Protozoa as parasites of a human being

1. Theme:
Medical and biological basics of
parasitism. Protozoa as parasites of a
human being

2. All animals are in constant interaction with other
organisms. These interactions can be divided
into two basic types: intra-specific
interactions and inter-specific interactions.
Intra-specific interactions are those that occur
between organisms of the same species.
Inter-specific interactions are those that take
place between different species of organism.
They are next kind of interactions for this type:

3. Mutualism: Relationships are those in which both
species benefit from the association in terms of their
growth and survival.
Symbiosis: Relationships of any two organisms living
in close association, commonly one living in or on the
body of the other.
Commensalism: Most definitions indicate that one
species benefits from the association and the other is
unharmed.
Parasitism: A close relationship in which one
organism, the parasite, is dependent on another
organism, the host, feeding at its expense during the
whole or part of its life.

4. Parasite lives upon or within another living organism
(host) at whose expense it obtains some advantage.
DIFFERENT KINDS OF PARASITES:
Ectoparasite – a parasitic organism that lives on the
outer surface of its host (on skin, hair).
Endoparasite – parasite that lives inside the body of it’s
host.
Obligate Parasite - this parasite is completely
dependent on the host during a segment or all of its
life cycle.
Facultative parasite – an organism that exhibits both
parasitic and non-parasitic modes of living and hence
does not absolutely depend on the parasitic way of
life, but is capable of adapting to it if placed on a host.
Temporary parasite – organism that visits the host only
for feeding and then leaves it.
Permanent parasite – parasite that lives in or on its
host without leaving.

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6. Host is an organism that harbours or nourishes another
organism (parasite).
DIFFERENT KINDS OF HOSTS:
Definitive host (final host) is a host that harbours the
adult or sexually mature parasite.
Intermediate host that harbours the immature or
asexual stages of the parasite.
Paratenic (transport) host – a host that serves as a
temporary refuge and vehicle for reaching an
obligatory host, usually the definitive host, i.e. it is not
necessary for the completion of the parasites life
cycle.
Reservoir host – a host that makes the parasite
available for the transmission to another host and is
usually not affected by the infection.

7. Life cycle of parasites is the route followed by a
parasite from the time of entry to the host to exit,
including the extracorporeal (outside the host) life. It
can either be simple, when only one host is
involved, or complex, involving one or more
intermediate hosts. A parasite’s life cycle consists
of two common phases one phase involves the
route a parasite follows inside the body.

8. Invasive diseases are caused by parasitic animals.
Protozoan diseases are caused by Protozoa.
• Anthroponotic diseases are characteristic for
humans.
• Anthropozoonotic diseases are characteristic for
humans and animals.
The main ways of agent transmission of invasive
diseases:
•contagion (by skin contact, sexual contact);
•alimentary or faecal-oral transmission (ingestion of
raw or undercooked food or use of drinking water
containing the infective stage of the parasite);
•by blood (by bite of vector containing the infective
stage, blood transfusion);
•congenital (through the placenta).

9. Parasitology is the science of parasitism and
parasites.
Medical Parasitology is the science or study of
parasites of humans.
Medical Parasitology consists of:
Medical Protistology is the study of human parasites
of Protozoa.
Medical Helminthology is the study of human
parasitic worms of Trematoda, Cestoda, Nematoda.
Medical Arachnoentomology is the study of
parasites of Arthropoda.

10. Medical Protozoology
CLASSIFICATION OF MEDICALLY IMPORTANT PROTOZOA
Phylum 1. Sarcomastigophora
- Subphylum Sarcodina
- Class Lobozea. Species: Entamoeba histolytica, E.
coli, E. gingivalis.
- Subphylum Mastigophora (or Flagellates)
- Class Zoomastigophorea. Species: Trypanosoma
brucei gambriense, T. b. rhodesiense, T. cruzi,
Leishmania donovani, L. tropica, Lamblia intestinalis,
Trichomonas vaginalis, T. hominis.
Phylum 2. Apicomplexa. Class Sporozoa. Species:
Plasmodium vivax, P. malariae, P. falciparum, P. ovale,
Toxoplasma gondii.
Phylum 3. Ciliophora. Class Ciliata. Species: Balantidium
coli.

