Download Protozoology

Protozoology
Medical protozoology deals with parasite of unicellular origin
.these parasites belong to a big phylum called protozoa … consists of
a single cell which performs all necessary function of metabolism and
reproduction.
Morphologically consists of
1 – Cytoplasm which differentiate
a) Outer membrane (ectoplasm) the ectoplasm functions in movement,
ingestion of food, excretion, respiration and protection, the organs of
locomotion are prolongation of ectoplasm – as. Pseudopodia Cilia,
flagella
b) An inner mass (endoplasm) is concerned with nutrition and
conations the nucleus, food vacuoles, food reserves, chromatoidal
body.
2 – One or more nuclei (nucleus)
a) Variation in structure.
b) Which are important for Identification and differentiation of
different protozoa ex. In malaria appears as mere mass of chromatin in
others appears consisting.
Outer nuclear membrane
chromatin particles
Which vary in size and arrangement?
According to species
The nucleus is essential for maintaining and reproduction life.
3 – Karyosomes
Compact chromatin which plays apart in promitosis.
a) Central (Centric)
in position is found.
b) Eccentric
4 – Fibrils
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May be present and appears joining the karyosome with the nuclear
membrane. In the mastigophera (flagellata) there may be present
kinotoplast (kineto-nucleus) consisting of two parts the parabolas
body and blepharoplast (from which the flagellum arises) .. for
instance in ciliates 2 nuclei are present, one is large and is called the
macro – nucleus, while the other is very small and called the micro –
nuclens. It's concerned with reproduction.
**Physiology of protozoa…. Locomotion may be undertaken by
pseudopodia, flagella, cilia.
**Protozoa respire either directly in oxygen and expelling carbon
dioxide or indirectly by using the oxygen librated from complex
substances by the action of enzymes.
**Nutrition may be affected by the absorption of liquid food and
ingestion of solid particles (surrounded by food vacuole).
**Excretion is effected through osmotic pressure, diffusion, and
precipitation.
**Protozoa secrete digestive ferment, pigment, and material for the
cyst wall. pathogenic protozoa also secrete proteolysic enzymes
hemolysins, cytolysins , and various toxic and antigenic substances .
**Certain protozoa at time enter an inactive cystic stats in which they
secrete a resistant membranous wall and usually undergo nuclear
divission .
**Reproduction … The nucleus is responsible for reproduction this
may occur.
a) A sexually by. A mitosis multiplication by simple binary fission
without formation of chromosomes.
b) Sexually Mitosis here male and female gametes after fertilization
units producing zygotic, which undergoes multiplication production
numerous organism (e.g. malaria insides mosquitoes).
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Classification of medical protozoa: Four classics those are important
medically.
1 – Rhizopoda or sarcodina (amebas)
2 – Flagellate or mastigophora (flagellates)
3 – Ciliate (ciliates)
4 – Sporazoa
(sporozoans)
Intestinal and luminal protozoa
There are several species of intestinal protozoa living in the human
gut lumen
Amoebas
The parasites of this family move by pseudopodia and have no fixed
shape. Amoebas may be free – living or parasitic 6 different amobae
which may be found in man.
1 – Entamoeba histolytica .
2 – E. coli
E. hartamanhi .
3 – Entomoeba gingivalis .
4 – Iodamoeba butschlii.
5 – Endolimax nane .
6 – Dientamoeba fragilis .
These amoebae inhabit the intestine, except E. gingival is which
lives in the buccal cavity. E histolytica is the only pathogenic amoeba,
while others Cause no damage to man and live as .commensalism
E hartamanni is non pathogenic. Though it resembles E. histolytica
very closely except for its smaller size and was therefore known as the
"small race"
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Entamoeba histolytica
Ambiasis, amebic dysentery amebic hepatitis
The parasite is cosmopolitan in distribution, and more sever and
abundant in tropical and subtropical countries among people living in low
hygienic standard.
Morphology
It shows morphological variation during its different stage of
multiplication. E. histolytica may be recognized in the stool as.
a) Trophozoite
b) Precyst
Stages
c) Cyst
A. Trophozoite
Or active vegetative E. histolytica it is mobile form and an amoeboid in
appearance.
Varies in size from about (15 – 40 microns, average 20 micro) the thin
fingerlike ectoplasmic pseudopodia are extended rapidly. The endoplasm
contains the nucleus, food vacuoles and granules.
The nucleus is not clearly seen in the living trophozoite, but can be
distinctly demonstrated in preparation stained.
