Protozoa Lecture Notes.ppt presentation

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1. The Protozoa
Introduction:
There are about 45,000 protozoan species; around
8000 are parasitic, and around 25 species are important
to humans.
Diagnosis - must learn to differentiate between the
harmless and the medically important. This is most
often based upon the morphology of respective
organisms.
Transmission - mostly person-to-person, via fecal-oral
route; fecally contaminated food or water; other means
include sexual transmission, insect bites or insect feces.

2. Protozoa of medical
importance

Amoebae

Flagellates

Ciliates

Sporozoa

3. The Amoebae
It is an intestinal Protozoa –
The definitive host ingests the infective cyst stage from fecal
contamination in environment.
The cyst passes into the small intestine & excystation occurs
with transformation to the trophozoite stage.
Trophozoites colonize the host, multiplying asexually via
binary fission. They can remain near the lumen (non-
pathogens) or invade the wall of the intestine & multiply
(pathogens).
Cysts and Trophozoites are passed in the feces of the
infected host.

4. The Pathogenic Amoebae
1. Entamoeba histolytica
Epidemiology - Occurs worldwide; the highest
incidence and prevalence is in areas with
poor sanitation.
Estimated that 50,000 - 100,000 deaths a
year are caused by this parasite.
 High incidence during natural and man-
made disasters.
Worldwide distribution, but more abundant
in the tropics.

5. Entamoeba histolytica cont..
Pathology and Clinical Manifestations -
the most pathogenic of all; causes
amoebic dysentery; can become
extra-intestinal; can be fatal.
Hepatic abscess is the most common
and dangerous complication.
Chronic infections may last for years;
often confused with colitis, cancer

6. Morphology of E.Histolytica

Morphology & Laboratory Identification - The
trophozoites range 12 to 30 microns in diameter;
nucleus has an even distribution of peripheral
chromatin and a small, compact, centrally located
karyosome; cytoplasm is smooth and granular;
inclusions, if present, are red blood cells.

7. Structure of E.Histolytica
under microscope
1: Smooth cytoplasm
and granular
2: Smooth cytoplasm
and granular with Red blood cells

8. Morphology
Endosome
{
Nucleus
Vacuoles
Erythrocytes in vacuoles

9. Morphology cont..

cysts range 10 to 20 microns in
diameter and contains four nuclei
when mature. Cigar-shaped chromatic
bars may be present in some cysts

10. The Amoebic cyst under
microscope

11. Non Pathogenic Amoebae
1. The Entamoeba coli
Significance - this is a harmless commensal; must
be differentiated from pathogens.

Morphology - trophozoites range from 10 to 35
microns in diameter; cysts range from 10 to 30
microns in diameter and contain 8 to 16 nuclei
when mature; the nucleus exhibits an eccentric
karyosome with irregular, coarse chromatin. The
cytoplasm is heavily vacuolated, containing yeast,
bacteria, and debris.

12. Structure of E.Coli under
microscope

13. Non Pathogenic Amoebae
2. Entamoeba gingivalis
Infective site - the mouth; the organism thrives in
diseased gums, but is not considered a causal
agent. It is destroyed in stomach if swallowed.
Transmission - contact with fomites (drinking
glasses, eating utensils, etc.); kissing.
It is the only species which ingests leucocytes.

14. Structure of E.G under
microscope

15. The Flagellates
The flagellates, inhabit the mouth, bloodstream, gastrointestinal, or
urogenital tracts.
Morphological Characteristics

Flagellum(ae) - organelles of locomotion; an extension of ectoplasm;
moves with a whip-like motion.

Axostyle - a supporting mechanism, a rod-shaped structure; not all
flagellates have these.

Undulating membrane - a protoplasmic membrane with a flagellar rim
extending out like a fin along the outer edge of the body of some
flagellates.

Costa - a thin, firm rod-like structure running along the base of the
undulating membrane.

Cytosome - a rudimentary mouth; also referred to as a gullet.

16. The Flagellates
Identification of a flagellate is based upon:

Size.

Shape.

Motility.

Number and morphology of nuclei.

Number and location of flagellae.

Location in the body of the host.

17. Pathogenic Flagellates
A. Intestinal flagellates
1. Giardia lamblia

Most common protozoan parasite

Life cycle - man ingests cysts from fecally contaminated
environment; the organism excysts in the upper intestine;
trophozoites multiply and attach to the intestinal mucosa;
often enter the gall bladder.

Trophozoites and cysts are passed in the feces.

