BLOOD, BONE MARROW, SPLEEN PARASITES
SPOROZOEA Order: Eucoccidiida

PLASMODIUM VIVAX

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.

pvT-ic

P.vivax: 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.

pv1-ic

Malaria diagnosis relies mainly 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.vivax trophozoites, GT-s.

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.

pv1a-ic	pvthick-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. vivax trophozoites, thick smear, Giemsa stain.

pv2-ic

P.vivax: young trophozoites are small with single (rarely double) chromatin,
with a loop of thin cytoplasm.
The red blood cell is sligthly enlarged and a few Shuffner's dots are present.
Parasitemia range form 0.5 to 2%, multiple infection is rare.

pv3-ic	pv4-ic	pv5-ic

P.vivax: the trophozoites increases in size and the cytoplasm
becomes ameboid with rapid movements ("vivax").
The red blood cell enlarges and prominet Shuffner's dots are present.
(Thin smear, Giemsa).

pv6-ic	P_vivax2-ic

P.vivax: in more advanced stage of development trophozoites occupy most
of the RBC, and have a large vacuole and fine rods of pigment.
The nucleus increases in size.

P_vivax2: P.vivax: trophozoite, gametocyte and Schüffners’s dots (thin film).

pv7-ic

P.vivax: late trophozoites have a more dense cytoplasm, and a large vacuole.

pv8-ic

P.vivax: in young schizonts the nucleus divides and the vacuole disappears;
the cytoplasm is dense.

pv9-ic	P_vivax1-ic

P.vivax: in about 48hours schizogony is completed.
Mature schizont may contain 12-24 merozoites.
In thick smears schizonts look smaller than in thin smears
and the Schuffner's dots are not always visible.

pv10-ic

P.vivax: gametocytes are round or oval without vacuole;
most of the RBC is occupied by the parasite.
Macrogametocytes have a compact chromatin mass while
microgametocytes have a more diffuse nucleus stained pink.

pv11-ic

P.vivax: 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. vivax (DAPI-PI).