plasmodium is the causative agent of malaria

2. • Malarial parasite, causative agent of malaria
• More than 70 species of M P are known to
infect human ,rodents , monkey, reptiles,and
birds.
• 4 sps of malarial plasmodium, which hosts man
• P vivax (grassi & felleti,1890)
• P malariae ( levaran 1881, grassi
&felleti,1890)
• P falciparum (welch,1890)
• P ovale (stephens,1922)
• P vivax & P falciparum account for 95%
infections.

3. HABITAT
• Distributed in tropics, sub tropics ,&temperate
zones.
P vivax ( benign tertian malaria ) – low death
rate
P falciparum ( malignant tertian malaria /
falciparum / pernicious malaria) - high D .R
P malariae ( quartan malaria) – low d.r
P ovale ( ovale malaria / mild tertian malaria )

4. • 4 sps differs from each other
Morphology
Duration of incubation period
Immunological
Epidemological characteristics and so on.

5. • Two hosts - man & female anopheles
mosquito.
• It undergoes
Asexual phase of lifecycle - man (
intermediate / 2 ͦ host & pathogenicaly
affected host)
Sexual phase of L .C - F. A mosquito (
primary host/ vector)

6. Anopheles vector

7. MORPHOLOGY
• Trophozoite -
• ( mature feeding and growing intracellular parasite
in man)
• It is amoeboid ,uninucleate form, enveloped by
double layered plasmolemma.
• Cytoplasm is granular& vacuolated
• It contains ER ,GC ,ribosomes , food vacuole
,mitochondria
• Food vacuole contain haemozoin
• Concentric body which is attached to double
layered plasmolemma ,have mitochondrial function

9. LIFE CYCLE
• Regular and cyclic alternation btw asexual
and sexual phases
• Asexual phase - human ( intra corporeal
phase)
• Sexual phase - mosquito ( extra corporeal
phase)

11. A) Intra corporeal phase
• Which involves repeating cycles of asexual
multiplication ( schizogony)
• Schizogony takes place in 2 stages
1)Liver cells( liver schizogony)
2 )Erythrocytes (erythrocytic schizogony)
 Phase begins with inoculation of parasites to human
body by mosquito
 This occurs when an infected mosquito bites a man
 Parasite thus injected to human body are called
sporozoites
 Sporozoites - are minute , thread like , curved forms,
with tapering ends & an elongated central nucleus

13. 1)Liver schizogony(pre erythrocyticcycle)
• Sporozoites circulate in the peripheral blood stream for
about 30 min
• They get into parenchyma cells of liver (hepatocytes) to
undergo liver schizogony (tissue schizogony)
• Liver schizogony lasts for nearly 8 days
• Inside hepatocyte ,each sporozoite absorbs nutrients &
grows to a spherical trophozoite known as cryptozoite
• Soon ,it transforms form called cryptoschizont or
cryptomeront
• It undergoes multipe fission ,& give rise to numerous
800- 1000 cryptomerozoites
• Now, liver cell collapses, liberating merozoites into the
liver sinusoids

14. • Cryptomerozoites invade
erythrocyte , undergo
endo-erythrocytic
schizogony & initiate
malarial disease
• During liver schizogony ,
plasmodium donot cause
clinical manifestation in
human.

15. 2) Erythrocytic schizogony (endo –
erythrocytic cycle)
• Merozoites ,entered in the erythrocyte , become
trophozoites
• They feed on host cells by ingesting haemoglobin &
other erythrocytic material
• The portion of erythrocyte,unoccupied by the
trophozoite ,shows a dotted or stipled appearance
These dots are called schuffner’s dots (characteristics of p
. vivax)
P. malariae – form red colored Zeiman’s dots.
P. falciparum- form green colored Maurer’s dots.
 Each trophozoite become vacuolated ring – signet ring

16.  Signet ring - large central vacuole , a
marginal ring of cytoplasm,nucleus,cell
organelles
 Vacuole of signet ring - nutrient vacuole
 Vacuole contain cleavage enzymes, which
breaks haemoglobin of RBC into haematin &
aminoacids
 Haematin is transformed into brownish
yellow, toxic ,malarial pigment haemozoin
which get concentrated in vacuole
 Soon , parasite increases size ,develop,
pseudopodia & becomes ameobiod

