Transcript GENERAL PROPERTIES OF PROTOZOA & HELMINTS Doç.Dr.Hrisi

GENERAL PROPERTIES
OF PROTOZOA
&
HELMINTS
Doç.Dr.Hrisi BAHAR
GENERAL
PROPERTIES OF
PROTOZOONS
Doç.Dr.Hrisi Bahar
General Characteristics
● Unicellular animal with full functions
● Distribute widely: water,soil, etc.
● Total species 65,000

Free-living: majority
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Parasitic: about 10,000
General Characteristics
● Size 2 - 100 micrometers
● Parasitic protozoa are most facultative
anaerobes;
● Mostly heterotrophic,chemoorganotrophs
● Nutrients assimilated via phagocytosis,
pinocytosis, diffusion
● Digestion may be both extracellular and
intracellular.
Medical Protozoa
● Pathogenic protozoa
● Opportunistic parasite

Not normally pathogens
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Become pathogenic due to impairment of
host resistance
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Clinical importance of the AIDS epidemic
Basic Structures
● Plasma membrane
● Cytoplasm
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Ectoplasm: locomotion , ingestion, etc
Endoplasm: metabolism
● Nuclear
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Vesicular form or compact form
● Locomotive organelle
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Pseudopodium, flagellum, cilia
Protozoon
Mode of Reproduction
●Asexual reproduction
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Binary fission: results in 2 daughter cells
Schizogony: multiple fission, results in multiple cells
●Sexual reproduction
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Conjugation: exchange of nuclear materials of 2 cells
Gametogony : sexually differentiated cells unit 
zygote
Life Cycle Patterns
● One stage form
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Trophozoite ( =vegetatif form.Take food, be
mobile, multiply)
● Two-stage form
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Trophozoite & cyst (not mobile, with cyst wall.
cyst=protective form)
● Two-host form
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Mammals – mammals
Mammals - insect vectors
Site of infections
● Gastrointestinal system
(E.histolytica,B.coli,G.intestinalis,D.fragilis,
Cryptosporidium,Isospora,Blastocystis,Sarcocystis,
Microsporidia)
● Urogenital system (T.vaginalis)
● Blood (Plasmodium,babesia)
● Tissue (T.gondii,Leishmania sp,E.histolytica,
Naegleria sp,Acanthamoeba sp)
A-The Sarcomastigophora
(Amoeboflagellates)
1-Sub phylum Sarcodina
(The amoebas)


Motility via Pseudopoda
 Extensions of the cell membrane
into which the cytoplasm flows
 Cyclosis
 No cell wall; thus, no uniform shape
 Shape changes with movement
 Reproduce asexually by mitosis;
 Sexually by meiosis

Trophozoite
 Motile vegetative stage
Cyst
 Latent survival stage

Medically important species
of this philum
1-Entamoeba histolytica which causes
amoebic dysentery .
 The organism produces
protective cysts which pass
out of the intestines of the
infected host and are
ingested by the next host
(fecal-oral route).
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Medically important
species of this philum
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2-Acanthamoeba .
Can infect the eye, blood, spinal cord,
and brain and is transmitted by
waterborne cysts picked up while
swimming in contaminated water,
crossing the mucous membranes.
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2-Subphylum Mastigophora
(Protozoa-flagellates)
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Motility via flagella
 One or more whip-like filaments move in counterclockwise fashion creating rapid movement
 A flagellum is a complex organelle composed of many
smaller tubules
 Flagella attach to the cell membrane and derive energy
from movement from this membrane
Most numerous of the protozoan types
 Several are pathogens of humans
All reproduce asexually; some reproduce sexually
Medically important species

a. Giardia lamblia :Can cause a
gastrointestinal infection called giardiasis.
Cysts pass out of the intestines of the
infected host and are ingested by the next
host (fecal-oral route).
Medically important species
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b-Trichomonas vaginalis infects the
vagina and the male urinary tract.
It does not produce a cysts stage and is
usually transmitted by sexual contact.
Medically important species
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c. Trypanosoma brucei gambiens
causes African sleeping sickness
and is transmitted by the bite of an
infected Tsetse fly.
B-The Ciliophora
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Protozoa-ciliates
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Motility via cilia
 Cilia surround the cell; their coordinated movement
Uses energy from the cell membran
Two nuclei per cell
 Small micronucleus governs sexually reproduction
 Large macronucleus governs metabolism and growth
 Both nuclei divide during asexual mitosis
 Intracellular organelles
 Function in digestion and excretion
Only one ciliate pathogen affects humans
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Pathogenic ciliate
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The only pathogenic ciliate is Balantidium
coli which causes a diarrhea-type
infection. Cysts pass out of the intestines
of the infected host and are ingested by
the next host (fecal-oral route).
C. The Apicomplexans
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No established means of movement
 Thus, not motile
All are intracellular parasites in a variety of
hosts
 Several parasitic species affect humans
 They possess a complex of organelles
called apical complexes
All lack intracellular organelles
All have three things in common
 No motility
 Sexual and Asexual mode of Reproduction
 Intracellular parasites
Medically important species

