- A parasite is an organism that lives on or inside another organism and obtains nutrients from its host without providing anything in return. Parasitology is the study of parasites, excluding bacteria, fungi, and viruses. Major human parasites are classified as intestinal or blood-borne. Important intestinal parasites include Entamoeba histolytica and Giardia intestinalis, while major blood parasites are Trypanosoma gambiense, Leishmania donovani, and Plasmodium species which cause malaria. The life cycles of these parasites involve transmission between human and insect hosts.

1. PARASITES
RATHEESH R.L

2. PARASITES
• A parasite is defined as an organism that lives
in or on another organism and derives it
nourishment without giving anything in
return.

3. PARASITOLOGY
• Parasitology: it is the study of parasites and
such does not include bacterial, fungal and
viral.
• Medical parasitology deals with the parasites
which cause disease in man and animals.

4. CLASSIFICATION
• Human parasites are mainly divided into
– Intestinal parasites
• For a parasite to be defined as intestinal it must have
an intestinal life-cycle stage, though it may have life
cycle stages in the heart, circulation, lung, tissue of
other animals or environment.

5. – Blood borne parasites:
• These are the parasites which are transmitted through
an anthropod vector.
• The most important anthropod for transmitting
parasitic infection is mosquito.

6. • A parasite is defined as an organism that lives
in or on another organism and derives it
nourishment without giving anything in
return.

7. • The parasite may be,
– Ectoparasite: parasite living on the body surface of
the host. Eg: lice
– Endoparasite: parasite living inside the body of the
host. Eg: roundworms
– Obligate parasite: parasites which are completely
depending the host. Eg: plasmodium
– Facultative parasite: parasite that may be capable
of living independently, although they can obtain
nourishment from the host too.

8. – Periodic parasite: parasite which live part of their lives
on a host and another part of life outside of the host.
– Accidental parasites: parasites which lives in an
unnatural host.
– Aberrant parasites: parasites which can live on
particular sites and when migrate to other sites it cant
be survive.
– Intermittent parasites: parasites which visits the hosts
at intervals.
– Specific parasites: parasites which complete the life
cycle in specific host only

9. HOST
• A host is an organism on which the parasites
lives.
• Types are,
– Definitive host: a host in which the parasites lives in
the adult form.
– Intermediate host: a host in which the parasites lives
in the larval form.
– Paratenic host: a host in which the parasites lives
without undergoing any development

10. – Accidental or casual host: a host in which the
parasites lives by accident.
– Natural host: a host in which the parasites lives
naturally.
– Reservoir host or carriers: host which makes the
parasite available for transmission to other host.
– Transport host: it’s a kind of host in which no
development of the immature parasite occurs. The
parasite does not develop within the transport host,
but can be transferred from one host to another.

11. HUMAN PATHOGEN PROTOZOON
PARASITES
• RHIZOPODA
• Entamoeba histolytica
• MASTIGOPHORA
– Intestinal flagellates
• Giardia intestinalis
• Trichomonous hominis
– Genital flagellates
• Trichomonous vaginalis
– Haemo flagellates
• Trypanosoma gambiense
• Leishmania donovani

12. • Sporozoa
• Plasmodium vivax
• Plasmodium falciparum
• Plasmodium malariae
• Plasmodium uvale
• Ciliata
• Balantidum coli

14. Entamoeba histolytica
HABITAT: The organism lives in the mucous
and sub mucous layer of the large
intestine.

15. LIFE CYCLE
• Infection by Entamoeba histolytica occurs by ingestion
of mature cysts in the fecally contaminated water , food
or hands.
• These cytes are reached to the bowel of the human
through consumption and passed with stools.
• When reaching the stomach the 4 nuclei in the stomach
will come out .each of the nuclei is surrounds itself by a
bit of protoplasm and forms amoebula, which grows
and is known as trophozoite.

16. • These trophozoits are actively motile and
move towards the ileosacral region and
affecting the wall of intestine.
• Then these are passed out through feces and
the life cycle is repeated.

