassin"
flies .Trypanosoma cruzi was once thought to be
confined to Brazil and its surrounding area, but
recently cases of Chagas' disease have been
reported as far north as southern North America.
Immigrants from Central America and Mexico
are thought to be the cause of the disease's
migration northward .
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Trypanosoma cruzi life cycle
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Trypanosoma cruzi
Amastigotes in stained rat skeletal
muscle section:
Intracellular Amastigotes.
• Size range: 3 by 5 um.
• Shape: Round to oval
• Nucleus: One, usually off center.
• Other feature: Present Kinetoplast
This is the dividing stage in host.
----------------------------------------------• Infective stage: Trypomastigote
• Vector: Triatoma spp. ( Triatomid
bug).
• Disease: American Trypanosomiasis
(chagas’ disease).
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Trypanosoma cruzi
• Epimastigotes in culture:
Size range: 9-15 um
Appearance: Long and slightly
wider than promastigote form.
Nucleus: One, located in posterior
end.
Other features:
Kinetoplast located anterior to the
nucleus.
Undulating membrane: Extending to
the half of body length.
Free flagellum, extending from
anterior end.
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Clinical features
Symptoms begin with fever, headaches, and joint
pains
As the parasites enter through both the blood and
lymph systems, lymph nodes often swell up to
tremendous sizes
Winterbottom's sign, the telltale swollen lymph
nodes along the back of the neck may appear
If untreated, the disease slowly overcomes the
defenses of the infected person, and symptoms
spread to include anemia, endocrine, cardiac,
and kidney diseases and disorders
The disease then enters a neurological phase
when the parasite passes through the bloodbrain barrier.
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• The symptoms of the second phase give
the disease its name; besides confusion
and reduced coordination, the sleep cycle
is disturbed with bouts of fatigue
punctuated with manic periods
progressing to daytime slumber and
nighttime insomnia. Without treatment,
the disease is invariably fatal, with
progressive mental deterioration leading
to coma and death. Damage caused in the
neurological phase can be irreversible.
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In addition to the bite of the tsetse fly, the
disease is contractible in the following ways:
• Mother to child infection: the trypanosome can
cross the placenta and infect the fetus, causing
prenatal death.
• Laboratories: accidental infections, for example,
through the handling of blood of an infected
person and organ transplantation, although this
is uncommon.
• Blood transfusion
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Laboratory diagnosis
• The diagnosis rests upon demonstrating
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trypanosomes by microscopic examination of
chancre fluid, lymph node aspirates, blood, bone
marrow, or, in the late stages of infection,
cerebrospinal fluid.
A wet preparation should be examined for the
motile trypanosomes, and in addition a smear
should be fixed, stained with Giemsa (or Field),
and examined.
Concentration techniques can be used prior to
microscopic examination. For blood samples,
these include centrifugation followed by
examination of the buffy coat;
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Treatment
The current standard treatment for first stage
disease is:
• Intravenous pentamidine (for T.b. gambiense);
or
• Intravenous suramin (for T.b. rhodesiense)
The drug Eflornithine — previously used only as an
alternative treatment for sleeping sickness due
to its labour-intensive administration — was
found to be safe and effective as a first-line
treatment for the disease in 2008, according to
the Science and Development Network's SubSaharan Africa news updates.
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Leishmania
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• Leishmania are protozoa belonging to the order
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Kinetoplastida and the family Trypanosomatidae. They
are dimorphic parasites which present as two principal
morphological stages : the intracellular amastigote,
within the mononuclear phagocytic system of the
mammalian host, and the flagellated promastigote within
the intestinal tract of the insect vector and in culture
medium.
The amastigote stage is a round or oval body about 2-6
µm in diameter, containing a nucleus, a kinetoplast and
an internal flagellum seen clearly in electron
micrographs. The amastigotes multiply within the
parasitophorous vacuoles of macrophages.
The promastigote stage has a long and slender body
(about 15-30 µm by 2-3 µm), with a central nucleus, a
kinetoplast and a long free anterior flagellum.
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Leishmania sp.
• Leishmania tropica ( causes cutaneous
leishmaniasis ).
• Leishmania braziliensis ( causes mucocutaneous leishmaniasis).