Species of Plasmodium .cause malaria
and are transmitted by the bite of an
infected female Anopheles mosquito. They
reproduces asexually by schizogony in
human liver cells and red blood cells
but also reproduce sexually by gametes
in the mosquito.
Medically important species
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Toxoplasma gondii causes
toxoplasmosis
It can infect most mammals and is
contracted by inhaling or ingesting cysts
from the feces of infected domestic cats,
where the protozoa reproduce both
asexually and sexually, or by ingesting raw
meat of an infected animal.
Medically important species

Cryptosporidium is an intracellular
parasite that causes diarrhea, although in
people who are immunosuppressed it can
also cause respiratory and gallbladder
infections. It is transmitted by the fecal-oral
route
Protozoan Diseases
Intestinal
Amebiasis.....................Entamoeba histolytica
Giardiasis.....................Giardia lamblia
Balantidiasis…………...Balantidium coli
Crytosporidosis……. ….Cryptosporidium
parvum
Urogenital
Trichomoniasis………….Trichomonas vaginalis
Protozoan Diseases
Blood and Tissue
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Malaria ……………………......Plasmodium spp
Meningoencephalitis…..……Naegleria fowleri
Toxoplasmosis…….………...Toxoplasma gondii
Trypanosomiasis
African Sleeping Sickness...Trypanosoma brucei
Chagas Disease......................Trypanosoma cruzi
Protozoan Diseases
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Leishmaniasis
 ●Visceral leishmaniasis( Kala-azar)
Leishmania donovanii
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● Cutaneous leishmaniasis
Leishmania topica/braziliensis
Virulence Factors that Promote
Colonization of Protozoans
The ability to:
1. Contact host cells;
2. Adhere to host cells and resist physical
removal;
3. Invade host cells;
4. Compete for nutrients;
5. Resist innate immune defenses such as
phagocytosis and complement; and
6. Evade adaptive immune defenses.
GENERAL
PROPERTIES OF
HELMINTES
HELMINTHS
●The helminths are worm-like parasites.
● Helminths are separated according to their
general external shape and the host organ
they inhabit.
● The definitive classification is based
on the external and internal morphology of
egg, larval, and adult stages
●Helminths are multicellular eukaryotes.
There are three classes of helminths
Nematodes – "roundworms"
● Adult and larval roundworms are
bisexual, cylindrical worms.
● They inhabit intestinal and
extraintestinal sites.
● The nematodes include Trichinella,
Ascaris, and Enterobius.
There are three classes of helminths
● Trematodes – "flukes"
● Adult flukes are leaf-shaped flatworms.
Prominent oral and ventral suckers help
maintain position.
● The life cycle includes an intermediate
host.
● An example is the organism that causes
schistosomiasis.
There are three classes of
helminths
Cestodes – pig and cattle "tapeworms"
● Adult tapeworms are elongated,
segmented, hermaphroditic flatworms
that inhabit the intestinal lumen.
● Larval forms, which are cystic or
solid, inhabit extraintestinal tissues
NEMATODES
● Some species require an intermediate
host to complete development.
● Intestinal nematodes all mature into
adults within the human intestinal
tract.
NEMATODES
The nematodes (nema: thread) are
threadlike, nonsegmented parasites.,
 A few mm to 1m in length, with
separated sexes.
 They possess a complex tegument and a
digestive tract.
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NEMATODES
● The males are usually smaller than the
females and are equipped with
copulatory organs that often show
features specific to each species.
NEMATODES
● Development from the egg includes
four larval stages andv four moltings
before the adult stage is reached.
● The larval forms of many of these
roundworms may be distributed widely
throughout the body
NEMATODES
Three of the intestinal nematodes are
acquired by the ingestion of nematode
eggs:
● Trichuris trichiura ("whipworm")
● Ascaris lumbricoides
● Enterobius vermicularis ("pinworm")
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NEMATODES
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Two worms are acquired when
their larvae penetrate through the
skin, usually of the foot:
● Necator americanus
("hookworm")
● Strongyloides stercoralis
NEMATODES