17. CLINICAL FEATURES
• It causes gastro intestinal infection known as
amoebiasis.
• The symptoms are,
– Dysentry
– Bloody diarrhea
– Mucous in stool
– Weight loss
– Fatigue
– Abdominal pain
• When the infection spreaded through the blood
means it can cause infection to the lungs, brain,
spleen and the liver

18. LAB DIAGNOSIS
• Macroscopic examination:
– Dark red stool mixed with blood and mucous
• Microscopic examination of the stool:
– Used to demonstrate trophozoites or cysts of the
organism
• Culture:
– Fresh specimen can be cultured in locks egg albumin
medium, craigs medium and balamuths medium
• Serological tests:
– ELISA, LAT and indirect haemagglutination test

19. TREATMENT
• Iodoquinol, paromomycin or diloxanide
furoate are the drug used incase of
asymptomatic infections.
• Metranidazole is the drug used in
symptomatic infections

20. TRANSMISSION
• Through human excreta
• Food handling by the infected individuals
• Through cockroach and house flies

21. PREVENTION
• Wash hands with soap and water
• Good sanitary practice
• Avoid sharing of the personal belonings
• Drink the boiled water only.

23. –Intestinal flagellates
• Giardia intestinalis
• Trichomonous hominis
–Genital flagellates
• Trichomonous vaginalis
– Haemo flagellates
• Trypanosoma gambiense
• Leishmania donovani

24. Giardia intestinalis
• Otherwise known as giardia lamblia or lamblia
intestinalis.
• HABITAT:
• Lives in the duodenum and upper parts of the
small intestine.

25. LIFE CYCLE
• The infection occurs by the ingestion of the
cysts in the contaminated food, water or fecal
oral route.
• These cysts can survive in the cold water for
several months.
• After reaching to the small intestine it release
trophozoites and these trophozoites will
attach to the villi of the small intestine and
multiplication occurs.

26. CLINICAL FEATURES
• The infection is commonly known as giardiasis
• Acute giardiasis develops after an incubation
period of 1-14 days.
• Symptoms are diarrhea, abdominal pain,
bloating, nausea and vomiting, malabsorption
etc

27. DIAGNOSIS
• Microscopy: done to demonstrate the cysts in
the stool and duodenal contents.
• Serological tests: ELISA, indirect
immunoflurescene, counter current immuno
electrophoresis, EIA.

28. TREATMENT
• Drugs for treatment are,
Metronidazole
Tinidazole
Furazolidone

29. TRANSMISSION
• Through contaminated water and food
• Unclean hands

30. PREVENTION
• Drink the boiled water
• Check the food and vegetables for any types
of fecal contents.

31. TRICHOMONOUS VAGINALIS
• HABITAT:
vagina of the females and urethra in
males.

32. LIFE CYCLE
• The parasite lives in the lower genital tract in the
females and males it lives in the urethra and
prostate.
• The total growth and the multiplication is taking
place in these sites.
• They does not appear in the form of cysts and
does not survive in the external environment.
• The transmission is mainly occuring during sexual
intercourse.

33. CLINICAL FEATURES
• The infection is commonly known as
trichomoniases
• Symptoms in females are,
– Vaginitis with purulant discharge
– Abdominal pain
– Dysuria
– Greenish or yellow secretions from the vagina
• Symptoms in males are,
– Urethritis
– Epididymitis
– prostatitis

34. DIAGNOSIS
• MICROSCOPY:
– Its helps to identify the actively motile organisms
in the specimen.
• CULTURE:
– The most commonly used media are cysteine
peptone liver maltose
• SEROLOGICAL TESTS:
– Indirect haemagglutination test

35. TREATMENT
• Metranidazole and tinidazole therapy is
usually succesful.

36. TRANSMISSION
• Unprotected sexual contact

37. PREVENTION
• SAFE SEX

38. LEISHMANIA
• The parasite coming under the group is
leishmania donovani.
• HABITAT: natural habitat is reticuloendothelial
system especially liver ,spleen, bone marrow ,
intestinal mucosa.it may be also find in
endothelial cells of kidney, lungs , CSF and
meninges.

39. LIFE CYCLE
• Leishmania is transmitted by by the bite of
female sand fly, phlebotomous ( a small
fly which bites at night).
• The organism exist in two forms amastigote form
also called aflagellar form(non motile form) and
mastigote form also called flagellar or
leptomonad form.

40. • The sand fly sucks the promastigote (motile) form
of organism along with the blood of the patient
during blood meals.
• The promasigote form after multiplication in the
body of sand fly ascend to pharynx and reaches
its buccal cavity .
• Eventually the buccal cavity of sand fly is blocked
by these promastigote form and are to be
released from mouth before taking second meal.

41. • During biting these promastigote form enters
the circulation and the cycle continues.