18. • Now, parasite occupies more than half of RBC
• This seminature trophozoite - juvenile trophozoite /
ameobula stage
• Parasite grow further ,loses its vacuole , pseudopodia
,becomes rounded ,fill, the whole of the RBC
• It is called mature trophozoite
• Trophozoites transform to a dividing form called
schizont or meront
• It undergoes multiple fission ( erythrocytic schizogony
or merogony ) & produces numerous merozoites /
schizozoites
• Inside RBC , merozoites are arranged concentrically (2
circles) around a compact cluster of pigment granules
• This stage -- rosette stage
• It may contain 8 -24 merozoites

19. • RBC breaks down, releasing merozoites to the
blood plasma
• This initiate malarial paroxysm ,characterized
by high recurring fever & chill
• The pigment & other products get
accumulated in the spleen or beneath the
skin,give a pale yellow colour to malarial
patients
• Some merozoites perish & other penetrate
into fresh RBC within 10-15 min to repeat the
cycle

20. • Hypnozoites (trophozoite which remain dormant for
longer periods & multiply at a later time ) --
responsible for relapse malaria ( exhibited by p.vivax ,p.
ovale)
• Penetration of merozoites into RBC occurs only in
presence of specific receptor molecules on erythrocyte
membrane
• Following penetration into RBC ,merozoites enlarge &
transform to trophozoite - cycle of golgi
• It takes 72 hrs in p. malariae, 48hrs in other sps
• Completed in peripheral circulation
• Parasitic multiplication & release of toxic products is
responsible for clinical attack of malaria - overt
malaria

21. 3) Formation of gametocytes
• Asexual multiplication is difficult (due to
massive destruction of parasite )
• Several merozoites transform to sexual form –
gametocytes
• They will not reenter fresh RBC to repeat cycle
• Gametocytes are of 2 kinds
Microgametocytes
macrogametocytes

22. • Formation occurs in RBC
• Only matured gametocytes appear in
superficial blood vessel
• Maturation takes ̴ 4 days .
• Gametocytes are infective to mosquito

24. B) EXTRA CORPOREAL PHASE
• In the midgut of mosquito ,ingested human RBC
break down ,release gametocyte
• Developmental cycle of plasmodium in mosquito
- cycle of Ross
• It takes 7 -10 days
• Completed in 3 stages
i. Gamogony
ii. Syngamy
iii. Sporogony - gut wall
Midgut cavity

25. GAMOGONY
• Gametocytes give rise to haploid gametes
• Microgametocyte - 4-8 microgametes
( long ,flagellate , motile)
• Macrogametocyte - single macrogamete
( nonflagellate ,nonmotile)
• Formation of macrogamete is a simple
maturation process - macrogametocyte
undergoes meiotic division ,forming
macrogamete & 3 polar bodies(polocytes)

26. • Formation of microgamete - complex
process - exflagellation
• Microgametes undergo meiotic
division followed by mitotic division ,
forming 8 haploid nuclei
• Centriole replicates & forms 8
daughter centrioles
• Centriole transforms to kinetosome -
associated with nucleus to form
flagellum
• Microgametes divides into 8 fragment
,each with a nucleus ,flagellum,
mitochondria etc.
• Shortly detach themselves as actively
moving microgametes

27. SYNGAMY
• Occurs - in gut cavity of mosquito
• Microgamete comes in contact with stationary
macrogamete ,fuse together to form a diploid
zygote
• Gametic fusion - syngamy
• Involves both plasmogamy & karyogamy
• Fusing gametes of plasmodium are dissimilar
- anisogametes fusion -- anisogamy

28. SPOROGONY
• Asexual multiplication of zygote
• Occurs in gut wall of mosquito
• During this, rounded ,immobile zygote
transforms to elongated ,actively moving form
- ookinete
• It pierces gut wall - becomes rounded - gets
encysted - oocyst
• It grows & mature to a dividing form -
sporont

29. • Sporont undergoes repeated mitotic division -
forming sporozoites ( as many as 10,000)
• Whole process - sporogony
• Sporozoites mature to form spindle shaped forms
• Oocyst membrane ruptures ,releases sporozoites
• Enter into haemolymph & reach the parts of
mosquito ( other than the ovaries )
• Large number will accumulate in salivary
apparatus
• Mosquito bites a man , large no: of sporozoites
enter to his blood

