This document discusses the diagnosis of malaria through microscopic examination of blood smears. Peripheral blood smears can be used to identify the asexual forms of the malaria parasite. Thick blood smears are more sensitive for detection of low-level parasitemia but thin smears are needed for species identification. Rapid diagnostic tests are also used to detect malaria antigens but cannot identify the parasite species or quantify the level of infection. Clinical symptoms may also indicate malaria in endemic areas but laboratory confirmation is needed for accurate diagnosis.

1. Malaria- Diagnosis

2. Demonstration of the Parasite
• asexual forms of the parasite - peripheral-blood
smears.
• negative blood smear- repeat smears .
• stains- Giemsa at pH 7.2 is preferred; Wright's,
Field's, or Leishman's stain .
• Both thin and thick smears .
• The level of parasitemia is expressed as the number
of parasitized erythrocytes per 1000 RBCs.
• advantage of concentrating the parasites (by 40- to
100-fold and thus increasing diagnostic sensitivity.

3. • Both parasites and WBCs are counted, and the
number of parasites per unit volume is calculated
from the total leukocyte count. This figure is
converted to the number of parasitized erythrocytes
per microliter.
• A minimum of 200 WBCs should be counted under
oil immersion. .
• 100–200 fields should be examined
• In high-transmission areas, the presence of up to
10,000 parasites/L of blood may be tolerated without
symptoms or signs in partially immune individuals.
Thus the detection of malaria parasites is sensitive
but only poorly specific in identifying malaria as the
cause of illness.

4. Method Advantage Disadvantage
Thick Sensitive Requires
(0.001% experience
Smear parasitemia); (artifacts may be
species specific; misinterpreted as
inexpensive low-level
parasitemia);
underestimates
true count
Thin Rapid; species Insensitive
specific; (<0.05%
Smear inexpensive; in parasitemia);
severe malaria, uneven
provides distribution of P.
prognostic vivax, as enlarged

5. Thin BF P.falciparum
young trophozoites

6. old trophozoites

7. . Pigment in polymorphonuclear cells
and trophozoites

8. Mature schizonts

9. Female gametocytes

10. Male gametocytes

11. Thin BF P.vivax
young trophozoites

12. old trophozoites

13. Mature schizonts

14. Female gametocytes

15. Male gametocytes

16. Thick BF P.falciparum
trophozoites

17. Gametocyte

18. Thick blood films ofPlasmodium
vivax
trophozoites

19. Schizonts

20. Gametocyte

21. Thick BF P.ovale
trophozoites

22. Schizonts

23. Gametocyte

24. Thick BF P.malariae
trophozoites

25. Schizonts

26. Gametocyte

27. Immunochromatographic Test
PfHRP2 dipstick or
card test
Robust and relatively
inexpensive; rapid;
Detects only
Plasmodium
sensitivity similar to falciparum; remains
or slightly lower than positive for weeks
that of thick films after infectionf; does
(~0.001% not quantitate P.
parasitemia) falciparum
parasitemia
lasmodium LDH dipstick Rapid; sensitivity similar difficult preparation
or card test to or slightly lower than may miss low-level
that of thick films for P. parasitemia with P. vivax,
falciparum (~0.001% P. ovale, and P. malariae
parasitemia) and does not speciate
these organisms; does not
quantitate P. falciparum
Microtube concentration Sensitivity similar or Does not speciate or
methods with acridine superior to that of thick quantitate; requires
orange staining films (~0.001% fluorescence microscopy
parasitemia); ideal for

28. Rapid Malaria Test
• Blood
• +buffer[hemolysing agent+ sp. Ab –labeled- coll.
Gold
• Ag *Ab complex – Migrate up the test strip to be
captured by predeposited capture Ab. Sp.
Againist the Ag & againist the labeled
Ab(control)
• pLDH-100-200 p/mcL
• PfHRP2- >40 p/mcL

31. • Malaria cannot be diagnosed clinically with
accuracy, but treatment should be started on clinical
grounds if the laboratory confirmation is likely to be
delayed. In areas of the world where malaria is
endemic and transmission is high, low-level
asymptomatic parasitemia is common in otherwise-
healthy people. Thus malaria may not be the cause
of a fever, although in this context the presence of
>10,000 parasites/L (–0.2% parasitemia) does
indicate that malaria is the cause. Antibody and
polymerase chain reaction tests have no role in the
diagnosis of malaria.

32. • Asexual parasites/200 WBCs x 40 = parasite
count/L (assumes a WBC count of 8000/μL).
• cGametocytemia may persist for days or weeks
after clearance of asexual parasites.
Gametocytemia without asexual parasitemia
does not indicate active infection.
• dParasitized RBCs (%) x hematocrit x 1256 =
parasite count/L

33. ; in general, patients with >105 parasites/L are at
increased risk of dying,
a poor prognosis - predominance of more mature P.
falciparum parasites (i.e., >20% of parasites with
visible pigment) in the peripheral blood film or by
the presence of phagocytosed malarial pigment in
>5% of neutrophils.
In P. falciparum infections, gametocytemia peaks 1
week after the peak of asexual parasites. Because the
mature gametocytes of P. falciparum are not
affected by most antimalarial drugs, their
persistence does not constitute evidence of drug
resistance.

34. • Phagocytosed malarial pigment seen inside
monocytes or polymorphonuclear leukocytes -clue
to recent infection . After the clearance of the
parasites, this intraphagocytic malarial pigment is
often evident for several days in the peripheral blood
or for longer in bone marrow aspirates or smears of
fluid expressed after intradermal puncture. Staining
of parasites with the fluorescent dye acridine orange
allows more rapid diagnosis of malaria (but not
speciation of the infection) in patients with low-level
parasitemia.

35. • Normochromic, normocytic anemia
• . The leukocyte count is generally normal, or rised
• slight monocytosis, lymphopenia, and eosinopenia, with
reactive lymphocytosis and eosinophilia in the weeks
after the acute infection.
• The erythrocyte sedimentation rate, plasma viscosity,
and levels of C-reactive protein and other acute-phase
proteins are high.
• The platelet count is usually reduced to ~105/L
• . Severe infections may be accompanied by prolonged
prothrombin and partial thromboplastin times and by
more severe thrombocytopenia. Levels of antithrombin
III are reduced even in mild infection.

36. electrolytes, blood urea nitrogen (BUN), and creatinine
are usually normal.
severe malaria may - metabolic acidosis, hypoglycemia,
low sodium, bicarbonate, calcium, phosphate, and
albumin together with elevations in lactate, BUN,
creatinine, urate, muscle and liver enzymes, and
conjugated and unconjugated bilirubin.
Hypergammaglobulinemia is usual in immune and semi-
immune subjects. Urinalysis generally gives normal
results. In adults and children with cerebral malaria, the
mean opening pressure at lumbar puncture is ~160 mm
of cerebrospinal fluid (CSF); usually the CSF is normal
or has a slightly elevated total protein level [<1.0 g/L ]
and cell count (<20/L)