( P. malariae, P. vivax, P. ovale
By: Vencinth Romano
The term malaria was derived from the Latin words
“mala aria or bad air”, denoting the diseases association
with the bad smelling air coming from stagnant water, a
favorite breeding sight of the mosquitoes that harbor the
Malaria is a disease of antiquity. It is characterized by
intermittent chills, fever and sweating, anemia &
splenomegaly. It is caused by protozoan parasites of the
genus Plasmodium which is transmitted to man when the
parasite infective stages are inoculated by the mosquito
during a blood meal.
FOUR MAIN TYPES OF MALARIA
1.Plasmodium Plasmodium malariae 1881 - intermittent
fever every 72 hrs. It is also known as Quartan Malaria.
2. vivax 1890 - intermittent fever every 48 hrs. It is also
known as benign Tertian Malaria.
3. Plasmodium falciparum 1897 - intermittent fever every
36 - 48 hrs. It is also known as Malignant tertian Malaria
4. Plasmodium ovale 1922 - intermittent fever every 48
hrs. It is also known as Ovale tertian Malaria.
1. Morphological features of P. malariae
All the asexual stages of the parasites may be observed in the
peripheral blood. The infected RBCs are normal in size. In the
trophozoite stage, the young forms are about 1/3 of the diameter of
the RBC and have a peculiarly solid appearance. The developing
trophozoites lacks vacuole is band-like in form and pigment granules
are large, numerous and dark.
There are 6-12 merozoites (usually 8) in the schizont stage. These
merozoites are usually arranged peripherally around a centrally
clumped pigment in a rosseste formation.
The gametocytes are spherical or oval in normal sized RBCs. There
are abundant prominent dark brown coarse pigment scattered inside
2. Morphological features of P. vivax
All the asexual stages are also seen in the peripheral
blood. The infected RBCs are enlarged and decolorized.
Shuffner’s dots are prominent. The ring form or young
trophozoite occupies 1/3 of the diameter of the RBC and
usually has 1 chromatin dot. The rings are definite but the
outlines are irregular. The developing and older
trophozoites are large with very irregular pseudopodial
processes of the cytoplasm.
The Schizont usally contains about 16 merozoites. The
gametocytes are spherical or ovoidal in shape in enlarged
RBC; the Shuffner’s dots are prominent.
3. Morphological features of P. falciparum
The infected RBC are not enlarged or discolored. The multiple
infection of the RBC is common. Normally, only the ring form or young
trophozoites and gametocytes are observed in the peripheral blood.
The ring forms have delicate, thread-like line of cytoplasm. Some
have double chromatin dots; some are found in the margin of the RBC
called “applique or acole forms”. Also, characteristically, red cells
maybe invaded by several rings, even up to 8.
Schizonts are usually not found in the peripheral blood. When seen,
the merozoites usually number 8-24.
The gametocyte seen in the peripheral blood are crescent or
sausage shaped. The gametocytes appear in peripheral circulation
after 8-11 days after patency, then disappear after about three (3)
4. Morphological features of P. ovale
The infected RBC is somewhat larger than normal, oval in shape
and usually with fringed or irregular edge. Schuffner’s dots
appear very early even in older rings.
All the stages are found in peripheral blood. The trophozoites
comprise a single bead of chromatin connected by a ring of
cytoplasm surrounding a vacoule. Merozoites which are 6-12 in
number, may be arranged in rossete formation arround a mass
of brown pigment granules. Gametocytes are rather large,
round or oval bodies and occupy th whole of the enlarged
infected red blood cell.
Characteristic of life cycle
Intermediate host : human
Final host : mosquito
Infective stage : sporozoite in mosquito
merozoites in human
Infective way : mosquito bite skin of human
Parasitic position : liver and red blood cells
The multiple organ pathology in malaria is essentially due to tissue anoxia (lack of
oxygen) and immunopathological mechanism.
The severity of tissue anoxia in malaria cannot be adequately explained by
obstruction of blood flow due to the clumping of the parasitized RBC alone. Another
factor has been recently implicated. Stasis resulting from sympathetic constriction of
renal cortical and portal circulation leads to cellular ischemia and damage to the
endothelium. Both of these as well as the release of kinins increase o the
endothelium water and protein molecules so that edema occurs outside the blood
vessels, while hyperviscosity and more red blood cells clumping and obstruction to
blood flow occur inside the blood vessels. The end result is tissue anoxia to which the
vital organs(brain, adrenals, kidneys, heart and lungs) are the most sensitive. Other
organs that become involved are GI, liver and placenta.
Under certain circumstances, the immune response may itself result in disease.
Such in the case in malaria, because some immunological factors have been
implicated in several malaria complication – glomerulonephritis, topical splenomegaly
syndrome (TSS), cerebral malaria and hemolytic anemia.
laboratory diagnosis of malaria is confirmed
by the demonstration of malarial parasites in
the blood film under microscopic
examination (using thick and thin blood
smears) (takendurind the febrile state &
stained with Giemsa or Wright’s stain)
Serology – Rapid Diagnostic Tests
Malaria is the leading cause of death and disease in many
developing countries. According to the World Health Organization’s
World Malaria Report 2011 and the Global Malaria Action Plan, 3.3
billion people worldwide live in areas at risk of malaria transmission
in 106 countries and territories.
In 2012 malaria led to 216 million clinical episodes, and
655,000 deaths. An estimated 91% of deaths in 2010 were in the
African Region, followed by 6% in the South-East Asian Region and
3% in the Eastern Mediterranean Region (3%). 86% of all deaths
worldwide are children.
In the Philippines, all provinces with slow flowing, partly shaded, clean
mountain streams are endimic because these are breeding sites of the
pricipal mosquito vector, Anopheles flavirostris. There are three secondary
vectors: Anopheles mangyanus, which is also a clean stream breeder,
Anopheles balabacensis, which is a forest rain fall breeeder; and Anopheles
litoralis, which thrive in brackish water. Anopheles maculatus also a stream
breeder, is a potential vector.
The annual parasite incidence is 15/1000, with 70% of cases caused by P.
falciparum and 30% of these cases are caused by P. vivax. Transmission is
perinial with two (2) peaks, one at the beginning and the other at the end of
P. Malariae is, with few exceptions, found only in Sulo Archipelago. Two
indigenous case of P. ovale infections were reported from Palawan Island in
Malaria can also be transmitted thru infected bood during blood
transfussion and also by congenital infection. In these cases the Exo-
erythrocytic phase in the liver is absent.
PREVENTION & CONTROL
Using Mosquito Net
Avoid outdoor night activities (particularly during
the vector's peak biting hours from 9pm - 3am
Using mosquito repellents/repellants
Reconstruction of environment: eradicate the
breeding places of mosquitoes.
House Spraying (using insecticides
Choloroquine is the drug of choice for treatment in area
where there is a little or no parasites resistance to this drug.
Sulfadoxine/pyrimethamine combination is used where there is
high level of resistance to Choloroquine. In areas where there is
resistance to both, Mefloquine or Mefloquine/
Sulfadoxine/pyrimethamine combination may be used.
Primaquine is the only drug currently available for the radical
treatment of relapsing vivax or ovale malaria.