BLOOD, BONE MARROW, SPLEEN PARASITES
SPOROZOEA Order: Eucoccidiida

PLASMODIUM FALCIPARUM

pf1-ic

Plasmodium sp.: life cycle

pf2-ic

Plasmodium sp.: geographic distribution.

pf2a-ic

Plasmodium sp.: the genus Anopheles includes more than 400 species of mosquitoes.
Many may act as vectors of human diseases such as malaria,
filariasis and some arbovirus.
Eggs present a pair of lateral floats and are laid singly on the water surface,
while larvae lay in a horizontal position under the water surface.

pf2b-ic

Plasmodium sp.: the resting position of the adult is characteristic
with the proboscid, head and abdomen in a straight line
at an angle of about 45° with the surface on which they rest.
Only about 60 species can transmit malaria and they greatly
differ in their efficiency as vectors according to man
biting behaviour, survival, fertility, adaptation to different breeding place.
The most efficient vectors belong to the A.gambiae complex,
widely distributed in tropical Africa, where also important is A.funestus.
In Asia important vectors are A.culicifaciens, A.dirus, A.sinensis and A.miminus;
in the Pacific area A.farauti and A.maculatus play a predominant role
in malaria transmission. The main vector in South America in A.albimanus.

pfT-ic

P.falciparum:  species identification is possible on the basis
of the appearance of parasites of each of the four malaria species.
Shape and size of asexual parasites and of macro- and microgametocytes,
developmental stages in peripheral blood, modifications of infected erythrocytes,
presence of dots or clefts on the red blood cells are the main differential characteristics.


Courtesy of Mr Graham Icke MSc MIBiol FIBMS Grad Dip Bus A/Principal Scientist, Laboratory Services, Royal Perth Hospital. and Dr Richard Davis PhD MSc FAACB FIBMS MASM Emeritus Consultant Haematologist, Royal Perth Hospital.

Image taken from "The Microscopic Diagnosis of Tropical Diseases", Published by BAYER in 1955 (Now Public Domain).

pf3-ic

Malaria diagnosis relies on observation of parasites in Giemsa-stained
thin or thick smears (G-TS).
Alternative techniques for identification of malaria parasites are based
on fluorochromes such as Acridine Orange (AO), DAPI-PI or BCP.
With these dyes malaria parasites are easily recognized under UV light,
reducing the time spent reading the slides.
Another method, based on fluorochromes, the quantitative buffy coat (QBC)
(Becton-Dickinson) analysis wich uses AO staining of centrifuged parasites
in a capillary tube containing a float, has been shown to be rapid and accurate.

pf-qbc-es-ic

P.falciparum: gametocytes of P.falciparum. QBC technique (60X).

Recently different immunochromatographic tests such as the ParaSight F
(Becton Dickinson) and the Malaquick (ICT) wich capture
and detect the histidine rich protein 2 (HRP-2) antigen,
and the OPTIMAL wich detects Plasmodium lactate dehydrogenase
(pLDH) have been developed and distributed.
The tests are highly sensitive and specific and are now able
to distinguish P.falciparum infections from non-falciparum infections.
P.falciparum trophozoites, thin smear, Giemsa stain.

plTT-ic

Malaria diagnosis:
whereas thin film gives more informations on parasite morphology
and permits an easier morphologic differentiation,
G-TS is more sensitive allowing a concentration of plasmodia (10-15 folds)
and it is the standard reference diagnostic test.

      pf3b-ic          pfthick-ic      

Malaria diagnosis:
G-TS needs careful stain (2% Giemsa) and experience in examining slides;
reasonable sensitivity is reached by observing at least 500-1.000 White Blood Cells (WBC).
Quantification of baseline parasitemia is necessary
for monitoring the response to therapy.
Parasites must be counted in parallel with leucocyte
and parasitemia expressed as parasites/µl.

P.falciparum trophozoites, thick smear, Giemsa stain.

pf4-ic	Pf_0410_42262-ic

P. falciparum: trophozoites are small rings with single or double small
chromatin dots, and regular cytoplasm; multiple infection and
high parasitemia (>5%) are common.
Dots or cleft (Maurer's) can be observed on the infected RBCs.
P.falciparum trophozoites, thin smear, Giemsa stain.

pf5-ic              pfthin-ic

P. falciparum: sometimes trophozoites appear at the edge
of the red blood cell (applique form) left.
Erythrocytes maintain regular shape and size.
P.falciparum trophozoites, thin smear, Giemsa stain.

pf6-ic           pfsev-ic

P. falciparum: late trophozoites and schizonts usually are not observed
in peripheral blood unless in severe infections.
Cerebral malaria: late trophozoites with a coarse granule of pigment in peripheral blood.
P.falciparum, thin smear, Giemsa stain.