11. Protozoa: general description
1. Protozoa are unicellular organisms.
2. Each protozoon performs all functions of life.
4. The protozoa have cytoplasm and nucleus.
5. The cytoplasm is differentiated into ectoplasm (the outer
layer) and endoplasm (the inner layer).
6. The ectoplasm functions are: protection, locomotion,
ingestion of food, excretion.
7. Locomotion either by pseudopodia, cilia and flagella.
8. The endoplasm encloses: organelles, contractive
vacuoles for osmoregulation, food vacuoles containing food
during digestion.
9. The nutrition of all protozoa is heterotrophic. Absorption
of liquid food through the body surface, or ingestion of solid
particles by the pseudopodia or through the cytostome.
10. they have different types of reproduction: asexual and
sexual.

12. Class LOBOZEA:
1. No fixed shape.
2. Motion is by pseudopodia.
3. Reproduction is by binary fission.
4. The production of a cyst is one of the stages in the
life cycle.
The pathogenic species for man is Entamoeba
histolytica, the non-pathogenic (commensal) species
are E. gingivalis, E. coli.
Parasite: Entamoeba histolytica
Disease: Amoebiasis, or amoebic disentery
Morphology: 1) forma magna; 2) forma minuta; 3) cyst.

13. Entamoeba histolytica: trophozoite (left) and
cyst (right)
10 μm

14. Amebiasis
Entamoeba histolytica,
trophozoite - forma
minuta
Entamoeba histolytica,
mature cyst

15. Life cycle of Entamoeba histolytica
Host: Homo sapiens
Transmission: alimentary (faecal-oral)
Infective stage: mature cyst
Localisation: large intestine
Pathogenicity:
1. Intestinal amoebiasis: formation of ulcers of the
wall of the intestine, acute or chronic diarrhoea, stool
containing blood and mucus; may be asymptomatic
infection.
2. Extra- intestinal amoebiasis: abscess of liver,
lungs, brain, skin.

16. Life cycle of Entamoeba histolytica

17. Entamoeba histolytica:
trophozoites

18. Amebic Colitis:
Severe dysentery with multiple ulcers in the large
bowel, and a bloody diarrhea

19. Amoebiasis
Laboratory diagnosis: Fresh stools are examined
under the microscope. E. histolytica (forma magna and
cysts with 4 nuclei) can be demonstrated in the stools.
Prevention: Treatment of patients and asymptomatic
cyst carriers; protection of foodstuffs and water from flies
and contamination with faeces; the staff of catering
establishments must be examined for cysts carriage;
health education of the population.

20. Class ZOOMASTIGOPHOREA:
1. Motion is by flagella.
2. Reproduction is by longitudinal binary fission.
3. Complex life cycles include alternation of hosts.
Parasitical species of tissues and blood:
a) Trypanosoma
b) Leishmania
Their transmission requires a biological vector.
Species living in the digestive tract and genitals:
a) Lamblia intestinalis
b) Trichomonas vaginalis
c) Trichomonas hominis
Their transmission does not require a biological vector.

21. Parasites: Trypanosoma brucei gambiense and
Trypanosoma brucei rhodesiense
Disease: African trypanosomiasis, or sleeping
sickness
Geographical distribution: Western and Central
Africa
Transmission: by bite of infected tsetse flies (Glossina
palpalis)
Reservoir hosts of T.b.gambiense are: man,
domestic pig, cattle, dog, antelope
Reservoir hosts of T.b.rhodesiense are: antelope,
lion, hyena
Localisation: blood, lymph nodes, cerebrospinal fluid,
brain, muscles

22. Morphology of Trypanosoma:
spindle-shaped cells with an undulatory membrane
and pointed flagella at the end.
The organisms are motile, 25-40 μm in length.

