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Theme:Medical Parasitology.


Chair of Medical Biology, Microbiology, Virology, and Immunology Theme:Medical Parasitology. Lecturer As. Prof. O.V. Pokryshko Pathogenicity: From the site of bite ... – PowerPoint PPT presentation

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Title: Theme:Medical Parasitology.

Chair of Medical Biology, Microbiology,
Virology, and Immunology
ThemeMedical Parasitology.
Lecturer As. Prof. O.V. Pokryshko
The main questions of the lecture
are 11. The forms of association between
organisms of different
species. 22. Medical Parasitology as a
science. 33. Classification of parasites and
hosts. 44. Protozoan diseases. 55. Classification
of Protozoa. 66. General characteristic of
Protozoa. 77. Parasites of different classes of
  • Symbiosis is the living together or close
    association of two dissimilar
    organisms. There are three forms of the
    symbiosis mutualism, commensalism and
  • Mutualism is symbiosis in which both parties
  • Commensalism is symbiosis in which one party
    (commensalis) is benefited and the other party
    (host) receives neither benefit nor harm.
  • Parasitism Gr.parasitios eating with another is
    symbiosis in which one party (parasite) benefits
    at the expense of the other (host).
  • Parasitology Gr. Parasitos parasite?-logy is
    the science of parasitism and parasites.
  • Medical Parasitology is the science or study of
    parasites of humans. Medical Parasitology
    consists of Medical Protozoology, Medical
    Helminthology and Medical Arachnoentomology.
  • Medical Protozoology is the study of human
    parasites of Protozoa.
  • Medical Helminthology is the study of human
    parasitic worms of Cestodes, Nematodes and
  • Medical Arachnoentomology is the study of
    parasites of Arthropoda.

  • Parasite lives upon or within another living
    organism (host) at whose expense it obtains some

  • External parasite (ectoparasite) lives on skin or
    hair of host.
    parasite (endoparasite) lives in body organs,
    body tissues, body cells, body cavities of host.
  • Facultative parasite is an organism which may be
    parasitic upon another but which is capable of
    independent existence.
  • Obligatory parasite cant live apart from its
  • Temporary parasite lives free of its host during
    part of its life cycle.
  • Permanent parasite lives in its host from early
    life until maturity or death.
  • Host is an organism that harbours or nourishes
    another organism (parasite). The hosts divide
    into definitive host, intermediate host and

  • Definitive host (final h.) is a host in which a
    parasite attains sexual maturity harbours the
    adult or sexually mature parasite.
  • Intermediate host harbours the immature or
    asexual stages of the parasite.
  • Reservoir host an animal that harbours the same
    species of parasites as man and constitute a
    source of infection to him.
  • Vector is an arthropod that carriers a parasite
    to its host.

Invasious diseases are caused by animals.
Protozoan diseases are caused by Protozoa.
Anthroponotic diseases are characteristic for
humans. Zoonotic diseases are characteristic for
animals. Anthropozoonotic diseases are
characteristic for humans and animals.  There
are four ways of agent transmission of invasious
diseases 1) contagion (by skin contact, sexual
contact) 2) alimentary or faecal-oral
transmission (ingestion of raw or undercooked
food or use of drinking water containing the
infective stage of the parasite) 3) by blood
(by bite of vector containing the infective
stage, blood transfusion) 4) congenital (through
the placenta).
  • Kingdom Animalia
  • Subkingdom Protozoa
  • Phylum 1. Sarcomastigophora
  • Subphylum Sarcodina. Class Lobozea. Type species
    Entamoeba histolytica, Entamoeba coli,
    Entamoeba gingivalis.
  • Subphylum Mastigophora (or Flagellates).
  • Class Zoomastigophorea. Type species Trypanosoma
    brucei gambriense, Trypanosoma brucei
    rhodesiense, Trypanosoma cruzi, Leishmania
    donovani, Leishmania tropica, Lamblia
    intestinalis, Trichomonas vaginalis, Trichomonas
    intestinalis, Trichomonas buccalis.
  • Phylum 2. Apicomplexa. Class Sporozoa. Type
    species Plasmodium vivax, Plasmodium malariae,
    Plasmodium falciparum, Plasmodium ovale,
    Toxoplasma gondii.
  • Phylum 3. Ciliophora. Class Ciliata. Type
    species Balantidium coli.

