Medical Parasitology

Examination of blood for parasitesMedical ParasitologyParasites found in bloodMicrofilaria.Malaria.Babesia.Lieshmania.Trypanosomes.Toxoplasma.Preparation of blood filmsThin blood filmPlace a small drop of blood near one end of a clean slide.Spread by another slide held at an angle, so that the blood drop will run along the back of the spreader edge.The spreader slide is then pushed forward to the other end of the slide spreading a thin film of blood.Air dry.Fixation by methyl alcohol.Stain in staining dishes.Wash with distilled water, air dry and examine.Thick blood filmPlace 4 drops of blood close together on the centre of a slide.Pool the drops together with the corner of another slide making a square of 1x1 cm.Dehaemoglobinize by immersion in distilled water until Hb dissolves and the film become transulescent.Air dry.Stain in staining dishes.Wash with distilled water, air dry and examine. BLOOD FILMS WITH GEIMSAThinThick Blood dropspreadAir dryFix by methyl alcohol10-30 secGeimsa stainWash & dryAir dryCircular motionDehaemoglobinzedGeimsa stain 45 minWash & dryBLOOD FILMS WITH LIESHMANsThinThickBlood dropspreadAir dryFix and stain1 minTransfere into 1 stain: 3 distilled water.Wash and dryAir dryFollow the same as in thin filmCircular motionDehaemoglobinzed3 Blood drops

Fixation with methanol. This step is not needed in Lieshmans stain as it contains methanol.Staining by immersion in the staining dishes

Washing of the thin film

Careful washing of the thick film Normal peripheral blood smear

Thick films allow to screen a larger volume of blood and is better with scanty infections.Mainly with sheathed microfilaria as the sheath is the characteristic for type of parasite may be disturbed by spreading the thin films.Mainly with intracorpuscular parasites as Malaria and Babesia for morphological description in relation to RBCs.

Thin blood filmsThick blood filmsMicrofilariaThe larval stage of the filarial worms.It is found in blood in cases of W. bancrofti and B. malayi -the causative organisms of lymphatic filariasis- showing periodicity.Lymphatic filariasis is a disease transmitted by bite of female mosquitoes of genus Culex, Aedes and Anopheles.Thick blood film is preferred for examining a blood film for microfilaria.Concentration techniques can be used prior to microscopic examination Knotts conc technique.

KNOTTS CONC. TECHNIQUE10 ml1 mlAir dryGeimsaCitrated bloodFormalin 2 %sediment2 mincentrifugeMicrofilaria

Thick blood film showing microfilaria of W. bancroftiThick blood film showing microfilaria of B. malayiMalariaFour species are considered true parasites of humans, as they utilize humans almost exclusively as a natural intermediate host: P. falciparum, P. vivax, P. ovale and P. malariae.It is transmitted through bite of female Anopheles mosquitoes.Microscopic identification by examining thick and thin blood films is the method most frequently used to demonstrate an active infection. In P. vivax, P. ovale and P. malariae ring, trophoziote, schizont, gametocyte stages can be seen in a blood film.In cases of P. falciparum only ring and gametocyte stages are seen because of the adhesion phenomena.

P. vivax Ring-forms

Thin blood filmThick blood filmP. vivax -Schizonts

Thin blood filmThick blood filmP. vivax -Macrogametocytes

Thin blood filmThick blood filmP. falciparum -Ring-forms

Thick blood filmThin blood filmP. falciparum -Gametocytes

Thin blood filmThick blood film

BabesiaIt is a zoonatic disease transmitted to human by tick bite.Microscopic identification by examining thick and thin blood films is the method most frequently used to demonstrate an active infection.

B. divergensB. microtiTrypanosomesTrypanosoma bruceiA wet blood preparation should be examined for the motile trypanosomes, and in addition a smear should be fixed, stained and examined. Thin and thick blood stained smears for visualization of parasites.Concentration techniques can be used prior to microscopic examination Buffy coat film.African trypanosomiasis sleeping sickness is transmitted by the bite of Tsetse fly.

Trypansoma brucei ssp. in thick blood film

Trypansoma brucei ssp. in thin blood filmTrypanosoma cruziA wet blood preparation should be examined for the motile trypanosomes, and in addition a smear should be fixed, stained and examined. Concentration techniques can be used prior to microscopic examination Buffy coat film.Thin and thick blood smears stained with Giemsa, for visualization of parasites. American trypanosomiasis Chagas disease is transmitted by the bite of Rudvid bug.

T. cruzi trypomastigotes in a thick blood smear stained with Giemsa

T. cruzi trypomastigotes in thin blood smears stained with GiemsaNote the typical C-shape of the trypomastigote that characterizes T. cruzi in fixed blood smears 24LieshmaniaConcentration techniques can be used prior to microscopic examination Buffy coat film.Thin and thick blood stained smears stained for visualization of parasites. Leishmania is transmitted by the bite of Sand fly.

Leishmania spp. amastigotes Buffy coat filmcentrifugeRBCWBC (BC)plasmaCitrated blood30 minAir dryFixspreadGeimsaTryp., L. donovaniToxoplasmaThin and thick blood stained smears for visualization of parasites in cases of acute toxoplasmosis.

Tachyzoite stage in thick blood film