One is acquired by the ingestion of
the encysted larvae in muscle (pork
meat):
Trichinella spiralis
NEMATODES
Ascaris lumbricoides
(Large Roundworm)
Causative agent
of
“ascariosis”
Ascaris lumbricoides
Occurrence
● The human large roundworm occurs
worldwide.
● The main endemic regions, with prevalence
rates of approx. 10–90%, include countries in
Southeast Asia, Africa, and Latin America.
● Autochthonous infections are rare in central
Europe.
Ascaris lumbricoides
Parasite and Lıfe Cycle
● The adult ascarids living in the small
intestine are 15–40cm in length, about as
thick as a pencil and of a yellowish pink
color.
Enterobius vermicularis
(Pinworm)
Causative agent of enterobiosis
(oxyuriosis)
Occurrence. The pinworm occurs in all parts
of the world and is also a frequent
parasite in temperate climate zones and
developed countries.
The age groups most frequently infected are fiveto nine-year-old children and adults
Enterobius vermicularis
Parasite and Lıfe Cycle
Enterobius vermicularis which belongs
to the Oxyurida has a conspicuous white color.
The males are 2–5mm long,
The females 8–13 mm.
The long, pointed tail of the female gives
the pinworm its name.
Enterobius vermicularis
Class Trematoda
(Flukes)
General characteristics
Most of the trematode species that parasitize
humans are dorsoventrally flattened with an
oval to lancet shape, although others have
different shapes such as the threadlike
schistosomes.
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Class Trematoda
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Most species are hermaphroditic.
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Snails are the first intermediate hosts;some
species require arthropods or fish as
second intermediate hosts
Class Trematoda
Schistosoma (Blood Flukes)
Causative agents of schistosomosis or bilharziosis.
Schistosomosis (bilharziosis) is one of
the most frequent tropical diseases with
about 200 million infected persons.
The occurrence of schistosomosis
depends on the presence of suitable
intermediate hosts (freshwater snails).
Schistosoma (Blood Flukes)
●Schistosomosis is also known as bilharziosis after
the German physician Th. Bilharz, who
discovered Schistosoma hematobium in human
blood vessels in 1851.
● Schistosomosis occurs endemically in 74 tropical
and subtropical countries of Africa, South
America, and Asia .
● The number of persons infected with
schistosomes is estimated at 200 million(WHO
2008)
Schistosoma (Blood Flukes)
● Human infections result from contact with
standing or slow-moving bodies of water
(freshwater) when Schistosoma cercariae
penetrate the skin.
● Schistosoma hematobium causes urinary
schistosomosis.
● S. mansoni, S. japonicum,S. intercalatum, and
S. mekongi are the causative agents of intestinal
schistosomosis and other forms of the disease.
Trematodes
Fasciola hepatica
Dicrocoelium dendriticum
Clonorchis spp
Paragonimus spp
Fasciola hepatica
F. hepatica is a flattened,
leaf-shaped parasite about
2–5 cm long and at most
1 cm wide.
Dicrocoelium dendriticum
The lancet liver fluke
(0.5–1.0 ! 0.2 cm)
Fasciola hepatica and F. gigantica are bile duct parasites of domestic
ruminants.In their life cycle freshwater snails act as intermediate host
Humans become accidentally infected when they eat plants to which
infectious parasite stages (metacercariae) adhere
Dicrocoelium dendriticum is a bile duct parasite in sheep,
cattle, and other herbivores, Its life cycle includes two intermediate hosts
(terrestrial snails and ants). Humans become infected accidentally when
they ingest ants containing infective metacercariae of the lancet liver fluke.
Fasciola hepatica egg
Dicrocoelium dendriticum egg
Cestoda (Tapeworms)
Taenia saginata
Taenia solium
Echinococcus granulosus
Cestoda (Tapeworms)
● General characteristics
*Parasitize in the small intestine of humans.
* They are hermaphrodites and consist of the
head (scolex), followed by an unsegmented
germinative section (neck) and a posterior
chain of segments (proglottids).
*There are no digestive organs, so nutrients are
taken up through the absorptive integument.
Cestoda (Tapeworms)
*The life cycle of cestodes include one or two
intermediate hosts.
* Humans can also be infected by larval stages of
various tapeworm species (cysticerci,
metacestodes).
* These stages develop in body tissues and generally
cause considerably greater pathological damage
than the intestinal cestode stages.
Taenia saginata
Echinococcus granulosus