31. P. falciparum
• Is the most dangerous of the malaria parasites
– Accounts for 50 % of all malaria cases
– Causes malignant tertian malaria
– Symptoms appear 9 to 14 days after initial infection
– Parasitemia levels are extremely high
• Up to 65% of erythrocytes infected
– Schizonts grow in liver cells
• Schizont ruptures in 5 1/2 days, releasing 30,000 merozoites
• Schizonts are more asymmetrical than other Plasmodium spp.
– Infected RBCs can attach to uninfected RBCs, forming rosettes
• Rosettes can clog venules
– Falciparum trophozoites secrete proteins that cause deformations of
erythrocytes
– Falciparum trophozoites extend pseudopodia, but are not as active as
P.vivax trophozoites

32. • RBC is normal size
• Maurer’s dots - 9 large red spots sometimes
basophilic stippling
• Dark brown or blackish one
• Gametocytes Crescent shaped, larger than a
red cell 9 -10 microns, male and female 12- 14
microns

33. P.vivax
• Trophozoites of P.vivax are much more motile than other plasmodium spp.
– This motility caused Italian researchers to nickname it “vivace”, Italian
for “quick and lively”
• P.vivax flourishes in temperate zones
– Most cases of P.vivax malaria now occur in Asia
– P.vivax is common in North Africa, but not in tropical Africa
• Africans have a natural resistance to this form of malaria
• Schizonts are formed in the liver parenchyma and release 10,000
merozoites upon maturation
• Trophozoites cannot penetrate mature red cells
– In addition, merozoites can only penetrate RBCs with mediated
receptor sites
• Receptor sites are genetically determined, conferring resistance
• A defining characteristic of P.vivax is the development of hypnozoites
– Hypnozoites cause relapse of malarial infection

34. • P.vivax gametocytes are rounded
– It appears that P.vivax gametocytes do not require several
generations to appear
• Causes benign tertian malaria
• Symptoms appear between 12 and 18 days after initial infection
• Number of merozoites 12 to 24 arranged in grape like
clusters
• RBC enlarged
• Schuffner’s dots present
• Yellowish brown fine granules
• Schizont 9-10 microns fills and enlarged Red cell
• Gametocytes – spherical or globular
• Size much larger than red cell
• Male 9 microns
• Female 10 – 11 microns

35. P. Malariae
• Causes quartan malaria
– Causes paroxysms every 72 hours
• Is cosmopolitan, but does not have continuous
distribution
– Is found in many regions of tropical Africa, Asia, South America,
and even Europe
• Is thought to be the only Plasmodium organism that lives
in wild animals
• Parasitemia levels are low
– One parasite per 20,000 red cells
• Symptoms appear between 18 and 40 days after initial
infection

36. • RBC Normal size
• Contain Ziemann’s stippling
• Contain dark brown coarse granules
• Schizont , 6 – 7 microns almost fills a normal
sized red cell.
• Gametocytes Spherical or globular
• Size much larger than a red cell

37. P. Ovale
• Rarest of the four malaria parasites
• Causes tertian malaria
• Symptoms appear between 12 and 18 days after
initial infection
• Common to western coastal Africa, also found in
India, the Philippines, New Guinea, and Vietnam
• Difficult to diagnose due to its similarity to P.vivax
• Gametocytes take longer to appear in blood than
those of other species

38. • Infected RBC slightly larger
• Contain Schuffner’s dots coarse granules
• Schizont 6.2 microns fills three quarters
• Merozoites 6 -12 fills three quarters
• Gametocytes Spherical or globular, much
larger than a red cell

39. TRANSMISSION
• Natural malaria is induced by sporozoite - infection is
transmitted by f.a. mosquito
• Trophozoite or merozoite induced malaria- infection
of blood from a malarial patient containing asexual
forms of erythrocytic schizogony induce malaria in
man
a) Transfusion malaria – transfusion of infected donor
blood
b) Malaria in drug addicts - shared syringes in which
one of them is infected
c) Congenital malaria - rarely from mother to foetus

