Coll.

Medicine \3rd stage

Lec.9
Parasitology

Prof. Dr. Amal KH. KH.

Malaria :
-
-

There are four species normally infecting humans, namely, Plasmodium

-
-

-
falciparum, Plasmodium vivax, Plasmodium ovale, and Plasmodium malariae. P.
-
-
-

falciparum causes the most fulminate disease . almost the death of malaria are due to
- -

P. falciparum . P. falciparum is the most dangerous of the 4 species. It causes a high

-

level of parasitemia with parasite density exceeding 250,000-300,000O

-

-
/ml of blood. -

Nearly 30-40% of RBCs may be infected. In contrast to other species, it invades

0
- -

erythrocytes of all ages (old and young).

-

e - -

- -

87-
-
13
-
. ·
Vivax 11 i
& 1,
-
/19 , 5 6
.

sl
T

Isl &

Morphology :

There are various morphological forms of malarial parasites . out of the these are
- -

occur in human and the other in mosquitoes:

&

Morphological forms seen in human :

-

1. forms inE
-
liver:

-Sporozoites :these forms are slender, banana shaped and are

- - -

infective forms for humans from mosquitoes.

-

- Merozoites : are the end- product of schizogony the merozoites .

- -

the merozoites come out from liver and enter RBC to initiate the
-
-

erythrocytic shcizogony . it is very difficult to demonstrates these

-

form in liver because very few hepatic are affected. .‫ﯾﺼﻌﺐ ﻛﺸﻔﮭﺎ ﻓﻲ اﻟﻜﺒﺪ ﻷﻧﮭﺎ ﺗﺼﯿﺐ ﻋﺪًدا ﻗﻠﯿﻼً ﺟًﺪا ﻣﻦ اﻟﺨﻼﯾﺎ اﻟﻜﺒﺪﯾﺔ‬
-
-

&
2- forms in RBC :
-

- Trophozoites : young trophozoites called ring forms . they have

- -

a vacuole in the centre . at a later they are called amoeboid

- -

-
forms .

1
 -
- Schizonts : this form occur -
- -
inside RBC after e
-
asexual
multiplication by dividing of nucleus without cytoplasm and this
- -
-

called immature schizont , after this ,cytoplasm condensed

-
-

around each daughter nucleus to became mature schizont , each

-

newly formed nucleus along with the surrounding cytoplasm

-

covered with a cell membrane . these newly formed

-
-

morphological forms are merozoites .

Merozoites . the number of merozoites varies from-O
-
-

- - - -
8 to 32
depending on the species of plasmodium. Merozoites infects
-

other RBC to repeat schizogony .

- -

- Gametocytes : there are - two types of gametocytes formed by

gametogony inside RBC and include&
-

-
female gametocytes or
S
-

macogametes and
-
male gametocytes or microgametes.
-

male Female

Morphological forms seen in mosquitoes :

-

-Macrogametes : the female gametocytes mature in the mid – gut

- -

of mosquito to develop into female gamete . one gametocyte

- -

-
develop to one gamete .
- Microgametes : one microgametocyte produced =
-

-
6 to 8 male
-

gametes be a process of exflagellation in the mid-gut of

- - -

mosquitoes. malesizid

- Ookinete : a male gamete fertilize female gamete to &

-

- -
form a
diploid zygote (syngamy) . the zygote quickly elongates to
- -
-
become a motile ookinete .
-

- Oocyst : ookinete penetrates the gut wall and comes to lie on the
-
-

This side whichhaemocoel side of gut , where it develop into oocyst .

Sporozoites: e
- -

connect with blood - meiosis (nuclear reduction division) in the oocyst

- -

circulation
-
.
results in development of haploid forms called sporozoites .
- - -

sporozoites break out of the oocyst into the haemocoel . they

- - -

reach the salivary gland of the mosquitoes to become infective

-
-

form to human .
-

2
 -
Plasmodium falciparum :

Plasmodium falciparum demonstrates no selectivity in host erythrocytes,e i.e. it-

>
invades young and old RBCs cells. The infected red blood cells also do not enlarge- wi
-

- - 5 ,55-H-
·

and become distorted.