42. CLINICAL PICTURE
• There are 3 main clinical forms of
leishmaniasis caused by different species of
leishmania.
– CUTANEOUS LEISHMANIASIS
– MUCOCUTANEOUS LEISHMANIASIS
– VISCERAL LEISHMANIA (KALA AZAR)

43. CUTANEOUS LEISHMANIASIS
• it is most common form relatively benign, self
healing skin lesions.
• These lesions are found in areas where sand
flies bite.
• One or more sores occur in skin which
changes in size and appearance.
• The infecting species are L.tropica, L.major,
L.aetiopica and L. infantum.

44. MUCOCUTANEOUS LEISHMANIASIS
• it is characterized by variable type of and size
of lesions.
• Initially there occurs simple skin lesions and
there is involvement of mucosal membranes
frequently in naso pharyngeal mucosa.

45. VISCERAL LEISHMANIA (KALA
AZAR)
• It is caused possibly by 3 related species of
leishmania.
• The onset is inscidious and Incubation period is 2-
6 months.
• Symptoms are,
– Irregular fever, malaise, loss of weight, weakness
– dry and pigmented skin, edema , epistaxis, severe
anaemia, leucopenia, thrombocytopenia.

46. LABORATORY DIAGNOSIS
• SPECIFIC TESTS
• Microscopy:
– Specimen is smeared on clear glass slide, fixed
with methyl alcohol and stained with Geimsa stain
and leishmania bodies are demonstrated.
• Culture :
– NNN (Novy,Mac Neal and Nicolle) medium
– Brain heart infusion agar medium
– Grace insect medium or Tobie’s medium

47. • Serological test:
– Include ELISA, CFT, indirect immunofluroscence
and hemagglutination test.

48. • NON-SPECIFIC TESTS
• TLC- Shows leucopenia
• DLC- S hows Neutropenia with lymphocytosis and
monocytosis
• WBC:RBC Ratio-1:2000 (NORMAL RANGE IS
1:750)
• Naplier aldehyde test:
– in this test 1 ml of patients serum is mixed with one
drop of formalin (40%) and incubated at room
temperature. Gel formation indicates positive test.

49. • OTHER TESTS ARE,
– Leishmanian skin test
– Animal inoculation test

50. TREATMENT
• Glucantime, pentostan, allopurinol and
amphoterecin B are the drug that are
effective.

51. TRANSMISSION
• Through the bite of sand flies

52. PREVENTION
• Use of mesh doors, mosquito nets and
repellants.
• Insecticidal sprays.

54. • There are four types of parasites that are causing
the malarial disease.
– Plasmodium vivax
– Plasmodium falciparum
– Plasmodium malariae
– plasmodium ovale
• HABITAT: liver cells, erythrocytes and other
organs.

55. LIFE CYCLE
• life cycle of plasmodium is completed in two
hosts, man and female anopheles mosquito.
• Man act as an intermediate hosts while
anopheles is a definitive host.
• Life cycle in man(schizogony or schizogenous
phase)
– When an infected female anopheles mosquito bites a
healthy person it introduces thousands of filarial
parasites into human blood along with saliva.
– These parasites are motile and spindle shaped and is
known as sporozoites (infective form of malarial
parasite)

56. – The sporozoite remains in the blood stream for few
minutes to half an hour and then migrates to liver
cells.
• Schizogony is divided into four phases:
– Pre erythrocytic phase/ cycle
– Exo- erythrocytic phase/ cycle
– Erythrocytic phase/ cycle
– Gametogony

57. Pre erythrocytic phase/ cycle
• The sporozoite enters into the liver cells by its
pointed ends, becomes round and is called as
a tropozoites which enlarges and form
schizont.
• The size of the schizont varies in different
species and contains 20000 to 50000
merozoites.

58. • when merozoites form in large number, the
wall of the schizont and liver cells ruptures
releasing merozoites in the space between
liver cells and ultimately into blood stream.

59. Exo- erythrocytic phase/ cycle
• Some sporozoites on entering the liver cells do
not undergo multiplication and enter into
dormant phase.
• This resting or dormant phase of parasite is
called hypnozoites.

