Transcript Protozoa - Dr Magrann

Pathologic Protozoa
CHARACTERISTICS OF
PROTOZOA
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1. Unicellular
2. Chemoheterotrophs (get their
energy by breaking down organic
matter).
3. Most ingest their food; thus, they
have special structures for this.
CHARACTERISTICS OF
PROTOZOA
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4. The vegetative form is the TROPHOZOA
(tropho = movement; zoite = animal; they move
like an animal). Trophozoa have special
organelles for movement.
5. Capable of reproduction
A. Asexual: fission, budding, or schizogony
(produces a large number of trophozoites)
B. Sexual: conjugation
CHARACTERISTICS OF
PROTOZOA
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6. Some produce cysts.
These are not tissue cysts like a human gets
under their skin; protozoa cysts are cellular.
They have a thick cell wall that allows for
survival in harsh environments better than
the trophozoite form.
PROTOZOA CYSTS
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Cysts are not as resistant as a bacterial
endospore.
You can kill cysts by boiling them.
They can live in the soil or water for months.
A cyst is no motile, so it is not trophozoic.
A cyst does not procure its nutrients or ingest
food, but it can absorb nutrients.
It has no organelles to ingest food.
Classification
Domain: Eukaryotes
Kingdom: Protista
Classification
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Traditional classification of protozoa phylae
was based on mode of locomotion.
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MASTIGOPHORA (flagella)
CILIOPHORA (cilia)
SARCODINA (amoebas)
SPOROZOA (spore-formers)
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Apicomplexa (attachment organ)
Modern Classification
Modern classification of protozoa is based on how they
evolved and how closely related they are (phylogenetic
taxonomy), as determined by their ribosomal RNA. The
human pathogenic protozoa may be classified as follows:
 METAMONADA (multiple flagella with feeding
grooves)
 AMOEBOZOA (amoebas)
 APICOMPLEXA (attachment organ)
 CILIOPHORA (cilia)
 EUGLENOZOA (flagella and disc-shaped cristae in
mitochondria)
METAMONADA
Characteristics: no mitochondria, multiple flagella
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Organisms
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Giardia lamblia
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Disease: Ghiardosis
Trichomonas vaginalis
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Disease: Trichomoniasis
AMOEBOZOA (amoebas)
Characteristics: move by pseudopods to get food;
consume red blood cells. In a fresh diarrheal
specimen, you can see RBCs in the cytoplasm.
 Organisms
Entamoeba histolytica
Naegleria fowleri
Disease: AMEBIASIS
APICOMPLEXA
Characteristics: has an organelle called an apical
complex which allows the organism to attach to the
host.
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Organisms
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Plasmodium
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Toxoplasma
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Disease: Malaria
Disease: toxoplasmosis
Cryptosporidium
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Disease: Cryptosporidiosis
CILIOPHORA
CILIOPHORA: has cilia
 Organism
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Balantidium coli
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Disease: Balantidiosis
EUGLENOZOA
EUGLENOZOA (older classification = Mastigophora):
has flagella and its mitochondria have disc-shaped cristae
 Organisms
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Trypanosoma
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Disease: Trypanosomiasis
Leishmania donovani
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Disease: Leishmaniasis
TERMS
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Mastigote = flagella
Promastigote: has single flagella
Amastigote: has no flagella
Kinetoplast: round mass of circular DNA
Leishmania donovani
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Domain:
Kingdom:
Phylum:
Class:
Order:
Genus:
Species:
Eukaryota
Protista
Euglenozoa
Kinetoplastida
Trypanosomatida
Leishmania
donovani
Protozoa to study
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Giardia lambia (Giardosis)
Trichomonas vaginalis (Trichomoniasis)
Entamoeba histolytica (amoebiasis)
Naegleria fowleri (amoebiasis)
Plasmodium vivax (malaria; most common)
Plasmodium falciparum (malaria; most deadly)
Cryptosporidium (Cryptosporidiosis)
Toxplasmosis gondii (toxoplasmosis)
Balantidium coli (Balantidiosis)
Trypanosoma brucei gambiense (African Trypanosomiasis “African Sleeping Sickness”)
Trypanosoma brucei rhodesiense (African Trypanosomiasis “African Sleeping Sickness”)
Trypanosoma cruzi (American Trypanosomiasis “Chaga’s Disease”)
Leishmania donovani (Leishmaniasis)
TERMS: Host Types
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The definitive host is the one in which the
parasite completes its sexual life cycle.
For instance, in Plasmodium, the definitive
host is the tropical mosquito anopheles.
The intermediate host is the human.
TERMS: Host Types
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Its sexual life cycle also starts in the human,
so that can be confusing.
What happens is the sporozoite form enters
the bloodstream when the mosquito bites the
human.
First it begins its asexual reproduction, but if
two mosquitoes inject one male and one
