Plasmodium

1. PLASMODIUM

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2. 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)

3. Plasmodia

4. Geographical Distribution
•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

5. Geographical Distribution
•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

7. 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

8. Anopheles, Culex and Aedes aegyptii

10. 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

11. 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

12. Plasmodia in RBCs

14. LIFE CYCLE
•HOST:
Definitive Host  Female anopheles (sexual cycle)
Intermediate Host  Man (asexual cycle)
•VECTOR:
Female Anopheles

15. 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)

16. Detailed Life Cycle

17. Oocysts in Mosquito

19. 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

20. 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

21. 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

22. PATHOGENESIS
•Commonly Involved Organs:
1.Changes in Blood
2.Spleen
3.Liver
4.Bone Marrow

23. Signs and Symptoms
•Abrupt fever, chills and rigors
•Headache
•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

25. 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

26. 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

27. 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

28. Thin and Thick Smear

29. Laboratory Diagnosis
1.Blood Exam:
b.TLC and DLC:
•TLC low  leucopenia
In fever may be high
•Monocytosis containing pigments

30. 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

31. 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)

32. 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

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