GAURAV PAL (12BSZBC021)ANDTANMAY SRIVASTAVA (12BSLSCFS015)

PLASMODIUM

(MALARIAL

PARASITE)

CLASSIFICATION

Phylum- Protozoa

Sub Phylum- Plasmodroma

Class- Sporozoa

Order- Haemosporidia

Genus- Plasmodium

Introduction

Reservoir host- Monkey.

Secondary host- Female Anopheles; where it completes mainly its sexual cycle.

Primary host- Human being; where it completes it asexual life cycle.

Members of order Haemosporidia show digenetic life cycle i.e. Plasmodium completes its life cycle in two hosts.

Members of class Sporozoa are parasite so locomotory organs are absent in Plasmodium

CONT….

Eradication of Plasmodium is not easy due to its several host.

Another reason is that vaccine can’t be formed because, Plasmodium don’t induce human body to form antibodies and hence no immunity against Plasmodium can develop.

Number of chromosome in Plasmodium= 10

Different species of Plasmodium

About 60 species are known but only

4 are pathogenic.

1)-Plasmodium

vivax

Most common species.

2)-Plasmodium falciparum

Most lethal

species.

3)-Plasmodium malariaeLess harmful

species.

4)-Plasmodium ovale

Absent in India and

present in Philippines

and Africa.

Life cycle of Plasmodium

Life cycle of Plasmodium in Humans

• Liver

• RBC

There are two sites for activity of Plasmodium in

human-

All the activities that occur in liver are known as Exo erythrocytic cycle.

Whereas activities in RBC are termed as Erythrocytic cycle.

Infective stage of Plasmodium for human is sporozoite.

These sporozoite are present in the salivary gland of female

Anopheles.

The amount of sporozoite are about 2,00,000.

Female Anopheles

Structure of sporozoite

It is spindle or some times sickle shaped.

Body is covered with pellicle which is made up of 11-15 microtubules.

Sporozoite contains an aperture at the apex called Micropyle.

A structure that covers micropyle is known as Apical cap.

This cap is made up of 3 concentric microtubules.

A pair of secretory organelles are related to micropyle.

It contains lytic enzymes which helps sporozoite to penetrate human liver

cells.

A big oral shaped nucleus is present in middle of sporozoite.

Just beneath it Mitochondria is present.

An anticoagulent(Anophilin) is

secreted when female Anopheles bites.

It do not allow

blood to clot so

that Anopheles can suck blood easily. With the saliva,

numerous of sporozoites

enters in human blood.

Within 30 minutes all

of the sporozoite

sapproaches the liver

and no sporozoiteis visible in the blood.

Pre erythrocytic cycle

First life cycle of Plasmodium in liver.

Plasmodium starts its life cycle from liver as:-

• To prevent itself from phagocytic action of WBC.

• It uses glycogen as food and liver is rich in glycogen.

• To multiply in number.

Sporozoite enter in the liver cell and

become spherical by phagocyting the

cytoplasm.

Now these are termed as

cryptozoites.

These undergo multiple division

called schizogony.

This results in the formation of 1000-

1500 small structures called as cryptomerozoites.

At this stage cryptozoites is called schizont.

Finally cell memberane of liver cell and schizont burts and cryptomerozoites are now free in blood sinusoides of

liver.

A few of these cryptomerozoites infect RBC and start the erythrocytic cycle.

Schizont stage

Rest of the cryptomerozoites go back in liver cells and start the post exoerythrocytic cycle.

Time taken to complete pre erythrocyticcycle is called Pre patent period.

In this period Plasmodium is not visible in blood.

Post exoerythrocytic cycle

In this cycle, cryptomerozoitesinfect the liver cells.

They phagocyte the cytoplasm and become big and spherical.

Now these are known as

metacryptozoite orphanerzoite.

Two types of metacryptozoites are

formed-

Micro metacryptozoites

(MICRO MCZ)

Macro metacryptozoites

(MACRO MCZ)MICRO MCZ are further converted into 100-1000

merozoites by the process of schizogony.

The product is called Micro meta

cryptomerozoite(Micro MCM).

Similarly Macro MCZ produces 64 merozoites which are called Macro meta crypto merozoite

(Macro MCM).

Micro MCM infect onlyRBC whereas MacroMCM infect liver cells.

This cycle goes on repeating again and again which causes

destruction of liver cells.

In case of an excessive malaria, liver may

damage and jaundice like symptoms may

appear.

Erythrocytic cycle

This cycle is also known

as Golgi cycle.

This cycle starts at first by Cryptomerozoites and further

carry on by micro meta

cryptomerozoites.

Cryptomerozoites infects RBC.

They phagocyte haemoglobin of

RBC and become big and spherical.

Now they are called as

trophozoites.

Later on a big

central vacuole is formed in

the cytoplasm

of trophozoit

es.

This makes

it appear like a ring.

So this stage is called Signet

ring stage.

After a while

vacuole is lost and

trophozoites

become irregular

in shape.