40. Pathogenesis & clinical features
• Clinical signs of malaria can be attributed to two
factors
– Host inflammatory response
• Produces chills and fever
• Correlated with maturation of merozoites, rupture of RBCs
• Toxins released from burst RBCs can stimulate secretion of TNF by
macrophages
• TNF overproduction and toxicity can cause most or all of malaria
symptoms
– Anemia
• Caused by destruction of RBCs

41. Incubation Period
• Pre-patent Period
–Time taken from infection to
symptoms
• Plasmodium falciparum 6-12 days
• Plasmodium vivax 10-17 days
• Plasmodium ovale 12-16 days
• Plasmodium malariae 28-30 days

42. Benign malaria
• Milder in nature
• Caused by all 4 sps
• Characterised by febrile paroxysm ,anemia , &
splenomegaly
Febrile paroxysm
• Fever comes depending on sps
• It occurs every 4 th day ( 72 hr cycle for P
.malariae ) & every 3 rd day ( 48 hr for other
sps)
• Paroxysm corresponds to the release of
successive broods of merozoites into the blood
stream ,at the end of RBC cycle

43. Paroxysm of fever is comprised of 3 stages

45. Anemia
• After a few paroxysm of fever ; patients
develops anemia
• Causes
• Parasite induced RBC destruction - lysis of
RBC due to release of merozoites
• Bone marrow suppression leading to decrease
RBC production
• Increased fragility of RBC
• Autoimmune lysis of coated RBC

46. SPLENOMEGALY
• After few weeks of febrile paroxysm - spleen
gets enlarged
• It is due to massive proliferation of
macrophages that engulf parasitized &
nonparasitized coated RBC

47. Falciparum malaria ( malignant tertian malaria)
• Possess a no of virulence factors
• So, disease is more acute & severe in nature
• Sequestration of the parasites :
• Important feature of the pathogenesis is its ability
to sequester (holding back) the parasites in the
blood vessels of deep visceral organs like brain,
kidney etc.
• Leads to blockage of vessels, congestion &
hypoxia of internal organs

48. Complications of falciparum malaria
Cerebral malaria
• Occurs due to plugging of brain
capillaries by the rosettes (adhesion
of infected RBCs to other RBCs) of
sequestered parasitized RBC
leading to vascular occlusion &
cerebral anoxia
• Other defects are retinal
hemorrhage ,neurologic sequelae
,rarely deep coma
• Brain appears congested

49.  Algid malaria
• Characterised by cold clammy skin, hypotension,
peripheral circulatory failure ,& profound shock
 Septicemic malaria
• Characterized by high degree of prostration
• High fever with dissemination of parasite - to various
organs leading to multi organ failure
 Perinicious malaria
• Results from anoxia due to obstruction of capillaries
followed by necrosis of tissues
• Organs affected - PM divided into 3 groups
1) affecting nervous system
2) Affecting GI system
3) Affecting other system ( cardiovascular,respiratory &
genito –urinary system)

50. Black Water Fever
• In malignant malaria a large
number of the red blood
corpuscles are destroyed.
Haemoglobin from the blood
corpuscles is excreted in the
urine, which therefore is dark
• It is characterized by
intravascular hemolysis fever,
and Haemoglobunuria
• Cardiovascular collapse and
shock
• Abnormalities in blood
coagulation and
thrombocytopenia (decrease in
blood platelets)

51. Laboratory diagnosis
laboratory diagnosis of malaria is confirmed by
the demonstration of malarial parasites in
the blood film under microscopic
examination.
PERIPHERAL BLOOD SMEAR - GOLD STANDARD
• Thin film - identifying specific sps
• Thick film - to detect the presence of MP

52. Malaria Blood Smear
 Thin films:
• Dry
• Fix
• Stain
• Used to determine the species entire thin film should be
examined about 20-40 minutes for an experienced
observer
 Thick films:
• Dry
• Do not fix but dehemoglobinate
• Stain
 Staining methods:
• Giemsa stain
• Leishman's stain
• Field’s stain

53. Interpreting Thick and Thin Films
• THICK FILM
• lysed RBCs
• larger volume
• 0.25 μl blood/100 fields
• more difficult to diagnose species
• good screening test
• THIN FILM
• fixed RBCs, single layer
• smaller volume
• 0.005 μl blood/100 fields
• good species differentiation
• requires more time to read
• low density infections can be missed

