Diagnosis of malaria

1. Diagnosis of malaria

2. Laboratory diagnosis
• Laboratory diagnosis of malaria requires
the identification of the parasite or its
antigens/ products in the patient’s blood.
• The requirements of a diagnostic test are
specificity, sensitivity, ease of performance
and a reasonable cost.

3. • Current available techniques can be
separated in three categories:
1. Microscopy
2. Immunological techniques
3. Molecular techniques

4. 1. Microscopy
• a) Thick and thin blood smear study
• Thick and thin blood smear study is the
gold standard method for malaria
diagnosis. The procedure follows these
steps: collection of peripheral blood,
staining of smear with Giemsa stain and
examination of red blood cells for malaria
parasites under the microscope.

6. Thick smear
• It is not fixed in methanol; this allows the
red blood cells to be hemolyzed, and
leukocytes and any malaria parasites
present will be the only detectable
elements. However, the hemolysis may
lead to distorted plasmodial morphology
making plasmodium species differentiation
difficult. Therefore, thick smears are
mainly used to detect infection and to
estimate parasitaemia.

10. Thin smear
• It is fixed in methanol. Thin smears allow
the examiner to identify malaria species,
quantify parasitemia, and recognize
parasite forms like schizonts and
gametocytes.

13. Advantages:
• It is an inexpensive method
• It gives the examiner the opportunity to
quantify parasites and differentiate malaria
species.

14. Disadvantages:
• The diagnostic accuracy depends on quality of
blood smear and equipment, abilities of the
microscopist, parasite density and the time spent
on reading the smear. All these may result in
therapeutic delays.
• Not suitable for large- scale epidemiological
studies.
• False positive. Defective blood film preparation
may lead to artifacts that can be incorrectly
regarded as malaria parasites. Sometimes,
platelets also confound diagnosis.
• False negative. It is associated with low parasite
density or low number of fields examined by the
microscopist.

15. The morphology of malaria
parasite in thin blood film

16. P. falipawm
P. malariae
P. ovale
P. vivax
normal
normal
Enlarged
Oval
Enlarged
irregular
Infected R.B.C.
size
1/6 of R.B.C.
multiple,
forming a
crescentic
masses ate the
periphery of the
red cell (Accoli
form)
1/3 of R.B.C.
Single
1/3 of R.B.C.
single
Schuffners dots
1/3 of R.B.C.
single
Schuffners dots
Ring stage

17. P. falipawm
P. malariae
P. ovale
P. vivax
small ring.
Band form.
Compact
R.B.C. is oval
with
fimbriated
edge
Schuffners dots
Filling R.B.C.,
vaculated
Schuffners dots
Trophozoite

18. P. falipawm
P. malariae
P. ovale
P. vivax
23 R.B.C.
24-32 not seen
in periph.
blood.
Filling R.B.C.
8-12, rosette
shaped
2/3 R.B.C.,
8-18
Filling R.B.C.
12-24
Schizont:
№ of
merozoites

19. P. falipawm
P. malariae
P. ovale
P. vivax
Bannana
shape
Filling
R.B.C., oval
2/3 R.B.C.,
oval
Fillinng
R.B.C., oval
Gametocyte

20. b) Quantative Buffy Coat (QBC) test
• This method involves centrifuged and
compressed red blood cell layer stained with
acridine orange and then examinated under an
ultra-violet light source. The whole procedure
takes place in a glass hematocrit tube which is
precoated internally with acridine orange stain
and potassium oxalate; it is filled with 55-65 μl of
blood. The tube is centrifuged and so the
components separate according to their
densities forming bands

22. 2. Immunological techniques
i. Antibody-based techniques
• a) Indirect fluorescent antibody test
(IFAT)
• b) Enzyme- linked immunosorbent assay
(ELISA)
ii. Antigen-based techniques
• Rapid Diagnostic Test (RDT)

23. Immuno-chromatographic Tests (ICT).
are based on the capture of the parasite antigens from the
peripheral blood using either monoclonal or polyclonal
antibodies against the parasite antigen targets. Currently,
immunochromatographic tests can target the histidine-rich
protein 2 of P. falciparum, a pan-
malarialPlasmodium aldolase, and the parasite specific
lactate dehydrogenase. These tests do not require a
laboratory, electricity, or any special equipment.
Rapid Diagnostic Test (RDT)

24. Histidine-rich protein 2 of P. falciparum (HRP2)
is a water soluble protein that is produced by the asexual
stages and gametocytes of P. falciparum,expressed on
the red cell membrane surface, and shown to remain in
the blood for at least 28 days after the initiation of
antimalarial therapy. Several RDTs targeting PfHRP2 have
been developed.

26. OptiMAL- IT
is a reference tool for the detection of
Plasmodium antigens (pLDH) using
monoclonal antibodies for individual
diagnosis and for therapy control

27. Parasite lactate dehydrogenase (pLDH)
Is a soluble glycolytic enzyme produced by the asexual and
sexual stages of the live parasites and it is present in and released
from the parasite infected erythrocytes. It has been found in all 4
human malaria species, and different isomers of pLDH for each
of the 4 species exist. With pLDH as the target, a quantitative
immunocapture assay, a qualitative immunochromatographic
dipstick assay using monoclonal antibodies, an immunodot
assay, and a dipstick assay using polyclonal antibodies have been
developed.

30. 3. Molecular techniques
• Polymerase Chain Reaction (PCR)

31. Prevention
1. Mosquito control.
2. Treatment of patients.
3. Chemoprophylaxis.