At this stage

Plasmodiumlooks like

Amoeba so

this is called

as Amoeb

oid stage.

Signet ring stage

This is active and

feeding stage of

Plasmodium.

It phagocyte

s haemoglobin quickly and grows

up and occupies whole of the RBC approx.

Particularly, at this stage

reddish brown

colored granules

are seen in the

cytoplasm.

These are called

haemozoingranules.

It is the non digested part

of the haemoglobin.

Haemozoin granules in food

vacoule

At the same time bright

yellow colored

granules appear in the cytoplasm of

RBC.

These are called

Schuffner’s dots which

are probably waste

products of Plasmodium.

These dots are used in diagnosis of malaria as

they are the most clear structures

that appear in blood.

Schuffner’s dots

There are two species of Plasmodium that do not form Schuffner’s dots.

1)- P. malariae – They form red colored Zeiman’s dots.

• Both of these are also helpful in diagnosis of malaria.

2)- P. falciparum- They form green colored Maurer’s dots.

Rosette stage

Brust RBC is called ghost RBC.

Spleen uptake this ghost RBC from the blood and destroy it by special type of phagocytic

cells called as macrophages.

These cells secrete an enzyme Lysolecithin which destroy ghost RBC.

In case of excessive malarial infection, spleen becomes large and swollen this disease is called Megaly of spleen or spleen index.

Spleen index Macrophage

cell

It is due to increase in number of

macrophages and

lysolecithincauses

swelling.

Excessive malarial infection may also lead to

Haemolytic anaemia

because more lysolecithin

secretion occurs which reaches to

blood and destructs the

healthy RBC’s.

So decrease in number of

healthy RBC’s causes

anaemia.

The time laps between infection of Plasmodium and first attack of malaria is called incubation

period.

Plasmodium shows biological clock system because

Erythrocytic cycle is completed exactly in 48 hours in case of P.

vivax, P. falciparum , P. ovalewhile 72 hours in case of P.

malariae .

Post Erythrocytic Cycle

Sometimes merozoites formed by erythrocytic cycle escapes from blood and enters the liver cells.

These merozoites remain inactive in liver.

After a long time, they become active and multiply in number.

This causes malaria again.

So after a long time, malaria is repeated again, this is called Relapse of malaria.

Post erythrocytic cycle is not found in P. falciparum.

So relapse malaria do not occur.

Longest relapse of malaria is found in P.malariae which may last up to 3 years.

Gametocyte stage

When many erythrocytic cycles completed then merozoites enter the RBC and form a new stage called as Gametocyte or Gamonts or Resistant Trophozoite schizont.

Gametocyte is the last stage in human.

Further development occurs in female Anopheles.

This is because high temperature in human is

unfavourable for gametocyte formation.

There is biological clock system in Plasmodium i.e.

it forms gametes when there is more probability

of attack of female Anopheles.

So gametes are formed in night, from late

evening up to midnight.

Gametocytes which reach in female Anopheles are developed and rest which are left in blood are destroyed in the morning.

Two types of gametocytes are formed-

• Micro gametocyte

• Macro gametocyte

These are formed in the ratio of 1:2 respectively.

LIFE CYCLE OF

Plasmodium in

female Anopheles

There are two types of cycles :-1)- Gametogony ( sexual cycle )2)- Sporogony ( asexual cycle )

Gametocyte is the infective stage of Plasmodium for female Anopheles.

When it sucks blood, many stages reach in its crop but only gametocyte stage remains, rest of all are digested.

Gametogenesis

Microgametocytes undergo the process of spermatogenesis

in which its nucleus is divided into 4 haploid

nuclei by meiotic division.

Further, mitosis occurs and these are

converted into 8 nuclei.

All nuclei are arranged on periphery.

At the site of every nucleus, plasmalemmaprojects outwards and

8 spindle shaped projections are formed.

Every projection contains a nucleus and few cytoplasm.

These projections are called sperms.

Every sperms detaches it self from microgametocytes

by constricting at its base.

So 8 sperms are formed by a single microgametocytes.

Exflagellation

Macro gametocytes forms ovum

by the process of oogenesis.

Meiosis occurs

resulting in the formation

of 1 ovum and 3 polar

bodies.

Polar bodies are

destroyed further.

A projection appears on ovum which

is called reception

cone.

This is the penetration

site of sperm at the time of fertilization.

Zygote is formed as a result of fertilization.

Whole of this process upto zygote formation occurs in lumen of crop.

Zygote can form in any type of mosquito e.g Anopheles, Culex, & Aedes etc , but further development of zygote is possible in female Anopheles.

This is the host specialization of Plasmodium. (as female Anopheles provides royal jelly.)

Development of zygote

Proposed by Grassi.

According to him all zygotes are converted into long worm like structures called ookineteor vermicule.

With the help of gliding and wriggling movement these ookinete enter the crop wall and are placed beneath the outermost layer called peritonium

of the crop wall.

At this stage 50-100 small projections of oocyst are found on the crop wall.