Morphology and Ultrastructure of
Protozoa 1) Protozoa are unicellular animal
organisms. 2) Each protozoon performs all
functions of life. 3) Sizes is from 1 microm
until 150 microm. 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 in protection, locomotion,
ingestion of food, excretion and respiration.
7) Locomotion either by pseudopodia, cilia and
flagella. 8) The endoplasm encloses
organelles, contractile vacuoles for
osmoregulation, food vacuoles containing food
during digestion. 9) The nutrition of all
protozoa is holozoic. Absorption of liquid food
through the body surface, or ingestion of solid
particles by the help of pseudopodia or through
the cytostome. 10) Reproduction may be asexual
or sexual.
Class Lobozea 1)          Motion is by
pseudopodia. 2)          Reproduction is by
binary fission. 3)          The production of a
cyst is one of the stages in the life cycle. 4)
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 Geographical distribution
Cosmopolitan Morphology Three forms 1) forma
2) forma minuta
3) cyst.
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           Life cycle of Entamoeba
histolytica Host Homo sapiens Transmission
faecal-oral (alimentary) Infective stage mature
cyst Localisation large intestine
Pathogenicity 1) Intestinal amoebiasis
formation of ulcerus 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, lung, brain, skin.
Laboratory diagnosis Fresh stools are examined
under the microscope. E. histolytica (forma
magna and cysts with 4 nuclei) can be
demonstrated in the stools. Prophylaxys
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
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Entamoeba coli. Cyst (8 nuclei)
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, Plasmodium malariae, Plasmodium
falciparum, Plasmodium ovale, Toxoplasma gondii.

Plasmodium vivax tertian malaria
Plasmodium malariae quartan malaria
Plasmodium falciparum tropical (falciparum) malaria
Plasmodium ovale tertian ovale-malaria

Geographical distribution in parts of Africa,
Asia, Turkey, the West Indies, Central and South
America, and Oceania
Blood stages of Plasmodium 1) young trophozoites
(ring forms) 2) growing trophozoites 3) mature
trophozoites 4) mature shizonts 5)macrogametocyt
es 6) microgametocytes
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 blood, liver Clinical
manifestations fever, anemia, splenomegaly,
hepatomegaly Laboratory diagnosis Microscopy of
thin and thick films blood smears. Different
stages of the parasite (trophozoites, schizonts,
and gametocytes) can be demonstrated in the
blood. Prophylaxis. Malaria may be prevented by
chemoprophylaxis and personal protective measures
against the mosquito vector (Anopheles).
PARASITE E Exoerythrocytic schizogony (liver
phase) 1.  Mosquito bites man, takes blood meal
and injecting 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 lyse 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.
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Patient with malaria. Clinical manifestations
fever, anemia, splenomegaly, hepatomegaly
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Malaria. Blood smear
Parasite Toxoplasma gondii
Disease toxoplasmosis Geographical
distribution Cosmopolitan Morphology
Four forms 1) pseudocysts
2) trophozoites 3) cysts 4) oocysts
Intermediate hosts birds and mammals,
including humans Definitive hosts cats
and other Felidae 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)
Toxoplasma gondii
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from cat intestine to cat faeces. 2. Oocysts
sporulate in soil and are viable for longer than
one year. 3. Humans ingest oocysts either from
soil or cat raw tissue infected with cysts. The
alimentary route of infection takes place on
ingestion of meat, milk, and dairy products of
animals sick with toxoplasmosis, uncooked egges
of affected birds, and water contaminated by sick
animals. 4. Transmitted via placenta when
mother develops infection during
gestation-congenital infection. 5. Invade
intestinal wall after entering host (usually
orally) and disseminate via lymphatics and
bloodstream forming trophozoites. Toxoplasma
gondii can spread to many host cells (of the
histophagocytic system, nerve tissue, liver,
placenta, etc).
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Class Zoomastigophorea 1) Motion is by flagella.
The flagellum arises from kinetoplast. The
kinetoplast is composed of the blepharoplast and
the parabasal body. 2) Vesicular nucleus with
central karyosome. 3) Reproduction is by
longitudinal binary fission. 4) Complex life
cycles include alternation of hosts. Intermediate
hosts commonly serve as vectors, which transport
developing parasites from one definitive host to
another. Parasitical species parasites 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.  
Parasites Trypanosoma brucei gambiense and
Trypanosoma brucei
rhodesiense Disease African trypanosomiasis, or
sleeping sickness Geographical distribution West
and Central Africa Morphology spindle-shaped
cells with an undulatory membrane and pointed
flagella at the ends. The organisms are motile,
25-40 microm in length. 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
hartebeest, lion, hyena. Localisation blood,
lymph nodes, cerebrospinal fluid, brain,
Trypanosoma brucei gambiense
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Scanning electron micrograph (5.500
magnification) of African trypanosome
(Trypanosoma brucei gambiense ) among host red
blood cells.
Tsetse fly (Glossina palpalis) is vector of T. b.
gambiense and T. b. rhodesiense
  • Pathogenicity
  • From the site of bite trypanosomes reach the
    blood and lymphatics where they multiply.
  • 2) There is perivascular infiltration with
    chronic inflammation, leading to
  • 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.

