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OUTLINEPROTOZOA
General Introduction to protozoa
DefinitionDiversity and Medical importance of protozoa
General morphology protozoa
Size, Shape etc
Cellular structure and organization Basic properties
Locomotion
Reproduction
Feeding, Metabolism, Excretion and Encystment Classification
General characteristics of the five main groups
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What are
Protozoa?
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What are Protozoa?
proto = first
zoa = animals
=single-celled eukaryotic organisms=kingdom Protista
=Vary in size (3-2000 mm).
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=Unknown until the invention of the microscope in 1675
=First recognized by antony van leewenhoek in 1676
= He describe it as little animal or animacula
What.?
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=protozoa are extremely diverseorganisms and found in a variety ofniches
=>200,000 named species
= Most species are free-living in
= Freshwater= marine environments= decaying organic matter and soil=Some are beneficial to mankind by:
= being part of the food chain
= serving as experimental subjects.
Protozoan diversity
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= Few are adapted to a parasitic life butall plant and animal species have atleast one protozoan parasite
= ~10,000 are parasites in a wide range of hosts= Vertebrate= invertebrate
= Plants=~20 human pathogens= Adapted to life in a wide range of sites within the
host
Protozoan Diversity
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Ecological Niches in the Human Body:
Skin: Leishmania
Eye: Acanthamoeba
Mouth: Amoebae and flagellates (usually non-
pathogenic)
Gut: Giardia, Entamoeba (and invasion to liver),
Cryptosporidium, Isospora, Balantidium
G.U. tract: Trichomonas
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Ecological.
Bloodstream: Plasmodium, Trypanosoma
Spleen: Leishmania
Liver: Leishmania, Entamoeba
Muscle: Trypanosoma cruzi
CNS: Trypanosoma, Naegleria, Toxoplasma,
Plasmodium
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Importance of protozoa
Medical importance
Cause of more sickness and death, than any other
disease-causing organisms
reduced working capacity
Loss of productivity
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Veterinary importance Loss of productivity
Death
reduced meat and milk production,
reduced reproductive potential
reduced working capacity
Potential losses
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Protozoa
..eukaryote..has genetic materialencased in a nuclear membrane (unlike
bacteria and Viruses)
..Classified traditionally by:morphology(eg. organelles of
locomotion)
life cycle
mechanisms of reproduction etc.
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Taxonomy of Protozoan
Subkingdom Protozoa
Phylum Sarcomastigophora Subphylum Sarcodina
Ex. Entamoeba
Subphylum Mastigophora Ex. Giardia
Leishmania
Trypanosoma
Phylum Apicomplexa Ex Plasmodia (malaria) Toxoplasma gondii
Phylum Ciliophora Balantidium
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Mastigophora: movement with flagella
- e.g. Trichomonas, Giardia
Sarcodina: pseudopodia
e.g. Entamoeba histolytica
Apicomplexa: apical complex, nolocomotor apparatus
e.g. cryptosporidium, malaria, toxoplasma
Ciliophora: movement with cilia
e.g. Balantidium.
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Terms in protozoans
Trophozoite: any stage in a protozoans life cyclewhich can ingest food. In practice also refers to themotile form.
Cyst: the non motile form which is protected by a
distinct membrane or cyst wall. This is an infectivestage of the parasite.
Excystation: the process of emergence of thetrophozoite from the cyst (vs. encystation)
Pseudopod: literally means false foot; temporarycytoplasmic processes at the surface of thetrophozoite
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Unlike their friend they do not lyse host tissue! Feed onbacteria, protozoa, yeasts and occasionally blood cells if available
VERY important to diagnose infection correctly or patient will
undergo unnecessary drug treatment
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Symptoms/Pathogenesis:Virulence factors: lectin, cysteine protease &
amoebaphore
The 1st stage invasive starts when adhesion to colonicmucins via parasite surface Gal/GalNAc lictin
The hallmark of amoebiais include:degradation extracellular matrix by amebicproteaseproduction of toxic factorsactivation of host cells from host immune systemkilling & phogocytosis human cells
E. histolyticainduces apoptosis and phagocytosis of thehuman target cells
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Persisting fever
Rarely diarrhea
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MECHANISMS OF CYTOTOXICITY
At least 5 mechanisms have been advanced to explain the pathogenicity of
virulent strains ofEntamoeba.