This stage is called oocyst.

A thin and elastic coat is secreted around these zygotes by both zygote and cells of crop wall.

Sporogony

Oocyst takes nutrition from the crop wall

and develop into 5-6 times bigger structure called

sporont.

Many small vacuoles are

now formed in the cytoplasm of

sporont.

Nucleus of sporont is

converted by free nuclear divisions into approximately 10,000 nuclei.

All these nuclei are arranged on

periphery of vacuoles.

Later on cytoplasm is divided and

converted into 10,000 parts around every

nucleus.

As a result 10,000

sporozoites are formed.

This sporont is called as

sporocyst.

Outer most layer of crop and wall of

sporont burst and these

sporozoites are now free in

haemoceal of mosquito.

Haemocoel is a blood filled cavity.

The blood is colorless and is called haemolymph.

All sporozoites are stored in salivary glands.

About 2 lacks sporozoites are stored in salivary glands of mosquito which further infect to human through saliva.

Invasive stages

Merozoite

• erythrocytes

Sporozoite

• salivary glands

• hepatocytes

Ookinete

• epithelium

Special points about P. falciparum

Malaria caused by P. falciparum called lethal malaria is the most dangerous malaria because infected RBC adhere and form thrombus which

may interfere in blood circulation.

Carotid artery is feeding artery of brain so when this artery is blocked by thrombus

then brain may suffer from less blood circulation which is unfavourable for it.

Longer duration of this condition may cause death.

When thrombus is formed in coronary arteries,

which gives nutrition to heart, heart attack may

occur.

Loss of Haemoglobinthrough urine( Haematuria )

occur in which color of

urine changes from

yellow to black.

Hence, it is also called as Black water

fever.

Double signet ring and crescent

gametocyte are

characterstics of P.

falciparum.

Types of malaria

Caused by P.vivax, P.falciparum, P.ovale.

Recurrence of fever is after every 48 hours i.e. every third day.

Three types of malaria are recognized on the basis of periodicity of paroxysms (recurrent attacks of fever)-

1.Tertain malaria or Common ague

2. Quartan malaria-

Paroxysms occur at intervals of about 72 hours (every 4th day)

Caused by P.malariae.

3. Quotodian malaria-

Paroxysms are irregular and almost daily.

May be due to multiple or mixed infections by more than species of Plasmodium.

4. Relapse malaria-

Exoerythrocytic cycles continue uninterrupted in P.vivax, P.ovale and P.malariae even after the disease is completely cured.

Merozoites of these cycles can anytime attack RBCs and cause a relapse of malaria.

History of malaria

Mc. Culloh - termed malaria.

Lancisi – suspected that there is any relation between mosquito and malaria.

Charles Laveran- discovered Plasmodium in human RBCs and revealed that malaria is caused by Plasmodium.

Sir Ronald Ross- proved the relation between mosquito and malaria.

About 25000 mosquitoes were dissected by Sir Ronald Ross in his life.

Female Anopheles is the carrier of Plasmodium.

Awarded by Noble Prize on 29th Aug. 1902.

This day is celebrated as malaria day.

Grassi- studied the life cycle ofPlasmodium in female Anopheles.

Symptoms of malaria

Due to toxic effects of

Haemozoin granules on

body, symptoms of

malaria appear.

Initial symptoms of malaria include,

• Nausea

• Constipation

• Body pain

• Dyspnea

• Weakness in body.

After 2 or 3 Erythrocytic cycles Haemozoingranules increase in number and actual

symptoms of malaria now begins to appear.

This is called Paroxysm of malaria.

• Rigor stage:- alternate contraction and relaxation in muscles causes shivering and cold sensations.

• Febrile stage:- after some time shivering stops and body temperature rises due to contraction of muscles.

It has 3 stages:-

Rise in temperature is beneficial for patients because internal high temperature is unfavourable for parasite Plasmodium. Temperature :- 104- 105 F

*Difervescent stage:- after rise in temperature excessive sweating occures and body temperature decreases.

• Now patient feels himselfs healthy.

• But at this time Erythrocytic cycle starts again and fever is repeated at a constant interval of time.

Prevention and

Control

Control of malaria

Two methods-

• Direct – by killing Plasmodium.

• Indirect- by killing mosquitoes.

Direct method-Plasmodium is destroyed by

chemotherapy.

Old medicines like Quinine, destroys only that stages of Plasmodium

which are present in

blood.

Mapacrimedestroys

merozoitespresent in

blood.

Paludrine & Sulphadoxinedestroys all the stages either in blood or liver but are not

generally used because the

cause harm to liver cells.

The most effective

medicine for malaria is Deraprim

which destroys

gametocytes.

Indirect method:-Following

procedures are used to

kill mosquitoes:-

• Insecticides like DDT (it is now banned), Gamaxene, Melathion etc are sprayed.

• Biological control:-more suitable procedure - in this larvivorousfishes are used which eat larvae of mosquitoes.

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