-

 Multiple merozoites can infect a single erythrocyte, and show multiple

Red infections of cells with small ring forms.
-
- -

 The trophozoite is often seen in the host cells at the very edge or periphery of
dots -

cell membrane at accole position.

- -

 Occasionally, reddish granules known as Maurer’s dots are observed

 Mature (large) trophozoite stages and schizonts are rarely seen in blood films,
- -

because their forms are sequestered in deep capillaries, liver and spleen.
-

 Peripheral blood smears characteristically contain only young ring forms and
- -

occasionally crescent shaped gametocytes. ‫أﺣﯿﺎﻧًﺎ ﺗﻈﮭﺮ اﻷﻣﺸﺎج اﻟﮭﻼﻟﯿﺔ اﻟﺸﻜﻞ‬

-
&

Plasmodium vivax:
-

P.vivax is selective in that it invades only young immature erythrocytes. Infections of

- -
- -

P. vivax have the following characteristics:

-

 -
Infected red blood cells are usually enlarged and contain numerous pink
Pink granules or schuffner’s dots.
-

 The trophozoite is ring-shaped but amoeboid in appearance.

More mature trophozoites and erythrocytic schizonts containing up toO
-

 24
dots -

merozoites are present.

-

 The gametocytes are round.

-

Plasmodium ovale: -

P. ovale is similar to P. vivax in many respects, including its selectivity for young,
-
-

pliable erythrocytes. As a consequence the classical characteristics include:

-

Pale • The host cell becomes enlarged and distorted, usually in an oval form.
- -
-

Pink
• Schiffner’s dots appear as pale pink granules.
-

dots
-

• The infected cell border is commonly fimbriated or ragged

-

• Mature schizonts contain about &

10 merozoites.
-

Plasmodium malariae:

In contrast with-
-
P.vivax and P.ovale, P.malariae can infect only old erythrocytes with
-

relatively rigid cell membranes. As a result, the parasite’s growth must conform to the
- -

3
.‫ﺤﻠويﺔ‬$‫ٮﻬﺎ اﻟ‬$‫ﺣﺪرا‬B ‫ى‬H‫ڡ‬$ ‫ٮ"ٮّﺔ‬B‫ٮﺴ‬$ ‫ٮﺔ‬B‫ٮﺼﻼ‬B ‫ڡ&ڡﻂ ﻛريﺎت اﻟﺪم اﻟﺤﻤراء اﻟ&ڡﺪٮ "ﻤﺔ اﻟﱵ ٮ&ﻤ&ٮﺎز‬$ ‫ ﺣ"ٮﺚ ٮ "ﺼ"ٮﺐ‬،P. ovale ‫ و‬P. vivax ‫ﺤ&ٮﻠﻒ ﻋﻦ‬$" ‫• ٮ‬
‫ﺤﻤﻬﺎ أو ٮ&ﺸﻮﻫﻬﺎ‬$‫ٮﺐ ٮ&ﻀ‬B‫ٮﺔ دون أن ٮ "ﺴ‬B‫ﺤﻢ وﺷكﻞ اﻟﻜريﺔ اﻟﻤﺼﺎ‬B‫ڡﻖ ﻣﻊ ﺣ‬$‫ڡ"ٮﲇ ﻟ"ٮ&ٮوا‬$‫ٮﻤﻮ اﻟﻄ‬$" ‫ ٮ‬،‫ٮﺐ ﻫﺬا اﻟ&ٮ&ڡ"ٮيﺪ‬B‫ٮﺴ‬B •
 :‫•ﯾُﻈﮭﺮ أﺷﻜﺎﻻً ﻓﺮﯾﺪة داﺧﻞ اﻟﺨﻠﯿﺔ اﻟﻤﻀﯿﻔﺔ ﻣﺜﻞ‬
• Band and bar forms (‫)أﺷﻜﺎل ﺷﺮﯾﻄﯿﺔ أو ﺧﻄﯿﺔ‬.
• ‫أﺷﻜﺎل ﻣﻀﻐﻮطﺔ ﻣﻊ ﺗﻠﻄﯿﺦ داﻛﻦ‬.