54. • FLUORESCENCE MICROSCOPY
• Kawamoto technique - fluorescent staining
method for demonstrating MP
• Blood smear are prepared on slides & are
stained with acridine orange & examined
under F.Microscope - nuclear DNA is
stained green

55. Quantitative buffy coat examination (QBC)
QBC malarial test is advanced microscopic
technique for malaria diagnosis
It consist of 3 steps
i. Concentration of blood by centrifugation
ii. Staining with acridine orange
iii. Examination under UV light

57. • Ag detection by rapid
diagnostic tests -- Card /
cassette / dipstick
• HRP-2 (histidine-rich protein 2)
• pLDH (parasite lactate
dehydrogenase)
 Serological tests
• IFA ,ELISA, RIA,IHA
 MOLECULAR DIAGNOSIS
• DNA probe
• PCR

58. Immunity in malaria
1) Innate immunity
 Biological resistance against malaria
 Some individuals living in endemic areas of malaria
possess natural & innate resistance to falciparum
malaria on the basis of inheritance of selected genes
expressed in red cells, which include :
 Haemoglobin s gene
 Thalassaemia gene
 Glucose 6- phoshate dehydrogenase (G6PD)
deficiency gene
 Ovalocytosis gene

59. Acquired immunity
a) HUMORAL IMMUNITY
 Specific immunity evident in endemic areas where :
1) An infant below age of 3 mon - protected by IgG Ab
2) Children, who suffer repeated attacks of malaria from
the age of few months , have a substantial immunity
for 6 yr
 Circulating Ab ( IgG, IgM,IgA) - against asexual forms
- protection - by inhibiting red cell invasion &
sequestration
 Ab - against sexual form - reduce the transmission
of malaria

60. Cell mediated immunity
• Cytokines released from T cells stimulate the
macrophage & also stimulate B cells to
produce Ab
• Activated macrophages phagocytize
paracitised RBC
• NK cells mediates cellular cytotoxicity –
against parasitized RBC
• immunity against malaria attack is species
specific, stage specific,& strain specific

61. EPIDEMIOLOGY
• Incidence - MP cause more than 250 million
infections & 1-2 million of death per year -
primarily in infants & non immune adults
• Distribution - world wide , but widespread in
tropical& subtropical developing countries -
where it is endemic
• Infection due to P vivax - tropical & subtropical
countries
• P malariae - 25% infection - in tropical africa
• P ovale - west africa - 10% infection
• P falciparum - highly pathogenic - 80% infection
– world wide

63. Epidemiological classification of
malaria depending on transmission

64. PROPHYLAXIS
 Chemoprophylaxis
• Recommended for travellers
going to endemic areas
• Drugs used are-
chloroquine /mefloquine
 Vector control strategies
• Residual spraying-
insecticides ( DDT ,
malathion, fenitrothion ) -
effective against adult
mosquito

65. • Individual protection -
bed nets, repellents &
protective clothing
• Antilarval measures
• Larvicide- use of mineral
oils / paris green - kill
mosquito larvae& pupae
• Source reduction -
environmental sanitation
,water management&
improvement of drainage
system
• Biological larvicide -
Gambusia affinis, guppy &
Bacillus thuringiensis

66. Malarial Vaccine
Vaccines developed are basically of three types:
• Pre-erythrocytic stage vaccine
• Blood stage vaccine and
• Transmission blocking vaccine
• SPf-66—1st malaria vaccine that was tried in
clinical trials in 1990s.
• RTS,S ( Mosquirix )- Most successful vaccine
candidate.

67. Treatment
• Treatment of malaria focuses on eradication of the blood
parasites
– Several drugs can be administered, such as
• Chloroquine
• Quinine
• Doxycycline
• Malarone
• Lariam
• Fansidar
• Treatment is dependent on several factors, including:
– Type of malaria
– Drug-resistance
• Nearly all strains of P.falciparum are now chloroquine resistant, in
addition to developing resistance to nearly all other currently
available antimalarial drugs
• P.vivax has also developed resistance to chloroquine and
primaquine, though they are not as widespread as P.falciparum

68. Anti malarial drugs and their activities

69. REFERENCES
• Rajesh bhatia,ichhpujani - medical
parasitology
• C k jayaram panicker – text book of medical
microbiology
• Burton bogitsh - human parasitology