60. • After certain time period (usually 2 years) the
hypnozoites reactivates and become
tropozoites, then schizonts and finally release
number of merozoites.These merozoites
attack RBCs and cause relapse of malaria

61. Erythrocytic phase/ cycle
• The merozoites released by rupture of schizonts
and liver cells after two or more cycles in liver
may re enter blood stream and attack RBC’s.
• In RBC’s each merozoites form tropozoites and
schizont.
• Depending upon the species, there may be 6-24
merozoites per RBC.

62. Gametogony
• Some merozoites formed in erythrocytic cycle
develop into male and female gametocytes
known as micro and macro gametocytes.

63. Life cycle in mosquito (sporogony or
sporogonic cycle)
• When a healthy female Anopheles bites
malarial patient, it sucks these gametocytes
(male and female) along with blood.
• In stomach of mosquito, all the components of
blood including RBCs are digested except
gametocytes.
• The male gametocyte nucleus divides and 8
sperms are formed. In female gametocytes,
nucleus does not divide.

64. • only one sperm enters the female
gametocytesand fuses with its nucleus
forming zygote.
• The zygote elongates and forms a worm like
stage known as ookinete.
• These ookinetes settles below the outer
epithelium , develops a cyst wall and form
oocyst.

65. • Within the oocysts nucleus divides and form a
large number of sporozoites. The wall of
oocysts and stomach ruptures releasing
sporozoites in the body cavity and enters to
the salivary gland.
• The mosquito at this stage is infected and
when it bite, it ejects these sporozoites into
blood along with saliva and life cycle is
repeated again.

66. Pathogenesis
• incubation period is different in different
species.
– P. vivax 10-14 days
– P. ovale 10-14 days
– P. falciparum 10-14 days
– P. malariae : 18 days to 6 weeks

67. • P .falciparum is most pathogenic to man. It
invades RBCs, the cells are ruptured , pyrogens
are released that cause characteristic chills.
• P vivax invades youngest RBCs where as P
malariae invades only older RBCs.
• Clinical symptoms include; peaks in fever(cold,
hot, sweating) splenomegaly and
hepatomegaly.

68. • The different types of fever produced are :
– 1)Benign tertian malaria fever
– 2) malignant tertian malaria fever
– 3) quartan malaria fever
– 4) quitodian malaria fever

69. Other complications are
• Cerebral malaria:
– it is characterized by high grade fever ,
coma,congestion and paralysis.
• Black water fever:
– it is characterized by sudden massive hemolysis
followed by fever and hemoglobinuria.
• Algid malaria:
– it is characterized by cold clammy skin leading to
peripheral vascular failure.
• Pernicious malaria:
– It is a life threatening condition that results due to
anoxia sue to blockage of capillaries.

70. LABORATORY DIAGNOSIS
• Microscopy:
– peripheral blood film (thick and thin smear) is studied
under microscope after staining with leishman
technique.
• Serological test:
– ELISA
– Indirect haemagglutination
• Other test
– -radio immunoassay
– Agar gel diffusion test
– Dot blot assay
– Buffy coat method

71. TRANSMISSION
• Mosquito bite
• Blood transfusion
• Use of contaminated syringes among drug
addicts.

72. TREATMENT
• Include use of quinine, chloroquin,primaquin,
and mixture of sulfadoxin and pyrimethamine.

73. PREVENTION
• Chemical sprays
• Mosquito repellants
• Mesh doors and mosquito nets
• Biological control measures ( use f gambien
fish which feeds on mosquito eggs )

75. BALANTIDIUM COLI
• HABITAT: large intestine of man, pigs and
monkeys.

76. LIFE CYCLE
• They are largest ciliated protozoan parasites.
• The female worms liberate cysts which are
passed in the stool.
• Infection occurs by the ingestion of these cysts
with contaminated water and food.
• Then the colonies will be formed in the large
intestine and the further growth and
multiplication is taking over there.
• Mature cysts are passed with feces and cycle
is repeated.

77. CLINICAL FEATURES
• The disease produced is commonly known as
blantidiasis.
• Mostly it will be asymptomatic
• Some times symptoms occurs like
– Nausea, vomiting, diarrhea, abdominal pain and
weight loss.

78. DIAGNOSIS
• MICROSCOPY:
– Cysts can be demonstrated in the stool specimens
under the microscope.

79. TREATMENT
• The drug of choice is tetracycline with
metranidazole and iodoquinol.

80. TRANSMISSION
• Contaminated water and food
• Unhygienic sanitation

81. PREVENTION
• Use clean, boiled purified water to drink.
• Improve personal hygiene
• Avoid contaminated food and water.