23. Scanning electron micrograph (5.500× magnification) of
Trypanosoma brucei gambiense among red blood cells

24. Tsetse fly (Glossina palpalis) is a vector of
Trypanosoma brucei

25. Life cycle of Trypanosoma brucei

26. Pathogenicity:
1. From the place of bite trypanosomes have spread in
the blood and lymphatics, where they multiply.
2. There is perivascular infiltration with chronic
inflammation, leading to meningoencephalitis.
3. The patient suffers from fever, rash, headache,
lymphadenopathy, oedema of the brain. There are
alternating periods of fever and apparent recovery.
This is followed by depression and progressive
lethargy.
4. Rhodesien form develops within weeks to months,
Gambian form develops within years. The disease
becomes chronic and persists for months and even
years.

27. Parasite: Trypanosoma cruzi
Disease: American trypanosomiasis or “Chagas’
disease” (discovered in 1909 by C. Chagas in Brazil)
Geographical distribution: Southern and Central
America
Transmission: 1) by bite of infected bug species of
family Triatomidae; 2) congenital; 3) by blood
transfusion
Reservoir hosts: armadillos, opossums, rodents,
monkeys, dogs, cats
Localisation: blood (in acute phase), cells of lymph
nodes, spleen, liver, brain, muscles

28. Bug of family Triatomidae is vector of Trypanosoma
cruzi

29. T. cruzi in a cardiac muscle

30. Clinical
manifestation:
fever, oedema of the
face, and
enlargement of the
thyroid glands, lymph
nodes, spleen, and
liver, heart alterations

31. Parasite: Leishmania tropica
Disease: Cutaneus leishmaniasis
Geographical distribution: Asia, Africa,
Europe
Transmission: by sand fly vector -
Phlebotomus sergenti (in Iran, Iraq, and
India); Phlebotomus papatasi (in southern
France, Italy, and certain Mediterranean
islands)
Hosts: man, dogs, wild rodents
Localisation: cells of skin

32. Morphology of
Leishmania
•Intracellular
amastigotes (without
flagellum) 2 - 6 μm; live
in man
Promastigotes (with
flagellum) develop in
the intestine of the sand
fly

33. Phlebotomus sandfly is vector of
Leishmania tropica

34. Clinical manifestation: development of a
cutaneous papule that evolves into a nodule,
breaks down to form an indolent ulcer, and heals,
leaving a depressed scar.
Laboratory diagnosis: detection of the
Leishmania parasites in cells of skin.
Prevention: early diagnosis, extermination of
sandflies and dogs and rodents infected with
leishmaniasis, and vaccination.

36. Parasite: Lamblia intestinalis
Disease: lambliosis
Geographical distribution: cosmopolitan
Host: man
Transmission: alimentary (faecal-oral)
Infective stage: cyst
Localisation: the small intestine (duodenum)
and gall-bladder

37. Life cycle
of Lamblia
intestinalis

38. Lamblia
intestinalis
Morphology: Trophozoites are symmetrical, pear-
shaped organisms with 2 nuclei. The body is 10-18
μm with four pairs of flagella. Cysts are oval-shaped
which are 10 - 14 micro;m and have 4 nuclei.

39. Pathogenicity: chronic duodenitis, enterocolitis;
cholecystitis and hepatitis.
Laboratory diagnosis: microscopic examination
of the duodenal contents or faeces.
Prophylaxis: Treatment of patients and
asymptomatic cyst passers; protection of
foodstuffs and water from flies and contamination
with faeces; the staff of catering establishments
must be examined for cysts carriage; health
education of the population.

40. Parasite: Trichomonas vaginalis
Disease: Urogenital trichomoniasis
Geographical distribution: Worldwide
Morphology: Trophozoite is a pear-shaped (7-23 μm long)
with 4 anterior flagella and a fifth forming the edge of an
undularing membrane. An axostyle extends of the body
Host: man
Transmission: by sexual contact; otherwise (through
contact with toilet seats and towels, for e.g.)
Localisation: vagina, urethra, prostate
Clinical Manifestations: vaginitis in women, more
commonly asymptomatic in men, but may lead to
prostatitis or urethritis. The main symptoms are dysuria,
pruritis, yellow and frothy discharge
Laboratory diagnosis: microscopic examination of the
vaginal fluid, scrapings, or washing

41. Trichomonas vaginalis

42. Class Sporozoa:
1. lack locomotory organelles;
2. complex life cycles (sexual and asexual phases);
3. alternation of hosts;
4. the pathogenic species for man are: Plasmodium
vivax, P. malariae, P. falciparum, P. ovale,
Toxoplasma gondii.