O
size and shape of red blood cell. This requirement produces no red cell enlargement or
- -

- -
O
distortion, but it results in distinctive shapes of the parasite seen in the host cell, “band -

and bar forms” as well as very compact dark staining forms. The schizont of
- - -
-

P.malariae is usually composed of eight merozoites appearing in a rosette.

-

So

Sivax
-
& P malariae
.

·
P falciparum
.

Early
seen in
peripheral
=> vale

blood .

Mode of malaria transmission :

-

O
Man gets infection mainly by the bite of infected female Anopheles mosquito.
- & -

However, infection may also be transmitted by:

-

1. Transfusion malaria: malaria can be transmitted in blood . the infective

- -

forms are merozoites and RBC stages except the gametocytes.

-

2. Congenital malaria: also called transplacental malaria and occur through

- -

defect of placenta .the infection acquired during childbirth but the parasitemia
are reduced in the infected newborn by passively transferrede
- -

- -
IgG from -

immune mother.
-

3. By the use of contaminated syringes particularly in drug addicts.

- -

:‫ اﻟﺘﺴﻤﻴﺔ‬.1
ً
.(‫ )اﻟﻤﻼرﻳﺎ اﻟﻤﻨﺘﻘﻠﺔ ﻋﺒﺮ اﻟﻤﺸﻴﻤﺔ‬Transplacental Malaria ‫• أﻳﻀﺎ ﺑـ‬

:‫ ﻃﺮﻳﻘﺔ اﻻﻧﺘﻘﺎل‬.2

.‫• ﺗﺤﺪث اﻹﺻﺎﺑﺔ ﺑﺴﺒﺐ ﻋﻴﺐ أو ﺧﻠﻞ ﻓﻲ اﻟﻤﺸﻴﻤﺔ ﻳﺴﻤﺢ ﻟﻠﻄﻔﻴﻠﻴﺎت ﺑﺎﻻﻧﺘﻘﺎل ﻣﻦ اﻷم اﻟﻤﺼﺎﺑﺔ إﻟﻰ اﻟﺠﻨﻴﻦ‬
ً
.‫• ﻗﺪ ﺗﺤﺪث اﻟﻌﺪوى أﻳﻀﺎ أﺛﻨﺎء اﻟﻮﻻدة‬

4 :‫ اﻟﻤﻨﺎﻋﺔ ﻓﻲ اﻟﻤﻮﻟﻮد اﻟﺠﺪﻳﺪ‬.3

.‫ إﻟﻰ اﻟﻄﻔﻞ ﻋﺒﺮ اﻟﻤﺸﻴﻤﺔ‬IgG ‫ ﻳﺘﻢ ﻧﻘﻞ اﻷﺟﺴﺎم اﻟﻤﻀﺎدة‬،‫• إذا ﻛﺎﻧﺖ اﻷم ﻣﺤﺼﻨﺔ ﺿﺪ اﻟﻤﻼرﻳﺎ‬

.‫( ﻓﻲ اﻟﻤﻮﻟﻮد اﻟﺠﺪﻳﺪ‬parasitemia) ‫• ﻫﺬه اﻷﺟﺴﺎم اﻟﻤﻀﺎدة ﺗﻘﻠﻞ ﻣﻦ ﺷﺪة اﻹﺻﺎﺑﺔ أو ﻛﻤﻴﺔ اﻟﻄﻔﻴﻠﻴﺎت‬
 &
Life cycle

The life cycle of malaria is complex passed in two hosts (alternation of hosts) and has
- - -

sexual and asexual stage (alternation of generations).

- -

Human -
Vertebrate host - man (intermediate host), where the asexual cycle takes
- -

place. The parasite multiplies by schizogony and there is formation of male

- -

and female gametocytes (gametogony).

 Invertebrate host – female mosquito of genus Anopheles -
-

- -
(definitive host)
where the sexual cycle takes place. Union of male and female gametes ends in
- - -

the formation of sporozoites (sporogony).

