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1. Malaria
Introduction & Lifecycle of Plasmodium

2. INTRODUCTION
• Malaria is a mosquito-borne infectious disease
caused by intracellular protozoan parasite
Plasmodium.
• Characterized by cycles of shaking, chills, fever,
sweating and anaemia.
• Affects 500 million and kills more than 1 million
people each year.
• Endemic in tropical and subtropical regions –
Sub-Saharan Africa, Asia and Latin America.
• In India, about 1.5 – 2 million cases and 1000
malarial deaths are reported annually (mostly from
tribal, hilly and inaccessible areas).

3. Causative Agents
Plasmodium species Human infection
Plasmodium vivax Benign tertian malaria
Plasmodium falciparum Malignant tertian / Pernicious malaria
(most common and fatal)
(complications – Cerebral malaria and Black
water fever)
Plasmodium malariae Quartan malaria
Plasmodium ovale Ovale tertian malaria

4. Contd..
• All forms are transmitted
by the infective bite of
female Anopheles
mosquitoes.
• Transmission through blood
transfusion can also occur.
• Man develops disease after
10 to 14 days of being
bitten by an infective
mosquito.

5. Ring-forms and gametocytes of Plasmodium falciparum in human blood.

6. Lifecycle of Plasmodium
• 2 stages
1) Sexual phase in the mosquito
2) Asexual phase in humans
a) Exoerthrocytic (Pre-erythrocytic)
shizogony
b) Erythrocytic shizogony
• The infectious stage of malaria - Sporozoite
(found in the salivary glands of female
mosquitoes).

7. Life cycle in humans
• Mosquito takes a blood meal → Sporozoites
released into human’s blood → infect liver cells
• EXO-ERYTHROCYTIC STAGE :-
Parasites inside heparocyte → Shizont (containing
thousands of merozoites) → infected hepatocytes
release about 30,000 Merozoites (asexual, haploid
forms) → quickly infect red cells.
* [P. vivax and P. ovale form latent Hypnozoites in
hepatocytes, which cause relapses of malaria long
after initial infection]

8. ERYTHROCYTIC STAGE :-
• Within the red cells the parasites grow in a
membrane-bound digestive vacuole, hydrolyzing
haemoglobin through secreted enzymes.
• A) Continuation of asexual reproduction - Most of
the parasites develop into Trophozoites →
Schizont → multiple chromatin in schizonts
develop into Merozoites → Red cell lysis &
merozoites infect other red cells.
B) Production of gametocytes - Some parasites
develop into sexual forms called Gametocytes →
infect the mosquito.

11. Thank you