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Malaria(plasmodium) Dr.Gogoi , Unuiversity of Fiji

Plasmodium (Malarial Parasites) :

Plasmodium ( Malarial Parasites)

What is malaria? :

What is malaria? Malaria is a serious and sometimes fatal disease caused by a parasite. Patients with malaria typically are very sick with high fevers, shaking chills, and flu-like illness. Four kinds of malaria parasites can infect humans: Plasmodium falciparum, P. vivax, P. ovale, and P. malariae .

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Infection with any of the malaria species can make a person feel very ill; infection with P. falciparum , if not promptly treated, may be fatal. Although malaria can be a fatal disease, illness and death from malaria are largely preventable.

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Blood parasites of the genus Plasmodium .   There are 156 named species of Plasmodium which infect various species of vertebrates.  

Four Plasmodium species are responsible for human malaria :

Four Plasmodium species are responsible for human malaria These are P. falciparum P.   vivax P. malariae and P. ovale

Biological characteristics:

Biological characteristics Sporozoa (without conspicuous locomotory organelles) Complicated life cycle: 1) Two types of hosts 2) Multiple stages 3) Human infection is caused by bite of an infected female mosquito.

In Human body:

In Human body 1 Exoerythrocytic stage ( schizogony ) (in liver) 2 Erythrocytic stage ( schizogony (in blood) 3 Formation of gametocytes

In mosquito:

In mosquito 1 Completion of gametogony 2 Sporogony

Life cycle:

Life cycle The malaria parasite life cycle involves two hosts.   During a blood meal, a malaria-infected female Anopheles mosquito inoculates sporozoites into the human host

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Sporozoites infect liver cells and mature into schizontswhich rupture and release merozoites

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Merozoitesinfect red blood cells .   The ring stage trophozoites mature into schizonts, which rupture releasing merozoites

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Some parasites differentiate into sexual erythrocytic stages (gametocytes)

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Blood stage parasites are responsible for the clinical manifestations of the disease.  

In mosquito:

In mosquito The gametocytes ) , male (microgametocytes) and female (macrogametocytes), are ingested by an Anopheles mosquito during a blood meal

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The parasites ’ multiplication in the mosquito is known as the sporogony   In the mosquito ‘ s stomach, the microgametes penetrate the macrogametes generating zygotes

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The zygotes in turn become motile and elongated (ookinetes) which invade the midgut wall of the mosquito where they develop into oocysts

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The oocysts grow, rupture, and release sporozoites, which make their way to the mosquito ‘ s salivary glands

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Inoculation of the sporozoites into a new human host perpetuates the malaria life cycle .  

Life cycle:

Life cycle

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1* The sporozoite is infective stage. 2* There are two kinds of sporozoites, tachy-sporozoiteand brady-sporozoite 3* When the brady-sporozoites get into the liver cells , they undergo dormancyand called hypnozoites


Exflagellation The process of male gametocyte to form male gamete.

Morphology :

Morphology Malarial parasite trophozoites are generally ring shaped, 1-2 microns in size, although other forms (ameboid and band) may also exist. The sexual forms of the parasite (gametocytes) are much larger and 7-14 microns in size. P. falciparum is the largest and is banana shaped, while others are smaller and round.

Morphology :

Morphology Ring form: ( Plasmodium vivax ) a ring of bluish cytoplasm with a dot-like nucleus

Trophzoite of Plasmodium vivax:

Trophzoite of Plasmodium vivax irregular cytoplasm and enlarged nucleus with malarial pigment ( hemozoin)

Schizont of P.vivax:

Schizont of P.vivax multiple masses of nuclear chromatin

Gametocytes :

Gametocytes Male gametocyte Female gametocyte Note: compact cytoplasm and absence of nuclear division.

Ring form of P. falciparum:

Ring form of P. falciparum Ring with double nuclei Multiple infections

Gametocyte of P. falciparum:

Gametocyte of P. falciparum banana shaped gametocyte ( P. falciparum)

Trophozoites of P.malariae :

Trophozoites of P.malariae band-like or elliptic

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In peripheral blood, every erythrocytic stages can be found in P. vivax and P. malariae infections. Only ring forms and gametocytes can be found in P. falciparum infection. Other stages of P. falciparum do not appear in the blood. (they hide in deep tissues)

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Malaria occurs in over 100 countries and territories. More than 40% of the world’s population is at risk. Large areas of Central and South America, the Caribbean island (that is divided between Haiti and the Dominican Republic), Africa, the Indian subcontinent, Southeast Asia, the Middle East, and Oceania are considered malaria-risk areas.