female gametocyte into the human, there can
be a sexual life cycle in the human as well.
TERMS
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Trophozoite: any stage in a protozoa’s life
cycle which can ingest food. In practice it
refers to the motile form (pseudopods, cilia,
flagella).
Cyst: Non-motile form, protected by a
membrane. *infective stage*
Excystation: process of emergence of the
trophozoite from the cyst.
Pseudopod: “false foot” temporary
cytoplasmic process at the surface of the
trophozoite.
ARCHAEZOA DISEASES
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Ghiardosis
Trichomoniasis
Ghiardosis
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Organism: Ghiardia lamblia
Cysts are resistant forms and are responsible
for transmission of giardiasis.
Both cysts and trophozoites can be found in
the feces.
Infection occurs by the ingestion of cysts in
contaminated water, food (includes
undercooked meat), or by the fecal-oral
route.
Ghiardia lamblia
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In the small intestine, excystation releases
trophozoites (each cyst produces two
trophozoites).
Trophozoites multiply, remaining in the lumen
where they can be free or attached to the
mucosa by a ventral sucking disk.
Encystation occurs as the parasites transit
toward the colon. The cyst is the stage found
most commonly in nondiarrheal feces.
Because the cysts are infectious when passed
in the stool or shortly afterward, person-toperson transmission is possible.
Ghiardia lamblia
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Trophozoite form: piroform (pear or teardrop
shape), looks like a happy face.
Discovered by Anton Van Leuwenhoek when he
examined his own feces when he had this infection.
You won’t see the flagella in lab because you need a
special stain for that.
Cyst form: oval shaped. Nuclei looks like two eyes.
Geographic Distribution:
Worldwide, more prevalent in warm climates, and in
children.
Life Cycle of Giardia lamblia
Ghiardia lamblia
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Trophozoite
Ghiardia lamblia
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Trophozoites
Ghiardia lamblia
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Trophozoites
Giardia lamblia trophozoite
Ghiardia lamblia
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Cysts
Trichomoniasis
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Organism:Trichomonas vaginalis
Trichomonas vaginalis resides in the female lower
genital tract and the male urethra and prostate.
The parasite is a trophozoite only; it does not have a
cyst form, and does not survive well in the external
environment.
Trichomonas vaginalis is transmitted among humans,
its only known host, primarily by sexual intercourse.
Trichomonas
vaginalis
Trichomonas vaginalis
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Trophozoite
Undulating
membrane
Trichomonas vaginalis
Trichomonas vaginalis
RHIZOPODA DISEASE
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Amebiasis
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Entamoeba histolytica
Naegleria fowleri
Entamoeba histolytica
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Disease: Amebiasis
This is a global disease that any traveler can get. As soon
as you cross the border into Mexico, you are exposed to it.
Several protozoan species in the genus Entamoeba infect
humans, but not all of them are associated with disease.
Entamoeba histolytica is associated with intestinal and
extraintestinal infections.
The other species are important because they may be
confused with E. histolytica in diagnostic investigations.
Geographic Distribution
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Worldwide, with higher incidence of
amebiasis in developing countries.
In industrialized countries, risk groups
include male homosexuals, travelers
and recent immigrants, and
institutionalized populations.
Entamoeba histolytica
Life Cycle
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Cysts and trophozoites are passed in feces.
Infection occurs by ingestion fecally contaminated
food (including undercooked meat), water, or hands.
Excystation occurs in the small intestine and
trophozoites are released, which migrate to the large
intestine.
The trophozoites multiply by binary fission and
produce cysts, and both stages are passed in the
feces.
Entamoeba histolytica
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Cysts can survive days to weeks in the
external environment and are
responsible for transmission.
Trophozoites passed in the stool are
rapidly destroyed once outside the
body, and if ingested would not survive
exposure to the gastric environment.
Entamoeba histolytica
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In many cases, the trophozoites remain
confined to the intestinal lumen (noninvasive
infection) of individuals who are
asymptomatic carriers, passing cysts in their
stool.
In some patients the trophozoites invade the
intestinal mucosa (intestinal disease), with
resultant pathologic manifestations.
E. histolytica can be observed with ingested
red blood cells.
Entamoeba histolytica
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Diverse mammals such as dogs and cats can
become infected but usually do not shed
cysts with their feces, thus do not contribute
significantly to transmission.
The active (trophozoite) stage exists only in
the host and in fresh feces; cysts survive
outside the host in water and soils and on
foods, especially under moist conditions on