-

The life cycle passes in four stages:

-

Three in-
man:-

- Pre (exo )- erythrocytic schizogony. liver

-

-
- Erythrocytic schizogony. RBCs
-- Gametogony.
One in mosquito – Sporogony.
-

Introduction into humans - when an - infective female Anopheles mosquito bites

man, it inoculates saliva containing sporozoites (infective stage).
-

Pre- Erythrocytic schizogony - : liver phase

Sporozoites reach the blood stream and within 30 minutes enter the parenchymal
- -

cells of the liver,e

-
initiating a cycle of schizogony. Multiplication occurs in tissue, to
-
-

form thousands of tiny merozoites from the schizont. Merozoites are then liberated on
rupture of schizonts aboutOf
- -
-

-
7th – 9th day of the bites and enter into the blood stream.
-
-

These merozoites either invade the RBC’s or other parenchymal liver cells. In case of
- - -

P. falciparum and possibly P. malariae, all merozoites invade RBC’s e

- -
without re-
-

invading liver cells. However, for P. vivax and P. ovale, some merozoites invade
- - - -

RBC’s and some re-invade liver cells initiating further Exo-erythrocytic schizogony,.
-

Some of the merozoites remain dormant -

-
~
(hypnozoites) becoming active later on
-

which is responsible for relapses.

-
&
- liver
-
Erythrocytic schizogony (blood phase) is completed in 48 hrs in P. vivax, P. ovale,
-
-

and P. falciparum, and&

-
72 hrs in P. malariae. The merozoites reinvade fresh RBC’s
repeating the schizogonic cycles Erythrocytic merozoites e
-
-

- -
do not reinvade the liver
cells. So malaria transmitted by blood transfusion reproduces only erythrocytic cycle -
- -
.

=
Gametogony :

Some merozoites that invade RBC’s develop into sexual stages (male and female
- - - -

gametocytes). These undergo no further development until taken by the mosquito.

-

5
- -

85
-
&

↓-

Sporogony (extrinsic cycle in mosquito) :

-

When a female Anopheles mosquito vector bites an infected person, it sucks blood
-

containing the different stages of malaria parasite. All stages other than gametocytes
- -

are digested in the stomach. The microgametocyte undergoes ex-flagellation. The

- -

nucleus divides by reduction division into *6-8 pieces, which migrate to the periphery.
- - -
formed-
At the same, time 6-8 thin filaments of cytoplasm are thrust out, in each passes a piece
e
- -
-

of chromatin. These filaments, the microgametes, are actively motile and separate
-
- -

from the gametocyte. The macrogametocyte by reduction division becomes a

- -

macrogamete. Fertilization occurs by entry of a micro gamete into the macro gamete
- -

forming a zygote. The zygote changes into a worm like form, the -
-
ookinete, which
-

penetrates the wall of the stomach to develop into a spherical oocyst between the
-

epithelium and basement membrane. The oocystes increase in size. Thousands of

- -

sporozoites develop inside the oocysts. Oocysts rupture and sporozoites are liberated
-

in the body cavity and migrate everywhere particularly to the salivary glands. Now
-

the mosquito is infective. The sporogonous cycle in the mosquito takes 8-12 days
-
-

depending on temperature .
-

6
 Recurrence of malaria :
-

This occur in malaria either from reinfection or due to certain events related to the
-
-

life cycle of parasite . two type of recurrence are known in malaria :

-

RBCs/lo,
1. malaria recrudescence : in which the erythrocytic form of parasite
-

- -

- ; may evade the host immunity and survive for months even after the
- - -

clinical illness has subsided . the number of these forms may increase
& -

later leading to reappearance of clinical symptoms and signs within a

-
year -
or two . this situation
- -
occur in P.falciparum.-
liversi: 98 &2. malaria relapse :In case of P.vivax and P.ovale some sporozoites
·

enter the hepatocytes and become dormant -

- -

- -
(resting) known as -

hypnozoite. After a period of time, up to two years, hypnozoites are

- -
-

reactivated to become secondary exo-erythrocytic schizonts and

- -

release merozoites that infect RBCs producing malaria relapse.

