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
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.
13.
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
16.
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’
19.
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
23.
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
27.
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
31.
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
36.
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.
39.
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