the latter. It is NOT caused by undercooked
meat.
Entamoeba histolytica
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Entamoeba histolytica, as its name suggests,
can actually bore through the enteric walls
(histolysis = destroying tissue) and reach the
blood stream.
From there, it can reach different vital organs
of the human body, like the liver, lungs,
brain, eyes etc.
A typical effect is a liver abscess caused by
such migrating Entamoeba histolytica, which
can be fatal.
Entamoeba histolytica
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Entamoeba histolytica infection can lead
to amebiasis or amebic dysentery.
Symptoms include dysentery, diarrhea,
weight loss, fatigue, and abdominal
pain.
It can be diagnosed by stool samples.
Trophozoites should be seen in a fresh
fecal smear and cysts in an ordinary
stool sample.
Entamoeba histolytica
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Treatment
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Metronidazole
Diagnostic Features
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Ingested RBC
Bull’s eye Karyosome
Entamoeba histolytica
Trophozoites
Entamoeba histolytica
Trophozoites of Entamoeba histolytica with ingested erythrocytes
Entamoeba histolytica
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Cysts
Entamoeba
histolytica
Entamoeba
histolytica
Naegleria fowleri
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Disease: Amebiasis; meningitis form
 Acute, usually lethal, central nervous
system (CNS) disease.
 Three stages:
 Cysts
 Trophozoites
 Flagellated forms
Naegleria fowleri
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Naegleria fowleri is found in fresh
water, soil, heated swimming
pools, hydrotherapy pools,
aquariums, and sewage.
Trophozoites infect humans or
animals by entering the olfactory
epithelium and reaching the brain.
Naegleria fowleri
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Trophozoites
APICOMPLEXA
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All members of this phylum have an organelle called an apical complex
(located at the apex of the cell) which allows the organism to attach to
the host. This is a type of adhesion complex.
They all require a biological vector for transmission (to get into the
blood of the host).
They have at least two hosts: the animal vector and the human host.
That makes it a complex life cycle. Because it uses an animal host,
there is an animal reservoir.
Definitive Host: where the parasite completes its sexual life cycle.
Intermediate Host: where the parasite goes through its asexual
cycle.
APICOMPLEXA DISEASES
Malaria
 Toxoplasmosis
 Cryptosporidiosis
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Malaria
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Causal Agents:
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Plasmodium vivax (most common)
Plasmodium falciparum (most deadly)
P. ovale
P. malariae.
Plasmodium
Malaria
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200-300 million infections a year
2-3 million deaths a year
Affects mostly young people and
teenagers
2/3 of the cases are in Africa
Plasmodium
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The malaria parasite life cycle involves two hosts.
Sporogenic Stage
 During a blood meal, a malaria-infected female Anopheles mosquito
inoculates sporozoites into the human host.
Hepatic Stage
 Sporozoites infect liver cells and mature into schizonts , which
rupture and release merozoites into the bloodstream.
Blood Stage
 Merozoites infect red blood cells
 The parasites undergo asexual multiplication in the erythrocytes.
 The ring stage trophozoites mature into schizonts, which rupture
releasing merozoites.
 Some parasites differentiate into male and female gametocytes.
 Blood stage parasites are responsible for the clinical manifestations
of the disease.
Plasmodium
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The male and female gametocytes are ingested by
another Anopheles mosquito.
The parasites’ multiplication in the mosquito is known
as the sporogonic cycle, generating zygotes.
The zygotes develop into oocysts.
The oocysts grow, rupture, and release sporozoites,
which make their way to the mosquito's salivary
glands.
Inoculation of the sporozoites into a new human host
perpetuates the malaria life cycle.
Malaria
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Symptoms
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Fever, chills, sweating, headaches, muscle pains
Severe complications (cerebral malaria, anemia,
kidney failure) can result in death.
Anopheles Mosquitoes
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Female mosquitoes need blood meals
to nourish their eggs.
Schizont: Hepatic Stage
Schizont: Hepatic Stage
Blood Phase: Rings
Blood Phase: Rings
Malaria
Merozoites
being released
from lysed RBC.
Gametocyte: Blood Stage
Gametocyte: Blood Stage
Toxoplasmosis
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Organism: Toxplasmosis gondii
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Infects most species of warm blooded
animals, including humans.
Toxplasmosis
gondii
Toxplasmosis
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Cats are the only known definitive hosts for the
sexual stages of T. gondii and thus are the main
reservoirs of infection.
Cats become infected by eating infected wild animals
(e.g. birds)
Tissue cysts or oocysts are excreted in the feces.
Oocysts can survive in the environment for several