The nucleus is spherical eccentric (6 microns in diameter) and contains a
small centric karyosome consists of several granules in a halo-Like
capsule from which a linin net work of fine fiberals radiator toward the
periphery of the nucleus giving ((Cart wheel appearance)) .
Trophozoite have wide clear hyaline ectoplasm sharply separated from
the endoplasm which some time includes red blood cells trophozoites are
delicate organism divides by binary fission .
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B. precytice stages
Are colorless, rounded or oval cells that are smaller, than trophozoite
but larger than the cyst they are devoid of food inclusions, pseudopodia
action is sluggish and there is no progressive movement?
C. Cyst
are rounded or oval hyaline bodies (> 10 um and less then 18 um) the
cytoplasm of the young cyst contain vacuoles with glycogen and dark
staining sausage shaped bars (cigarettes shape) with rounded ends called
chromatoid bodies ..
The immature cyst has a single nucleus or two.
The mature infictive cyst contain four smaller nuclei.
Thus cyst containing from one to four uncles may be passed in the feces .
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Habitat
The parasite inhabits the large intestines (Caecum) asending colon,
sigmoid colon and rectum.
Mode of transmission.
1. Cysts reach humans through water and food, vegetables contaminated
with infective stage.
2. The main source of infection is the cyst passing chronic patient or
asymptomatic carrier.
3. Flies play role.
Life cycle
The life history of E. histolytic is comparatively simple.
The resistant infective cyst formed in the lumen of the large intestine pass
out in the feces and are immediately infective (Few if any cyst are voided
in acute dysentery but they predominate in chronic infection and carriers ,
human beings are the principal host and source of infection) .
When the human swallow the mature cysts, which are resistant to the
acidic digestive juices of stomach pass to the lower part of small intestine
(SI).
Here Under the influence of the neutral or alkaline digestive juices and
the activity of the ameba (Causing a tear in the cyst wall).
The cyst wall disintegrates liberating a four – nucleated metacystic
ameba.
The nnclei in metacyst undergo division to form 8 nuclei, each get
surrounded by its own cytoplasm to form 8 metacystic trophozoites.
If excystations take place in intestines, trophozoites migrate to colon and
there are of 2 way occurs ..
a. Some trophozoites feed on colonic content and develop into
precysitic form, then secret cyst wall and become cyst which
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passed in feces to repeat the cycle (encystations) . These persons
will become a carrier and not suffer from any disease.
b. Other trophozoites may reach the mucosa with acid of cytolytic
enzymes, change their diet by consuming the RBC. escaps from
damage capillary and cause flask – shaped ulcer .
*When the amoeba become capable of invading the mucosa they cause
((amoebic ulcers)) they begin as minute ulcers at points of invasion and
then gradually penetrate actively into the deeper tissue first through the
muscularis mucosa, then into the submucose .
*An amoebic ulcer is typically – flack shaped – has acrateriform
appearance, with a wide base and narrow with irregular edges, and the
amoebae are found in the periphery and the base of ulcer.
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*The invading tropozoite may find their way to the submucosal
tributaries of the portal vein producing metastatic extra – intestinal lesion.
*The liver is the most frequently involved organ. Necrosis in the liver
usually begins as multiple small foci which later Join together (by
liguifactive enzymes secreted by the trophozoites) to from a solitary
larger amoebic abscess.
*If resistance is low liguifactive necrosis allows pus with the amoebae to
reach the lung by direct extension through the diaphragm producing a
lung abscess . From the lung amoebae may reach the brain or any other
organ through the heart and systemic circulation.
*Extra intestinal invasion may occur in patient with clinical dysentery or
in these with mild or latent infections.
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Signs and symptoms
Intestinal
Extraintestinal
**Acute intestinal amebiasis has an incubation period (1 – 14 week
commonly) – that mean not sudden onsets …. This may resemble to
bacillary dysentery, but can be differentiated.
Acute intestinal amoebic dysentery Severe with numerous small stools
containing blood, mucus and shreds of necrotic mucosa accompanied by
acute abdominal pain and tenderness. Trophozoites of E. histolytic are
found in the stools .
**Chronic amebiasis is characterized by
.Recurrent attacks of dysentery.
.Intervening period of mild or moderate gastrointestinal disturbances and
constipation.
.Localized abdominal tenderness is present.
.Liver may be enlarged.
**Extra – intestinal symptoms
Symptoms of hepatic amoebiasis:.Pain and tenderness in the right upper guardant.
.The mild form of disease is accompanied with slight enlargement and
tenderness of the liver.