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Laboratory diagnosis 1) microscopic
examination of blood and of material obtained by
puncture of the enlarged lymph nodes 2)
examination of the cerebrospinal fluid
(availability of trypanosomes).
Prophylaxis 1) treatment of patients 2)
protection of the population from the bites of
tsetse flies (Glossina palpalis) 3) the use of
insect repellents, extermination of vector
Trypanosoma brucei gambiense in blood.
Parasite Trypanosoma cruzi Disease American
trypanosomiasis, or Chagas disease Geographical
distribution South and Central
America Morphology typical, small (20 microm)
trypomastigotes (with flagella) are found in
peripheral blood and amastigotes (intracellular
without flagella) - in tissues. Transmission 1)
by bite of infected bug species of the 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. Clinical manifestation fever, oedema of
the face, and enlargement of the thyroid gland,
lymph nodes, spleen, and liver, heart
alterations. Laboratory diagnosis 1) examination
of patients blood 2) guinea pig inoculation
with 5-10 ml of patients blood 3) serologic
tests. Prophylaxis 1) extermination of bugs
2) chemoprophylaxis with special preparations in
endemic areas.
American trypanosomiasis (Chagas Disease) was
discovered in 1909 by C. Chagas in Brazil.
Bug of family Triatomidae is vector of
Trypanosoma cruzi
Parasite Leishmania tropica Disease Cutaneus
leishmaniasis Geographical distribution Asia,
Africa, Europe Morphology Intracellular
amastigotes (without flagellum) 3 to 6 microm
long by 1.5 to 3 microm in diameter live in men.
Promastigotes (with flagellum) develop in the
intestine of the sand fly. Transmission by sand
fly vector - Phlebotomus sergenti (in Iran, Iraq,
and India) Phlebotomus papatasi (in southern
France, Italy, and certain Mediterranean
islands). Reservoir hosts man, dogs, wild
rodents. Localisation cells of skin.
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Phlebotomus sandfly is vector of Leishmania
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. Prophylaxis early diagnosis,
extermination of sandflies and dogs and rodents
infected with leishmaniasis, and vaccination.
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Parasite Leishmania donovani Disease Visceral
leishmaniasis, or kala-azar Geographical
distribution India, Pakistan, China, and Central
Africa, Central America. Transmission by sand
fly vector Phlebotomus Reservoir hosts man,
dogs (except in India), cats, rodents. Localisatio
n cells of visceral organs (liver, spleen, lymph
nodes, bone marrow). Clinical manifestation
hepatosplenomegaly, irregular fever, chills,
vomiting, anemia, an earth-grey color of the
skin. Laboratory diagnosis examination of
sternal bone marrow obtained by sternal puncture.
Prophylaxis early diagnosis, opportune
treatment, rodent control, and extermination of
sandflies and of dogs infected with
Parasite Lamblia intestinalis Disease
lambliosis Geographical distribution
cosmopolitan. Morphology Trophozoites are
bilateral, symmetrical, pear-shaped organisms
with an elongated posteri?r and two symmetrically
placed nuclei. The body of the parasite is from
10 to 18 microm long with four pairs of
flagella. Cysts are oval-shaped which are 10-14
microm and have four nuclei. Host
man. Transmission faecal-oral (alimentary). Infec
tive stage cyst. Localisation the small
intestine (duodenum) and gall-bladder.
Life cycle of Lamblia intestinalis
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
Lamblia intestinalis
Scanning electron micrograph (5.500
magnification) of Lamblia intestinalis in
Parasite Trichomonas vaginalis Disease
Urogenital trichomoniasis Geographical
distribution cosmopolitan. Morphology
Trophozoite is a pear-shaped (7 to 23 microm
long) with four anterior flagella and a fifth
forming the edge of an undularing membrane. The
axostyle extends the length of the body. Host
man Transmission by sexual contact otherwise
(through contact with toilet seats and towels,
for example). 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
Trichomonas vaginalis
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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.  
Parasite Balantidium coli Disease
Balantidiasis Geographical distribution
cosmopolitan. Morphology The trophozoite is from
75 to 200 microm in length, asymmetrical, oval,
with cilia, a cytostome, anal pore, the
macronucleus, the micronucleus, two contractile
vacuoli. Cyst with a double-layer membrane, from
30 to 60 microm in diameter. Hosts man,
domestic swine Transmission faecal-oral
(alimentary) 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. Prophylaxis
protection of foodstuffs and water from
contamination with swine faeces and observation
of individual hygiene when talking care of the
animals (domestic swine).
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Thank you for attention!