Diagnosis - identification of cysts or Trophozoites in stool
specimens or duodenal contents.

18. Giardia lamblia cont..
Morphology - very distinctive. Dorsal-
ventrally flattened, and Bi-laterally
symmetrical.
Cyst - 9 x 12 micrometers and contain 2 to 4
nuclei; parabasal bodies are present.
Trophozoite - Four pairs of flagella - one pair
located anterior, two pair located ventrally,
and one pair located posteriorly. An axostyle
and parabasal bodies are present.

19. Giardia lamblia cont…

Epidemiology - prevalence 1 to 30%, common in
children’s day care centers; can be transmitted in
water. Sexual transmission has been well
documented.

Pathology and Clinical Manifestations - symptoms
can be severe; diarrhea, foul-smelling, greasy,
mucus-laden stools, flatulence, nausea, cramps.
Most infections are asymptomatic; chronic cases
experience weight loss, malabsorption of fat,
protein, folic acid, and fat-soluble vitamins.

20. Structure of G.Lambilia under
microscope

22. 2. Trichomonas vaginalis
Life cycle - trophozoite lives in the vagina,
urethra, epididymis, and prostate; multiplies via
longitudinal fission; no cyst stage.
Mode of infection - sexual intercourse or
fomites.
Diagnosis - identification of trophozoites in body
fluids (wet mounts of discharges) or on PAP
smears.

23. Trichomonas vaginalis cont..
Signs and symptoms:
Females: vaginal discharge; burning, Itching, or
chafing. Frequency of urination or dysuria.
Males: frequently asymptomatic. If the prostate is
involved, the patient may develop discharge,
dysuria, and enlargement of prostate with
tenderness.
Morphology - has an axostyle and short
undulating membrane that extends less than half
the body length; 4 flagellae.

24. Structure of T.V under
microscope

25. Non Pathogenic Flagellates
1. Trichomonas hominis

Commensal - must differentiate from pathogens.

Transmission - direct person-to-person fecal
transmission; no cyst stage.

Morphology - “arc-shaped” exhibits a wobbly,
jerky, motility.

Must differentiate from T. vaginalis - in instances
where feces is contaminated with urine.

26. T.H under microscope

27. Haemoflagellates

The blood and tissue of humans may be
infected by one of the several

species of flagellate protozoa belonging
to the family Trypomastidea.

There are six genera but only two of
them are responsible to causedisease to
man. These are Genus Leishmania and
genus Trypanosoma.

28. A. Leishmania

Leishmania species are transmitted by
Sandflies (Phlebotomus, Lutzomia)

Mode of Transmission

1. Inoculation by infected sandfly

2. Direct contact with the ulcer

3. Autoinfection

It contains five developmental stages
from the vector to humans

29. 1. Leishmania stages
Spherical, no free flagellum,
No undulating membrane,
The only intracellular forms of all leishmania
species

30. 2. Promastigote stage

Elongated, Single free flagellum,

single nucleus, no undulating

membrane, nucleus is.near the

middle. The kinetoplast is just in

the anterior portion. This form is

found in the invertebrate host,

and in culture media (of all

Leishmania species

32. 3. Epimastigote stage

Elongated body, single free

flagellum, single nucleus,

undulating membrane, the

kinetoplast is just anterior to the

nucleus.

34. 4. Trypomastigote stage

It can be as “U” or “C” shaped, single free
flagellum, single nucleus, undulating
membrane.

The kinetoplast and axonemes are found
at the posterior end relative to the
nucleus.This form is found in the
peripheral blood

36. 5. Metacyclic stage

Morphologically similar to
trypomastigote stage but it is short and
stumpy.

It is the final developmental stage in the
gut of the insect vectors and is

the infective stage from the insect vector
to man.

37. Laboratory Diagnosis

Amastigotes in stained smears taken
from infected ulcers, lesions, sores
and nodules

Promastigotes from culture media.

Immunologic tests for all stages

38. B. Trypanosoma
gambiense

Geographical Distribution:
West and western central Africa,
extending from Senegal across to Sudan,
South Sudan and down to Angola.

The parasites is transmitted by a bite of
teste fly and can also be transmitted
through blood transfusion, and
congenitally.