.In acute form there is severe right hypochondriac pain, with marked liver
enlargement & tenderness.
.Abscess if formed it is usually near the superior surface of the liver,
where it causes diaphragmatic irritation with pain referred to right
shoulder.
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Diagnosis
A. intestinal amoebiasis
1 - Stools examination detection of trophozoites, sedimented gives more
positive result… For cyst..zincsulfate
and flotation test give more
positive result
2 – Stool Culture: to detect the amoeba.
3 – Sigmoidoscopy and biopsy. Lesions appear as shallow ulcers
surrounded with narrow zane of hyperaemia.
4 – Bariu meal investigation … X – ray may reveal presence of a funnel –
shaped deformity or filling defects in the colon especially in the ceacum.
B. extra – intestinal amaebiasis
In case of amoebic liver abscess – confirmed by needling and aspiration
Contents examined for odor and appearance.
Indirect
by serological test.
Increase of ESR < 50mm/h neutrophil up to 80º %
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Treatment
For symptomatic intestinal a mebiasis or hepatic abscesses is
metronidazol (flagyl) plus iodoguinol .Asymptomatic cyst carriers treated
with iodoguinol.
The differences between Amoebic dysentery and Bacillary dysentery
Feature
Amebic dysentery
Bacillary dysentery
Onset
gradual
Acute
fever
absent
Present
Toxicity
Absent
Present
Tenesmus
Uncommon
Common
Vomiting
Absent
present
Freyuency
6 – 8 per day
Over 10 per day
Odour
Offensive
Nil
Colour
Dark red
Bright red
Nature
Faeces mixed with blood and mucus
Blood and mucus with little or no faeces
Clinical
Stool
Lack of response to antiamebic drugs
N. B .….The clinical diagnosis of intestinal amebiasis requires
differentiation from other dentures and intestinal disease.
Hepatic abscess from viral and bacterial hepatitis, hydrated cyst,
gallbladder infection and others
Pathogenesis
The ability to hydrolyse host tissues. Once in contact with the mucosa,
the amebas secrete proteolysis enzymes, which enable them to penetrate
the epithelium and begin moving deeper, the intestinal lesion: - usually
develop initially in the cecum, appendix or upper colon and then spreads
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the length of the colon. The number of parasites builds up in the ulcer in
encreasing the speed of mucosal destruction .
Early lesions usually are not complicated by bacterial invasion and
there is little cellular response by the host. In older lesions the amebas
assisted by bacteria may break through the muscularis mucosa,then
infiltrate in the submucosa and even penetrate the musle layers and serosa
this enables trophozoites to carried by blood and lymph to ectopic sites
throughout the body where secondary lesions then form which have been
found in nearly every organ of the body but the liver is most commonly
affected
results when tropozoites enter
mesenteric venules
travel to the liver through the hepatoportal system
capillaries
through portal
sinusoids they begin to form abscesses .
* The abscess may rupture, where they attack other organs.
Endameba coli …. Also has two stages in its Life cycle… it does not
invade tissue and thus is nonpathogenic trophozoites are usually larger
than the vegetating forms of E. histolytica. In fresh stools they move by
short blunt. They do not normally ingest red blood cells, and
differentiation between the ectoplasm and endoplasm can be made only
difficulty. The karyosome appears course, thick and usually eccentrically
located. The cysts are predominately spherical., splintered stick like
clromatodial bars and typical nuclei up to eight in number .
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Flagellate
Are those protozoa which are provided with flagella? According to their
habitation man body, flagellates can be grouped into three categories
1 – Intestinal flagellates.
2 – urogenital flagellates .
3 – Blood (haemo -) flagellates.
Intestinal flagellates
1.Giardia lamblia …. Pathogenic (duodenum, Jejunum).
2.Embadomonas intestinalis (colon) .
3.,Enteromonas hominis (colon)
4.Chilomastix mesnili (caecum)
5.Trichamonas hominis (caecum)
6.Trichomenas tenax (buccalis) (buccal cavity)
Luminal flagellates are non pathogenic commensals except Geiardia
lamblia
Urogenital flagellates
-Trichomonas vaginalis (pathogenic) in habits the vagina and prostate
Blood flagellates
A. Extra cellular (outside r. b. c. in the plasma)
1. Trypanosome gambinese
2. Trypanosome rhodesiense
3. Trypanosome cruzi
Trypanosomal form All are pathogenic .
B. Intracellular (inside r, b, cs)
1. Leishmania tropica
2. Leishmania braziliense
3. Leishmania donovarni
4. Leishmania form of T. cruzi
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All are pathogenic
Giardia lamblia is a flagellate of world-wide distribution.
