Malaria and Plasmodium

MALARIA & PLASMODIUM

Dr. Shahab Riaz

Plasmodium

• > 100 species• Both animals and humans

1. P. vivax Benign Tertian Malaria (humans)

2. P. ovale Benign Tertian Malaria (humans)

3. P. malariae Benign Quartan Malaria (humans/chimpanzees)

4. P. falciparum Malignant Tertian Malaria (humans)

Plasmodia

Important Terms• Cycle: Asexual cycle in man, sexual cycle in mosquito

• Trophozoites: Growing form in human blood (ring form and all stages

onwards except fully grown gametocytes and Schizonts)

• Schizont: Asexually dividing form i) Immature schizont ii) Mature schizont

• Schizogony: Asexual reproduction N/C divides Merozoites in RBC and

liver

• Sporogony: Sexual reproduction forming sporozoites (mosquitoes)

Important Terms• Sporozoite: the morphological form which develops in the mosquito salivary gland and is injected

when the mosquito feeds, infecting humans.

• Gametocyte: From some trophozoites or merozoites in RBCs ??? It is infective to mosquito

• Gametes: From micro and macro-gametocytes Macro-gamete/female (nuclear reduction 1:1) Micro-gamete/male (exflagellation 1:4-8)

• Zygote: Fertilized macro-gamete

• Ookinete: A motile zygote

• Oocyst (Spore): Rounded, immotile ookinete, membranous cyst wall, containing many sporozoites

EPIDEMIOLOGY

• P. vivax and P. falciparum more common

P. ovale rarest of the 4 species

• > 200 million people worldwide

> 1 million deaths per year

Most common lethal infectious disease

EPIDEMIOLOGY

• Tropical & subtropical areas

esp. Asia, Africa, Central and South America

Certain regions in SE Asia, S. America, E. Africa Chloroquine Resistant strains of P. falciparum

• I/V drug use & blood transfusions

HABITAT

• Female Anopheles sexual cycle

• Liver & RBCs of man asexual cycle

RBC Age Variable: P. vivax youngest erythrocytes P. malariae oldest erythrocytes P. falciparum RBCs of every age

Anopheles, Culex and Aedes aegyptii

MORPHOLOGY

• Peripheral blood stained with Leishman’s stain

1. Small Trophozoites (Ring forms):

Infected RBC at first ring form

a) Dot/rod shaped nucleus (red)b) Peripheral rim of cytoplasm (blue)c) Central clear vacuole like area (not stained)

Different species have different rings

MORPHOLOGY

2. Large Trophozoite:

• Ring form Large trophozoite• Fine grains of pigment Hematin

3. Schizont:

Large trophozoite schizont N/C fragments merozoites

4. Gametocytes:

• Male and female distinguishable• Fully grown rounded occupies most of RBC• P. falciparum sausage shaped crescent in RBC

Plasmodia in RBCs

LIFE CYCLE

• HOST:

Definitive Host Female anopheles (sexual cycle)

Intermediate Host Man (asexual cycle)

• VECTOR: Female Anopheles

LIFE CYCLE

• Sexual cycle initiated in Humans Gametocytes (gametogony in RBCs) mosquitoes fusion of M/F gametes oocyst many sporozoites (sporogony)

• Sexual cycle Sporogony (sporozoites)

• Asexual cycle Schizogony (schizonts)

Simple Life Cycle Of Plasmodium

LIFE CYCLE

• ASEXUAL CYCLE ; SCHIZOGONY (man)

a. Pre-erythrocytic schizogony or Primary Exo-erythrocytic schizogony

b. Para-erythrocytic schizogony or Secondary Exo-erythrocytic schizogony

c. Erythrocytic schizogony

LIFE CYCLE• Primary Exo-erythrocytic Schizogony

Salivary glands Sporozoites human circulation parenchymal liver cells

(mosquitoes) (spindle shaped) (30 mins)

rounded and mature

to schizonts

Micro-merozoites

(circulation)

Nuclear division to

Macro-merozoites Cell rupture EEM released exo- erythrocytic merozoites

(re-enter liver cells)

LIFE CYCLE

• Secondary Exo-erythrocytic Schizogony

• P. vivax and P. ovale latent form (Hypnozoites) Relapses

in liver

• P. vivax, ovale and malariae erythrocytic and pre-erythrocytic merozoites Re-enter liver cells

LIFE CYCLE• Erythrocytic Schizogony

Micro-merozoites RBCs differentiation into amoeboid form schizonts

ring shaped trophozoites filled with

merozoites

grows by Globin

Hematin accumulates

(48 hours P.ovale, vivax & falciparum)

Infect other merozoites released RBC rupture

Erythrocytes

(72 hours for P. malariae)

LIFE CYCLE• SEXUAL CYCLE; SPOROGONY

(mosquito 1-3 weeks)

RBCs macro-gametocytes die in man RBCs containing MGs mosquito

micro-gametocytes live in mosquitoes or free MGs

Injects into humans

and sucks MGs macro-gamete

Salivary glands 4-8 micro-gametes

Release sporozoites in body cavities

micro-gametes enter at

macro-gamete projection

Oocyst ruptures

diploid zygote

Haploid sporozoites N/C division Oocyst Gut wall of mosq. motile ookinete

Detailed Life Cycle

Oocysts in Mosquito

PATHOGENESIS• Usual Incubation periods:

Vivax : 14 days

Malariae: 28 days

Falciparum: 11 days

• Transmission: Mosquito bite

I/V drug abuse

Blood transfusion

Transplacental (congenital)

FEVER, ANEMIA, SPLENOMEGALY

PATHOGENESIS

• Malignant Tertian Malaria (P. falciparum)

aka pernicious malaria Most likely to be fatal / RBC lysis 24-48 hours 3 weeks or more Large no. of parasites in blood RBCs of all ages Infected red cells sticky Clogged capillaries cerebral malaria (coma & death)

PATHOGENESIS

• Malignant Tertian Malaria (P. falciparum)

Life threatening hemorrhage and necrosis Extensive hemolysis hemoglobinuria renal damage Black water fever (dark urine) Reddish, dark brown or black Oxy-hemoglobin, met-hemoglobin, Hematin, bile RE system activation and Hemolysin adds to hemolysis 50% mortality rate

PATHOGENESIS

• Splenomegaly (all malarias):

• ed RBC destruction ed splenic sequestration sinusoidal congestion

• ed lymphocytic and macrophages production

PATHOGENESIS

• Malarial Relapses:

• P. vivax 2 years• Para-erythrocytic stage liver parenchyma dormant

but viable• Resistance lowered released and activated

complete erythrocytic cycle• Not in P. falciparum as no para-erythrocytic stage• Transmission other than mosquito bites no relapses

Natural Protection

• Sickle cell trait (heterozygous)• Duffy blood group antigen –ve (homozygous recessive)

(P.vivax)• G6PD deficiency

• Premunition:

• Partial immunity• Humoral antibodies block merozoites from invading

RBCs• Low level of parasitemia low grade symptoms

PATHOGENESIS

• Commonly Involved Organs:

1. Changes in Blood:• Anemia (hemolytic)• Leucopenia (exception febrile)• Monocytosis (pigmented)

Commonly Involved Organs:

2. Spleen:

Gross: • Enlarged• Congested• Pigmented (black colour)• Soft

Micro:• Congested capillaries• Infected RBCs• Hyperplasia of RE cells, containing pigments

Commonly Involved Organs:

3. Liver:

Gross:• Enlarged • Congested

Micro:• Congested sinusoidal capillaries• Infected RBCs• Increased Kupffer cells (pigmented)• Fatty degeneration

Commonly Involved Organs:

4. Bone Marrow:

Gross:• Pigmented (black)

Micro:• Hyperplasia• RE cells contain pigments• Infected RBCs

Organs Involved in P. Falciparum Infection

1. Kidney:

Gross:

• Congested

Micro:

• Nephritis• Congested capillaries• Infected RBCs• Areas of hemorrhage and necrosis

Organs Involved in P. Falciparum Infection

2. Brain:

Gross:

• Congested • Petechiae

Micro:

• Congested and blocked capillaries• Infected RBCs• Areas of hemorrhage and necrosis

Organs Involved in P. Falciparum Infection

3. Intestine:

• Dysenteric syndrome

4. Black water fever

Signs and Symptoms

• Abrupt fever, chills and rigors• Headache, myalgia, arthralgia• Initially may be continuous then periodic• Upto 41ºC or 106 ºF• Nausea, vomiting, abdominal pain, anorexia, distaste of mouth• Drenching sweats afterwards• Well between febrile episodes• Splenomegaly• 1/3 hepatomegaly• Anemia• Falciparum fatal bcz of brain and kidney damage

Laboratory Diagnosis

1. Blood Exam:

a. Microscopic Exam:

• Take blood during pyrexia• Not after even single dose of anti-malarials• Thick and thin smears made, dried and stained• Thick smear presence of organisms• Thin smear identification of species

Laboratory Diagnosis

• Thin Smear:

• Single drop of blood• Spread to allow single cell layer • Leishman’s stain• Oil immersion lens• Ring shaped trophozoites in RBCs• P. falciparum gametocyte banana, sausage or crescent

shaped• Other species gametocytes are spherical• > 5 % RBCs infected Dx of P. falciparum

Laboratory Diagnosis

• Thick Smear:

• 3-5 drops on slide allowed to dry• Several cell layers thick• Field’s stain or Giemsa stain• Oil immersion lens• Stain removes Hb from RBCs, MP easily viewed

Thin and Thick Smear

Laboratory Diagnosis

1. Blood Exam:

b. TLC and DLC:

• TLC low leucopenia

In fever may be high• Monocytosis containing pigments

Laboratory Diagnosis

2. Biopsy:• BM and liver biopsies in difficult cases

3. Therapeutic Test:• Anti-malarials given if fever subsides Dx made

4. Serological Tests: • Fluorescent antibody testing• Complement fixation test• Flocculation test• Hemagglutination test

Treatment

• Falciparum easily treated before complications as no relapses and no para-erythrocytic stage

• Chloroquine is treatment of choice for sensitive strains of plasmodia (merozoites)

• Primaquine (Hypnozoites)• Mefloquine or quinine and doxycycline

(chloroquine resistant strains of falciparum) • Atovaquone and proguanil (Malarone) (CR

falciparum)• Artemether and lumefantrine  (newer)

Prevention

• Chemoprophylaxis• Mosquito netting• Window screens • Mosquito repellants • Protective clothing• Special care during night time• DDT or kerosene oil spray over pools of water• Drainage of stagnant water• No vaccine presently available