months and are remarkably resistant to disinfectants.
Toxplasmosis
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Human infection may be acquired in
several ways:
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A) ingestion of undercooked infected meat
B) ingestion of the oocyst from fecally
contaminated hands or food
C) organ transplantation or blood transfusion
D) transplacental transmission
Toxplasmosis
Geographic Distribution:
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Serologic prevalence data indicate that toxoplasmosis
is one of the most common of humans infections
throughout the world.
Infection is more common in warm climates and at
lower altitudes than in cold climates and
mountainous regions.
High prevalence of infection in France has been
related to a preference for eating raw or
undercooked meat
High prevalence in Central America has been related
to the frequency of stray cats.
Toxplasmosis Cyst
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Cyst in brain tissue
Toxplasmosis Tachyzoites
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Tachyzoites
Toxoplasmosis Trophozoites
Toxplasmosis
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Oocyst
Toxoplasma tachizoites
Toxplasmosis
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Ocular toxoplasmosis
Cryptosporidiosis
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Organism: Cryptosporidium
Spread through the fecal-oral route,
often through contaminated water
Causes self-limiting diarrhea in people
with intact immune systems.
In immunocompromised individuals
(such as AIDS patients), symptoms are
severe and often fatal.
Cryptosporidium
CILIOPHORA DISEASE
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Disease: Balantidiosis
Organism: Balentidium coli (The name tells you
it lives in the colon)
The animal reservoir is the pig. Its
geographical distribution is world-wide,
wherever humans and pigs live nearby
each other.
This is the only ciliated protozoan that
causes disease in humans.
Balantidiosis
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Causal Agent: Balantidium coli
This is almost identical to Enamoeba
histolytica.
The cyst form is infective.
It has a thick wall to protect it from
stomach acid.
It enters the human (and dogs) by
ingestion of fecal contaminants on food,
water, and hands.
Balantidiosis
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Once in the colon, it undergoes
excystment (cyst transforms into
trophozoite).
In the trophozoite form, they reproduce
in the large intestine, invade the colon
wall, and cause ulcerations in the colon.
Like Entamoeba, it leaves a flaskshaped ulcer.
Symptoms include diarrhea and GI
discomfort.
Balantidiosis
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Cysts are the parasite stage responsible
for transmission.
The host acquires the cyst through
ingestion of contaminated food or water
(NOT in undercooked meat).
Common in pigs
Balantidium coli
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Following ingestion, excystation occurs in the
small intestine, and the trophozoites colonize
the large intestine.
The trophozoites reside in the lumen of the
large intestine of humans and animals, where
they replicate by binary fission, during which
conjugation may occur.
Trophozoites undergo encystation to produce
infective cysts.
Mature cysts are passed with feces.
Balantidium
coli
Balantidium coli
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Trophozoites characterized by:
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Large size (40 µm to more than 70 µm).
Presence of cilia on the cell surface
A cytostome.
A bean shaped macronucleus which is often visible
and a smaller, less conspicuous micronucleus.
Balantidium coli
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Trophozoites
Cytostome
Cytostome
Balantidium coli
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Trophozoites
Balantidium coli Trophozoite
Balantidium coli Cyst
Balantidium coli
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Cysts
MASTIGOPHORA
DISEASES
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Trypanosomiasis
Leishmaniasis
Trypanosomiasis
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African Trypanosomiasis
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(African Sleeping Sickness)
American Trypanosomiasis
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(Chaga’s Disease)
“African Sleeping Sickness”
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Disease: African Tryptanosomiasis
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Causal Agents:
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Trypanosoma brucei gambiense
Trypanosoma brucei rhodesiense
Geographic Distribution
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T. b. gambiense is found in foci in large
areas of West and Central Africa.
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Humans are the main reservoir for
Trypanosoma brucei gambiense, but this
species can also be found in animals.
T. b. rhodesiense is found in East and
Southeast Africa.
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Wild game animals are the main reservoir
of T. b. rhodesiense.
Trypanosomiasis
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Trypanosomiasis has a biological vector,
the tsetse (pronounced “set-see”) fly.
Wild animals may also be a reservoir
(Zooinotic is when a disease is
transmitted to animals as well as
humans.)
Trypanosomiasis