It is more common in warm climates than temporal climates.
It is the most common flagellate of the intestinal tract,
causing Giardiasis. Humans are the only important reservoir
of the infection. The infection is most common in parts of the
world where sanitation is at its lowest. Giardiasis is an
infection of the upper small bowel, which may cause
diarrhoea. Only Giardia spreads disease.
Diagnostic morphologhy … It has 2 stages the trophozoite and the cyst.
Trophozoite
1. Pear – shaped or heart shaped broad and rounded anterierly and
tapering posterior.
2. 10 – 18 × 2 microns.
3. Presence of aventral bilobed sucking disc which occupies almost the
entire anterior half of the body.
4. With two over nucler one on each lobe of the disc,
5. Nucleus has a central karysome.
6. with 4 pairs of flagella.
7. 2 axostyles running along the midline.
8. 2 sausage shaped parabasal or medium bodies lying transversely,
posterior to the sucking disc.
Cyst
1. Oval in shape and thick welled.
2. With 4 round nuclei grouped at one pole
3. Presence of axostyles and fibrils.
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Life cycle
 When the human ingest the cyst with contaminated food. It
excyct in upper GIT and liberate trophozoites that multiply
by binary fission.
 When the trophozoite drop off it lives in the duodenum and
upper part of the jejunum, attached by means of the sucking
disc to epithelial cells of the velli feeding by pinocytosis.
 Trophozoites which reach lower part of the small intestine or
the large intestine start encystations the trophozoite retracts
its flagella into the axaonemes which remain as curved
bristles in the cyst.
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 When there is diarrhea, trophozoites are found in stools.
 10 cysts being capable of initiating infection.
 Within half an hour of ingestion, the cyst hatch’s out into two
trophozoites Which multiply successively by binary fission and
colonies the duodenum .
 The trophozoites as they pass down the colon develop into cyst.
Mode of clinical picture
1 – The incubation period is variable, but is usually about 2 weeks.
2 – Sever diarrhea a (Steatorrhea) . Stool is pale, offensive & fatty.
3 – Flatulence, upper abdominal pain and tenderness.
4 – Anorexia – vomiting (in early stage).
5 – Malabsorption, weight loss due to large number of the parasite
adhering to the mucosal surface of the small intestine may interfere with
absorption, competition of parasite & normal flare for nutrient.
Steatorrhoea?
Diagnosis
 The cysts and trophozoites can be found in drarrhoeal stools.
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 trophozoite may be recovered by duodenal aspiration .
(Early stage
cyst + trophzoite)
(Late stage
cyst).
 Fatty and offensive stool confirm diagnosis.
 Laboratory Diagnosis
 Cysts can be found by examination of the deposit of a formol-ether
concentrate of a stool preparation. The oval cysts with thick walls
serve as characteristic features for these organisms. The flagella
disintegrate and form a central ‘streak’ which becomes visible
when stained with iodine or MIF (merthiolate-iodineformaldehyde). Cysts may be excreted intermittently; therefore it is
important to examine more than one stool. Stools are usually
passed 3-8 times / day and are usually pale, offensive, rather bulky
and accompanied by much flatus.
 Trophozoites are found by examination of saline wet preparations
of fresh, diarrhoeic stool, duodenal or jejunal aspirate or in a
permanently stained faecal preparation.
 Trophozoites can also be found in the jejunal aspirate. These can
be recovered by the String Test or Enterotest capsule and the
material examined microscopically for motile trophozoites.
 Trophozoites and cysts can be found to be scarce in chronic
infections. Serological methods of diagnosis are proving to be
useful as means of diagnosis. An ELISA to detect IgM in serum
provides evidence of a current infection. A polyclonal antigencapture ELISA can be used to demonstrate submicroscopic
infections in faeces and an IgA-based ELISA will detect specific
antibodies in saliva.
Treatment
Metronidazole and tinidezole are the drugs of choice.
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Trichomods are widely distributed, there are three human species.
1 – T. vaginalis of the vagina
2 – T. hominis of the intestine
(only pathogen)
heavy
Caused diarrhea.
3 – Tenux of the mouth.
They may be differentiated site of origin.
T. vagnalis
is a sexually transmitted flagellate. Members of both
sexes are equally susceptible to this infection, but women tend to remain
infected for longer periods of time.
Trichomonas vaginelis is a common sexually transmitted infection it
was described by Donne – 1836
1837
regarded as a commensal
describe vaginalis infection
Trichomonas vaginalis is role as a primary phages of human urogenital
tract is now undisputed.
