Malaria lecture 1

Malaria

By : Najat Elhaj

Introduction:

a vector-borne disease caused by single celled parasites,

the Plasmodium protozoa, and transmitted by female

Anopheles mosquitoes.

Still an enormous pubic health problem and one of the

most common infectious diseases.

The word Malaria comes from 18th century Italian

mala meaning “bad” and aria meaning “air”.

Also known as jungle fever also marsh fever

Associated and cause of poverty and obstacle to

economic development.

History of the Disease:

Dr. Alphonse Laveran,

a military doctor in

France armed forces

health service

discovered malarial

parasite in 1880.

Cont

Later Sir Ronald Ross

,born in India, a British

doctor discovered

malarial parasite in GIT

of anopheles mosquito

that led to realization of

cause.

Malaria in Africa:

According to WHO, the

majority of death occur

among children in sub-

saharan Africa killing an

African child every 30

second.

Taxonomic Classification

Kingdom Animal

Subkingdom Protozoa

Phylum Apicomplexa

Class Sporozoasida

Order Eucoccidiorida

Family Plasmodiidae

Genus Plasmodium

Species falciparum, malariae,

ovale, vivax

Causal agent

The parasite which causes malaria (Plasmodium)

requires two different host:

a vertebrate intermediate host such as a human.

an insect definitive host, also known as the vector.

vertebrate host (Man) Invertebrate host

Female Anopheline mosquito

Transmission of Malaria

Mother to child

(rare)

Blood transfusion

(rare)

TRANSMISSION CYCLE

SPOROZOITES

LIVER

MEROZOITES

RBCs

SHIZONTS GAMETOCYTES

IN MOSQUITO GUT

GAMETE>

ZYGOTE>OOKINETE

Species and Morphology

Species Infecting Humans

Plasmodium falciparum

Malignant tertian malaria

Plasmodium vivax

Benign tertian malaria

Plasmodium ovale

Benign Tertian or ovale malaria

Plasmodium malariae

Quartan malaria

Plasmodium falciparum

(producing malignant tertian malaria)

The name was derived by Welch 1897 from “falx”

(sickle or crescent-like)

Distribution:

Tropics and sub-tropics Africa.

Subtropics Asia.

It is common in southern united states.

Life- cycle & Morphology

Gametes: produce eight microgamete (10 min).

Ookinetes: form in 12 to 18 hours after the insect

takes its blood meal (2.5 µm in breadth and 11 to

13 µm).

Oocysts: mature in 9 days at 30ºC and 23 at 20ºC.

Sporozoites: They are sickle-shaped 10.5-12 µm

They invade the salivary glands of the host

mosqiuto in 9 days after the insect’s blood meal.

Ex-oerythrocytic stages:

There is no secondary generation.

Fully mature EE schizont measure 60 µm and liberate

some 30,000 merzoites or more.

Erythrocytic stages:

Trophozoites are hair-like rings

Nuclei are prominent and may be in two parts that are

opposite to each other or side by side.

Some rings characteristically lie along the edges of red

cells “accolé” forms.

Red cell is invaded by several merzoites even eight.

When the ring become thicker, the host red cell shift from

the peripheral circulation to that of internal organs.

Cont

Schizont: Average of 16-8-32 merzoites.

Maurer’s dots appear as the parasite developed.

Gametocytes:

They are more Banana shape than crescentic shape.

Appear in peripheral blood after 8-11days of the

parasite patency.

Note:

Plasmodium falciparum invade old and young

RBCs.

Plasmodium faciparum invasion may reach 50%.

Schizogony of plasmodium faciparum completed

from 36-48 hours.

Usually only young trophozoites or :ring stage and

gametocytes are seen in peripheral blood smear.

Shizont my be seen in severe pernicious infection.

