Malaria is an infectious disease caused by the
parasite called Plasmodia. There are four
identified species of this parasite causing human
malaria, namely, Plasmodium vivax, P.
falciparum, P. ovale and P. malariae. It is
transmitted by the female anopheles mosquito
scientifically known as Anopheles minimus
flavirostris. It is re-emerging as the # 1 Infectious
Killer and it is the Number 1 Priority Tropical
Disease of the World Health Organization.
• Malaria affects more than 2400 million people,
over 40% of the world's population, in more than
100 countries in the tropics from South America
to the Indian peninsula. The tropics provide ideal
breeding and living conditions for the anopheles
mosquito, and hence this distribution.
• Every year 300 million to 500 million people
suffer from this disease (90% of them in sub-
Saharan Africa, two thirds of the remaining
cases occur in six countries- India, Brazil, Sri
Lanka, Vietnam, Colombia and Solomon
• WHO forecasts a 16% growth in malaria cases
• About 1.5 million to 3 million people die of
malaria every year (85% of these occur in
Africa), accounting for about 4-5% of all fatalities
in the world.
• One child dies of malaria somewhere in Africa
every 20 sec., and there is one malarial death
every 12 sec somewhere in the world.
• Malaria kills in 1 year what AIDS killed in 15
years. In 15 years, if 5 million have died of AIDS,
50 million have died of malaria.
~* GENUS *~
• The malarial parasites of humans are caused by species of
the genus Plasmodium of the class Sporozoa.
• The asexual cycle (schizogony) takes place in the red
blood cells of vertebrates and the sexual cycle (sporogony)
•he members of this genus, which cause malaria in mammals
and birds, have closely similar morphology and life cycles.
~* LIFE CYCLE *~
• The life of the plasmodia is passed in two hosts, a
vertebrate and a mosquito.
• The asexual cycle in the vertebrate host is known as
schizogony, and the sporulating sexual cycle in the mosquito
P. vivax P. malariae P. falciparum P. ovale
Quartan Malignant tertian
14 (8 – 27) 15 - 30 12 (8 – 25) 15 (9 – 17)
Yes No No Yes
50,000 - 500,000
Up to 2,500,000
1.5 – 4.0 1.0 – 30 0.5 – 2.0 Probably 1.5 –
~* CLINICAL DIFFERENTIATION OF
THE MALARIAS *~
~* DISEASES *~
• Malaria, are known by several names among which are
paludism, intermittent fever, chills and fever, Roman fever,
Chagres fever, marsh fever, tropical fever, coastal fever and
• The term malaria is derived from two Italian words, mal
(bad) and aria (air).
~* Species Pathogenic to Man *~
• P. malariae was described in 1880 by Laveran.
~ has an affinity for mature or older red cells
• P. vivax was named in 1890 by Grassi and Feletti.
~ prefer to invade young red cells
• P. falciparum in 1897 by Welch.
~ infects cells of all ages
• P. ovale in 1922 by Stephens.
~ prefer to invade young red cells
~* MORPHOLOGY *~
• Some general characteristics are common to all malaria
parasites, but differential features make it possible to
• The earliest form after invasion of the re blood cell is a
ring of bluish cytoplasm with a dot-like nucleus of red
• As this early stage, the trophozoite, grows the
erythrocyte hemoglobin is metabolized to produce a darkly
staining malarial pigment, hemozoin.
• Depending upon the species of parasite, the cytoplasm may
become irregular in shape, and the red blood cell may show
• When the growing parasite divide, it is called a schizont,
showing multiple masses of nuclear chromatin.
• Some of the trophozoites develop into gametocytes, or
sexual stages, which are differentiated by compact
cytoplasm and the absence of nuclear division.
~* PLASMODIUM VIVAX *~
• The infected red cell is enlarged, but this may be partly
explained by the affinity of the parasite for larger
• As the signet-ring appearing trophozoite grows, it becomes
irregular in shape, with amoeboid extensions of the
• Schuffner’s dots make their appearance in properly stained
smears of P. vivax infected cells; these are fine, round, pink
or reddish granules, distributed uniformly over the red cell.
• Increasing amounts of the of pigment accumulate in the
• After 36 hours, the parasite fills over half the enlarged
red cell, and the nucleus divides, becoming a schizont.
• By 48 hours the schizont has segmented into 16 distinct
cells, the merozoites, each with a red nucleus and blue
cytoplasm condensed about it. And the rupture of the
erythrocyte takes place.
• The gametocytes resemble a late trophozoite prior to
• They are oval, nearly filling the red cell – the
microgametocyte with less deeply staining nucleus and
cytoplasm, the macrogametocyte with darker blue cytoplasm
and more compact nucleus.
RING RING RING RING
TROPH TROPH TROPH TROPH
AMOEBOID SCHIZONT SCHIZONT SCHIZONT
~* PLASMODIUM MALARIAE *~
• The early ring form of P. malariae resembles that of
P.vivax, but the parasite is smaller, less irregular, and more
compact, the cytoplasm is a deeper blue.
• The growing trophozite acquires coarse granules of dark
brown or black pigment and may assume a band shape across
• Infected red cells are normal or even smaller than most in
size since old cells are preferentially infected.
• A period of 72 hours is required for the development of
the mature schizont, which resembles a daisy or rosette
with only eight to ten oval merozoites.
• A compact mass of greenish black pigment is often located
centrally, surrounded by merozoites.
• The gametocytes are similar to those of P. vivax but are
RING TROPH TROPH COMPACT TROPH
BAND FORM IMMATURE SCHIZONT MATURE SCHIZONT SCHIZONT
SCHIZONT SCHIZONT SCHIZONT FEMALE GAMETOCYTE
~* PLASMODIUM FALCIPARUM *~
• This differs from other plasmodia of humans in that,
except in infections with very high parasitemia, only in the
ring forms of early trophozoites and the gametocytes are
ordinarily seen in the peripheral blood.
• Schizogony takes place in the capillaries of the muscles
and viscera, and very few schizont are found in the
• The infected red blood cells are of normal size.
• The presence of more than one ring form in a cell is
• Double chromatin dots are frequently found in P.
falciparum ring forms, and only occasionally in the rings of
• The schizonts, seldom found in the blood, resemble those
of P. vivax but have smaller and a few more merozoites
when mature and ready to rupture.
• The immature gametocytes gradually acquire an elliptical
shape, stretching but remaining within the red cell.
• When fully developed, they have a characteristic banana
shape, the so-called crescent.
• In cells, infected with P. falciparum there are sometimes
cytoplasmic precipitates known as Maurer’s dots that
appear as irregularly distributed red spots or clefts.
APPLIQUE FORM DOUBLE RING MULTIPLE RING
OLD RING RING TROPHOZOITES
MATURE SCHIZONT GAMETOCYTE MALE GAMETOCYTES
~* PLASMODIUM OVALE *~
• Commonly found in West Africa, but infrequently
encountered elsewhere, is similar to P. vivax and P. malariae
in several characteristics.
• The infected red blood cells are slightly enlarged, can be
of oval shape, and show Schuffner’s dots.
• An important diagnostic feature is the irregular or
fimbriated appearance of the edges of the infected red
• Schizonts have centrally massed pigment and only about
eight merozoites when mature.
RING RING RING
TROPH TROPH TROPH
SCHIZONT SCHIZONT MATURE SCHIZONT