BLOOD, BONE MARROW, SPLEEN PARASITES
SPOROZOEA Order: Eucoccidiida

PLASMODIUM OVALE

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.

poT-ic

P.ovale: 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.

po1a-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.ovale, thin smear, Giemsa stain.

pITT-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.

po1b-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.ovale, thick smear, Giemsa stain.

poLon-ic	po1c-ic

                  poLon-ic Plasmodium ovale: trophozoite

po1c-ic P.ovale: all stages are seen in blood films; prominent Shuffner's
dots are present at all stages.
Trophozoites appear as rings with, usually, a compact cytoplasm;
they do not have ameboid cytoplasm.
The parasites are smaller than P.vivax.

po2-ic	P_ovale1-ic

P.ovale: red blood cells are enlarged, ovalized and distorted with fimbriae at poles.
Schizonts have usually 8-10 merozoites.

P_ovale1: P.ovale: enlarged oval red cell with one trophozoite
(Giemsa, thin film).

P_ovale1: Courtesy of Dr. Marc Lontie: Director of the laboratory of the Medisch Centrum voor Huisartsen, Maria Theresiastraat 63a; B-3000 Leuven, Belgium.

po3-ic

P.ovale: micro- and macrogametocytes are sometimes difficult
to differentiate from late trophozoites;
they are round and occupy almost the entire erythrocyte.
Microgametocytes have a more scattered chromatin.