Pathogenesis Paroxysm Cold stage Fever ( 39- 41degrees C ) Profuse perspiration and the temperature begins to drop. Within a few hours the patient feels exhausted but symptom-less and remains symptomatic until the next paroxysm

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2 Typical symptoms Chill stage (30min – 1 hr, cold and shivering) hot stage (1-4 hr, intense heat and delirium sweating and crisis stage (1-2 hr)copious perspiration ( Three successive stages ) Fever is associated with severe headache, nausea (vomiting) and convulsions

3 The mechanism of the paroxysm Rupture of R B Cs (schizonts) merozoites, metabolic substances, hemozoin engulfed by white cells and monocytes to produce pyrogens temperature regulating center(hypothalamus) Fever:

3 The mechanism of the paroxysm Rupture of R B Cs (schizonts) merozoites, metabolic substances, hemozoin engulfed by white cells and monocytes to produce pyrogens temperature regulating center(hypothalamus) Fever

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4 Relapse: Some patients relapse back in to disease weeks, months even years after the apparent cure. (The cause of relapse is hypnozoite activation) 5 RecrudenscenceThe paroxysm appears in some patients after inadequate or incomplete treatment. ( The cause is the remained erythrocytic stage multiplication )

Malaria Relapses :

Malaria Relapses In P. vivax and P. ovale infections, patients having recovered from the first episode of illness may suffer several additional attacks ("relapses") after months or even years without symptoms. Relapses occur because P. vivax and P. ovale have dormant liver stage parasites (hypnozoites)that may reactivate.

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Malaria during pregnancy(especially P. falciparum ) may cause severe disease in the mother, and may lead to premature delivery or delivery of a low-birth-weight baby.

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On rare occasions, P. vivax malaria can cause rupture of the spleen or acute respiratory distress syndrome (ARDS).

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Nephrotic syndrome (a chronic, severe kidney disease) can result from chronic or repeated infections with P. malariae .

Clinical manifestations:

Clinical manifestations 1 Anemia 2 Splenomegaly 3 Cerebral malaria 4 Malaria nephropathy (nephrosis) 5 Congenital malaria usually fatal 6 black water fever…

Diagnosis :

Diagnosis Diagnosis is based on symptoms and detection of parasite in Giemsa stained blood smears. There are also antibody tests (left).

How People Get Malaria (Transmission) :

How People Get Malaria (Transmission) Usually, people get malaria by being bitten by an infected female Anopheles mosquito. Only Anopheles mosquitoes can transmit malaria and they must have been infected through a previous blood meal taken on an infected person.

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When a mosquito bites, a small amount of blood is taken in which contains the microscopic malaria parasites. The parasite grows and matures in the mosquito’s gut for a week or more, then travels to the mosquito’s salivary glands. When the mosquito next takes a blood meal, these parasites mix with the saliva and are injected into the bite.

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Once in the blood, the parasites travel to the liver and enter liver cells to grow and multiply. During this "incubation period", the infected person has no symptoms. After as few as 8 days or as long as several months, the parasites leave the liver cells and enter red blood cells.

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Once in the cells, they continue to grow and multiply. After they mature, the infected red blood cells rupture, freeing the parasites to attack and enter other red blood cells. Toxins released when the red cells burst are what cause the typical fever, chills, and flu-like malaria symptoms.

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Hyperreactive malarial splenomegaly (also called "tropical splenomegaly syndrome") occurs infrequently and is attributed to an abnormal immune response to repeated malarial infections. The disease is marked by a very enlarged spleen and liver, abnormal immunologic findings, anemia, and a susceptibility to other infections (such as skin or respiratory infections).

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If a mosquito bites this infected person and ingests certain types of malaria parasites ("gametocytes"), the cycle of transmission continues.

Control and treatment:

Control and treatment Treatment: 1 Cloroquine, Qinghaosu, etc. (blood cycle) 2 Primaquine, Pyrimethamine,etc.(liver stage) 3 Primaquine.(Gametocytes) Mosquito control Malaria supervision

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