pf7-ic    pfgam-ic

P.falciparum: micro- and macrogametocytes are easily
recognized by their crescentic, cigar- or banana-like shape.
Microgametocytes have a diffuse chromatin,
while macrogametocytes have thickened chromatin.
Microgametocyte, Giemsa thin smear.

pf8-ic	pfJosefsson-ic

P.falciparum: in thick films red blood cells are not visible and leucocytes
and parasites appear smaller than in thin smears.
Trophozoites have a ring or comma shape, with one or two dots of chromatin.
The pigment, when present, is compact.
Field´s staining, at Bamu Hospital in
southwest Uganda in May 2007 (pfJosefsson).

pf9-ic

P.falciparum: trophozoites in Giemsa-stained thick films
have a wide range of shapes.
Maurer's clefts are not visible.

pf10-ic

P.falciparum: micro- and macrogametocytes have an evident malaric pigment,
scattered through in the cytoplasm in the microgametocyte.
Microgametocyte, Giemsa thick smear.

pf11-ic

P.falciparum: staining with fluorochromes is rapid (less than 1 min)
and observation of slides can be performed at low magnification (400X)
allowing rapid screening of smears even with low parasitemia. P.falciparum (DAPI-PI).

pf13-ic

P.falciparum trophozoites. Acridine Orange stain.

pf14-ic

P.falciparum: the sensitivity of different isolates of P.falciparum to drugs
can be assessed with the WHO "in vitro test".
The development to mature schizont in presence of therapeutic levels
of the drug demonstrates resistance of the isolate.

pf15-ic

P.falciparum: severe P.falciparum infections are clinical forms characterized
by potentially fatal manifestations or complications:cerebral malaria,
defined by a state of unrousable coma in absence of other causes,
is the most common manifestation.
Celebral malaria: parasitized RBCs in brain vessels (H&E stain).

pf16-ic

P.falciparum: rosetting of infected and uninfected red blood cells and
cytoadherence of parasitized erythrocytes to the vascular endothelium,
play a crucial role in sequestration of parasites and obstruction of brain vessels.
Induction of host cytokines and soluble mediators such as oxygen radicals
and NO play an important role in the pathogenesis of the infection.

pf17-ic

P.falciparum: the brain appears oedematous, hyperaemic and with pigment
deposition; the capillaries, expecially of the white matter,
appear dilated and congested and obstructed by parasitized RBCs.

pf18-ic

P.falciparum: renal failure may result from sequestration of RBCs
and alteration of the renal microcirculation.
Glomerulal and interstitial vessels present RBCs adhering to the endothelium.

pf19-ic

P.falciparum: renal failure may also result from releasing of compounds secondary
to intravascular haemolysis (not haemoglobin itself) that can cause
acute tubular necrosis especially in presence of dehydratation and acidosis.

pf20-ic

P.falciparum: sequestration and cytoadherence of parasitized RBCs in heart
microcirculation is frequent but myocardial dysfunctions
and cardiac arrhythmias are uncommon in severe falciparum malaria.

pf21-ic

P.falciparum: jaundice and abnormalities of liver function tests are frequent findings
in severe falciparum malaria but hepatic failure is rare even in heavily infected individuals.

pf22-ic

P.falciparum: histological abnormalities include Kuppfer hyperplasia,
mononuclear hyperplasia and sinusoid dilatation;
swollen hepatocytes contain haemosiderin.
Kuppfer cells contain a lot of malaria pigment.

mal1-ic

A fatal case of P.falciparum malaria (liver): 
malarial pigment within Kupffer cells (H&E X 400)

mal2-ic

A fatal case of P.falciparum malaria (liver): 
note a parasitized erytrocyte (H&E X1000)

pf23-ic

P.falciparum: pulmonary, non specific complications,
such as atypical pneumonia, lobar pneumonia or bronchopneumonia,
frequently occur during malaria infections.
Pulmonary oedema is a specific and severe complication of P.falciparum infection: 3-10%
This syndrome, wich resembles the Acute Respiratory Distress Syndrome (ARDS),
has a relative late onset (wich may be abrupt) in the course of the infection
and is often associated with other manifestations of the severe falciparum malaria.
Different pathogenic mechanisms have been suggested:
-increased capillary membrane permeability
[due to microemboli or to Disseminated Intravascular Coagulation (DIC)]
-impaired function of the alveolar capillaries;
-severe disfunction of the pulmonary microcirculation;
-allergic phenomena;
-therapeutic fluid overload.
The chest radiograph, in severe cases, shows widespread bilateral,
confluent intraalveolar and interstitial infiltrates.

pf24-ic

Severe P.falciparum malaria: disseminated intravascular coagulation
with spontaneous bleedings is uncommon:
severe P.falciparum malaria in a child in Cameroun