Hallmarks of amoebiasis include: degradation of the extracellular matrix (ECM)by amoebic proteases, production of toxic factors, activation of cells from thehost immune system, killing and phagocytosis of human cells,
1. Direct contacts with the host tissues.Example: adherence to the host cell by the release of adhesin molecules.
2. Release of soluble toxic metabolites.Example: amoebapore are capable of forming a hole in a target cell.
3. High enzymatic activities of the amoebasExample: enzymes released by the parasite damaging the host cell. .4. Interfering with the immune response of the host. Example: Antigensreleased by the amoeba cell can lead to:
inflammatory reaction allergies Immunodepression over stimulation of cytokines
formation of immune complexes formation of autoantibodies
5. E. histolytica induces apoptosis of the host cells during tissue invasion
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E. histolytica vs E. dispar
Brumpt 1949, proposed to establish a newspecies ofEntamoeba amoebae that are notpathogenic.
In 1993, it was decided that the invasionform will be called called E. histolytica.
The non-invasive invasive form will be calledE. dispar.
The 2 amoebae cant be distinguished bymicroscopic observation.
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Phylum: Sarcomastigophora
Flagellates Amebas
Giardia, Trichomonas Entamoeba Early-diverging Eukaryotes
Facultative Anaerobes
Carbohydrate metabolism is anaerobic
Lack mitochondria Extracellular parasites
Do not invade host cells
Adhere to plasma membrane of host cells
Contact-dependent cytotoxicity
Mechanical damage to host tissues
Replicate and divide within the host by binary fission
All are killed by treatment with Metronidazole, a drug that
selectively kills anaerobic cells
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GIARDIASISInfection with the protozoan parasite Giardia lamblia
Giardia duodenalis most common name
used. G. intestinales and G. lamblia are
also used.
Giardia spp. can parasitize the intestinal
tract of a wide range of vertebrates,
including humans.
Disease is prevalent in children attendingday care centers.
In addition the domestic dog and certain
wild animals serve as hosts.
Most common protozoan disease in the
United States.The distribution is cosmopolitan.
Transmission ofGiardia is predominantly
by ingestion of food or water
contaminated with cyst
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EPIDEMIOLOGY
Worldwide distribution
Common in areas with poor sanitary conditions
Seasonal with peak during late summer in UK, USA
and Mexico
Prevalence: 2-5% in industrialized countries
20-30% in developing countriesTravelers, hikers, campers are at risk. Swallowing
water while swimming, drinking tap water, eating
lettuce.
Risk groups in the US: travelers, children in daycares and homosexual men
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TRANSMISSION
Reservoir-human and possibly other
mammals (zoonotic?)
Infective cysts in feces: 10-25 cysts sufficient
Fecal contamination of water Feces for fertilizer
Defective piping
Flies Soiled hands
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CLINICAL FEATURES
Incubation period : 1-2 weeks
Majority of infected individual are asymptomatic
SYMPTOMS:
Diarrhea with loose, foul-smelling stools
FlatulenceAbdominal cramps and bloating
Nausea
Anorexia
MalaiseWeight loss
Prolonged symptoms
Malabsorption
DIAGNOSIS
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DIAGNOSIS
Identification of cysts or trophozoites in fecal
specimens
May need to be repeated Detection ofGiardia antigens in feces.
Serodiagnosis is not useful
TREATMENTMetronidazole:
Quinacrine-
Tinidazole-
Furazolidone- approved by the FDA for giardiasisParanomycin- used for pregnant women
Nitazoxanide: recently approved for giardiasis and
cryptosporidosis in children
T i h i i
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22 August 2013 47
Trichomoniasis
Trichomonas
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Trichomonas
Life cycle of T vaginalis
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22 August 2013 49
Life cycle of T. vaginalis
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22 August 2013 50
Morphology ofT. vaginalis
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22 August 2013 51
Epidemiology T. vaginalis
Clinical symptoms T vaginalis
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22 August 2013 52
Clinical symptoms T. vaginalis
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22 August 2013 53Yellow vaginal discharge due to T. vagin alis
Treatment of Trichomoniasis
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22 August 2013 54
Treatment of Trichomoniasis
I t ti l idi
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Intestinal coccidianCryptosporidium,Isospora,Cyclospora
General characteristics
Considered as opportunistic parasite in
immunocompromissed person
Complete entire life cycle in single host
Within the intestinal epithelial cells
of the host
Characterized by a thick walled oocyst
excreted in feces
Are transmitted by the fecal-oral route
Cryptosporidium
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Cryptosporidium
Species:
C. parvumA coccidean parasite implicated in intestinal Disease primarily among immune-compromised patient
1985 first reported case in philippines associated with
intractable diarrhea in immune-compromised (AIDS)patient
Self-limiting diarrhea in immuno-competent persons
Profuse, watery diarrhea associated with AIDS (life
threatening)
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1976 considered as natural parasite of animal especially
calves causing diarrheal diseases
Infect wide range of animal hosts (fish-humans)
C. hominis & C. parvumare species mostly causing
disease in humans
C. hominisinfects only humans but C. parvumalso
infects many other mammals
C. felis, C. meleagridis, C. canis, and C. murisinfections have also been reported
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Geog. Dist.: = Worldwide distribution
Morphology: = oocyst round or slightly oval-shaped,
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Transmission
Mainly through the ingestion and possibly inhalation ofsporulated oocysts
mainly through contaminated water &
Occasionally food sources, such as chicken salad
fecal-oral transmission (monoxenous)
anthroponotic transmission
autoinfection
zoonotic transmission
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Waterborne Cryptosporidiosis
human infection usually waterborne and acquired by
fecal-oral route
highest prevalence of disease in areas with unreliable
water and food sanitation
Factors Favoring
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Factors FavoringWaterborne Cryptosporidiosis
Small size of oocysts (4-5 mm)
Reduced host specificity and monoxenous development
Close associations between human and animal hosts
Large number of oocysts excreted (up to 100 billion per calf per day)
Low infective dose (
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Disease: Cryptosporidiosis
= human infection usually waterborne and acquired by
fecal-oral route= highest prevalence of disease in areas with unreliable water and foodsanitation= extraintestinal infection of the respiratory tract, biliary
tract and pancreas may occur.
