2. Parasite: is an organism that lives, grow and multiply in
or on another organism which called the host.
Parasites classification: There are three main classes of
parasites that can cause disease in humans:
Protozoa
Eelminths
Ectoparasites
3. Protozoa
Protozoa are defined as a diverse group of unicellular
eukaryotic organisms, exist as structurally and functionally
independent individual cells.
Four main groups of protozoa are recognized on the basis of their
locomotion
4. 1) Amoebae
use pseudopodia (singular: pseudopodium) to creep or crawl
over solid substrates.
They change their shape continuously.
In human ,they live as parasites or commensals in the
alimentary canal.
Life cycle include two stages the trophozoites and the cysts.
Entamoeba histolytica and Entamoeba coli will be
demonstrated.
5. Entamoeba histolytica
Pathogenic amoeba infecting humans, cats, dogs and other
primates causing amoebiasis or amoebic dysentery
(gastrointestinal illness)
It occurs usually in the large intestine.
E. histolytica has the ability to infect other parts of the body
such as the liver (liver abscesses), heart or brain where it can
cause long term damage.
This illness is more severe in people with compromised immune
systems and mostly occur in tropical countries in areas of poor
sanitation.
6. Trophozoite
It inhabits anterior part of large intestine, i.e. colon of
human.
Asymmetrical amoeboid form about 10-60 µm.
cytoplasm is differentiated into ectoplasm and endoplasm.
There is a single large, broad and blunt pseudopodium
formed of ectoplasm.
Endoplasm contains single spherical nucleus and food
vacuoles (ingested RBCs may be present ) .
Nucleus has peripheral crown of small, regular chromatin
granules and a centrally located karyosome.
7. cysts
are spherical and contain four nuclei
the usual size ranges from 12-15 mm.
Except for their smaller size, the structures of the nuclei in
the cysts are similar to those in the trophozoites.
Cyst contains characteristic refractile rod-like structures with
rounded ends known as the chromatoid bodies or chromatoid
bars.
E. histolytica is spread by the fecal-oral route.
This is achieved through food or water contaminated with
the infective stage (cysts)
8.
9. Entamoeba coli
Entamoeba coli is a non-pathogenic species of Entamoeba
that frequently exists as a commensal parasite in the large intestine
of human.
E.coli trophozoite
Asymmetrical,15-50µm.
Ectoplasm is not separated from endoplasm.
One nucleus with slightly large eccentric karyosome.
Large, irregular chromatin lining the nuclear membrane.
Cytoplasm contains numerous vacuoles containing food particles
and bacteria with no RBCs .
10. E.coli cyst
Round, 10-35 µ,containing 1-8 nuclei and contains
thin pointed splinter-like chromatoid bodies.
E.coli may be difficult to distinguish from E.
histolytica, this is important in medicine because it
can be confused during microscopic examination of
stained stool specimens
E. coli is spread by the fecal-oral route. This is
achieved through food or water contaminated with
the infective stage (cysts).
11. 2- Flagellata(Mastigophora)
Flagellates are protozoa that are found in the group Mastigophora.
Flagellates use elongate flagella (singular: flagellum) which
undulate to propel the cell through liquid environments, flagellates
includes two main groups:
A-Intestinal flagellates such as Giardia and Trichomonas
B-Blood and tissue flagellates such as Leishmania and
Trypanosoma
12. Intestinal flagellates
Giardia lamblia
also known as Giardia intestinalis , Giardia duodenalis
is a pathogenic flagellates that colonizes and reproduces in the
small intestine
causing giardiasis or lambliasis which demonstrated by the
occurrence of greasy, watery but not bloody diarrhea.
Giardia infects humans, but is also one of the most common
parasites infecting cats, dogs , birds and other Mammalian.
The life cycle include trophozoite and cyst
13. Trophozoite:
looks like a clown face
two nuclei
large centric karyosome,
these nuclei outlined by two adhesive
discs above two dark median bodies
eight flagella(forming four pairs)arise
anteriorly and extend posteriorly.
trophozoite
14.
15. Cyst
Cysts are oval
have four nuclei situated as a pair on each cyst pole
karyosomes smaller than trophozoite and eccentric
have clearly visible two axostyles and two median
bodies.
Giardia infection can occur through ingestion of the
infective stage (cyst) in contaminated water, food, or
by the fecal-oral route (through poor hygiene practices
cyst
16. Trichomonas vaginalis
Trophozoite: is oval to pear shaped 9x7µm.. Five flagella arise near the
cytostome; four of these immediately extend outside the cell together,
while the fifth flagellum wraps backwards along the margins of the
undulating membrane which is supported by a costa of the same length.
Axostyle extends along the whole body and protrude from the end of the
body as a spine. One oval nucleus is situated anteriorly
The most common symptoms among women are:
vaginal discharge, which can be white, gray, yellow, or green, and usually frothy with an
unpleasant smell
vaginal spotting or bleeding
genital burning or itching
genital redness or swelling
17.
18. Ciliates use numerous small cilia (singular: cilium)
which undulate in waves allowing cells to swim in
fluids
Sporozoa were originally recognized not on the basis of
their locomotion, but because they all formed non-
motile spores as transmission stages. Recent studies,
however, have shown that many pre-spore stages move
using tiny undulating ridges or waves in the cell
membrane imparting a forward gliding motion
