1. Malaria BY Dr. Hala Ahmed El Nahas Professor of Medical Parasitology, 2.

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Malaria

BY

Dr. Hala Ahmed El Nahas

Professor of Medical Parasitology,

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OUTCOMES:1. Classification (Species) of Malaria

Parasites.

2. Geographical Distribution of Malaria.

3. Biology and Life Cycle of Plasmodia parasites.

4. Differentiation Between Erythrocytic Forms of Plasmodia.

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Phylum Apicomplexa

Plasmodium speciesDisease: Malaria, tropical fever .Species: Human malaria is caused by 4 species of

Plasmodia include:Plasmodium vivax producing benign tertian

malaria.Plasmodium ovale producing ovale tertian malaria.Plasmodium malariae producing benign quartan

malaria.Plasmodium falciparum producing tertian or

subtertian malignant malaria. 4

Malaria Distribution

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Geographical distribution:P. vivax The most widely distributed species found in

tropical, subtropical and temperate areas.

P. oval West Africa, India and Far East.

P. malariae tropical Africa, India and Far East.

P. falciparum tropics and Far East.

Hosts:Definitive host: female Anopheles mosquito.

Intermediate host: man (schizogony cycle).

Reservoir host: No, except chimpanzee in P. malariae.

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Habitat:- In mosquito: gut, salivary glands.

- In man: Intracellular location inside:

a- Parenchymal liver cells Pre-erythrocytic cycle.

b- R.B.Cs Eryhrocytic cycle and gametocytes.

Life cycle:

Is heteroxenous where there is alternation of generation between man and female Anopheles.

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I- In Man (I.H) asexual cycle:a) Pre-erythrocytic cycle (exo-erythrocytic): Sporozoites (infective stage) are inoculated during

mosquito bites blood stream 1/2 hour invade the liver parenchyma cells i hypnozoites

ii trophozoites schizonts thousands of merozoites.

b) Erythrocytic cycle (inside R.B.Cs):Merozoites (from liver cells enter R.B.Cs ring forms

(48-72h) trophozoites schizonts rupture merozoites re-enter R.B.Cs

c) Gametocyte formation (inside R.B.Cs):After some repeated cycles of asexual multiplication:Merozoites i microgametocytes ii macrogametocytes

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• Malaria.flv

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II- In mosquito (gametogony, sporogony cycle or sexual multiplication):

Mosquito bite of infected person ingestion of all blood forms digestion of all except gametocytes.

- Macrogametocyte Macrogamete (♀)

- Microgametocyte exflagellation 6-8 Microgametes (♂)

both ♂ & ♀ gamete fusion zygote.

Zygote ookinete enter between epithelium and basement membrane of the stomach of mosquito oocyst sporocyst rupture & release thousands of sporozoites (infective stages) salivary gland of the mosquito infect man during the bite act.

- The cycle take 10-20 days in mosquito.- Transmission of parasite by mosquito is cyclopropagative.

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Malaria Life Cycle of Plasmodium.flv

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Methods of infection:1. Bite of infected female Anopheles.

2. Blood-borne transmission :

a. Blood transfusion.

b. Intravenous injections by needles contaminated with infected blood (drug addicts).

c. Trans-placental or congenital

transmission.

d. Through organ transplantation.

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Differentiation between human Plasmodia

a- Exo erythrocytic cycle

Difference P. vivax P. ovale P. malariae P. falciparum

Maturation 8 days 9 days 15 days 6 days

No. of merozoites

10.000 15.000 2000 30.000

Hypnozoites Present Present Absent Absent

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b- Erythrocytic cycle (infected R.B.Cs)

Difference P. vivax P. ovale P. malariae P. falciparum

Type of RBC affected

Reticulocytes(young cells)

Young cells Old & mature

All types

Size & shape Enlarged, pale

Oval slightly enlarged, ragged ends

Normal or small

Normal size, knobbed RBCs

Pigments(stippling)