-

7
 Pathology and clinical features of malaria :

All the pathology associated with malaria caused by asexual multiplication of

-

-
plasmodia in bloodstream - (erythrocytic schizogony ) . There are certain people, who
-

are resistant to malaria infection, including those with:

-

1. Duffy antigen blood group negative (esp. for vivax).

2. Sickle cell traits.
-

3. Thalassemia.
4. Glucose-6-phosphate-dehydrogenase deficiency.
After an incubation period of 12 days for P.falciparum, 13-17 days for P.vivax, and
- -

-
P. ovale, and 28-30 days for P. malariae, patient will develop typical picture of
-

malaria that consists of:=

-

-
Febrile paroxysm,-Anaemia, Splenomegaly and jaundice .
-

Febrile paroxysm:
-

It generally begins in the early afternoon and comprises of 3 stages;

chills
- cold stage : 15-60 min, the patient experiences intense cold and shivering.
-

-
hot stage : lasting for 2-6 hours, when the patient feels intense hot. Patient develops
-
-

-
high fever (40-41 C), severe headache, nausea, and vomiting.
-

-
sweating stage.: fever ends by a crisis of profuse sweating.
- -
-

Periodic fever (Febrile paroxysm ) in malaria is characteristic . it is related to life

-
-

cycle of parasite . usually the erythrocytic schizogony is synchronous ; this means that
-
-

schizogony begins and ends at the same time in all infected RBC in a particular cycle.
- - -

Thus , at the end of each erythrocytic cycle all the infected RBC rupture at the same
-

- -

time . this releases toxic waste by –products along with merozoites . macrophages
-
- -

engulf merozoites (some merozoites escape from macrophages to repeat the

- -

erythrocytic schizogony ) . the macrophage release interleukin -1 which is act on

thermo-regulatory centre situated in brain , to set it at -
- -

- -
higher temperature (41 Cْ or
-

higher ) . the normal body temperature of 37 is now considered low by the thermo-
- -
-

regulatory centre . the patient at this stage feels cold. The thermo- regulatory
-
- -

activates temperature raising mechanism in the form of shivering . the mascular

- -
-

constructions leads to rise in the body temperature upto the set mark in the thermo-
-

regulatory centre (41 Cْ or higher ). The feeling of coldness, attending with

- -

shivering is calledO
-
chill . the consequent raising of body temperature ise
-
fever.

Subsequently , the IL-1 level in bloode

-
falls . the thermo-regulatory centre is reset at
-

-
the normal body temperature of that individual . now, the patient feel hot , severe
- -

headache, nausea, and vomiting . the thermo- regulatory centre activates temperature
- -

reducing mechanism . patients sweats profusely , leading to a drop in his body

- -

-
temperature bringing it back to normal . the patient feel s tired and generally sleep at
-

8
 -
0
the end of this episode.. this episode consisting of chill – fever – sweating is typical
-

of malaria fever.
-

These paroxysms usually reappear periodically (generally-

-
>every 48 hours) as the cycle
-

of infection, replication, and cell lyses progresses , so it is tertian in the case of :

- -

Plasmodium falciparum.(malignant tertian malaria) ~

-

Plasmodium vivax (benign tertian malaria)-

-

Plasmodium ovale (benign tertian malaria) -

-

While paroxysms usually reappear periodically (generally every 48 hours) as the

- -

cycle of infection, replication, and cell lyses progresses every

- - - -
& 72 hours in the case of
-

Plasmodium malariae (quatrain malaria )

-

Anaemia after few paroxysms, anemia of microcytic or normocytic hypochromic

-

type develops as a result of:

1. Mechanical destruction of parasitized RBCs.

-

2. Reduced erythropoiesis in the bone marrow.

-

3. Lysis and phagocytosis of uninfected RBCs.

-
P falciparum
.

4. In a small number of patients with malignant tertian malaria there is

-
-

autoimmune destruction of RBCs.