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Clinical Features
Varry from asymptomatic to severe, life-threatening
illness; infection usually self-limiting diarrhea of 1-2 weeks
duration charactrized by copious watery diarrhea,
vomiting, intense abdominal pain, anorexia and
weakness
among immunocompromised patient (AIDS) develops
severe chronic diarrhea which may last for months
malabsorption
Cyclospora
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y p
Specie: C. cayetanensis
= was established to cause human diarrhea in 1990
=1986 cases of prolonged watery diarrhea among
immunocompromised (AIDS) patient has been reported
worldwide
=Species Name C.Cayetanensiswas given in 1993
=Initially called cyano-bacteria like body (CLB) or large cryptosporidium
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Epidemiology:
= More common in tropical and sub-tropical areas
= case of cyclospora infection was reported in
papua, new guinea= Subsequent cases has been reported from most
part of the world
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Epidemology
= Infection caused by cyclospora can be acquired by
drinking contaminated water (fecal-oral)
=
More associated with food-borne outbreaks ( socialevents, weddings, etc)
= Parasite infect vertebrates including reptiles, insect
& rodents
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Disease:Cyclosporiasis
= disease is clinically indistinguishable from
cryptosporidiosis and Isosporiasis
= self-limiting, characterized by persistent watery diarrhea
that ends to recur in a relapsing pattern and last for
3-4 wks,
= associated with abdominal cramps, nausea, vomiting,
low grade fever, weight loss and anorexia
Clinical Features
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Isospora
Specie:Isospora belliEpidemiology
wide geographical distribution (higher prevalence in warmer
climates)
the least common of the three intestinal coccidia that infecthumans
transmitted through intake of fecally contaminated food and
drink with oocyst
Cli i l f t
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Clinical feature Disease: Isosporosis/Intestinal coccidiosis
often asymptomatic (seldom reported)
symptoms range from mild gastro-intestinal distress
to severe dysentery
mild self-limiting infection charac. by fever, colicky
abdominal pain, severe diarrhea, steatorrhea (fatty
stool) and weight loss.
often self-limiting, but can become chronic (wasting,
anorexia)
symptoms more severe in AIDS patients
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Pathology
intracellular development occurs in the intestinal
mucosa mucosal atrophy
chronic diarrhea (months to years) abdominal
discomfort, low grade fever
Intestinal Coccidia
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Intestinal CoccidiaTreatment paromomycin for Cryptosporidium
modest benefit lowers parasitemia in AIDS
trimethoprim-sulfamethoxazole for Cyclosporaand Isospora
l d
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Intestinal coccidian
Summary are opportunistic parasite in
immunocompromissed person
Have both sexual and asexual reproduction
Require single host to comlete their entire life cycle characterized by a thick walled oocyst excreted in
faeces
Are transmitted by the fecal-oral route
Laboratory diagnosis is by finding the oocyst infaeces
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Intestinal Coccidia- Summary
Got medical attention after the emergence of HIV/AIDS
Fecal-oral or contaminated food and water are means oftransmission
Simple lifecycle and reproduce Sexually and asexually
infection leads to acute, watery diarrhea; self limiting in
immunocompetent individuals but significant, chronicillness in the immunosuppressed may occur
characterized by a thick walled oocyst excreted infaeces
oocyst stage :Infective and diagnostic stage
Laboratory dx; finding oocyct in stool specimen