Fine, Pink, rounded, (Schuffner's dots)

Numerous (Schuffner's dots)

Fine, pink (Ziemann's dots)

Irregular red clefts (Maurer's dots)

No. of affected cells

Moderate Moderate Low Very high

Rupture 48 hrs 48 hrs 72 hrs Irregular15

C- Erythrocytic cycle (parasite)

1- Ring stage:Differences P. vivax P. ovale P. malariae P. falciparum

-No. inside RBCs

-Size of parasite

-Shape

-One

-1/3 RBC

-Thin cytoplasmic rim

-Fine chromatin dot

-One

1/3 RBC

-Thin rim

-Large nucleus

-One

1/3 RBC

-As P. vivax but more regular

-May be multiple

1/6 RBC

-May be double chromatin

-Accole form

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2- Trophozoite stage:

Differences P. vivax P. ovale P. malariae P. falciparum

-Movement

-Shape

-Pigment

-Presence in peripheral blood

-Very active

-Amoeboid

-Yellowish brown haemozoin granules

-Present

-Sluggish

Amoeboid

-The same but appear early

-Present

-Less active

May be Band shape

-Dark brown or black

-Present

-Less active than P. vivax

-Amoeboid

-Dark brown or black coarse pigments

-Absent

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3- Schizont stage:Differences P. vivax P. ovale P. malariae P. falciparum

Maturation time

-No of merozoites

-Shape

-Pigment

-Presence in peripheral blood

48 hrs

12-24

average 16

-large fill cell

-rounded merozoites

-Yellowish brown

-Present

48 hrs

4-12

average 8

-1/2 cell size

-oval

-Dark brown

-Present

76 hrs

6-12

average 8

-Rosette around pigments

-Coarse Dark brown

-Present

36-48 hrs

8-36

average 16

-Compact, less symmetrical

-Dark pigments

-Absent

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4- Gametocytes stage:Diff. P. vivax P. ovale P. malariae P. falciparum

Male

female

-To

mature

-Small, pale blue nucleus diffuse ½ size of parasite-Coarse pigment

Large, fill cell, bright blue- dark compact nucleus diffuse pigments

-14 days

-Blue cytoplasm large nucleus pigments in rings

-Purplish cytoplasm small nucleus at one side

3 weeks

-Grayish cytoplasm large nucleus diffuse pigments

-Appear as uninucleate asexual stage

2 weeks

-Crescent, blunt ends, diffuse nucleus 1/2 size, pigments around nucleus

-Longer, slender, pointed ends, compact

darker nucleus

10 days19

P. falciparum ring & gametocytes stages.

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Notes:

1- Exflagellation:Is a process in which the ingested male microgametocyte in

mosquito stomach

undergoes division of its chromatin dot into 6-8 nuclei that migrate to the periphery of the parasite

they form whip like actively motile filaments they detach from parent cell forming individual microgamete

(uninuclear microgamete)

that fuse later with female macrogamete forming the zygote.

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2- The entrance of merozoites into R.B.Cs:

It involves:

proper orientation of anterior end of merozoite & exposing special organelles to the red cell surface

recognition of a specific receptor site on the red cell which differ by the type of plasmodia

e.g. In P. vivax: Duffy blood group antigen,

When this antigen is lacking as in most African Negroes the parasite can’t enter the red blood cell resistance to P. vivax infection.

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3- Relapse:- In P. vivax and P. ovale, some of the exo-erythrocytic

forms (called Hypnozoites) remain in dormant state then resume their development later causing the relapse. Not present in P. malariae or P. falciparum.

- So Relapse is : recurrence of the disease after complete initial clearance of erythrocytic forms due to reinvasion of blood by hypnozoites coming from exo-erythrocytic stages.