43. MALARIA PARASITES OF MAN
PARASITES DISEASES
Plasmodium vivax tertian malaria
Plasmodium malaria quartan malaria
Plasmodium falciparum tropical (falciparum) malaria
Plasmodium ovale tertian ovale-malaria

44. Geographical distribution of malaria:
in parts of Africa, Asia, Turkey, the West Indies,
Central and South America, Oceania

45. Life cycle of Plasmodium species

46. LIFE CYCLE OF THE MALARIA PARASITE
Exoerythrocytic schizogony (liver phase)
1.Mosquito bites man, takes blood meal and injects sporozoites from its
salivary gland into the blood.
2.Sporozoites travel through blood to the liver, multiply asexually to form
merozoites, which upon liver cell rupture, are released into the bloodstream
and infect erythrocytes.
Erythrocytic schizogony (blood phase)
1.Merozoites enter the erythrocytes, forming a ring-like trophozoite; mature
trophozoites asexually divide to form schizonts.
2.Schizont develops into merozoite daughter cells, then lyses the
erythrocytes membrane, leading to periodic paroxysms of disease due to
resultant parasitemia. P. ovale, P. vivax, P. falciparum - membrane lysis in 48
hours, P. malariae - membrane lysis in 72 hours.
3.Some merozoites develop into macrogametocyte and microgametocyte.
Sporogony
1.Mosquito ingests gametocytes with blood meal.
2.Gametocytes enter mosquito gut.
3.Zygote, formed from fertilization, invades gut wall to form an oocyst within
24 hours following ingestion
4.Sporozoites are formed, released into the stomach, migrate to salivary
glands, then injected into human with blood meal.

47. MALARIA PARASITES OF MAN
Intermediate host: Homo sapiens
Definitive host: Anopheles mosquito
Transmission: by bite of female Anopheles mosquito
Infective stage for man: sporozoite
Infective stage for mosquito: gametocyte
Localisation: liver, blood
Prevention: chemoprophylaxis and personal
protective measures against the mosquito vector
(Anopheles).

48. Laboratory diagnosis of malaria:
Microscopy of thin and thick films blood smears.
Different stages of the parasite (trophozoites,
schizonts, and gametocytes) can be demonstrated in
the blood.

49. Parasite: Toxoplasma gondii
Disease: toxoplasmosis
Intermediate hosts: birds and mammals, including
humans
Definitive hosts: cats
Localisation: brain, eyes, skeletal and cardiac
muscles, liver, and lungs
Transmitted to humans by:
1) ingestion of undercooked infected meat (cysts
and pseudocysts);
2) contamination of food or drink with infected cat
faeces (oocyts);
3) transplacental (congenital)

50. Toxoplasma gondii in human liver

51. lung heart muscle

52. Life cycle of Toxoplasma gondii

53. Prevention of toxoplasmosis:
washing of hands before meals and after handling
animals and animal products;
the prohibition of preparing food from insufficiently
cooked meat products, in particular liver;
all women with a history of spontaneous abortion
must be examined by laboratory methods for
prevention of congenital toxoplasmosis.

54. Class Ciliata
1. Move by cilia, which are numerous and cover most
of the body
2. Have 2 nuclei, macronucleus containing vegetative
chromatin and micronucleus containing generative
chromatin
3. Reproduce by transverse binary fission, and
sometimes by conjugation

55. Parasite: Balantidium coli
Disease: Balantidiasis
Geographical distribution: Worldwide
Morphology: The trophozoite is 75-200 μm, oval, with cilia.
Cyst is 30-60 μm
Hosts: man, domestic hog
Transmission: alimentary (faecal-oral)
Localisation: large intestine
Clinical Manifestations: colitis, ulcers and abscesses of
colon, diarrhoea, blood and mucus in the stool
Laboratory diagnosis: microscopic examination of the
faeces
Prevention: protection of foodstuffs and water from
contamination with swine faeces and observation of
individual hygiene when talking care of the domestic hog

56. Balantidium coli trophosoite

57. The lecture is over,
thanks for your attention