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The tsetse fly bites a human and injects
the trypanomastigotes into the skin.
This causes a chanchre (pronounced
“shanker”), which is an ulcer on the
skin.
Then it enters the lymphatic system.
Trypanosomiasis
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It is characterized by Winterbottom’s
Sign: swelling of the cervical lymph
nodes in the head and neck area.
CNS symptoms include a shuffling gait
(like a stroke victim), slurred speech,
and malaise (needing to sleep longer
and longer each day).
They are also restless at night.
Trypanosomiasis
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CNS symptoms
 Shuffling gait
 Slurred speech
 Malaise (sleeping all day)
Treatment
 Melarsoprol: which has dangerous side-effects like
chemostherapy. This drug requires administration with a
substance called ethylene glycol, which will break down
regular plastic tubing, so the drug must be administered
with special plastic iv tubing.
Trypanosoma brucei
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Trypomastigote stages are the only
form found in patients.
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Posterior kinetoplast
Centrally located nucleus
Undulating membrane
Anterior flagellum
Trypanosoma brucei
Trypanosoma brucei
gambiense
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trypomastigote
Trypanosoma
Trypanosoma brucei rhodesiense
Trypanosoma brucei
UM
Tsetse Fly
“Chaga’s Disease”
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Disease: American Tryptanosomiasis
A zoonotic disease (can infect animals)
that can be transmitted to humans by
blood-sucking bugs.
Causal Agent: Trypanosoma cruzi
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This organism is a little smaller than T.
bruceii and has a pronounced gametoplast.
“Chaga’s Disease”
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This disease is NOT found in Africa.
This disease is also zoonotic; it can infect animals as
well as humans.
The vector is a large bug called the “Kissing Bug”.
It is found in warm regions and crowded areas,
especially in the cracks of adobe huts.
It comes out at night and crawls on a human while
they sleep.
“Chaga’s Disease”
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It prefers the lips because the blood supply is close
to the surface.
It sucks the blood there, but they don’t transmit the
organism this way.
When they suck the blood, they also defecate, and
the organism is in the feces.
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When the human wakes up to scratch the itch, feces
get into the tiny wound.
This is a fecal blood route.
“Chaga’s Disease”
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Symptoms include fever, anorexia, swollen lymph
nodes, hepatosplenomegally (enlarged liver and
spleen), and myocarditis (inflammation of the heart),
which usually causes death.
They also have megacolon (large colon) and
megaesophagus (large esophagus).
Trypanosoma cruzi
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Insect vector is the “kissing” bug. It takes a
blood meal and releases trypomastigotes in
its feces near the site of the bite wound.
Trypomastigotes enter the host through the
wound or through intact mucosal
membranes, such as the conjunctiva.
Trypanosoma cruzi can also be transmitted
through blood transfusions, organ
transplantation, transplacentally, and in
laboratory accidents.
Trypanosoma cruzi
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Geographic Distribution:
The Americas from the southern United
States to southern Argentina. Mostly in poor,
rural areas of Central and South
America. Chronic Chagas disease is a major
health problem in many Latin American
countries. With increased population
movements, the possibility of transmission by
blood transfusion has become more
substantial in the United States.
Trypanosoma cruzi
Trypanosoma cruzi
Trypanosoma cruzi
large kinetoplast
Trypanosoma cruzi
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Triatomine bug, Trypanosoma cruzi
vector, defecating on the wound after
taking a blood meal.
Kissing Bug
Romana’s sign
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Swollen eye,
seen in
Chagra’s
disease.
TERMS
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Promastigote: has single flagella
Amastigote: has no flagella
Kinetoplast: round mass of circular DNA
Leishmania donovani
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Domain:
Kingdom:
Phylum:
Class:
Order:
Genus:
Species:
Eukaryota
Protista
Mastigophora
Kinetoplastida
Trypanosomatida
Leishmania
donovani
Leishmania donovani
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Disease: Leishmaniasis
Vector-borne disease transmitted by
sandflies.
Leishmania Life Cycle
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It starts out as a
spindle-shaped, single
flagellated cell called a
promastigote
(mastigote means
flagella).
You can also see the
nucleus and a
kinetoplast (mass of
circular DNA).
Kinetoplast
Leishmania rosette
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In prepared slides
you can see
promastigotes
align their nose in
a circle, called a
rosette.
Leishmaniasis rosette
Leishmania Life Cycle
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It reproduces in the gut of a female
sandfly, and migrates to her proboscis
(mouth part).
It is introduced into the human by her
bite.
It then enters a macrophage and
becomes intracellular.
Here, it loses its flagella and is now
known as an amastigote.
Leishmaniasis