• Leishmania donovani ( causes visceral
leishmaniasis)
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History
Leishmaniasis is a disease caused by protozoan
parasites that belong to the genus Leishmania
and is transmitted by the bite of certain species
of sand fly, including flies in the genus
Lutzomyia in the New World and Phlebotomus in
the Old World. The disease was named in 1901
after the Scottish pathologist William Boog
Leishman and Donovan in India. This disease is
also known as Leichmaniosis, Leishmaniose,
leishmaniose, and formerly, Orient Boils,
Baghdad Boil, kala azar, black fever, sandfly
disease, Dum-Dum fever or espundia.
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Life cycle
• Leishmaniasis is transmitted by the bite of female
phlebotomine sandflies. The sandflies inject the
infective stage, metacyclic promastigotes, during
blood meals. (1) Metacyclic that reach the puncture
wound are phagocytized by macrophages (2) and
transform into amastigotes. (3) Amastigotes multiply
in infected cells and affect different tissues,
depending in part on which Leishmania species is
involved. (4) These differing tissue specificities cause
the differing clinical manifestations of the various
forms of leishmaniasis. Sandflies become infected
during blood meals on an infected host when they
ingest macrophages infected with amastigotes. (5,6)
In the sandfly's midgut, the parasites differentiate into
promastigotes, (7) which multiply, differentiate into
metacyclic promastigotes and migrate to the
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proboscis (8).
Life cycle
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Leishmania sp.
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Leishmania tropica
Promastigotes
Promastigote in culture:
Size range: 9-15 um
Appearance: Long and slender.
Nucleus: One, located in or near
center.
Other features: Kinetoplast, located
in anterior end.
Single free flagellum, extending from
anterior end.
----------------------------------------------Infective stage: Promastigote
Diagnostic stage: Amastigote culture
from skin lesion.Immunological
techniques.
Disease: Cutaneous Leishmaniasis
(Also known as Old World
leishmaniasis, Oriental sore,and
or Delhi boil).
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Leishmania braziliensis
Promastigote
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Skin ulcer smear (Amastigotes):
Size range: 3 by 5 um.
Shape: Round to oval
Nucleus: One, usually off center.
Other feature: Present
Kinetoplast
----------------------------------------------Infective stage: Promastigote.
Diagnostic stage: Amastigotes in
stained Biopsy of the infected ulcer
Disease: Mucocutaneous leishmaniasis
Or espundia
Vector: Lutzomyia spp. (sandfly).
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Leishmania donovani
Amastigotes
Bone Marrow aspirate Showing
Amastigotes:
• Size range: 3 by 5 um.
• Shape: Round to oval
• Nucleus: One, usually off center.
• Other feature: Present Kinetoplast.
--------------------------------------------Infective stage: Promastigote.
Diagnostic stage: Amastigotes in stained
aspirate of the infected bone marrow.
Disease: Visceral leishmaniasis
Or kala azar
Vector: Phlebotomus spp. (sandfly).
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Signs and symptoms
The symptoms of leishmaniasis are skin
sores which erupt weeks to months after
the person affected is bitten by sand flies.
Other consequences, which can become
manifest anywhere from a few months to
years after infection, include fever,
damage to the spleen and liver, and
anaemia.
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• Visceral leishmaniasis - the most serious form and
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potentially fatal if untreated.
Cutaneous leishmaniasis - the most common form
which causes a sore at the bite site, which heal in a
few months to a year, leaving an unpleasant looking
scar. This form can progress to any of the other three
forms.
Diffuse cutaneous leishmaniasis - this form produces
widespread skin lesions which resemble leprosy and
is particularly difficult to treat.
Mucocutaneous leishmaniasis - commences with
skin ulcers which spread causing tissue damage to
(particularly) nose and mouth.
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Cutaneous leishmaniasis ulcer on left forearm
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Diagnosis
Leishmaniasis is diagnosed in the haematology
laboratory by direct visualization of the amastigotes
(Leishman-Donovan bodies). Buffy-coat
preparations of peripheral blood or aspirates from
marrow, spleen, lymph nodes or skin lesions should
be spread on a slide to make a thin smear, and stained
with leishman's or Giemsa's stain (pH 7.2) for 20
minutes. Amastigotes are seen with monocytes or,
less commonly in neutrophil in peripheral blood and
in macrophages in aspirates. They are small, round
bodies 2-4um in diameter with indistinct cytoplasm, a
nucleus and a small rod shaped kinetoplast.
Occasionally amastigotes may be seen lying free
between cells.
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Treatment
There are two common therapies containing
antimony (known as pentavalent antimonials),
meglumine antimoniate (Glucantime) and
sodium stibogluconate (Pentostam). It is not
completely understood how these drugs act
against the parasite; they may disrupt its
energy production.
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