39. Clinical Features and Pathology

chancer, fever,haedache,
sweating, post cervical
enlargement of the lymph node,
splenomegally, hepatomegally,
meningoencephalilis

40. Habitat:

Blood vessels

Lymph nodes

Spleen

Liver,

Brain

CSF

41. Structure under microscope

42. Laboratory Diagnosis

Wet thick or thin stained blood films -to
observe motilit,

Aspirate from enlarged lymph gland,
chancher fluid, CSF

Testing serum for anti-trypanosomal
antibodies.

43. The Ciliates
1. Balantidium coli
Epidemiology - This is the only ciliate parasite of
humans.
Largest parasitic protozoan - trophozoite is 30-120
x 25-125 microns; the cyst averages 50 - 70
microns in diameter.
Life cycle - The cyst is ingested via fecal
contamination in environment; cysts resides in the
small intestine; trophozoites migrate to large
intestine.

44. Balantidium coli
Morphology - Large, oval shape; two
nuclei, 1 large kidney shaped
(macronucleus) & 1 small micronucleus
(micronucleus not often seen); body
surface covered by longitudinal rows of
cilia; cytostome present.
Primary animal reservoir - pigs, monkeys.

45. Balantidium coli cont..
Pathology & Symptoms - Many infections
are asymptomatic, organism feeding on
bacteria at surface of mucosa. Severe
infections - the organism burrows into
submucosa, producing ulcers. Symptoms -
dysentery, abdominal pain, nausea &
vomiting, fever, headache.
Diagnosis - Diagnosed by observing cysts &
trophozoites in fecal samples.

46. Balantidium coli under microscope

47. SPOROZOA

Sporozoa contains two classes of medical
importance which include Intestinal
(Coccidia) and Blood (Hematozoa)

The intestinal sporozoa contains the
human parasites like Cryptosporidium
Parvum and Isospora Belli

The class Haematozoa contains the blood
sporozoans like the Plasmodium species

48. a. Coccidia sporozoa
Mode of Transmission

Through ingestion (faecal-oral) in
contaminated food and water

In healthy human hosts, the median
infective dose is 132 oocysts

The life cycle begins with oocysts which
contain 4 naked sporozoites.

Oocysts are infective at the time of
excretion

49. 1. Cryptosporidium Parvum

The ingested oocysts resides in small intestine and
sporozoites

The sporozoites invade epithelial cells of small intestine
and become intracellular.

The sporozoites undergo development to form schizonts

Schizonts burst to release merozoites which invade other
epithelial cells.

Some of the merozoites changes to macrogamonts and
microgarmonts and initaiate the sexual life cycle where by
oocyct are produced.

Ocysts are passed into faeces and cause infections to other
hosts

50. Diagnosis
1. Specimen

Stool

Serum
2. Serological tests

ELISA

51. Single arrow indicate a budding yeast cells in a wet mount of stool
Double arrows indicate C. parvum oocyst
Structure of C.Parvum under microscope

52. 2. Isospora Belli

It is opportunistic parasite associated with
AIDS

The oocyst is in a rugby ball shape

The wall is smooth and colourless

Its size measures about 28 x 14µm (microns)

It causes diarrhoea (usually self-limiting) in
immunocompetent patients and Chronic
diarrhoea in the immunocompromised
patients like in HIV&AIDS

 

53. Diagnosis
1. Specimen

Stool

Serum
2. Serological tests

ELISA

54. I. Belli under microscope

55. b. Haematozoa

Plasmodium is one of the genus in the class
hematozoa

They are parasites of human that reside in the
red blood cells

There are four species of plasmodium of medical
importance namely

Plasmodium falciparum

P. vivax

P. ovale

P. Malariae

The four species of plasmodium are responsible
for causation of malaria to human

56. Life Cycle of Plasmodium
Plasmodium undergoes four major forms
throughout its life cycle. These include

Sporozoite stage (from mosquito)

Trophozoite stage (in blood stream)

Merozoites stage (in liver)

Gametocytes stage (in Red Blood Cells)

57. Life Cycle of Plasmodium cont..

Sporozoites from the salivary glands of an infected
female anopheles are injected into the blood stream
when the mosquito takes a blood meal

Within 30 minutes enter liver cells in which they develop
into liver schizonts. This is exo-erythrocytic

Liver schizonts burst and produce merozoites which
enter the circulation

In the circulation, these merozoites enter red blood
cells to form trophozoites. These form schizonts

The blood schizonts burst to release the merozoites

58. Structures under microscope

62. Laboratory Diagnosis of
Plasmodium
Specimen

Blood smear (thick or thin smear) for
all species
 Malaria Rapid Diagnostic Test
(mRDT) for P.falciparum only  

63. THE END
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