Malaria parasite

1. MALARIA PARASITES

2. Classification
• Kingdom- Animalia
• Subkingdom- Protozoa
• Phylum- Apicomplexa
• Class- Sporozoa
• Order – Eucoccidea
• Suborder – Haemosporina
• Genus- Plasmodium

3. MALARIA PARASITES
• Four species of Plasmodium cause malaria in man
- P. vivax
- P. falciparum
- P. ovale
- P. malariae
• P. vivax
- Commonest and most widely distributed species
- Prevalent in both temperate and tropical zones
- Cause benign tertian malaria
•

4. MALARIA PARASITES
- Benign; less dangerous than
falciparum malaria
- Tertian; 48 -hour cycle of
development in man and the fever
recurs
P. falciparum
- Prevalent in the tropics
- cause malignant tertian/subtertian
malaria

5. MALARIA PARASITES
- Malignant ; more dangerous
malaria(often lethal)
- Tertian/subtertian; 40 – 48 -hour
cycle of development
- infection runs a shorter course,
seldom lasting more than 8 to 10
months without reinfection

6. MALARIA PARASITES
P. malariae
- found in both tropical and temperate
zones
- less common than vivax and
falciparum
- cause quartan malaria
- quartan; it has 72-hour cycle
- causes the infection of many years
duration

7. MALARIA PARASITES
• P. ovale
- rare species
- found in West Africa, South
America, Russia, New Guinea
- cause ovale tertian malaria
- ovale; due to irregular oval shape
of infected RBCs

8. MALARIA PARASITES
• P. vivax and P. falciparum account
for about 95 % of all malaria
worldwide

9. MALARIA PARASITES
• Vectors
- Human malaria is transmitted by
female Anopheles mosquito
- The female needs at least two
blood meals before 1st batch of
eggs can be laid

10. Life Cycle and Morphology
• Human Phase
• Human infection comes by the bite
of infective female Anopheles
mosquito.
• Sporozoites which are the infective
forms are present in salivary gland
of the mosquito
• Sporozoites are injected into blood
capillaries when mosquito feeds on
blood of man

11. Life Cycle and Morphology

12. Life Cycle and Morphology
• In the bloodstream sporozoites
reach the liver and enter the cells/
hepatocytes
• Exo-erythrocytic Stage
• In the hepatocytes, the
sporozoites which are elongated
and spindle shaped bodies
become rounded.

14. Life Cycle and Morphology
• Then sporozoites enlarge in size
and undergo repeated nuclear
division to form several daughter
nuclei
• Each daughter nucleus becomes
surrounded by cytoplasm

15. Life Cycle and Morphology
• This stage of parasite is the exo-
erythrocytic schizont and the
parasite multiplies by multiple
fission /division called schizogony

17. Life Cycle and Morphology
• The schizont continue to enlarge
thus distending the hepatocytes
• The schizont matures within 5 to
15 days and bursts releasing
thousand of merozoites
• Merozoites are pear-shaped
bodies about 1.5 um in length,
possessing an apical complex

18. Life Cycle and Morphology
• Erythrocytic stage
• The merozoites enter bloodstream
and invade erythrocytes
• In the RBC, the merozoites
appears as rounded body having a
vacuole in the center surrounded
by ring of cytoplasm with nucleus
at one side, and this resemble a
ring thus called ‘ring stage’

20. Life Cycle and Morphology
• The parasite feeds on the
hemoglobin of the RBC.
• It leaves behind a residue called
malaria /haemozoin pigment
because it does not metabolize
hemoglobin completely
• The pigment accumulate in body
of parasite as dark granules

21. Life Cycle and Morphology
• The ring form continue to develop
and enlarge in size becoming
irregular in shape and shows
amoeboid motility and the parasite
is called trophozoite

22. • At a certain stage of development
of the amoeboid form, the
nucleus starts dividing and the
parasite is called schizont

24. Life Cycle and Morphology
• As the parasite grows, the nucleus
divides into two, then four, eight and
more parts
• As maturity approaches, each
daughter nucleus becomes
surrounded by cytoplasm becoming
merozoites

25. Life Cycle and Morphology
• Mature schizont burst releasing
the merozoites into circulation.
These merozoites attack new
RBCs and repeat the process

26. • The pigment and other waste
products left behind when parasite
breaks up are released into blood
stream and deposited in spleen and
under the skin

28. Life Cycle and Morphology
• The characteristic chills and fever
in malaria are felt at the time of
bursting of RBCs and release of
waste products
- Duration of the erythrocytic
schizogony varies according to
species of the parasite

29. Life Cycle and Morphology
- P. vivax , P. ovale and P. falciparum
usually take about 48 hours in
which to complete schizogony. P.
malariae takes 72 hours

30. • Gametogony
- After few cycles of erythrocytic
schizogony, some merozoites after
infecting RBCs develop into gametocytes

32. Life Cycle and Morphology
- Gametocytes grow in size and
almost fill RBCs.
- Mature gametocytes are round in
shape except in P. falciparum in
which they are crescent-shaped
- Female gametocytes are larger and
more numerous than male

33. Life Cycle and Morphology
• Gametocytes do not develop
further or divide in the vertebrate
host and unless taken up by
mosquito they die within 4 to 5
days

34. Life Cycle and Morphology
• Mosquito Phase
- Female Anopheles mosquito
ingests parasitized erythrocytes
along with its blood meal

35. Life Cycle and Morphology
• In the stomach, gametocytes
undergo further development
• The male gametocyte divide into 8
nuclei, from each of which protrudes
a long, motile whip-like filament and
becomes male gametes /
microgametes

37. Life Cycle and Morphology
• Female gametocytes undergoes a
process of maturation to become
female gametes/macrogametes
• Fertilisation of the female gamete
by male gamete lead to formation of
zygote which is round and non-
motile

38. Life Cycle and Morphology
• Zygote later elongates and
become a motile form with an
apical complex anteriorly called
ookinete.
• Ookinete penetrates epithelial
lining of the mosquito stomach
wall and lies just below the
basement membrane.

40. Life Cycle and Morphology
• Then become rounded into a sphere with
an elastic membrane called oocyst
• Oocyst matures, increasing in size, with
the nucleus undergoing multiple
divisions called sporogony

41. • This leads to development within
oocyst of about a thousand
sporozoites, each with a central
nucleus and anterior apical complex

42. Life Cycle and Morphology
• Mature oocyst ruptures and
sporozoites enter body cavity
• Sporozoites reach the salivary
glands situated in the thorax,
penetrate the cells and enter the
salivary ducts

43. Life Cycle and Morphology
• The mosquito is now infective, and
when it feeds on humans, the
sporozoites are injected into the
skin capillaries to initiate infection