-

5. Consumption of more than& 70% of haemoglobin in RBCs by the parasite.

6. Failure of the liver to convert liberated iron.
-

Splenomegaly: After few paroxysms, spleen gets enlarged and becomes palpable.
- -
-

Splenomegaly is due to massive proliferation of macrophages which phagocytize both

-
-

parasitized and non-parasitizedO

-

-
RBCs.

Jaundice : can also occur due to rupture of RBCs.

-

Clinical features :
-

Plasmodium falciparum :
-

-
Sever malaria (malignant ) is caused by P. falciparum may be fatal , hence
- - -

it is called pernicious malaria . Of all the four Plasmodia, P. falciparum has the
-
-

shortest incubation period, which ranges from 7 to 10 days. After the early flu-like
- - -

symptoms, P.falciparum - rapidly producese daily (quotidian) chills and fever as

-

- -
well as severe nausea, vomiting - -
, diarrhea and bleeding -
from gum, nose and GIT .
The periodicity of the attacks then becomes tertian -
-
(48 hours), and fulminating
-

disease develops which is include :

-

1- Involvement of the -- brain (cerebral malaria) is most often seen in

-

P.falciparum infection. Capillary plugging from an adhesion of infected red

-

Cerebral
9
glucose
a
 blood cells with each other and endothelial linings of capillaries causes
-
hypoxic injury to the brain that can result in coma and death.
- -

2- Kidney damage is also associated with P.falciparum malaria, resulting in an

-
- -

illness called “black

-
water” fever (dark red to blackish urine). Intravascular
-

hemolysis with rapid destruction of red blood cells produces a marked

-

hemoglobinuria and can result = in acute renal failure, tubular necrosis,

-

nephrotic syndrome, and-

-
-

-
death.
3- Liver involvement is characterized by abdominal pain, vomiting of bile,
- -
-

hypoglycemia , hepatosplenomegally, severe diarrhea, and rapid dehydration.

-
-
-

Hypotension \ shock : also called -

-

4- -
-
Algid Malaria resembles surgical shock
-

with cold clammy skin, peripheral circulatory failure and profound shock.
-
-
-

5- Pregnant women have an increased risk of abortion, stillbirth, premature -

T
-
-

delivery and of low birth weight of their infants.

- -

The birth of
infant that has
died in uterus .

Treatment:

Plasmodium falciparum:
-

Because chloroquine – resistant stains of P.falciparum are present in many parts of

-

the world, infection of P.falciparum may be treated with other agents including
-

mefloquine, quinine, guanidine, pyrimethamine – sulfadoxine, and deoxycycline.

--

Plasmodium vivax and Plasmodium ovale:

=
Chloroquine is the drug of choice for the suppression and therapeutic treatment of
- -

P.vivax, followed by premaquine for radical cure from relapse and elimination of
-
-

gamatocytes.
-

The treatment regimen with P. ovale, including the use of primaquine to prevent
- -

relapse from latent liver stages is similar to that used for P.vivax infection.
-

-
Plasmodium malariae :

Treatment is similar to that for P.vivax and P.ovale.

-

Diagnosis :
fever
-

1. Clinical picture is highly suggestive, esp. the characteristic paroxysm.

-

· 2. Ab detection can detect past (not active) infections.

-

·S 3. Rapid Diagnostic tests (RDTS) are based on detection of Ag derived from lysed
-
~

,s - -

blood cells using immunochromatographic methods.

4. Molecular diagnostic techniques can complement other tests, esp. in species
-

-
identification like PCR
5. Microscopic identification of parasiteO (stages) in blood film is the method most
-
-

frequently used to demonstrate an active infection through thick and thin smear
-

-
- -

stained with geimsa , Leishman and wright ْ s Romanowsky stain (contains

azure dyes and--
O
-

eosin). as follow :
-

10
-
Stages in thick smears :

=
- -

O -

- -

②
-

O
-

-
-
e
-

- -

11
-
-

12
Control & Prevention :

1. Spraying insecticides.
2. Spraying larvicides in breeding sites.
3. Using biological larvicides .
4. Wearing long sleeve clothing and trousers to avoid bites.
5. Using bed nets.
6. Early diagnosis and prompt treatment of patients.

GOOD LUCK

13