Therapy of human trichomoniasis was inadequate until the 1960 when
metrenidozol (and derivatives) were found.
Diseases.. Trichomonal virginities, urthritis, prestatovesiculitis
Mode of infection …
1 – Sexual transmission: it is the most prevalent.
2 – Bathing water.
3 – Contaminated cloths.
Epidemiology.. The incidence of infection is about 10 – 25 % in Women
it is higher in groups in which feminine hygiene is deficient.
Morphology …
T.vaginalis occurs only as the trophozoite, there being no cystic form
in trichomonas. The tropthozoit is a void or pear – shape with a short
undulating membrane reaching up to the middle of the body. It has 4
anterior flagella and a fifth running along the margin of undulating
membrane.,
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Which is supported at its base by a flexible rod, its Costa? A
prominent axostyle runs throughout the length of the body and projects
posterior. The cytoplasm shows prominent granules which are most
numerous alongside the axostyle and Costa.
Life cycle.. After infection with T.vaginalis the trophozoite live in close
association with, and at times even attached to the epithelium of the
urogental tract.
The normal habitats are the human vagina in the female host, the
organism typically feeds on the mucosal surface of the vagina ingesting
bacteria and leukocytes and at times being phagocytosed by macrophage.
In male T.vaganilis habitats in urethra, epididymis and prostate hence
it is frequently found in the urine.
T.veginalis divides by longitudinal binary fission which is initiated
by division of the nucleus followed by division of neuromotor apparatus
and finally separation of the cytoplasm into two daughter organisms.
Note … the trophozoite is one of the most resistant of the parasitic
protozoa. It loses its vitality below ph.4.9 hence it cannot live in the
normally acid vaginal secretion ph. 3.8 to 4.4 of healthy adults.
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Pathology & symptomatology ..
The causative agent is responsible for a low – grade inflammation by
its toxic action on cells and production of viginitis.
 The bacterial flora and the physiologic status of the vagina
including pH. Are among the factors that determine infection.
 Hyperemia & petechial hemorrhages.

In a advanced Cases
granular area.
 The surface is covered with creamy or yellowish discharge.
 Vaginal and cervical inflammation
itching and burning.
 In male there may be arthritis and prostatovesiculitis .
Diagnosis …
1 – Clinical diagnosis is based on symptoms.
2 – The microscopic examination in a drop of saline for motile
trichomonads of the fresh vaginal discharge.
Obtained with a
speculum on cotton – tipped applicator and dipped in normal saline
Solution
is the most practical method of diagnosis.
 Cultures will reveal the organism when microscopic examination is
negative.
3 – Prostatic secretion following prostatic massage and urine of the male
should be examined.
Acridin orang
 staining : looking for morphology of parasite by
Note...
Giemsa station
1- Care should be taken to prevent contamination to the specimen with
feces since T. hominis may be seen and misdiagnosed as T. vaginalis.
2 – If more than 10 minutes has passed since the collection & specimen
motility can often be increased by incubation the sample at 35 – 37 for a
few minutes.
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Treatment …
1 – Metronidazales (flagyl) . 0.5 gm twice daily for (5) days
2 – Acidifying agents (as lactic acid) used as I table spoon in I liter warm
water.
For mild …
Restoration of normal acid PH of the vagina will suppress
trichomonas below PH. 5.0 - silver picrate – use
Habitat …
 ♀. The vagina especially when vaginal secretion is less acid than
normal (average ph 5.5).
 Cervix, uterus or the urethra, urinal bladder In ♂ it may inhabit the
urethra, urinary bladder, prostate and seminal vesicle.
Pathogenesis and symptomatology …
In female the patient feeling itching in the external genitals:
 Burning sensation and frequency of urination.
 Milky yellowish exudates from the vagina.
In male
 Infection is generally asymptomatic.
 When symptoms occur, they consist of burning sensation during
urination, accompanied with a yellowish discharge from the
urethra.
 If infection extends to posterior urethra and prostate, urethritis
becomes chronic.
Trachomas homins …
 Carries 5 anterior flagella and undulating membrane that
extends the full length of the body. It is a very common
harmless commensal of the Caecum .
 Undulating membrane with a free trailing posterior end.
 The semi rigid axostyle with a spiked posterior end
protruding through the posterior portion of the cytoplasm.
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 Thick Costa that extends the full length of the undulating
membrane.
Trichomonas tenax …
It is a harmless commensally which lives in the mouth. This is smaller
than T. vaginalis
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