These amastigotes multiply in various organs
including the spleen, liver, and lymph nodes.
Symptoms include hepatosplenomegaly,
lymph adenopathy, fever, weight loss, and a
decrease in all blood cells: WBC, RBC, and
platelets.
The treatment is almost as bad as the disease
because of the side effects. It is best to catch
it early.
Leishmania Life Cycle
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

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The female sandflies inject the infective
stage, promastigotes, during blood meals.
Macrophages phagocytize them and they
transform into amastigotes.
Other sandflies become infected during blood
meals when they ingest infected
macrophages.
In the sandfly's midgut, the parasites
differentiate into promastigotes, which
multiply and migrate to the proboscis.
Leishmaniasis Life Cycle
Leishmania donovani (Promastigote)
Single flagellum found in sand flies
Leishmaniasis
Macrophage
rupturing
Amastogotes
Amastogotes with
nucleus and
kinetoplast
Leishmania

Amastigotes
Sandfly

This looks like a
mosquito,
except its body
is hairy and the
wings are
feathery.
Leishmaniasis


Geographic Distribution:
More than 90 percent of the world's cases of
visceral leishmaniasis are in India,
Bangladesh, Nepal, Sudan, and Brazil.
Leishmaniasis is also found in Mexico, Central
America, and South America, southern
Europe, Asia, the Middle East, and Africa.
Leishmaniasis

There are three forms of Leishmaniasis:
Cutaneous
 Mucocutaneus
 Visceral

Cutaneous Leishmaniasis





The disease is only at the site of the bite.
This form is seen in Texas, Mexico, Asia, and the
Middle East (our Iraq troops are coming down with
this form).
It manifests as a large, wet sore with raised edges. It
looks like a volcano with weepy serum coming out of
the center.
The wound is not contagious, just the sandfly bite.
Dogs can get this disease, too.
Leishmaniasis (cutaneous)
Leishmaniasis (cutaneous)
Leishmaniasis (cutaneous)
Leishmaniasis (mucocunateous)


This is when the disease located in the
mucous membranes of the nose and
mouth.
The most gruesome photos are of this
form.
Leishmaniasis
(mucocunateous)
Leishmaniasis (visceral)

This is the most serious form. It occurs
especially in immunocompromised
people, especially HIV patients.



The amastagotes reproduce inside
macrophages.
Only T-cells can kill infected macrophages,
but HIV is a disease that infects T-cells.
This form is known as Kala Azar.
Kala Azar
Hepatosplenomegaly
Kala Azar (duodenum)