4- Recrudescence:- It means recurrence of symptoms after apparent

clinical cure, due to the persistence of low level of parasitaemia. It occur in all types of malaria especially P. malariae can live in blood up to 30 years. 23

5- Absence of trophozoites & schizonts of P. falciparum from peripheral blood:

- Trophozoites produce specific protein inserted in plasma membrane of RBCs leading to appearance of electron dense Knobs at the RBCs surface.

- Focal junctions between these knobs and endothelial lining of capillaries sequestration of infected RBCs along the vascular endothelium of deep tissues (as brain, spleen).

- Gametocytes does not form this protein No knobs RBCs with gametocytes not sequestered.

- So in P. falciparum only RBCs containing ring stages & gametocytes are seen in peripheral circulation. 24

Pathogenesis of malaria:

The major clinical symptoms are attributed to:I- Anaemia and tissue anoxia due to massive

destruction of erythrocytes.

II- Host-inflammatory response as an immune response of the host to librated parasite metabolites and pigments.

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III- Additional factors associated with P. falciparum:- Sequestration of infected R.B.Cs in deep vessels & ability of the parasite to infect all types of erythrocytes functional and actual tissue anoxia which result in: 1- Brain oedema and congestion (cerebral malaria). 2- Pulmonary oedema 3- Cardiac oedema 4- Acute renal failure & tubular necrosis Massive intravascular haemolysis dark black urine

(Black Water Fever). 5- Adrenal & retinal haemorrhage. 6- Spontaneous abortion. 7- Dysenteric malaria. 8- Hyponatraemia, hypovolaemia, hypoglycemia &

↑ capillary permeability.

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Clinical picture:1- Incubation period:

- It is the time between sporozoite infection and appearance of symptoms (1st paroxysm).

- It represent the duration of exo-erythrocytic cycle.

- The patient may feel malaise, muscle pain, headache, loss of appetite and slight fever.

2- Malarial Paroxysm:

- It happens with maturation of schizont form & rupture of R.B.Cs releasing merozoites.

- It may be synchronous or not.

P. vivax P. ovale P. malariae P. falciparum

8 days 9 days 15 days 6 days

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The Paroxysm consist of:a- Cold stage: due to activation of hypothalamus

shivering & cyanosis. It takes 1/2 -1 hour, followed by:

b- Hot stage: fever, flushing, intense nausea, vomiting and headache, it takes 4-6 hours.

c- Sweating stage: ↓ temperature, profuse sweating, relief of symptoms, it takes 2-3 hours.

- The paroxysms are repeated regularly according to the type of malaria.

• Every 48 hours (third day) in P. vivax & P. ovale (tertian malaria).• Every 72 hours (fourth day) in P. malariae (quartan malaria).• Every 36-48 hours or irregular in P. falciparum (sub-tertian)

- The patient feels exhausted (or quite well) in the period between paroxysms.

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Diagnosis:I) Clinical diagnosis: Clinical picture represents typical malarial paroxysm or

history of travel to or residence in a malarious area.

II) Laboratory diagnosis: a- Direct:

1- Thin and thick Giemsa stained blood films reveal the presence of erythrocytic stages.

**in all types of malaria, all stages of the parasite could be detected in peripheral blood except in P. falciparum, only rings & gametocytes are seen.

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2- Provocative test

In chronic malaria, the parasite may not be seen in peripheral blood, so we use this test to stimulate deep organs to squeeze their blood contents to the peripheral circulation By: - injection of TAB vaccine

- injection of milk - cold showers

- injection of 0.5 ml of 1/1000 adrenaline subcutaneous (Ascole’s test) contraction of spleen blood contents pass to the peripheral circulation.

B- Indirect:

- Serological tests: as IHA, IEP and IFA.

- PCR.

- Therapeutic test: the non- subsidence of symptoms after administration of an antimalarial drug for 3 days means that the case is not malaria. 30

Control of malaria:1- Mass treatment of cases.

2- Mosquito control.

3- Protection from mosquito bite.

4- Chemoprophylaxis.

5- Vaccination.

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Thank You33