Thin blood film Giemsa's stain

Gametocyte of P.faciparum (Banana shape)

Plasmodium malariae

(producing malariae or quartan malariae)

Grassi & Feletti 1892

Distribution:

It is common in tropical africa, Burma, Sri lanka,Parts

of Inonesia

Life- cycle & Morphology

Gamete: Eight in number measure 16 µm

Ookinetes: little is Known about Plamodium

malariae ooknietes

Oocysts: mature oocyst rupture in 14 days at 30ºC.

Sporozoites:They are thicker and coarser.(13 to 14

µm).

Ex-oerythrocytic Stages:

EE schizogony is propably completed from 13 to

16 days.

Erythrocytic Stages:

Ring stage has thicker cytoplasm

stained deep blue colour.

Band form may seen.

Birds-eye also seen

Schizont:

Average 12 to 18 typically 16

Rosettes or rosette shape resemble P.vivax (infected

RBCs

aren’t enlarged in P.malariae infection.)

Gametocytes:

Resemble those of P.vivax but they are smaller in size

and less richly pigmented.

Note

Plasmodium malariae invade mature red blood

cell.

Trophozoites:

Ziemanns stippling are present in developed

stages.

Plasmodium malariae characterized by enrich

pigmentation.

Trophozoite of P.malariae (Band form)

Schizont of P.malariae

"Birds-eye" trophozoite of P. malariae in a thin blood smear.

Gametocyte of P.malariae

Plasmodium vivax

(producing vivax or tertian malaria)

Grassi and Feletti 1890.

Distribution:

It found in temperate than in tropical between 16º

to 20º north and 20º south

( Egnhland,Siberia,Argentina and south Africa.)

Life- cycle & Morphology

Gametes: Microgamete six in number

(20 to 25 µm).

Ookinetes: 15 to 22 in length and 3 µm in

width , mature in 24 to 48 hours after the

blood meal has been ingested.

Sporozoites :Narrow and slightly curved.

(14 µm in length).

Erythrocytic stages:

EE schizogony is probably completed from 7 to 8

days. It measure 40 µm I diameter, liberates 10,000

merzoites.

Secondary EE schizogony have been observed 14

days after infection and as late as 9 months after

infection.

Erythrocytic stages:

Delicate blue stained ring of cytoplasm with

red chromatin dot

Late trophozoite: markedly amoeboid,

abundant chromatin.

Schizont: schizont and merzoites large

12 to 24, usually 12 to 18.

Gametocytes: Spherical and compact.

Note

Plasmodium vivax invade young RBCs.

RBCs: Enlarged and decolourized; schüffners

dot usually seen

Ring-stage of P.vivax

Trophozoite of P.vivax

Schizont of P.vivax

Gametocyte of P.vivax

Plasmodium ovale

(producing ovale malaria)

Stephens 1922

Distribution:

Common in tropical Africa, principally on the West

Coast.

Cont

Gametes: Microgamete up to eight, smaller in size than those of Plasmodium vivax.

Ookinetes: smaller in size than those of Plasmodium vivax , appear some 18 to 24 hours after the blood meal has been ingested.

Oocysts: require two weeks to mature at 27ºC

Sporozoites: Elongate, pointed at one end

(11 to 12 µm in length).

Ex-oerythrocytic Stages:

EE schizogony is completed in 9 days. Secondary

EE schizogony occurs.

Erythrocytic stages:

Early trophozoites Compact with one chromatin dot

Two rings in one cell uncommon.

Late trophozoite: Small, compact , not

amoeboid, pigment coarse

Schizont: schizont small but merzoites large 6 to12, usually 8.

Note:

Gametocytes: Similar to P.vivax, but somewhat smaller

RBCs: Enlarged and decolourized; schüffners dot usually seen, infected cell may be oval-shape with fimbriation ends(20 % of the infected cells).

Ring-form trophozoites of P. ovale in thin blood smears.

Trophozoite of P. ovale in a thin blood smear. Note the

fimbriation and Schüffner's dots.

Trophozoites of P. ovale in a thin blood smear.

Schizont of P. ovale in a thin blood smear.

Macrogametocytes of P. ovale in thin blood smears.